Direct bandgap narrowing in Ge LED’s on Si substrates

doi:10.1364/OE.21.002206

Direct bandgap narrowing in Ge LED’s on Si substrates

Michael Oehme, Martin Gollhofer, Daniel Widmann, Marc Schmid, Mathias Kaschel, Erich Kasper, and Jörg Schulze »View Author Affiliations

Optics Express, Vol. 21, Issue 2, pp. 2206-2211 (2013)
http://dx.doi.org/10.1364/OE.21.002206

View Full Text Article

Acrobat PDF (1802 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. Epitaxial growth and device fabrication
3. Electrical and optical characterization
4. 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 (22)
Cited By
Figures (5)
Metrics

Abstract

In this paper we investigate the influence of n-type doping in Ge light emitting diodes on Si substrates on the room temperature emission spectrum. The layer structures are grown with a special low temperature molecular beam epitaxy process resulting in a slight tensile strain of 0.13%. The Ge LED’s show a dominant direct bandgap emission with shrinking bandgap at the Γ point in dependence of n-type doping level. The emission shift (38 meV at 10²⁰ cm^-3) is mainly assigned to bandgap narrowing at high doping. The electroluminescence intensity increases with doping concentrations up to 3x10¹⁹ cm⁻³ and decreases sharply at higher doping levels. The integrated direct gap emission intensity increases superlinear with electrical current density. Power exponents vary from about 2 at low doping densities up to 3.6 at 10²⁰ cm⁻³ doping density.

1. Introduction

Light sources are an important requirement for future photonic applications in Si photonic integrated circuits. Efficient light sources from a Si based heterostructure will gain importance in the growing field of Si based photonics [1

B. Jalali and S. Fathpour, “Silicon photonics,” J. Lightwave Technol. 24(12), 4600–4615 (2006). [CrossRef]

, 2

R. Soref, “Silicon Photonics: A review of recent literature,” Silicon 2(1), 1–6 (2010). [CrossRef]

]. However the realization of integrated light emitters with Si, SiGe and Ge are still challenging because of the indirect band structure. Recent Ge based laser work proved that an indirect semiconductor with a direct transition not far above the indirect one (136 meV in case of Ge) could be a light source with high integration potential on Si [3

J. Liu, R. Camacho-Aguilera, J. T. Bessette, X. Sun, X. Wang, Y. Cai, L. C. Kimerling, and J. Michel, “Ge-on-Si optoelectronics,” Thin Solid Films 520(8), 3354–3360 (2012). [CrossRef]

, 4

R. E. Camacho-Aguilera, Y. Cai, N. Patel, J. T. Bessette, M. Romagnoli, L. C. Kimerling, and J. Michel, “An electrically pumped germanium laser,” Opt. Express 20(10), 11316–11320 (2012). [CrossRef] [PubMed]

]. A direct semiconductor could be obtained by high tensile strain (1.8%) in Ge [5

X. Sun, J. Liu, L. C. Kimerling, and J. Michel, “Toward a germanium laser for integrated silicon photonics,” IEEE J. Sel. Top. Quantum Electron. 16(1), 124–131 (2010). [CrossRef]

] or by the incorporation of the larger atom Sn in the Ge lattice. It is predicted that Ge_1-ZSn_Z alloys turn into direct group IV semiconductor crystals if Z amounts to more than 10% [6

K. Alberi, J. Blacksberg, L. D. Bell, S. Nikzad, K. M. Yu, O. D. Dubon, and W. Walukiewicz, “Band anticrossing in highly mismatched SnxGe1−x semiconducting alloys,” Phys. Rev. B 77(7), 073202 (2008). [CrossRef]

]. In the last years different groups already demonstrated room temperature direct band gap electroluminescence (EL) from indirect semiconductor Ge [7

X. Sun, J. Liu, L. C. Kimerling, and J. Michel, “Room-temperature direct bandgap electroluminesence from Ge-on-Si light-emitting diodes,” Opt. Lett. 34(8), 1198–1200 (2009). [CrossRef] [PubMed]

–11

T. Arguirov, M. Kittler, M. Oehme, N. V. Abrosimov, E. Kasper, and J. Schulze, “Room temperature direct band-gap emission from an unstrained Ge p-i-n LED on Si,” Solid State Phenomena 178–179, 25–30 (2011). [CrossRef]

] on Si. Tensile strain from thermal expansion mismatch (typically 0.15% to 0.25%) and high n-doping increase the luminescence emission efficiency.

