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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 10 — May. 7, 2012
  • pp: 11574–11580
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First principles study of Bismuth alloying effects in GaAs saturable absorber

Dechun Li, Ming Yang, Shengzhi Zhao, Yongqing Cai, and Yuanping Feng  »View Author Affiliations


Optics Express, Vol. 20, Issue 10, pp. 11574-11580 (2012)
http://dx.doi.org/10.1364/OE.20.011574


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Abstract

First principles hybrid functional calculations have been carried out to study electronic properties of GaAs with Bi alloying effects. It is found that the doping of Bi into GaAs reduces the bandgap due to the intraband level repulsions between Bi induced states and host states, and the Bi-related impurity states originate from the hybridization of Bi-6p and its nearest As-4p orbitals. With the increase of Bi concentration in GaAs, the bandgap decreases monotonously. The calculated optical properties of the undoped and Bi-doped GaAs are similar except the shift toward lower energy of absorption edge and main absorption peaks with Bi doping. These results suggest a promising application of GaBixAs1-x alloy as semiconductor saturable absorber in Q-switched or mode-locked laser.

© 2012 OSA

1. Introduction

Semiconductor saturable absorber Q-switched all-solid-state lasers are desirable for many potential applications in remote sensing, ranging, micromachining, and nonlinear wavelength conversion. In comparison with other saturable absorbers, GaAs has the advantages of stable photochemical property and saturable absorption, good thermal conductivity, non-degradability, and high damage threshold [1

1. Z. Zhang, L. Qian, D. Fan, and X. Deng, “Gallium arsenide: a new material to accomplish passively mode-locked Nd:YAG laser,” Appl. Phys. Lett. 60(4), 419–421 (1992). [CrossRef]

4

4. J. Gu, F. Zhou, W. Xie, S. C. Tam, and Y. L. Lam, “Passive Q-switching of a diode pumped Nd:YAG with GaAs output coupler,” Opt. Commun. 165(4-6), 245–249 (1999). [CrossRef]

]. Since the operating photon energy at 1.06 μm wavelength is far below the bandgap of GaAs, the absorption at this wavelength in the GaAs saturable absorber is believed to be due to the deep donor EL2 defects [5

5. A. L. Smirl, G. C. Valley, K. M. Bohnert, and T. F. Boggess, “Picosecond photorefractive and free-carrier transient energy transfer in GaAs at 1μm,” IEEE J. Quantum Electron. 24(2), 289–303 (1988). [CrossRef]

]. However, the concentration of EL2 deep-level defects is very low, and it is a challenge to control the amount of EL2 defects in GaAs saturable absorber to design its Q-switching parameters, such as linear loss, non-linear loss, recovery time, and modulation depth.

2. Method of calculations

We have calculated the electronic properties of GaAs, GaBi, and the ternary alloy GaBixAs1-x, in which super-cells of 64 atoms were used. The calculations were performed using the plane-wave projector augmented-wave (PAW) [23

23. P. E. Blöchl, “Projector augmented-wave method,” Phys. Rev. B Condens. Matter 50(24), 17953–17979 (1994). [CrossRef] [PubMed]

, 24

24. G. Kresse and D. Joubert, “From ultrasoft pseudopotentials to the projector augmented-wave method,” Phys. Rev. B 59(3), 1758–1775 (1999). [CrossRef]

] method applying the semilocal Perdew-Burke-Ernzerhof (PBE) [25

25. J. P. Perdew, K. Burke, and M. Ernzerhof, “Generalized gradient approximation made simple,” Phys. Rev. Lett. 77(18), 3865–3868 (1996). [CrossRef] [PubMed]

] exchange-correlation functional and the Heyd-Scuseria- Ernzerhof (HSE) [26

26. J. Heyd, G. E. Scuseria, and M. Ernzerhof, “Hybrid functionals based on a screened Coulomb potential,” J. Chem. Phys. 118(18), 8207–8219 (2003). [CrossRef]

] hybrid functional as implemented in VASP code. Hybrid functional were mixed by about 25% nonlocal Hartree-Fock and 75% semilocal exchange, and the HSE screening parameter [27

