Effect of active-layer structures on temperature characteristics of InGaN blue laser diodes

doi:10.1364/OE.16.010849

« Show journal navigation

Effect of active-layer structures on temperature characteristics of InGaN blue laser diodes

Han-Youl Ryu and Kyoung-Ho Ha »View Author Affiliations

Optics Express, Vol. 16, Issue 14, pp. 10849-10857 (2008)
http://dx.doi.org/10.1364/OE.16.010849

View Full Text Article

Acrobat PDF (748 KB)

Journal Search
Article Lookup

Article Tools

Citations

Alert me when this article is cited
Export Citation/Save

Article Navigation

▸ Article Outline
– Abstract
1. Introduction
2. LD structures
3. Measurement results of LD characteristics
4. Simulation results
5. Conclusion
– References and links

Article Tools
Full Text
Article Info
References
Cited By
Figures
Metrics
Download PDF

Viewing Equations in the
HTML Article

Optimal Viewing Recommendations

Full Text
Article Info
References (19)
Cited By
Figures (6)
Metrics

Abstract

We investigate temperature characteristics of 445-nm-emitting InGaN blue laser diodes (LDs) with several types of active-layer structures. The double quantum-well (QW) LD structures having an n-type doped barrier show negative or very high characteristic temperature depending on the barrier In composition. On the contrary, the double QW structures having an undoped barrier and the single QW structure show normal temperature dependence of LD characteristics. From the simulation of carrier density and optical gain, it is found that the anomalous temperature characteristics of blue LDs are closed related to the inhomogeneous hole distribution between QWs due to the low hole mobility of InGaN materials.

1. Introduction

Recently, the InGaN blue laser diode (LD) with an emission wavelength near 450 nm has attracted growing interest due to the expectation as a blue light source in the future full-color laser display systems [1-6

T. Kozaki, H. Matsumura, Y. Sugimoto, S. Nagahama, and T. Mukai, “High-power and wide wavelength range GaN-based laser diodes,” Proc. SPIE 6133, 613306 (2006). [CrossRef]

]. High-performance characteristics of blue InGaN LDs operating in the wavelength range of 440 nm ~460 nm have been reported such as low threshold-current density (<2 kA/cm²) [1

T. Kozaki, H. Matsumura, Y. Sugimoto, S. Nagahama, and T. Mukai, “High-power and wide wavelength range GaN-based laser diodes,” Proc. SPIE 6133, 613306 (2006). [CrossRef]

, 2

H. Y. Ryu, K. H. Ha, S. N. Lee, T. Jang, J. K. Son, H. S. Paek, Y. J. Sung, H. K. Kim, K. S. Kim, O. H. Nam, Y. Park, and J. I. Shim, “High-performance blue InGaN lase diodes with single-quantum-well active layers,” IEEE Photon. Technol. Lett. 19, 1717–1719 (2007). [CrossRef]

], high wall-plug efficiency (>15%) [3

U. Strauß, S. Brüninghoff, M. Schillgalies, C. Vierheilig, N. Gmeinwieser, V. Kümmler, G. Brüderl, S. Lutgen, A. Avramescu, D. Queren, D. Dini, C. Eichler, A. Lell, and U. T. Schwarz, “True blue InGaN laser for pico size projectors,” Proc. SPIE 6894, 689417 (2008). [CrossRef]

, 4

T. Miyoshi, T. Kozaki, T. Yanamoto, Y. Fujimura, S. Nagahama, and T. Mukai, “GaN-based high-output-power blue laser diodes for display applications,” J. Soc. Inf. Display 15, 157–160 (2007). [CrossRef]

], and high-power (>500 mW) operation [4

, 5

M. Ohta, Y. Ohizumi, Y. Hoshina, T. Tanaka, Y. Yabuki, K. Funato, S. Tomiya, S. Goto, and M. Ikeda, “High-power pure blue laser diodes,” Phys. Status Solidi (a) 203, 2068–2072 (2007). [CrossRef]

]. These LD performances are comparable with those of the already commercialized violet InGaN LDs emitting at 405 nm. The advances in device design and growth optimization have led to the significant improvements in blue LD performances.

For the practical applications of LD devices, temperature stability of lasing characteristics is strongly required. Temperature dependence of semiconductor lasers is usually described by the empirical expression, I _th=I ₀ exp(T/T ₀), where I _th and T are threshold current and absolute temperature, respectively. The characteristic temperature (T ₀), defined in this exponential equation, is an important parameter that represents temperature dependence of LD devices. T ₀ values in nitride LDs emitting around 405 nm have been reported upto ~190 K [7

M. Ikeda, T. Mizuno, M. Takeya, S. Goto, S. Ikeda, T. Fujimoto, Y. Ohfuji, and T. Hashizu, “High-power GaN-based semiconductor lasers,” Phys. Status Solidi State (c) 1, 1461–1467 (2004). [CrossRef]

, 8

M. Shono, Y. Nomura, and Y. Bessho, “High-power blue-violet laser diode fabricated on a GaN substrate,” Proc. SPIE 5365, 282 (2004). [CrossRef]

]. However, as the lasing wavelength of nitride LDs increases from 405 nm to the blue wavelength range, various kinds of temperature dependence of threshold current have been reported including anomalous behaviors of characteristic temperature. The Polish group demonstrated abnormally high T ₀ of ~300 K from 415 nm-emitting InGaN LDs [9

T. Świetlik, G. Franssen, P. Wiśniewski, S. Krukowski, S. P. Lepkowski, L. Marona, M. Leszczyński, P. Prystawko, I. Grzegory, T. Suski, S. Porowski, P. Perlin, R. Czernecki, A. Bering-Staniszewska, and P. G. Eliseev, “Anomalous temperature characteristics of single wide quantume well InGaN laser diode,” Appl. Phys. Lett. 88, 071121 (2006). [CrossRef]