In highly doped semiconductors the bandgap shrinks with increasing doping level because of the effect of bandgap narrowing. Band gap narrowing in heavily doped semiconductors is caused by ionized impurity potentials, by impurity band formation and many electrons interaction. In electronic devices it is described by an apparent increase in intrinsic carrier concentration [12

D. B. M. Klaassen, J. W. Slotboom, and H. C. de Graaff, “Unified apparent bandgap narrowing in n- and p-type silicon,” Solid-State Electron. 35(2), 125–129 (1992). [CrossRef]

]. In Si the bandgap narrows by 90 meV at 10²⁰ cm⁻³ doping. In Ge different values are assigned for the indirect L minimum and the direct Γ gap narrowing [13

J. I. Pankove and P. Aigrain, “Optical absorption of arsenic-doped degenerate Germanium,” Phys. Rev. 126(3), 956–962 (1962). [CrossRef]

]. The direct gap narrowing varies between 30 meV and 70 meV (extrapolated) at doping levels from 10¹⁹ cm⁻³ to 6x10¹⁹ cm⁻³. The L minimum (indirect transitions) shows a slightly larger narrowing (by 15 meV to 30 meV) compared to the direct narrowing [13

J. I. Pankove and P. Aigrain, “Optical absorption of arsenic-doped degenerate Germanium,” Phys. Rev. 126(3), 956–962 (1962). [CrossRef]

, 14

S. C. Jain and D. J. Roulston, “A simple expression for bandgap narrowing (BGN) in heavily doped Si, Ge, GaAs and Ge_xSi_1-x strained layers,” Solid-State Electron. 34(5), 453–465 (1991). [CrossRef]

]. In Ref [14

]. the indirect L minimum narrowing is dependent on the doping type described as slightly larger for p-doping than n-doping (95 meV vs. 80 meV at 6x10¹⁹ cm⁻³). The effect of bandgap narrowing is observed with photoluminescence (PL) measurements at Ge LED’s [15

E. Kasper, M. Oehme, J. Werner, T. Arguirov, and M. Kittler, “Direct band gap luminescence from Ge on Si pin diodes,” Front. Optoelectron. 5, 256–260 (2012).

]. In this paper we investigate the influence of n-type doping (doping concentration between 5x10¹⁷ cm⁻³ and 1x10²⁰ cm⁻³) of the direct band gap EL of Ge LED’s.

2. Epitaxial growth and device fabrication

The Ge heterojunction p⁺nn⁺ LED’s are fabricated in a quasi-planar technology with a heterostructure top contact [16

M. Oehme, M. Kaschel, J. Werner, O. Kirfel, M. Schmid, B. Bahouchi, E. Kasper, and J. Schulze, “Germanium on silicon photodetectors with broad spectral range,” J. Electrochem. Soc. 157(2), H144–H148 (2010). [CrossRef]

]. The technology is based on a sequential growth of layers by solid source molecular beam epitaxy (MBE) [17

M. Oehme, J. Werner, M. Kaschel, O. Kirfel, and E. Kasper, “Germanium waveguide photodetectors integrated on silicon with MBE,” Thin Solid Films 517(1), 137–139 (2008). [CrossRef]

]. The MBE machine is equipped with a Si electron beam evaporator and a special Ge effusion cell. As n and p dopant sources, Sb and B effusion cells are used. The layer sequence and the annealing steps are grown with one epitaxial run. The schematic cross section of the layer stack is shown in Fig. 1(a) . B-doped Si (100) substrates with a high specific resistance ρ > 1000 Ωcm are used.

Fig. 1 (a) Schematic cross section of a p⁺nn⁺ Ge LED structure. (b) A plan view scanning electron microscopy image of the complete fabricated p⁺nn⁺ Ge LED with a mesa radius of 5 µm.

The growth starts with the buried layer (BL) contact which is very high B doped of about 10²⁰ cm⁻³. This BL contact consist of a 100 nm thick virtual substrate (VS) and a 300 nm p⁺ Ge layer. The VS accomplishes the accommodation of the lattice constant of Ge (4.2% larger than Si) to the underlying Si by a dense network of misfit dislocations at the Si interface. The technical realization of the VS is performed by low temperature growth of 50 nm Ge (330 °C) followed by a high temperature annealing step (810 °C). A second 50 nm thick p⁺ doped Ge layer grown at 330 °C smooth the annealed surface and a further temperature annealing step at 750 °C completes the VS. The 300 nm p⁺ Ge layer completes the layer growth of the buried layer (BL) contact. A third annealing step at 750 °C adjusts the tensile strain in the BL material. This is an important step for the following growth steps, because Sb-doped Ge cannot be annealed at temperatures higher than 500 °C. The surface segregation of Sb in Ge is very strong depending on growth temperature [18

M. Oehme, J. Werner, and E. Kasper, “Molecular beam epitaxy of highly antimony doped germanium on silicon,” J. Cryst. Growth 310(21), 4531–4534 (2008). [CrossRef]