27. A. V. Krukau, O. A. Vydrov, A. F. Izmaylov, and G. E. Scuseria, “Influence of the exchange screening parameter on the performance of screened hybrid functionals,” J. Chem. Phys. 125(22), 224106 (2006). [CrossRef] [PubMed]

] was set to a value of 0.2 Å−1. The outermost s- and p-electrons of the As atom, the outermost s-, p- and d-electrons of the Ga atom, and the Bi atom were treated as valence electrons. The electronic wave functions were expanded into plane-waves with a cutoff energy of 300 eV. Brillouin-zone was sampled by 2 × 2 × 2 Г-centered mesh, and a small Gaussian broadening σ = 0.05 eV was used, such that the peaks of the defect states are resolvable from the valence band continuum, for the calculations of density of states (DOS).

3. Bi-related impurity states in GaBixAs1-x

The band structure and the total DOS of the perfect GaAs has been shown in Ref [28

28. D. C. Li, M. Yang, Y. Q. Cai, S. Z. Zhao, and Y. P. Feng, “First principles study of the ternary complex model of EL2 defect in GaAs saturable absorber,” Opt. Express 20(6), 6258–6266 (2012). [CrossRef] [PubMed]

], from which we can see that the perfect GaAs has a direct bandgap of 1.5 eV at the Г point. However, from the band structure and the total DOS of the perfect GaBi in Fig. 1
Fig. 1 The band structures and the total DOS of GaBi.
, we can see that a very small overlap between the bottom of the conduction band and the top of the valence band in the band structure of GaBi, and noticeable density of states at the Fermi level in the total DOS. Therefore, it can be concluded that GaBi has no bandgap, and is expected to exhibit characteristics of a semimetal [15

15. A. Janoti, S. H. We, and S. B. Zhang, “Theoretical study of the effects of isovalent coalloying of Bi and N in GaAs,” Phys. Rev. B 65(11), 115203 (2002). [CrossRef]

].

The origin of these impurity states can be explored by using the local density of states (LDOS), as shown in Fig. 3
Fig. 3 Density of states of GaAs and GaBixAs1-x. (a). Total DOS of GaAs; (b). Total DOS of GaBixAs1-x; (c). LDOS of the Bi atom.
, in which Figs. 3(a) and 3(b) show the total DOS of perfect GaAs and GaBixAs1-x, respectively, and Fig. 3(c) is the LDOS of the Bi atom in GaBixAs1-x. It can be seen clearly that the impurity states in Fig. 3(b) (highlighted by red line) and those of Bi atom (the four peaks highlighted in red in Fig. 3(c)) are located at the same positions. Charge transfer between Bi and surrounding Ga atoms induces new electronic states located at 0.33~1.27 eV below the VBM. These impurity states result in the reduction of GaAs bandgap, and also are the transition states to assist photon absorption.

4. Bandgap of GaBixAs1-x with different Bi composition

The bandgap versus composition x for GaBixAs1-x is plotted in Fig. 6
Fig. 6 The bandgap of GaBixAs1-x versus Bi concentration x.
(black line). We found that the dependence of the bandgap (Eg) of GaBixAs1-x on Bi composition x can be well described by a 3rd-order polynomial, Eg=1.525.386x+16.596x212.734x3, for x values ranging from 0 to 0.15 (red curve in Fig. 6). By setting Eg to 1.17eV (photon energy at 1.06 um) and solving the equation numerically, we can obtain that the photon at the wavelength of 1.06 um can be absorbed in GaBixAs1-x with the Bi concentration of about 8.97%.

5. Optical absorption spectra

Figure 7
Fig. 7 The absorption coefficients of GaAs and GaBixAs1-x.
shows the absorption coefficients of perfect GaAs, GaBixAs1-x (x = 1/32), and GaBixAs1-x (x = 1/16). The inset of Fig. 7 is the magnified absorption edges that move to the lower energy after Bi doping, which are in good agreement with the above band structure results. It is known that the absorption edge is mainly from the interband transitions between the top of the valence band and the bottom of the conduction band. For the absorption edge of GaAs, it was due to the transitions from As 4p states to Ga 4s states, while for GaBixAs1-x the transitions were from As 2p and Bi 6p states to Ga 4s. Beyond the absorption edges, the both doped spectra of GaBixAs1-x have two main peaks, which show obvious redshifts compared with the corresponding peaks of GaAs.