]. On the contrary, Nichia reported normal temperature dependence of threshold current with T ₀ of ~140 K from blue LDs emitting at 445 nm [1

T. Kozaki, H. Matsumura, Y. Sugimoto, S. Nagahama, and T. Mukai, “High-power and wide wavelength range GaN-based laser diodes,” Proc. SPIE 6133, 613306 (2006). [CrossRef]

]. Recently, the authors reported highly stable temperature dependence of threshold current or even negative characteristic temperature from ~450-nm emitting blue LDs having double quantum-well (QW) active layers [10

H. Y. Ryu, K. H. Ha, S. N. Lee, T. Jang, H. K. Kim, J. H. Chae, K. S. Kim, K. K. Choi, J. K. Son, H. S. Paek, Y. J. Sung, T. Sakong, O. H. Nam, and Y. J. Park, “Highly stable temperature characteristics of InGaN blue laser diodes,” Appl. Phys. Lett. 89, 031122 (2006). [CrossRef]

]. This unusual temperature characteristic has been explained by the inhomogeneous distribution of hole carrier density between two QWs due to the poor hole mobility in InGaN layers. In this case, the hole carriers need additional thermal energy to overcome the barrier between QWs, implying that high temperature has an positive influence on the more homogeneous distribution of hole carriers and consequently abnormally stable high-temperature LD performances have been obtained. In order to elucidate the role of the carrier transport on temperature characteristics of InGaN LDs, single-QW InGaN blue LDs have also been experimented and normal dependence of threshold current on temperature has been observed with T ₀ of ~170 K [2

From these previous investigations on the temperature characteristics of InGaN blue LDs, we have found that active layer structures have an important role on the hole carrier transport, optical gain, and consequently temperature behaviors of lasing characteristics. However, there has been lack of studies to comprehensively explain the various kinds of temperature characteristics in InGaN blue LDs. Here, we systematically study the effects of active layer structures on the temperature characteristics of InGaN blue LDs. Comparison of the temperature characteristics has been made for the number of QWs (single QW or double QW), the effect of barrier doping (n-type doped barrier or undoped barrier), and the barrier height (In composition of the InGaN barrier). It has been reported, by simulation, that these structural parameters have strong influences on carrier distribution and LD performances [11

Y. K. Kuo and Y. A. Chang, “Effects of electronic current overflow and inhomogeneous carrier distribution on InGaN quantum-well laser performance,” IEEE J. Quantum Electron. 40, 437–444 (2004). [CrossRef]

, 12

S. M. Thahab, H. Abu Hassan, and Z. Hassan, “Performance and optical characteristic of InGaN MQWs laser diodes,” Opt. Express 15, 2380–2390 (2007). [CrossRef] [PubMed]

]. In this work, LD devices with different active layer structures are grown and fabricated, and temperature dependence of lasing characteristics are compared. In addition, carrier density distribution and optical gain at QWs are calculated to interpret the measured results on temperature characteristics, and consistent agreements between experiments and calculation will be demonstrated. From these experimental and theoretical studies, the important effect of active layer structures on the hole carrier distribution and the novel temperature characteristics of InGaN blue LDs will be discussed.

2. LD structures

LD layers used in this work were grown on a c-plane sapphire substrate by metal-organic chemical vapor epitaxy using the lateral epitaxial overgrowth technique. The laser structure is basically the same as our recent reports on blue LDs [1

T. Kozaki, H. Matsumura, Y. Sugimoto, S. Nagahama, and T. Mukai, “High-power and wide wavelength range GaN-based laser diodes,” Proc. SPIE 6133, 613306 (2006). [CrossRef]

, 10

]. Both single-QW (SQW) and double-QW (DQW) LD structures have been grown. The In composition and thickness of the In_xGa_1-xN QW layer is ~15% and 2.5 nm, respectively, which has been designed to correspond to the lasing wavelength around 445~450 nm. In the case of DQW structures, a 15-nm-thick In_yGa_1-yN barrier layer is embedded between the QWs. Three types of DQW structures have been prepared: an n-type doped barrier with 1%-In composition (y=0.01), an n-type doped barrier with 3%-In composition (y=0.03), and an undoped barrier with 1%-In composition. In the case of the n-type doped barrier, Si was used as the dopant and the doping level is ~5×10¹⁸ cm^-3. In Fig. 1, energy band diagrams in the conduction band near the active layers are shown schematically for the structures considered in this study. Figures 1(a), 1(b), and 1(c) represent the DQW with the n-type doped barrier, the DQW with the undoped barrier, and the SQW structure, respectively. Each structure is labeled as type I, type II, and type III. For the type-I case, 1%- and 3%-In composition in the barrier layer is each labeled as type I-1 and type I-2, respectively.

The LD samples have been fabricated in the form of narrow-stripe ridge waveguides. The ridge width and the cavity length of fabricated LD samples are 2.6 µm and 650 µm, respectively. High reflection coatings consisting of multi-pairs of quarter-wave AlN/SiO₂ dielectric films were deposited on both LD facets. The reflectance on the front and the rear facet is 56% and 95%, respectively. The fabricated LD samples were placed on the AlN submount by epi-down bonding for efficient heat dissipation with the thermal resistance of ~30 K/W [13

H. Y. Ryu, K. H. Ha, J. H. Chae, O. H. Nam, and Y. J. Park, “Measurement of junction temperature in GaN-based laser diodes using voltage-temperature characteristics,” Appl. Phys. Lett. 87, 093506 (2005). [CrossRef]

Fig. 1. Schematic diagrams of conduction band energy are shown for several active-layer structures: (a) double QW with an n-type doped barrier (type I), (b) double QW with an undoped barrier (type II), (c) single QW (type III).