]. To achieve an abrupt transition of Sb-doping the growth temperature is decreased in a growth interruption to 160 °C. In a growth series the doping concentration n_var of the 300 nm thick n-Ge layer are varied between 5x10¹⁷ cm⁻³ and 1x10²⁰ cm⁻³. In addition a reference pin LED is grown. The n⁺-doped top contact is finally realized as a highly Sb-doped (10²⁰ cm⁻³) Ge/Si heterojunction contact [16

]. The device processing by mesa etching, passivation and metallization is the same as with earlier reported vertical Ge pin photodiodes [16

, 17

M. Oehme, J. Werner, M. Kaschel, O. Kirfel, and E. Kasper, “Germanium waveguide photodetectors integrated on silicon with MBE,” Thin Solid Films 517(1), 137–139 (2008). [CrossRef]

]. The complete realized LED is shown in a plan view scanning electron microscopy image in Fig. 1(b).

The tensile strain (caused by the larger thermal expansion coefficient of Ge compared to the Si substrate) of the LED’s is engineered by a high temperature annealing step at the end of the BL growth. A tensile strain increases the lattice constant of Ge and shifts the bandgap slightly more into the infrared [19

M. Schmid, M. Oehme, M. Gollhofer, M. Kaschel, E. Kasper, and J. Schulze, “Electroluminescence of unstrained and tensile strained Ge-on-Si LEDs,” IEEE 9th International Conference on Group IV Photonics (GFP) 135 – 137 (2012).

]. In a following growth step the Ge layers are grown with the same lattice parameters as the underlying BL. The determination of the strain status of the LED’s is possible with EL peak position measurements at a reference pin LED grown with the same procedure [19

]. In principal, the Sb doping could decrease the tensile strain in the n-Ge layer because the Sb atom has got a higher covalent radius (0.138 nm) as the Ge atom (0.122 nm). However the concentration of Sb in Ge is smaller than 0.2% and its influence (below 0.03%) can be neglected for the strain analyses of the p⁺nn⁺ Ge LED’s.

3. Electrical and optical characterization

The room temperature current density -voltage (J-V) characteristics are measured with a Keithley 4200 semiconductor parameter analyzer. Figure 2(a) displays the corresponding J-V characteristics of p⁺nn⁺ Ge LED’s with different doping concentrations n_var. The current increases dramatically with increasing doping concentration n_var because of additional tunneling current parts (Zener tunneling, Esaki tunneling).

Fig. 2 (a) J-V characteristics of p⁺nn⁺ Ge LED’s with different doping concentrations n_var in the n-Ge layer. (b) J-V characteristics of a p⁺nn⁺ Ge LED with different device areas at a constant doping concentration of n_var = 3x10¹⁹ cm⁻³. The inset shows the linear plot of the J-V curve with a negative differential resistance.

The J-V characteristics of the Ge LED with different device areas (doping concentration n_var = 3x10¹⁹ cm⁻³) are presented in Fig. 2(b). In the forward characteristics the current scales with the device area up to 0.4 V. For higher voltages (> 0.4 V) the J-V characteristics does not scale with the device area because the series resistance of the devices is limiting the current. In the reverse characteristics the Zener tunneling current scales with device area up to 0.1 V. At higher voltages the influence of the series resistance is seen, too. The inset in Fig. 2(b) shows the linear plot of the J-V curve of the smallest device with a radius of 1 µm. A negative differential resistance (NDR) is found with a peak to valley current ratio (PVCR) of 1.07. A diode with this I-U characteristic is called Esaki diode. An NDR is a strong indicator for abrupt junctions and excellent layer quality [20

M. Oehme, M. Sarlija, D. Hähnel, M. Kaschel, J. Werner, E. Kasper, and J. Schulze, “Very high room temperature peak to valley current ratio in Si Esaki Tunneling Diodes,” IEEE Trans. Electron. Dev. 57(11), 2857–2863 (2010). [CrossRef]

]. The challenges for the Esaki structures are the abrupt doping transitions and the defect levels in the epi layers which should be low in order to avoid high excess currents.

For light emission the p⁺nn⁺ Ge LED is operated in forward direction at high current densities where the impact of series resistance is strong. In order to minimize the series resistance it is beneficial to use a layout with both contacts on the upper side of the wafer to circumvent the high resistance of the substrate.

The setup for the EL measurements consists of a semiconductor parameter analyzer, a probe station with a glass fiber and an Ando AQ6315A optical spectrum analyzer (OSA). A multimode glass fiber with 800 µm core radius is adjusted above the emitting surface of the Ge heterojunction pin LED to collect the light and is directly connected to the OSA. The range of the OSA goes from 350 nm to 1750 nm, but low signals are difficult to detect at > 1700 nm due to increasing noise of the internal InGaAs detector. Figure 3(a) shows the typical room temperature EL spectra I_EL as function of energy of p⁺nn⁺ Ge LED’s at different forward injection current densities. The active n-type region is n_var = 3x10¹⁹ cm⁻³ (left) and n_var = 4x10¹⁹ cm⁻³ (right) doped. This small difference in the doping concentration changes the emission of more of a factor of 2.3. The EL measurements are analyzed in two steps, the integral gap EL versus injected current and the EL peak position as function of electrical power.