From Fig. 7, it can be seen that the calculated optical properties of the undoped and Bi-doped GaAs are similar except the shift toward longer wavelength of absorption edge and main absorption peaks with Bi doping. Therefore, the incorporation of Bi into GaAs leads to a reduction of the optical bandgap, but does not change the good saturable absorption property of GaAs.

6. Conclusion

In summary, via first-principles calculations, we show that bandgap engineering of GaBixAs1-x can be realized by tuning Bi the concentration. The incorporation of Bi into GaAs leads to a reduction of bandgap, and the gap decreases with the increase of Bi concentration, due to the Bi induced intraband repulsions. The Bi alloying induced bandgap narrowing effect may make the absorption of light in GaBixAs1-x more efficient, suggesting that GaBixAs1-x alloy a promising new semiconductor saturable absorber in Q-switched or mode-locked laser in the future.

Acknowledgments

This work was partially supported by the National Science Foundation of China (60876056, 21173134), the founding of the National Municipal Science and Technology Project (No. 2008ZX05011-002), the China Postdoctoral Science Foundation funded project (20090461210), and the Postdoctoral Special Innovation Foundation of Shandong Province (200903067).

References and links

1.

Z. Zhang, L. Qian, D. Fan, and X. Deng, “Gallium arsenide: a new material to accomplish passively mode-locked Nd:YAG laser,” Appl. Phys. Lett. 60(4), 419–421 (1992). [CrossRef]

2.

T. T. Kajava and A. L. Gaeta, “Q-switching of a diode-pumped Nd:YAG laser with GaAs,” Opt. Lett. 21(16), 1244–1246 (1996). [CrossRef] [PubMed]

3.

J. Gu, F. Zhou, K. T. Wan, T. K. Lim, S.-C. Tam, Y. L. Lam, D. Xu, and Z. Cheng, “Q-switching of a diode-pumped Nd:YVO4 laser with GaAs nonlinear output coupler,” Opt. Lasers Eng. 35(5), 299–307 (2001). [CrossRef]

4.

J. Gu, F. Zhou, W. Xie, S. C. Tam, and Y. L. Lam, “Passive Q-switching of a diode pumped Nd:YAG with GaAs output coupler,” Opt. Commun. 165(4-6), 245–249 (1999). [CrossRef]

5.

A. L. Smirl, G. C. Valley, K. M. Bohnert, and T. F. Boggess, “Picosecond photorefractive and free-carrier transient energy transfer in GaAs at 1μm,” IEEE J. Quantum Electron. 24(2), 289–303 (1988). [CrossRef]

6.

T. Tiedje, E. C. Young, and A. Mascarenhas, “Growth and properties of the dilute bismide semiconductor GaAs1−xBix a complementary alloy to the dilute nitrides,” Int. J. Nanotechnol. 5, 963–983 (2008). [CrossRef]

7.

A. R. Mohmad, F. Bastiman, C. J. Hunter, J. S. Ng, S. J. Sweeney, and J. P. R. David, “The effect of Bi composition to the optical quality of GaAs1−xBix,” Appl. Phys. Lett. 99(4), 042107–042109 (2011). [CrossRef]

8.

K. Oe and H. Okamato, “New semiconductor alloy GaAs1-xBix grown by metal organic vapor phase epitaxy,” Jpn. J. Appl. Phys. 37(Part 2, No. 11A), L1283–L1285 (1998). [CrossRef]

9.

K. Oe, “Characteristics of semiconductor alloy GaAs1-xBix,” Jpn. J. Appl. Phys. 41(Part 1, No. 5A), 2801–2806 (2002). [CrossRef]

10.