3. Measurement results of LD characteristics

The fabricated LD samples have been characterized under continuous-wave operation condition with varying heat sink temperatures. The center wavelength of all types of LDs is ~445 nm just above threshold. In Fig. 2, light-current (L-I) curves of four types (type I-1, type I-2, type II, type III) of LDs are shown for the temperature range from 20 °C to 80 °C. Different temperature behaviors of LDs are observed for each type of active layer structures. In Fig. 3, LD characteristics such as threshold current, slope efficiency (SE), and wall plug efficiency (WPE) at 30mW are plotted as a function of temperature. The SE is determined by the average slope of the L-I curve between 10 mW and 30 mW.

In the type I-1 structure, negative characteristic temperature is observed. The threshold current decreases from 86 mA to 75 mA as temperature increases from 20 °C to 80 °C. In this case, although temperature dependence of the threshold current does not strictly follow the exponential relationship, T ₀ has been roughly evaluated to be -500 K. In the type I-2, only a little increase of threshold current with temperature is observed. Threshold current increases by only ~5 mA in the measured temperature range, corresponding to T ₀ of ~550 K. The only difference between the type I-1 and the type I-2 is the In composition at the barrier between QWs. As the In composition increases from 1% to 3%, T ₀ changes from negative to positive. In our previous work, highly stable temperature characteristics have been demonstrated with the evolution of T ₀ from the negative to the large positive value (T ₀~1000 K) as temperature increases [10

]. Actually, the barrier In composition in the previous work was 1.5%~2%. Therefore, by combining the previous result and current data of the type I-1 and the type I-2, one can observe a consistent trend of temperature dependence with increasing barrier In composition. As the barrier In composition increases from 1% to 3%, the difference in the In composition between QWs and the barrier reduces from 14% to 12%. Therefore, with increasing barrier In composition, hole transport between QWs is improved and thermal contribution of hole carrier overflow is reduced. Consequently, temperature dependence of threshold current can be changed from anomalous characteristics (negative or very large positive T ₀) to more normal ones (smaller positive T ₀) as the barrier In composition increases. The results of temperature characteristics in the type I-1 and the type I-2 imply that one can control T ₀ of LDs to a large extent simply by changing the height of the n-type doped barrier.

Fig. 2. L-I curves of typical blue LD samples when temperature varies from 20 °C to 80 °C. (a). Type I-1 (n-type doped barrier, 1%-In composition). (b). Type I-2 (n-type doped barrier, 3%-In composition). (c). Type II (undoped barrier, 1%-In composition), (d) Type III (single QW)

Fig. 3. (a). Threshold current is plotted as a function of temperature for the 4-types of LD structures. (b). Slope efficiency is plotted as a function of temperature for the 4-types of LD structures.

In the type II and the type III structures, normally observed temperature dependence of L-I curves is obtained. T ₀ in these cases is evaluated to be in the range of 150~170 K, which is similar to the typically reported T ₀ of nitride LDs [1

T. Kozaki, H. Matsumura, Y. Sugimoto, S. Nagahama, and T. Mukai, “High-power and wide wavelength range GaN-based laser diodes,” Proc. SPIE 6133, 613306 (2006). [CrossRef]

, 7

]. Here, the temperature dependence of threshold fits quite well with the exponential expression, implying that the temperate dependence in these cases is quite normal. So, one can see that the DQW structure having the undoped barrier or the SQW structure do not undergo the problems related to the poor hole carrier transport which has been ascribed to the cause of anomalous temperature characteristics in the type I structures. In the case of the SQW structure (type III), the normal temperature behavior can be easily understood because there is only one QW in the active layers [2

]. The normal temperature characteristics in the type II structure can also be explained within the framework of the hole carrier transport and the inhomogeneous hole carrier distribution. The n-type doping at the barrier effectively increases the barrier height for holes whereas it decreases the height for electrons. Therefore, hole carriers see lower barrier height in the undoped barrier case compared with the n-type doped one, which results in the reduced influence of temperature on the hole carrier transport between QWs and consequently normal temperature characteristics in the undoped barrier case. If the barrier is doped by p-type dopant, the opposite situation to the n-type doping case will be expected. That is, the effective barrier height for holes should be decreased even more, which leads to the improved hole carrier transport and more uniform hole distribution. The positive effect of the p-type doping on the hole carrier distribution has also been predicted by the theoretical study [14

J. Y. Chang and Y. K. Kuo, “Simulation of blue InGaN quantum-well lasers,” J. Appl. Phys. 93, 4992–4998 (2003). [CrossRef]

]. However, it is difficult to apply the p-type doping to the actual LD structure because QW quality would be degraded significantly due to the p-type doping at the barrier.

Note that the SQW structure shows the lowest threshold current for all temperature range. The threshold current in this case varies from 34 mA to 46 mA between 20 °C to 80 °C. The lower threshold current at the SQW structure over the DQW one in the blue InGaN LDs has also been predicted at Ref. [11

] where the importance of inhomogeneous carrier distribution in the LD performances has been pointed out. In the DQW structures, the threshold current at low temperature (below 50 °C) increases in the order of the type II, type I-2, and type I-1. That is, the more inhomogeneous is the hole carrier distribution, the larger the threshold current becomes. The type I-1 structure exhibits much higher threshold current than other structures. It will be shown later that, in the type I-1, the optical gain at the n-side QW is much lower than that at the p-side QW due to quite inhomogeneous distribution of hole carriers, which results in the high threshold current. At high temperature >60 °C, the type I-2 shows lower threshold current than the type II due to the very high T ₀ of the type I-2 structure. This indicates the positive influence of barrier doping or nonuniform carrier distribution on the high-temperature performance of DQW blue LDs.