Fig. 3 (a) Direct gap room temperature EL spectra of 80 µm radius Ge p⁺nn⁺ LED’s under different injection current densities. Active n-type region is 3x10¹⁹ cm⁻³ (left) and 4x10¹⁹ cm⁻³ (right) doped. (b) Integral EL intensity of a 80 µm radius p⁺nn⁺ Ge LED’s as function of doping concentration at different current densities.

The integral direct gap EL intensity P_Γ is calculated with:

P_{Γ} = \int I_{E L} (E) d E

(1)

The result of P_Γ versus doping concentration of the complete growth series is shown in Fig. 3(b). The intensity increases with increasing of the n-type doping up to 3x10¹⁹ cm⁻³. For higher doping concentration an abrupt decrease of the emission is found. We found for all doping concentrations a superlinear relation P_Γ ~j^m with the power exponent m. This implies that the LED is more efficient when operated under high injected current. An example for the dependence of P_Γ versus j at a doping concentration of n_var = 3x10¹⁹ cm⁻³ is shown in the inset in Fig. 4 . The extracted exponent m is here 2.25. The complete overview of the exponents m of all samples is shown in Fig. 4. The exponent m is in the range of 2 between 5x10¹⁷ cm⁻³ and 3x10¹⁹ cm⁻³. At higher doping concentration n_var the exponent increases up to 3.61 for 1x10²⁰ cm⁻³.

Fig. 4 Exponent m versus doping concentration n_var of the P_Γ ~j^m characteristics of the investigated LED’s. Inset: Integrated emission to current density characteristics of a 80 µm radius p⁺nn⁺ Ge LED with a doping concentration of n_var = 3x10¹⁹ cm⁻³. The exponent m is 2.25.

The EL spectra exhibit a band to band optical transition with peaks around the direct bandgap energy. The energy of the EL peak shifts with increasing injection current because the high injection currents increase the device temperature by heating. Nevertheless, temperature can be deduced from the shape of the spectrum. The emission intensity I_EL(E) is composed of the contributions of the 3D density of states which constrains the low energy emission and of the approximated Boltzmann-distribution for the high energy tail:

I_{E L} (E) ~ \sqrt{E - E_{g}} \cdot \exp (- \frac{E}{k_{B} T})

(2)

where E is the photon energy, E_g the direct bandgap energy, k_B the Boltzmann constant and T the absolute temperature. Therefore the EL maximum E_max is located at a photon energy of:

E_{\max} = E_{g} + \frac{k_{B} T}{2}

(3)

Accordingly curve fitting of the emission spectra leads to an independent identification of the parameters E_g and T. The inset in Fig. 5 shows the direct bandgap energy as function of electrical power for the p⁺nn⁺ Ge LED with n_var = 3x10¹⁹ cm⁻³. A clear linear dependence is found. The intersection with the energy axis i.e. the extrapolation to zero electrical power leads to the direct bandgap energy at room temperature. For this Ge LED a value of 0.759 eV is calculated.

Fig. 5 Direct bandgap energy E_g as function of doping concentration of tensile strained p⁺nn⁺ Ge LED’s. Inset: Maximum positions E_max of EL spectra as function of the injected electrical power.

The bandgap energy as function of doping concentration n_var is plotted in Fig. 5. The bandgap shrinks with increasing of the Sb doping level. This effect is caused by the bandgap narrowing in heavily doped semiconductors. Figure 5 shows also the bandgap of the pin Ge reference LED (blue hexagon). The sole difference between the reference pin and the p⁺nn⁺ Ge LED is the doping of the n zone. The intrinsic region has got a background doping of p-type with a doping concentration of 10¹⁶ cm⁻³. For the pin Ge LED a direct Γ gap of 0.79 eV is calculated from the EL measurements. This means that the direct bandgap shifts in the infrared about 10 meV compared with unstrained Ge. A shift of 10 meV corresponds with a tensile strain of 0.13% [21

]. The growth strategy particularly with regard to growth temperature profile of all samples is the same. This means that all samples have got roughly a tensile strain of 0.13% and the direct bandgap in all samples is decreased by 10 meV compared with unstrained, low doped Ge. The bandgap of n-doped Ge as calculated from peak emission energies (equ. 2) follows in a semilog plot (Fig. 5) a linear relation above a threshold of about 10¹⁸ cm⁻³. The slope (red line in Fig. 5) is weaker than expected from published absorption curves [13

J. I. Pankove and P. Aigrain, “Optical absorption of arsenic-doped degenerate Germanium,” Phys. Rev. 126(3), 956–962 (1962). [CrossRef]

, 14

, 22

C. Haas, “Infrared Absorption in Heavily Doped n-Type Germanium,” Phys. Rev. 125(6), 1965–1971 (1962). [CrossRef]

]. The peak emission shifts 38 meV to lower energy at a doping level of 10²⁰ cm⁻³.