B. Fluegel, S. Francoeur, A. Mascarenhas, S. Tixier, E. C. Young, and T. Tiedje, “Giant spin-orbit bowing in GaAs1-xBix.,” Phys. Rev. Lett. 97(6), 067205–067208 (2006). [CrossRef] [PubMed]

11.

S. Francoeur, M. J. Seong, A. Mascarenhas, S. Tixier, M. Adamcyk, and T. Tiedje, “Band gap of GaAs1−xBix, 0<x<3.6%,” Appl. Phys. Lett. 82(22), 3874–3876 (2003). [CrossRef]

12.

S. Tixier, M. Adamcyk, T. Tiedje, S. Francoeur, A. Mascarenhas, P. Wei, and F. Schiettekatte, “Molecular beam epitaxy growth of GaAs1−xBix,” Appl. Phys. Lett. 82(14), 2245–2247 (2003). [CrossRef]

13.

E. C. Young, M. B. Whitwick, T. Tiedje, and D. A. Beaton, “Bismuth incorporation in GaAs1−xBix grown by molecular beam epitaxy with in-situ light scattering,” Phys. Status Solidi 4(5c), 1707–1710 (2007). [CrossRef]

14.

K. Alberi, O. D. Dubon, W. Walukiewicz, K. M. Yu, K. Bertulis, and A. Krotkus, “Valence band anticrossing in GaBixAs1−x,” Appl. Phys. Lett. 91(5), 051909–051911 (2007). [CrossRef]

15.

A. Janoti, S. H. We, and S. B. Zhang, “Theoretical study of the effects of isovalent coalloying of Bi and N in GaAs,” Phys. Rev. B 65(11), 115203 (2002). [CrossRef]

16.

Y. Zhang, Z. Mascarenhas, and L. W. Wang, “Similar and dissimilar aspects of III-V semiconductors containing Bi versus N,” Phys. Rev. B 71(15), 155201 (2005). [CrossRef]

17.

D. Madouri, A. Boukra, A. Zaoui, and M. Ferhat, “Bismuth alloying in GaAs: a first-principles study,” Comput. Mater. Sci. 43(4), 818–822 (2008). [CrossRef]

18.

A. Abdiche, H. Abid, R. Riane, and A. Bouaza, “Structural and electronic properties of zinc blend GaAs1-xBix solid solutions,” Physica B 405(9), 2311–2316 (2010). [CrossRef]

19.

J. Hwang and J. D. Phillips, “Band structure of strain-balanced GaAsBi/GaAsN superlattices on GaAs,” Phys. Rev. B 83(19), 195327 (2011). [CrossRef]

20.

J. Heyd, J. E. Peralta, G. E. Scuseria, and R. L. Martin, “Energy band gaps and lattice parameters evaluated with the Heyd-Scuseria-Ernzerhof screened hybrid functional,” J. Chem. Phys. 123(17), 174101 (2005). [CrossRef] [PubMed]

21.

G. Kresse and J. Furthmüller, “Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set,” Comput. Mater. Sci. 6(1), 15–50 (1996). [CrossRef]

22.

G. Kresse and J. Furthmüller, “Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set,” Phys. Rev. B Condens. Matter 54(16), 11169–11186 (1996). [CrossRef] [PubMed]

23.

P. E. Blöchl, “Projector augmented-wave method,” Phys. Rev. B Condens. Matter 50(24), 17953–17979 (1994). [CrossRef] [PubMed]

24.

G. Kresse and D. Joubert, “From ultrasoft pseudopotentials to the projector augmented-wave method,” Phys. Rev. B 59(3), 1758–1775 (1999). [CrossRef]

25.

J. P. Perdew, K. Burke, and M. Ernzerhof, “Generalized gradient approximation made simple,” Phys. Rev. Lett. 77(18), 3865–3868 (1996). [CrossRef] [PubMed]

26.

J. Heyd, G. E. Scuseria, and M. Ernzerhof, “Hybrid functionals based on a screened Coulomb potential,” J. Chem. Phys. 118(18), 8207–8219 (2003). [CrossRef]

27.