The L-I curves shown in Fig. 2 are linear and kink-free in the entire range of injection current and temperature except for the type I-1 structure. In the type I-2, type II, and type III, the slope efficiency (SE) is maintained well with increasing temperature. In these structures, the relative decrease of the SE is less than 5% from 20 °C to 80 °C. The order of the SE is the same as that of the threshold current below 50 °C. It is the highest for the SQW structure, and decreases in the order of the type II, the type I-2, and the type I-1. This implies that the inhomogeneous carrier distribution also has an effect on the slope efficiency as well as the threshold current. The type I-1, which has the most inhomogeneous hole carrier distribution, also shows the lowest SE. The relatively unstable L-I curves in type I-1 can be regarded as another signature of the anomalous temperature characteristics as described in Ref. [9

]. The SE increases slightly as temperature increases from 20 °C to 40 °C, which is a similar behavior of the SE to that demonstrated in Ref. [9

In Fig. 4, the wall plug efficiency (WPE) at 30-mW output power is plotted as a function of temperature for the 4-types of active layer structures. The WPE is defined as the ratio of output optical power to input electrical power. Normally, it decreases with increasing temperature as in the type II and the type III which have shown normal temperature dependence of threshold current. On the contrary, in the DQW structures having an n-type doped barrier (type I), the WPE increases with temperature. In the case of the type I-2, in spite of the increase in the operation current with temperature as shown in Fig. 2(b), the WPE increases by ~5% from 20 °C to 80 °C. This is because the operation voltage of GaN-based LDs decreases significantly as temperature increases [13

, 15

S. Uchida, M. Takeya, S. Ikeda, T. Mizuno, T. Fujimoto, O. Matsumoto, S. Goto, T. Tojyo, and M. Ikeda, “Recent progress in high-power blue-violet lasers,” IEEE J. Sel. Top Quantum Electron. 9, 1252–1259 (2003). [CrossRef]

]. Due to the large decrease in the operation voltage and only small increase in the operation current, the WPE of the type I-2 structure can be increased with increasing temperature. Similarly to the behavior of the threshold current, the WPE of the type I-2 becomes better than that of the type II when temperature rises higher than 60 oC. In the case of the type I-1, due to the decrease in the operation current with temperature, the relative increase in the WPE is even larger, ~25% from 20 °C to 80 °C although the absolute value of the WPE is much smaller than other structures.

From the above measurement results, the SQW structure has shown the best LD performances in terms of threshold current, slope efficiency, and wall plug efficiency. This is mainly because the SQW LD does not undergo the problem related to the hole carrier transport as discussed in previous works [2

, 11

]. However, for stable high-temperature operation or temperature-insensitive applications of blue LDs, the LD characteristics of the type I-2 structure might be more advantageous. Therefore, depending on the application, the blue InGaN LD can be designed to exhibit favorable LD performances and temperature characteristics by the modification of active layer structures.

Fig. 4. Wall plug efficiency (WPE) at 30-mW output power is plotted as a function of temperature for the 4-types of LD structures.

4. Simulation results

In the previous section, the distinctive features in temperature characteristics between the type I and the type II has been attributed to the difference in the homogeneity of hole carriers between QWs. In this section, we calculate carrier density and gain distribution in the DQW structures corresponding to the type I-1 and the type II in order to interpret the experimental results. The simulation program, laser technology integrated program (LASTIP), has been employed for the calculation. The LASTIP has been successfully applied to theoretically study the characteristics of InGaN LD devices [11

, 16-18

J. Piprek and S. Nakamura, “Physics of high-power InGaN/GaN lasers,” IEE Proc. Optoelectron. 149, 145–151 (2002). [CrossRef]

]. Here, the carrier distribution is governed by the drift-diffusion model including thermionic emission at hetero-boundaries, and gain calculation is based on the wurtzite band structure employing the non-Lorentzian line broadening model. Most material parameters such as the band gap and the effective mass are adopted from the Ref [18

H. Y. Ryu, “Effect of ridge shape on the fundamental single-mode operation of InGaN laser diode structures,” J. Korean Phys. Soc. 52, 1779–1785 (2008). [CrossRef]

, 19

I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors,” J. Appl. Phys. 94, 3675–3696 (2003). [CrossRef]

]. The band-offset ratio of In_xGa_1-xN/In_yGa_1-yN MQWs is set to be 0.7/0.3. The mobility of electrons and holes in the GaN layers is assumed to be 500 cm²/Vs and 10 cm²/Vs, respectively.

Figure 5 and Fig. 6 show calculation results of below-threshold hole density and gain distribution when temperature varies from 20 °C to 80 °C. Results for the type I-1 (n-type doped barrier with 1%-In composition) and the type II (undoped barrier with 1%-In composition) are shown in Fig. 5 and Fig. 6, respectively. In each figure, the p-side QW and the n-side QW is positioned at the right and the left part of the figure, respectively. In the case of the type I, the hole density distribution is quite inhomogeneous between QWs. The hole density at the n-side QW is much smaller than that at the p-side QW due to the low mobility of hole carriers. Actually, the electron density has also been calculated and found to be quite uniform between two QWs compared to the hole density because the mobility of electrons is much higher than that of holes in the InGaN material. Therefore, the gain at two QWs is mainly determined by the hole carrier distribution, which results in the negative gain at the n-side QW and the positive gain at the p-side QW. In the case of the type II, however, the hole density distribution at QWs is reasonably uniform as shown in Fig. 6(a). The hole carrier density between two QWs is almost similar level. The strong contrast of hole carrier distribution between the type I-1 and the type II originates whether the barrier is n-type doped or not. The n-type doping at the barrier effectively increases the barrier height for holes, which prevents holes from transporting from the p-side QW to the n-side one. This resulted in the quite inhomogeneous hole distribution in the type I-1 structure. On the contrary, hole carriers have little difficulty in transporting through the undoped barrier, so hole carriers can be uniformly distributed in the type II. Consequently, the overall gain of the type II is much larger than that of the type I, which has resulted in the lower threshold current in the type II structure as shown in Fig. 2 and Fig. 3.

Fig. 5. Distribution of hole density (a) and optical gain (b) at two quantum wells for the type I-1 structure (n-type doped barrier) when temperature varies from 20 °C to 80 °C.

Fig. 6. Distribution of hole density (a) and optical gain (b) at two quantum wells for the type II structure (undoped barrier) when temperature varies from 20 °C to 80 °C.