4. Conclusion

In conclusion, we analyzed the direct bandgap EL from tensile strained Ge heterojunction p⁺nn⁺ LED’s on Si substrates as function of doping concentration. The layer structure is grown with MBE with a special heterostructure top contact. The NDR in the LED with a doping concentration of 3x10¹⁹ cm⁻³ shows the excellent layer quality. A maximum room temperature emission at a LED with a radius of 80 µm is found at a doping level of n_var = 3x10¹⁹ cm⁻³. For higher doping concentrations an abrupt decrease of the emission is seen. We found for all doping concentrations a superlinear relation between the optical power and the injected current. For doping concentrations larger than n_var = 3x10¹⁹ cm⁻³ the exponent m increase up to 3.61 for 1x10²⁰ cm⁻³. The tensile strained Ge LED’s shows a shrinking of direct bandgap in dependence of the Sb doping concentration with a maximal shift of 38 meV at n_var = 1x10²⁰ cm⁻³. This effect is caused by the bandgap narrowing in heavily doped semiconductors but the slope is smaller than expected from published absorption curves in highly n-doped Ge.

References and links

1.	B. Jalali and S. Fathpour, “Silicon photonics,” J. Lightwave Technol. 24(12), 4600–4615 (2006). [CrossRef]
2.	R. Soref, “Silicon Photonics: A review of recent literature,” Silicon 2(1), 1–6 (2010). [CrossRef]
3.	J. Liu, R. Camacho-Aguilera, J. T. Bessette, X. Sun, X. Wang, Y. Cai, L. C. Kimerling, and J. Michel, “Ge-on-Si optoelectronics,” Thin Solid Films 520(8), 3354–3360 (2012). [CrossRef]
4.	R. E. Camacho-Aguilera, Y. Cai, N. Patel, J. T. Bessette, M. Romagnoli, L. C. Kimerling, and J. Michel, “An electrically pumped germanium laser,” Opt. Express 20(10), 11316–11320 (2012). [CrossRef] [PubMed]
5.	X. Sun, J. Liu, L. C. Kimerling, and J. Michel, “Toward a germanium laser for integrated silicon photonics,” IEEE J. Sel. Top. Quantum Electron. 16(1), 124–131 (2010). [CrossRef]
6.	K. Alberi, J. Blacksberg, L. D. Bell, S. Nikzad, K. M. Yu, O. D. Dubon, and W. Walukiewicz, “Band anticrossing in highly mismatched SnxGe1−x semiconducting alloys,” Phys. Rev. B 77(7), 073202 (2008). [CrossRef]
7.	X. Sun, J. Liu, L. C. Kimerling, and J. Michel, “Room-temperature direct bandgap electroluminesence from Ge-on-Si light-emitting diodes,” Opt. Lett. 34(8), 1198–1200 (2009). [CrossRef] [PubMed]
8.	S. L. Cheng, J. Lu, G. Shambat, H. Y. Yu, K. Saraswat, J. Vuckovic, and Y. Nishi, “Room temperature 1.6 μm electroluminescence from Ge light emitting diode on Si substrate,” Opt. Express 17(12), 10019–10024 (2009). [CrossRef]