A. V. Krukau, O. A. Vydrov, A. F. Izmaylov, and G. E. Scuseria, “Influence of the exchange screening parameter on the performance of screened hybrid functionals,” J. Chem. Phys. 125(22), 224106 (2006). [CrossRef] [PubMed]

28.

D. C. Li, M. Yang, Y. Q. Cai, S. Z. Zhao, and Y. P. Feng, “First principles study of the ternary complex model of EL2 defect in GaAs saturable absorber,” Opt. Express 20(6), 6258–6266 (2012). [CrossRef] [PubMed]

OCIS Codes
(140.3540) Lasers and laser optics : Lasers, Q-switched
(160.2220) Materials : Defect-center materials
(160.6000) Materials : Semiconductor materials
(190.4400) Nonlinear optics : Nonlinear optics, materials

ToC Category:
Materials

History
Original Manuscript: March 28, 2012
Revised Manuscript: April 29, 2012
Manuscript Accepted: April 30, 2012
Published: May 4, 2012

Citation
Dechun Li, Ming Yang, Shengzhi Zhao, Yongqing Cai, and Yuanping Feng, "First principles study of Bismuth alloying effects in GaAs saturable absorber," Opt. Express 20, 11574-11580 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-10-11574


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References

  1. Z. Zhang, L. Qian, D. Fan, and X. Deng, “Gallium arsenide: a new material to accomplish passively mode-locked Nd:YAG laser,” Appl. Phys. Lett.60(4), 419–421 (1992). [CrossRef]
  2. T. T. Kajava and A. L. Gaeta, “Q-switching of a diode-pumped Nd:YAG laser with GaAs,” Opt. Lett.21(16), 1244–1246 (1996). [CrossRef] [PubMed]
  3. J. Gu, F. Zhou, K. T. Wan, T. K. Lim, S.-C. Tam, Y. L. Lam, D. Xu, and Z. Cheng, “Q-switching of a diode-pumped Nd:YVO4 laser with GaAs nonlinear output coupler,” Opt. Lasers Eng.35(5), 299–307 (2001). [CrossRef]
  4. J. Gu, F. Zhou, W. Xie, S. C. Tam, and Y. L. Lam, “Passive Q-switching of a diode pumped Nd:YAG with GaAs output coupler,” Opt. Commun.165(4-6), 245–249 (1999). [CrossRef]
  5. A. L. Smirl, G. C. Valley, K. M. Bohnert, and T. F. Boggess, “Picosecond photorefractive and free-carrier transient energy transfer in GaAs at 1μm,” IEEE J. Quantum Electron.24(2), 289–303 (1988). [CrossRef]
  6. T. Tiedje, E. C. Young, and A. Mascarenhas, “Growth and properties of the dilute bismide semiconductor GaAs1−xBix a complementary alloy to the dilute nitrides,” Int. J. Nanotechnol.5, 963–983 (2008). [CrossRef]
  7. A. R. Mohmad, F. Bastiman, C. J. Hunter, J. S. Ng, S. J. Sweeney, and J. P. R. David, “The effect of Bi composition to the optical quality of GaAs1−xBix,” Appl. Phys. Lett.99(4), 042107–042109 (2011). [CrossRef]
  8. K. Oe and H. Okamato, “New semiconductor alloy GaAs1-xBix grown by metal organic vapor phase epitaxy,” Jpn. J. Appl. Phys.37(Part 2, No. 11A), L1283–L1285 (1998). [CrossRef]
  9. K. Oe, “Characteristics of semiconductor alloy GaAs1-xBix,” Jpn. J. Appl. Phys.41(Part 1, No. 5A), 2801–2806 (2002). [CrossRef]
  10. B. Fluegel, S. Francoeur, A. Mascarenhas, S. Tixier, E. C. Young, and T. Tiedje, “Giant spin-orbit bowing in GaAs1-xBix.,” Phys. Rev. Lett.97(6), 067205–067208 (2006). [CrossRef] [PubMed]
  11. S. Francoeur, M. J. Seong, A. Mascarenhas, S. Tixier, M. Adamcyk, and T. Tiedje, “Band gap of GaAs1−xBix, 0<x<3.6%,” Appl. Phys. Lett.82(22), 3874–3876 (2003). [CrossRef]