The simulation results in Fig. 5 and 6 can also be used to explain the difference in the temperature characteristics between the type I-1 and the type II. In the type I-1 structure shown in Fig. 5, as temperature increases, the hole density at the n-side QW increases due to thermally enhanced hole carrier transport from the p-side to the n-side QW. With increasing temperature, hole carriers acquire thermal energy to overcome the quantum barrier between QWs, which results in the increase in the gain at the n-side QW with temperature. The hole density at the p-side QW does not change much with temperature, and so does the gain at the p-side QW. Therefore, the overall gain at two QWs increases as temperature increases, which has led to the decrease in the threshold current with temperature or negative T ₀ as observed in Fig. 2. In the case of the type II shown in Fig. 6, hole carrier density is maintained well as temperature varies, implying that thermal overflow of holes has negligible influence on the hole carrier distribution. So, the overall gain tends to decrease as temperature increases due to the temperature-dependent reduction of material gain. This has resulted in the normal temperature characteristics: increase in the threshold current with increasing temperature. Like this way, the different temperature behaviors of the lasing threshold in the structure type I-1 and the type II can be explained. The temperature characteristics of the type I-2 can also be explained based on this model although the calculation results are not shown here. In the type I-2, the barrier In composition is lower than that of the type I-1 by 2%. The reduced barrier height of the type I-2 would result in more homogeneous hole distribution compared with the result of Fig. 5(a), so reduced threshold current and positive T ₀ could be expected consistent with the experimental results.

From the above simulation results, it has been found that barrier doping is an important factor that strongly influences hole carrier distribution and consequently temperature characteristics of InGaN blue LDs. In fact, in addition to the barrier doping, the hole density distribution is closely related to the In composition and the width of the QWs and the barrier. So, the temperature dependence of threshold current should be dependent on these structural parameters of active layers. For example, we found that 450-nm blue LDs may show anomalous temperature characteristics depending on the QW structures whereas 405-nm violet LDs have always shown normal temperature characteristics regardless of the barrier doping. This is because the depth of QWs in the 405-nm LDs is almost two times shallower than that in the 450-nm blue LDs. From this point of view, for the same active layer structures, it is expected that bluish green LDs with >470-nm emission wavelength could exhibit much more inhomogeneous hole carrier distribution than violet or blue LDs. Therefore, in order to improve lasing performances and to tailor temperature characteristics, careful design of active layers should be developed according to the color of InGaN LDs.

5. Conclusion

In this work, we investigated various temperature characteristics from InGaN blue LDs emitting around 445 nm. Temperature-dependent LD performances are compared for several LDs with different active-layer structures: the number of quantum wells (QWs), barrier doping, and the In composition at the barrier. In the double QW LD structures having an n-type doped barrier, negative characteristic temperature or very high characteristic temperature of >500 K have been observed depending on the barrier In composition. However, the double QW LD structures having an undoped barrier and the single QW LD structure showed normal temperature dependence with the characteristic temperature of ~160 K. The calculation results of carrier density and optical gain at QWs indicate that the anomalous temperature characteristics of InGaN blue LDs with the n-type doped barrier could originate from inhomogeneous distribution of hole carrier density between QWs due to the low hole mobility in InGaN materials. The demonstrated large dependence of temperature characteristics on active layer structures implies that the optimization of InGaN active layers could lead to interesting and improved temperature characteristics of blue InGaN LDs.

Acknowledgments

H. Y. Ryu acknowledges the support of J. K. Son, S. N. Lee, H. S. Paek, Y. J. Sung, K. S. Kim, and H. K. Kim for providing LD samples. He is also grateful to Prof. J. I. Shim and Prof. O. H. Nam for valuable discussions.