9.	M. de Kersauson, R. Jakomin, M. El Kurdi, G. Beaudoin, N. Zerounian, F. Aniel, S. Sauvage, I. Sagnes, and P. Boucaud, “Direct and indirect band gap room temperature electroluminescence of Ge diodes,” J. Appl. Phys. 108(2), 023105 (2010). [CrossRef]
10.	M. Oehme, J. Werner, M. Gollhofer, M. Schmid, M. Kaschel, E. Kasper, and J. Schulze, “Room-Temperature Electroluminescence From GeSn Light-Emitting Pin Diodes on Si,” IEEE Photon. Technol. Lett. 23(23), 1751–1753 (2011). [CrossRef]
11.	T. Arguirov, M. Kittler, M. Oehme, N. V. Abrosimov, E. Kasper, and J. Schulze, “Room temperature direct band-gap emission from an unstrained Ge p-i-n LED on Si,” Solid State Phenomena 178–179, 25–30 (2011). [CrossRef]
12.	D. B. M. Klaassen, J. W. Slotboom, and H. C. de Graaff, “Unified apparent bandgap narrowing in n- and p-type silicon,” Solid-State Electron. 35(2), 125–129 (1992). [CrossRef]
13.	J. I. Pankove and P. Aigrain, “Optical absorption of arsenic-doped degenerate Germanium,” Phys. Rev. 126(3), 956–962 (1962). [CrossRef]
14.	S. C. Jain and D. J. Roulston, “A simple expression for bandgap narrowing (BGN) in heavily doped Si, Ge, GaAs and Ge_xSi_1-x strained layers,” Solid-State Electron. 34(5), 453–465 (1991). [CrossRef]
15.	E. Kasper, M. Oehme, J. Werner, T. Arguirov, and M. Kittler, “Direct band gap luminescence from Ge on Si pin diodes,” Front. Optoelectron. 5, 256–260 (2012).
16.	M. Oehme, M. Kaschel, J. Werner, O. Kirfel, M. Schmid, B. Bahouchi, E. Kasper, and J. Schulze, “Germanium on silicon photodetectors with broad spectral range,” J. Electrochem. Soc. 157(2), H144–H148 (2010). [CrossRef]
17.	M. Oehme, J. Werner, M. Kaschel, O. Kirfel, and E. Kasper, “Germanium waveguide photodetectors integrated on silicon with MBE,” Thin Solid Films 517(1), 137–139 (2008). [CrossRef]
18.	M. Oehme, J. Werner, and E. Kasper, “Molecular beam epitaxy of highly antimony doped germanium on silicon,” J. Cryst. Growth 310(21), 4531–4534 (2008). [CrossRef]
19.	M. Schmid, M. Oehme, M. Gollhofer, M. Kaschel, E. Kasper, and J. Schulze, “Electroluminescence of unstrained and tensile strained Ge-on-Si LEDs,” IEEE 9th International Conference on Group IV Photonics (GFP) 135 – 137 (2012).
20.	M. Oehme, M. Sarlija, D. Hähnel, M. Kaschel, J. Werner, E. Kasper, and J. Schulze, “Very high room temperature peak to valley current ratio in Si Esaki Tunneling Diodes,” IEEE Trans. Electron. Dev. 57(11), 2857–2863 (2010). [CrossRef]
21.	M. Schmid, M. Oehme, M. Gollhofer, M. Kaschel, E. Kasper, and J. Schulze, “Electroluminescence of unstrained and tensile strained Ge-on-Si LEDs,” IEEE 9th International Conference on Group IV Photonics (GFP) 135 – 137 (2012).
22.	C. Haas, “Infrared Absorption in Heavily Doped n-Type Germanium,” Phys. Rev. 125(6), 1965–1971 (1962). [CrossRef]