  12. S. Tixier, M. Adamcyk, T. Tiedje, S. Francoeur, A. Mascarenhas, P. Wei, and F. Schiettekatte, “Molecular beam epitaxy growth of GaAs1−xBix,” Appl. Phys. Lett.82(14), 2245–2247 (2003). [CrossRef]
  13. E. C. Young, M. B. Whitwick, T. Tiedje, and D. A. Beaton, “Bismuth incorporation in GaAs1−xBix grown by molecular beam epitaxy with in-situ light scattering,” Phys. Status Solidi4(5c), 1707–1710 (2007). [CrossRef]
  14. K. Alberi, O. D. Dubon, W. Walukiewicz, K. M. Yu, K. Bertulis, and A. Krotkus, “Valence band anticrossing in GaBixAs1−x,” Appl. Phys. Lett.91(5), 051909–051911 (2007). [CrossRef]
  15. A. Janoti, S. H. We, and S. B. Zhang, “Theoretical study of the effects of isovalent coalloying of Bi and N in GaAs,” Phys. Rev. B65(11), 115203 (2002). [CrossRef]
  16. Y. Zhang, Z. Mascarenhas, and L. W. Wang, “Similar and dissimilar aspects of III-V semiconductors containing Bi versus N,” Phys. Rev. B71(15), 155201 (2005). [CrossRef]
  17. D. Madouri, A. Boukra, A. Zaoui, and M. Ferhat, “Bismuth alloying in GaAs: a first-principles study,” Comput. Mater. Sci.43(4), 818–822 (2008). [CrossRef]
  18. A. Abdiche, H. Abid, R. Riane, and A. Bouaza, “Structural and electronic properties of zinc blend GaAs1-xBix solid solutions,” Physica B405(9), 2311–2316 (2010). [CrossRef]
  19. J. Hwang and J. D. Phillips, “Band structure of strain-balanced GaAsBi/GaAsN superlattices on GaAs,” Phys. Rev. B83(19), 195327 (2011). [CrossRef]
  20. J. Heyd, J. E. Peralta, G. E. Scuseria, and R. L. Martin, “Energy band gaps and lattice parameters evaluated with the Heyd-Scuseria-Ernzerhof screened hybrid functional,” J. Chem. Phys.123(17), 174101 (2005). [CrossRef] [PubMed]
  21. G. Kresse and J. Furthmüller, “Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set,” Comput. Mater. Sci.6(1), 15–50 (1996). [CrossRef]
  22. G. Kresse and J. Furthmüller, “Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set,” Phys. Rev. B Condens. Matter54(16), 11169–11186 (1996). [CrossRef] [PubMed]
  23. P. E. Blöchl, “Projector augmented-wave method,” Phys. Rev. B Condens. Matter50(24), 17953–17979 (1994). [CrossRef] [PubMed]
  24. G. Kresse and D. Joubert, “From ultrasoft pseudopotentials to the projector augmented-wave method,” Phys. Rev. B59(3), 1758–1775 (1999). [CrossRef]
  25. J. P. Perdew, K. Burke, and M. Ernzerhof, “Generalized gradient approximation made simple,” Phys. Rev. Lett.77(18), 3865–3868 (1996). [CrossRef] [PubMed]
  26. J. Heyd, G. E. Scuseria, and M. Ernzerhof, “Hybrid functionals based on a screened Coulomb potential,” J. Chem. Phys.118(18), 8207–8219 (2003). [CrossRef]
  27. A. V. Krukau, O. A. Vydrov, A. F. Izmaylov, and G. E. Scuseria, “Influence of the exchange screening parameter on the performance of screened hybrid functionals,” J. Chem. Phys.125(22), 224106 (2006). [CrossRef] [PubMed]
  28. D. C. Li, M. Yang, Y. Q. Cai, S. Z. Zhao, and Y. P. Feng, “First principles study of the ternary complex model of EL2 defect in GaAs saturable absorber,” Opt. Express20(6), 6258–6266 (2012). [CrossRef] [PubMed]

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