References and links

1.	T. Kozaki, H. Matsumura, Y. Sugimoto, S. Nagahama, and T. Mukai, “High-power and wide wavelength range GaN-based laser diodes,” Proc. SPIE 6133, 613306 (2006). [CrossRef]
2.	H. Y. Ryu, K. H. Ha, S. N. Lee, T. Jang, J. K. Son, H. S. Paek, Y. J. Sung, H. K. Kim, K. S. Kim, O. H. Nam, Y. Park, and J. I. Shim, “High-performance blue InGaN lase diodes with single-quantum-well active layers,” IEEE Photon. Technol. Lett. 19, 1717–1719 (2007). [CrossRef]
3.	U. Strauß, S. Brüninghoff, M. Schillgalies, C. Vierheilig, N. Gmeinwieser, V. Kümmler, G. Brüderl, S. Lutgen, A. Avramescu, D. Queren, D. Dini, C. Eichler, A. Lell, and U. T. Schwarz, “True blue InGaN laser for pico size projectors,” Proc. SPIE 6894, 689417 (2008). [CrossRef]
4.	T. Miyoshi, T. Kozaki, T. Yanamoto, Y. Fujimura, S. Nagahama, and T. Mukai, “GaN-based high-output-power blue laser diodes for display applications,” J. Soc. Inf. Display 15, 157–160 (2007). [CrossRef]
5.	M. Ohta, Y. Ohizumi, Y. Hoshina, T. Tanaka, Y. Yabuki, K. Funato, S. Tomiya, S. Goto, and M. Ikeda, “High-power pure blue laser diodes,” Phys. Status Solidi (a) 203, 2068–2072 (2007). [CrossRef]
6.	M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, “Continuous-wave operation of blue laser diodes based on nonpolar m-plane gallium nitride,” Appl. Phys. Express 1, 011102 (2008). [CrossRef]
7.	M. Ikeda, T. Mizuno, M. Takeya, S. Goto, S. Ikeda, T. Fujimoto, Y. Ohfuji, and T. Hashizu, “High-power GaN-based semiconductor lasers,” Phys. Status Solidi State (c) 1, 1461–1467 (2004). [CrossRef]
8.	M. Shono, Y. Nomura, and Y. Bessho, “High-power blue-violet laser diode fabricated on a GaN substrate,” Proc. SPIE 5365, 282 (2004). [CrossRef]
9.	T. Świetlik, G. Franssen, P. Wiśniewski, S. Krukowski, S. P. Lepkowski, L. Marona, M. Leszczyński, P. Prystawko, I. Grzegory, T. Suski, S. Porowski, P. Perlin, R. Czernecki, A. Bering-Staniszewska, and P. G. Eliseev, “Anomalous temperature characteristics of single wide quantume well InGaN laser diode,” Appl. Phys. Lett. 88, 071121 (2006). [CrossRef]
10.	H. Y. Ryu, K. H. Ha, S. N. Lee, T. Jang, H. K. Kim, J. H. Chae, K. S. Kim, K. K. Choi, J. K. Son, H. S. Paek, Y. J. Sung, T. Sakong, O. H. Nam, and Y. J. Park, “Highly stable temperature characteristics of InGaN blue laser diodes,” Appl. Phys. Lett. 89, 031122 (2006). [CrossRef]
11.	Y. K. Kuo and Y. A. Chang, “Effects of electronic current overflow and inhomogeneous carrier distribution on InGaN quantum-well laser performance,” IEEE J. Quantum Electron. 40, 437–444 (2004). [CrossRef]
12.	S. M. Thahab, H. Abu Hassan, and Z. Hassan, “Performance and optical characteristic of InGaN MQWs laser diodes,” Opt. Express 15, 2380–2390 (2007). [CrossRef] [PubMed]
13.	H. Y. Ryu, K. H. Ha, J. H. Chae, O. H. Nam, and Y. J. Park, “Measurement of junction temperature in GaN-based laser diodes using voltage-temperature characteristics,” Appl. Phys. Lett. 87, 093506 (2005). [CrossRef]
14.	J. Y. Chang and Y. K. Kuo, “Simulation of blue InGaN quantum-well lasers,” J. Appl. Phys. 93, 4992–4998 (2003). [CrossRef]
15.	S. Uchida, M. Takeya, S. Ikeda, T. Mizuno, T. Fujimoto, O. Matsumoto, S. Goto, T. Tojyo, and M. Ikeda, “Recent progress in high-power blue-violet lasers,” IEEE J. Sel. Top Quantum Electron. 9, 1252–1259 (2003). [CrossRef]
16.	J. Piprek and S. Nakamura, “Physics of high-power InGaN/GaN lasers,” IEE Proc. Optoelectron. 149, 145–151 (2002). [CrossRef]
17.	S. H. Yen, Y. K. Kuo, M. L. Tsai, and T. C. Hsu, “Investigation of violet InGaN laser diodes with normal and reversed polarizations,” Appl. Phys. Lett. 91, 201118 (2007). [CrossRef]
18.	H. Y. Ryu, “Effect of ridge shape on the fundamental single-mode operation of InGaN laser diode structures,” J. Korean Phys. Soc. 52, 1779–1785 (2008). [CrossRef]
19.	I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors,” J. Appl. Phys. 94, 3675–3696 (2003). [CrossRef]

OCIS Codes
(140.5960) Lasers and laser optics : Semiconductor lasers
(140.6810) Lasers and laser optics : Thermal effects
(230.5590) Optical devices : Quantum-well, -wire and -dot devices

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: May 21, 2008
Revised Manuscript: June 30, 2008
Manuscript Accepted: June 30, 2008
Published: July 3, 2008

Citation
Han-Youl Ryu and Kyoung-Ho Ha, "Effect of active-layer structures on temperature characteristics of InGaN blue laser diodes," Opt. Express 16, 10849-10857 (2008)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-14-10849