OCIS Codes
(130.3120) Integrated optics : Integrated optics devices
(160.3380) Materials : Laser materials
(230.3670) Optical devices : Light-emitting diodes

ToC Category:
Optical Devices

History
Original Manuscript: November 28, 2012
Manuscript Accepted: January 9, 2013
Published: January 22, 2013

Citation
Michael Oehme, Martin Gollhofer, Daniel Widmann, Marc Schmid, Mathias Kaschel, Erich Kasper, and Jörg Schulze, "Direct bandgap narrowing in Ge LED’s on Si substrates," Opt. Express 21, 2206-2211 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-2-2206

Sort: Author | Year | Journal | Reset

References

B. Jalali and S. Fathpour, “Silicon photonics,” J. Lightwave Technol.24(12), 4600–4615 (2006). [CrossRef]
R. Soref, “Silicon Photonics: A review of recent literature,” Silicon2(1), 1–6 (2010). [CrossRef]
J. Liu, R. Camacho-Aguilera, J. T. Bessette, X. Sun, X. Wang, Y. Cai, L. C. Kimerling, and J. Michel, “Ge-on-Si optoelectronics,” Thin Solid Films520(8), 3354–3360 (2012). [CrossRef]
R. E. Camacho-Aguilera, Y. Cai, N. Patel, J. T. Bessette, M. Romagnoli, L. C. Kimerling, and J. Michel, “An electrically pumped germanium laser,” Opt. Express20(10), 11316–11320 (2012). [CrossRef] [PubMed]
X. Sun, J. Liu, L. C. Kimerling, and J. Michel, “Toward a germanium laser for integrated silicon photonics,” IEEE J. Sel. Top. Quantum Electron.16(1), 124–131 (2010). [CrossRef]
K. Alberi, J. Blacksberg, L. D. Bell, S. Nikzad, K. M. Yu, O. D. Dubon, and W. Walukiewicz, “Band anticrossing in highly mismatched SnxGe1−x semiconducting alloys,” Phys. Rev. B77(7), 073202 (2008). [CrossRef]
X. Sun, J. Liu, L. C. Kimerling, and J. Michel, “Room-temperature direct bandgap electroluminesence from Ge-on-Si light-emitting diodes,” Opt. Lett.34(8), 1198–1200 (2009). [CrossRef] [PubMed]
S. L. Cheng, J. Lu, G. Shambat, H. Y. Yu, K. Saraswat, J. Vuckovic, and Y. Nishi, “Room temperature 1.6 μm electroluminescence from Ge light emitting diode on Si substrate,” Opt. Express17(12), 10019–10024 (2009). [CrossRef]
M. de Kersauson, R. Jakomin, M. El Kurdi, G. Beaudoin, N. Zerounian, F. Aniel, S. Sauvage, I. Sagnes, and P. Boucaud, “Direct and indirect band gap room temperature electroluminescence of Ge diodes,” J. Appl. Phys.108(2), 023105 (2010). [CrossRef]
M. Oehme, J. Werner, M. Gollhofer, M. Schmid, M. Kaschel, E. Kasper, and J. Schulze, “Room-Temperature Electroluminescence From GeSn Light-Emitting Pin Diodes on Si,” IEEE Photon. Technol. Lett.23(23), 1751–1753 (2011). [CrossRef]
T. Arguirov, M. Kittler, M. Oehme, N. V. Abrosimov, E. Kasper, and J. Schulze, “Room temperature direct band-gap emission from an unstrained Ge p-i-n LED on Si,” Solid State Phenomena178–179, 25–30 (2011). [CrossRef]
D. B. M. Klaassen, J. W. Slotboom, and H. C. de Graaff, “Unified apparent bandgap narrowing in n- and p-type silicon,” Solid-State Electron.35(2), 125–129 (1992). [CrossRef]
J. I. Pankove and P. Aigrain, “Optical absorption of arsenic-doped degenerate Germanium,” Phys. Rev.126(3), 956–962 (1962). [CrossRef]
S. C. Jain and D. J. Roulston, “A simple expression for bandgap narrowing (BGN) in heavily doped Si, Ge, GaAs and GexSi1-x strained layers,” Solid-State Electron.34(5), 453–465 (1991). [CrossRef]
E. Kasper, M. Oehme, J. Werner, T. Arguirov, and M. Kittler, “Direct band gap luminescence from Ge on Si pin diodes,” Front. Optoelectron.5, 256–260 (2012).
M. Oehme, M. Kaschel, J. Werner, O. Kirfel, M. Schmid, B. Bahouchi, E. Kasper, and J. Schulze, “Germanium on silicon photodetectors with broad spectral range,” J. Electrochem. Soc.157(2), H144–H148 (2010). [CrossRef]
M. Oehme, J. Werner, M. Kaschel, O. Kirfel, and E. Kasper, “Germanium waveguide photodetectors integrated on silicon with MBE,” Thin Solid Films517(1), 137–139 (2008). [CrossRef]
M. Oehme, J. Werner, and E. Kasper, “Molecular beam epitaxy of highly antimony doped germanium on silicon,” J. Cryst. Growth310(21), 4531–4534 (2008). [CrossRef]
M. Schmid, M. Oehme, M. Gollhofer, M. Kaschel, E. Kasper, and J. Schulze, “Electroluminescence of unstrained and tensile strained Ge-on-Si LEDs,” IEEE 9th International Conference on Group IV Photonics (GFP) 135 – 137 (2012).
M. Oehme, M. Sarlija, D. Hähnel, M. Kaschel, J. Werner, E. Kasper, and J. Schulze, “Very high room temperature peak to valley current ratio in Si Esaki Tunneling Diodes,” IEEE Trans. Electron. Dev.57(11), 2857–2863 (2010). [CrossRef]
M. Schmid, M. Oehme, M. Gollhofer, M. Kaschel, E. Kasper, and J. Schulze, “Electroluminescence of unstrained and tensile strained Ge-on-Si LEDs,” IEEE 9th International Conference on Group IV Photonics (GFP) 135 – 137 (2012).
C. Haas, “Infrared Absorption in Heavily Doped n-Type Germanium,” Phys. Rev.125(6), 1965–1971 (1962). [CrossRef]

Front. Optoelectron.

E. Kasper, M. Oehme, J. Werner, T. Arguirov, and M. Kittler, “Direct band gap luminescence from Ge on Si pin diodes,” Front. Optoelectron.5, 256–260 (2012).

IEEE J. Sel. Top. Quantum Electron.

X. Sun, J. Liu, L. C. Kimerling, and J. Michel, “Toward a germanium laser for integrated silicon photonics,” IEEE J. Sel. Top. Quantum Electron.16(1), 124–131 (2010). [CrossRef]

IEEE Photon. Technol. Lett.