Sort: Author | Year | Journal | Reset

References

T. Kozaki, H. Matsumura, Y. Sugimoto, S. Nagahama, and T. Mukai, "High-power and wide wavelength range GaN-based laser diodes," Proc. SPIE 6133, 613306 (2006). [CrossRef]
H. Y. Ryu, K. H. Ha, S. N. Lee, T. Jang, J. K. Son, H. S. Paek, Y. J. Sung, H. K. Kim, K. S. Kim, O. H. Nam, Y. Park, and J. I. Shim, "High-performance blue InGaN lase diodes with single-quantum-well active layers," IEEE Photon. Technol. Lett. 19, 1717-1719 (2007). [CrossRef]
U. Strau?, S. Brüninghoff, M. Schillgalies, C. Vierheilig, N. Gmeinwieser, V. Kümmler, G. Brüderl, S. Lutgen, A. Avramescu, D. Queren, D. Dini, C. Eichler, A. Lell, U. T. Schwarz, "True blue InGaN laser for pico size projectors," Proc. SPIE 6894, 689417 (2008). [CrossRef]
T. Miyoshi, T. Kozaki, T. Yanamoto, Y. Fujimura, S. Nagahama, and T. Mukai, "GaN-based high-output-power blue laser diodes for display applications," J. Soc. Inf. Disp. 15, 157-160 (2007). [CrossRef]
M. Ohta, Y. Ohizumi, Y. Hoshina, T. Tanaka, Y. Yabuki, K. Funato, S. Tomiya, S. Goto, and M. Ikeda, "High-power pure blue laser diodes," Phys. Status Solidi A 203, 2068-2072 (2007). [CrossRef]
M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, "Continuous-wave operation of blue laser diodes based on nonpolar m-plane gallium nitride," J. Appl. Phys. 1, 011102 (2008). [CrossRef]
M. Ikeda, T. Mizuno, M. Takeya, S. Goto, S. Ikeda, T. Fujimoto, Y. Ohfuji, and T. Hashizu, "High-power GaN-based semiconductor lasers," Phys. Status Solidi State C 1, 1461-1467 (2004). [CrossRef]
M. Shono, Y. Nomura, and Y. Bessho, "High-power blue-violet laser diode fabricated on a GaN substrate," Proc. SPIE 5365, 282 (2004). [CrossRef]
T. ?wietlik, G. Franssen, P. Wi?niewski, S. Krukowski, S. P. Lepkowski, L. Marona, M. Leszczy?ski, P. Prystawko, I. Grzegory, T. Suski, S. Porowski, and P. Perlin, R. Czernecki, A. Bering-Staniszewska, and P. G. Eliseev, "Anomalous temperature characteristics of single wide quantume well InGaN laser diode," Appl. Phys. Lett. 88, 071121 (2006). [CrossRef]
H. Y. Ryu, K. H. Ha, S. N. Lee, T. Jang, H. K. Kim, J. H. Chae, K. S. Kim, K. K. Choi, J. K. Son, H. S. Paek, Y. J. Sung, T. Sakong, O. H. Nam, and Y. J. Park, "Highly stable temperature characteristics of InGaN blue laser diodes," Appl. Phys. Lett. 89, 031122 (2006). [CrossRef]
Y. K. Kuo and Y. A. Chang, "Effects of electronic current overflow and inhomogeneous carrier distribution on InGaN quantum-well laser performance," IEEE J. Quantum Electron. 40, 437-444 (2004). [CrossRef]
S. M. Thahab, H. Abu Hassan, and Z. Hassan, "Performance and optical characteristic of InGaN MQWs laser diodes," Opt. Express 15, 2380-2390 (2007). [CrossRef] [PubMed]
H. Y. Ryu, K. H. Ha, J. H. Chae, O. H. Nam, and Y. J. Park, "Measurement of junction temperature in GaN-based laser diodes using voltage-temperature characteristics," Appl. Phys. Lett. 87, 093506 (2005). [CrossRef]
J. Y. Chang and Y. K. Kuo, "Simulation of blue InGaN quantum-well lasers," J. Appl. Phys. 93, 4992-4998 (2003). [CrossRef]
S. Uchida, M. Takeya, S. Ikeda, T. Mizuno, T. Fujimoto, O. Matsumoto, S. Goto, T. Tojyo, and M. Ikeda, "Recent progress in high-power blue-violet lasers," IEEE J. Sel. Top Quantum Electron. 9, 1252-1259 (2003). [CrossRef]
J. Piprek and S. Nakamura, "Physics of high-power InGaN/GaN lasers," IEE Proc. :Optoelectron. 149, 145-151 (2002). [CrossRef]
S. H. Yen, Y. K. Kuo, M. L. Tsai, and T. C. Hsu, "Investigation of violet InGaN laser diodes with normal and reversed polarizations," Appl. Phys. Lett. 91, 201118 (2007). [CrossRef]
H. Y. Ryu, "Effect of ridge shape on the fundamental single-mode operation of InGaN laser diode structures," J. Korean Phys. Soc. 52, 1779-1785 (2008). [CrossRef]
I. Vurgaftman and J. R. Meyer, "Band parameters for nitrogen-containing semiconductors," J. Appl. Phys. 94, 3675-3696 (2003). [CrossRef]

?wietlik, T.
Abu Hassan, H.
Avramescu, A.
Bering-Staniszewska, A.
Bessho, Y.
Brüderl, G.
Brüninghoff, S.
Chae, J. H.
Chang, J. Y.
Chang, Y. A.
Choi, K. K.
Czernecki, R.
Dini, D.
Eichler, C.
Eliseev, P. G.
Franssen, G.
Fujimoto, T.
Fujimura, Y.
Funato, K.
Gmeinwieser, N.
Goto, S.
Grzegory, I.
Ha, K. H.
Hashizu, T.
Hassan, Z.
Hoshina, Y.
Hsu, T. C.
Ikeda, M.
Ikeda, S.
Jang, T.
Kim, H. K.
Kim, K. S.
Kozaki, T.
Krukowski, S.
Kubota, M.
Kümmler, V.
Kuo, Y. K.
Lee, S. N.
Lell, A.
Lepkowski, S. P.
Leszczy?ski, M.
Lutgen, S.
Marona, L.
Matsumoto, O.
Matsumura, H.
Meyer, J. R.
Miyoshi, T.
Mizuno, T.
Mukai, T.
Nagahama, S.
Nakamura, S.
Nam, O. H.
Nomura, Y.
Ohfuji, Y.
Ohizumi, Y.
Ohta, H.
Ohta, M.
Okamoto, K.
Paek, H. S.
Park, Y.
Park, Y. J.
Perlin, P.
Piprek, J.
Porowski, S.
Prystawko, P.
Queren, D.
Ryu, H. Y.
Sakong, T.
Schillgalies, M.
Schwarz, U. T.
Shim, J. I.
Shono, M.
Son, J. K.
Strau?, U.
Sugimoto, Y.
Sung, Y. J.
Suski, T.
Takeya, M.
Tanaka, T.
Thahab, S. M.
Tojyo, T.
Tomiya, S.
Tsai, M. L.
Uchida, S.
Vierheilig, C.
Vurgaftman, I.
Wi?niewski, P.
Yabuki, Y.
Yanamoto, T.
Yen, S. H.

Appl. Phys. Lett.

T. ?wietlik, G. Franssen, P. Wi?niewski, S. Krukowski, S. P. Lepkowski, L. Marona, M. Leszczy?ski, P. Prystawko, I. Grzegory, T. Suski, S. Porowski, and P. Perlin, R. Czernecki, A. Bering-Staniszewska, and P. G. Eliseev, "Anomalous temperature characteristics of single wide quantume well InGaN laser diode," Appl. Phys. Lett. 88, 071121 (2006). [CrossRef]
H. Y. Ryu, K. H. Ha, S. N. Lee, T. Jang, H. K. Kim, J. H. Chae, K. S. Kim, K. K. Choi, J. K. Son, H. S. Paek, Y. J. Sung, T. Sakong, O. H. Nam, and Y. J. Park, "Highly stable temperature characteristics of InGaN blue laser diodes," Appl. Phys. Lett. 89, 031122 (2006). [CrossRef]
H. Y. Ryu, K. H. Ha, J. H. Chae, O. H. Nam, and Y. J. Park, "Measurement of junction temperature in GaN-based laser diodes using voltage-temperature characteristics," Appl. Phys. Lett. 87, 093506 (2005). [CrossRef]
S. H. Yen, Y. K. Kuo, M. L. Tsai, and T. C. Hsu, "Investigation of violet InGaN laser diodes with normal and reversed polarizations," Appl. Phys. Lett. 91, 201118 (2007). [CrossRef]

IEE Proc. :Optoelectron.

J. Piprek and S. Nakamura, "Physics of high-power InGaN/GaN lasers," IEE Proc. :Optoelectron. 149, 145-151 (2002). [CrossRef]

IEEE J. Quantum Electron.

Y. K. Kuo and Y. A. Chang, "Effects of electronic current overflow and inhomogeneous carrier distribution on InGaN quantum-well laser performance," IEEE J. Quantum Electron. 40, 437-444 (2004). [CrossRef]

IEEE J. Sel. Top Quantum Electron.

S. Uchida, M. Takeya, S. Ikeda, T. Mizuno, T. Fujimoto, O. Matsumoto, S. Goto, T. Tojyo, and M. Ikeda, "Recent progress in high-power blue-violet lasers," IEEE J. Sel. Top Quantum Electron. 9, 1252-1259 (2003). [CrossRef]

IEEE Photon. Technol. Lett.

H. Y. Ryu, K. H. Ha, S. N. Lee, T. Jang, J. K. Son, H. S. Paek, Y. J. Sung, H. K. Kim, K. S. Kim, O. H. Nam, Y. Park, and J. I. Shim, "High-performance blue InGaN lase diodes with single-quantum-well active layers," IEEE Photon. Technol. Lett. 19, 1717-1719 (2007). [CrossRef]

J. Appl. Phys.

J. Y. Chang and Y. K. Kuo, "Simulation of blue InGaN quantum-well lasers," J. Appl. Phys. 93, 4992-4998 (2003). [CrossRef]
M. Kubota, K. Okamoto, T. Tanaka, and H. Ohta, "Continuous-wave operation of blue laser diodes based on nonpolar m-plane gallium nitride," J. Appl. Phys. 1, 011102 (2008). [CrossRef]
I. Vurgaftman and J. R. Meyer, "Band parameters for nitrogen-containing semiconductors," J. Appl. Phys. 94, 3675-3696 (2003). [CrossRef]

J. Korean Phys. Soc.

H. Y. Ryu, "Effect of ridge shape on the fundamental single-mode operation of InGaN laser diode structures," J. Korean Phys. Soc. 52, 1779-1785 (2008). [CrossRef]

J. Soc. Inf. Disp.

T. Miyoshi, T. Kozaki, T. Yanamoto, Y. Fujimura, S. Nagahama, and T. Mukai, "GaN-based high-output-power blue laser diodes for display applications," J. Soc. Inf. Disp. 15, 157-160 (2007). [CrossRef]

Opt. Express

S. M. Thahab, H. Abu Hassan, and Z. Hassan, "Performance and optical characteristic of InGaN MQWs laser diodes," Opt. Express 15, 2380-2390 (2007). [CrossRef] [PubMed]

Phys. Status Solidi

M. Ohta, Y. Ohizumi, Y. Hoshina, T. Tanaka, Y. Yabuki, K. Funato, S. Tomiya, S. Goto, and M. Ikeda, "High-power pure blue laser diodes," Phys. Status Solidi A 203, 2068-2072 (2007). [CrossRef]

Phys. Status Solidi State

M. Ikeda, T. Mizuno, M. Takeya, S. Goto, S. Ikeda, T. Fujimoto, Y. Ohfuji, and T. Hashizu, "High-power GaN-based semiconductor lasers," Phys. Status Solidi State C 1, 1461-1467 (2004). [CrossRef]

Proc. SPIE

M. Shono, Y. Nomura, and Y. Bessho, "High-power blue-violet laser diode fabricated on a GaN substrate," Proc. SPIE 5365, 282 (2004). [CrossRef]
T. Kozaki, H. Matsumura, Y. Sugimoto, S. Nagahama, and T. Mukai, "High-power and wide wavelength range GaN-based laser diodes," Proc. SPIE 6133, 613306 (2006). [CrossRef]
U. Strau?, S. Brüninghoff, M. Schillgalies, C. Vierheilig, N. Gmeinwieser, V. Kümmler, G. Brüderl, S. Lutgen, A. Avramescu, D. Queren, D. Dini, C. Eichler, A. Lell, U. T. Schwarz, "True blue InGaN laser for pico size projectors," Proc. SPIE 6894, 689417 (2008). [CrossRef]

2008, Strau?, Proc. SPIE
2008, Kubota, J. Appl. Phys.
2008, Ryu, J. Korean Phys. Soc.
2007, Yen, Appl. Phys. Lett.
2007, Thahab, Opt. Express
2007, Miyoshi, J. Soc. Inf. Disp.
2007, Ohta, Phys. Status Solidi
2007, Ryu, IEEE Photon. Technol. Lett.
2006, Kozaki, Proc. SPIE
2006, ?wietlik, Appl. Phys. Lett.
2006, Ryu, Appl. Phys. Lett.
2005, Ryu, Appl. Phys. Lett.
2004, Kuo, IEEE J. Quantum Electron.
2004, Ikeda, Phys. Status Solidi State
2004, Shono, Proc. SPIE
2003, Chang, J. Appl. Phys.
2003, Uchida, IEEE J. Sel. Top Quantum Electron.
2003, Vurgaftman, J. Appl. Phys.
2002, Piprek, IEE Proc. :Optoelectron.

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Click here to see a list of articles that cite this paper