M. Oehme, J. Werner, M. Gollhofer, M. Schmid, M. Kaschel, E. Kasper, and J. Schulze, “Room-Temperature Electroluminescence From GeSn Light-Emitting Pin Diodes on Si,” IEEE Photon. Technol. Lett.23(23), 1751–1753 (2011). [CrossRef]

IEEE Trans. Electron. Dev.

M. Oehme, M. Sarlija, D. Hähnel, M. Kaschel, J. Werner, E. Kasper, and J. Schulze, “Very high room temperature peak to valley current ratio in Si Esaki Tunneling Diodes,” IEEE Trans. Electron. Dev.57(11), 2857–2863 (2010). [CrossRef]

J. Appl. Phys.

M. de Kersauson, R. Jakomin, M. El Kurdi, G. Beaudoin, N. Zerounian, F. Aniel, S. Sauvage, I. Sagnes, and P. Boucaud, “Direct and indirect band gap room temperature electroluminescence of Ge diodes,” J. Appl. Phys.108(2), 023105 (2010). [CrossRef]

J. Cryst. Growth

M. Oehme, J. Werner, and E. Kasper, “Molecular beam epitaxy of highly antimony doped germanium on silicon,” J. Cryst. Growth310(21), 4531–4534 (2008). [CrossRef]

J. Electrochem. Soc.

M. Oehme, M. Kaschel, J. Werner, O. Kirfel, M. Schmid, B. Bahouchi, E. Kasper, and J. Schulze, “Germanium on silicon photodetectors with broad spectral range,” J. Electrochem. Soc.157(2), H144–H148 (2010). [CrossRef]

J. Lightwave Technol.

B. Jalali and S. Fathpour, “Silicon photonics,” J. Lightwave Technol.24(12), 4600–4615 (2006). [CrossRef]

Opt. Express

Opt. Lett.

X. Sun, J. Liu, L. C. Kimerling, and J. Michel, “Room-temperature direct bandgap electroluminesence from Ge-on-Si light-emitting diodes,” Opt. Lett.34(8), 1198–1200 (2009). [CrossRef] [PubMed]

Phys. Rev.

J. I. Pankove and P. Aigrain, “Optical absorption of arsenic-doped degenerate Germanium,” Phys. Rev.126(3), 956–962 (1962). [CrossRef]
C. Haas, “Infrared Absorption in Heavily Doped n-Type Germanium,” Phys. Rev.125(6), 1965–1971 (1962). [CrossRef]

Phys. Rev. B

K. Alberi, J. Blacksberg, L. D. Bell, S. Nikzad, K. M. Yu, O. D. Dubon, and W. Walukiewicz, “Band anticrossing in highly mismatched SnxGe1−x semiconducting alloys,” Phys. Rev. B77(7), 073202 (2008). [CrossRef]

Silicon

R. Soref, “Silicon Photonics: A review of recent literature,” Silicon2(1), 1–6 (2010). [CrossRef]

Solid State Phenomena

T. Arguirov, M. Kittler, M. Oehme, N. V. Abrosimov, E. Kasper, and J. Schulze, “Room temperature direct band-gap emission from an unstrained Ge p-i-n LED on Si,” Solid State Phenomena178–179, 25–30 (2011). [CrossRef]

Solid-State Electron.

D. B. M. Klaassen, J. W. Slotboom, and H. C. de Graaff, “Unified apparent bandgap narrowing in n- and p-type silicon,” Solid-State Electron.35(2), 125–129 (1992). [CrossRef]
S. C. Jain and D. J. Roulston, “A simple expression for bandgap narrowing (BGN) in heavily doped Si, Ge, GaAs and GexSi1-x strained layers,” Solid-State Electron.34(5), 453–465 (1991). [CrossRef]

Thin Solid Films

M. Oehme, J. Werner, M. Kaschel, O. Kirfel, and E. Kasper, “Germanium waveguide photodetectors integrated on silicon with MBE,” Thin Solid Films517(1), 137–139 (2008). [CrossRef]
J. Liu, R. Camacho-Aguilera, J. T. Bessette, X. Sun, X. Wang, Y. Cai, L. C. Kimerling, and J. Michel, “Ge-on-Si optoelectronics,” Thin Solid Films520(8), 3354–3360 (2012). [CrossRef]

Other

M. Schmid, M. Oehme, M. Gollhofer, M. Kaschel, E. Kasper, and J. Schulze, “Electroluminescence of unstrained and tensile strained Ge-on-Si LEDs,” IEEE 9th International Conference on Group IV Photonics (GFP) 135 – 137 (2012).
M. Schmid, M. Oehme, M. Gollhofer, M. Kaschel, E. Kasper, and J. Schulze, “Electroluminescence of unstrained and tensile strained Ge-on-Si LEDs,” IEEE 9th International Conference on Group IV Photonics (GFP) 135 – 137 (2012).

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