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性能优越的Si基高效发光材料与器件的制备一直是Si基光电集成电路中最具挑战性的课题之一.Si基Ge材料不仅与成熟的硅工艺相兼容，而且具有准直接带特性，被认为是实现Si基激光器最有希望的材料.对Si基Ge材料N型掺杂的研究有利于提示出其直接带发光增强机理.本文研究了N型掺杂Si基Ge材料导带电子的晶格散射过程.N型掺杂Si基Ge材料具有独特的双能谷（能谷与L能谷）结构，它将通过以下两方面的竞争关系提高直接带导带底电子的占有率：一方面，处于能谷的导带电子通过谷间光学声子的散射方式散射到L能谷；另一方面，处于L能谷的导带电子通过谷内光学声子散射以及二次谷间光学声子散射或者直接通过谷间光学声子散射的方式跃迁到能谷.当掺杂浓度界于1017 cm-3到1019 cm-3时，适当提高N型掺杂浓度有利于提高直接带能谷导带底电子占有率，进而提高Si基Ge材料直接带发光效率.Silicon-based light emitting materials and devices with high efficiency are inarguably the most challenging elements in silicon (Si) photonics. Band-gap engineering approaches, including tensile strain and n-type doping, utilized for tuning germanium (Ge) to an optical gain medium have the potential for realizing monolithic optoelectronic integrated circuit. While previous experimental research has greatly contributed to optical gain and lasing of Ge direct-gap, many efforts were made to reduce lasing threshold, including the understanding of high efficiency luminescence mechanism with tensile strain and n-type doping in Ge. This paper focuses on the theoretical analysis of lattice scattering in n-type Ge-on-Si material based on its unique dual-valley transition for further improving the efficiency luminescence of Ge direct-gap laser. Lattice scattering of carriers, including inter-valley and intra-valley scattering, influence the electron distribution between the direct valley and indirect L valleys in the conduction of n-type Ge-on-Si material. This behavior can be described by theoretical model of quantum mechanics such as perturbation theory. In this paper, the lattice scatterings of intra-valley scattering in valley and L valleys, and of inter-valley scattering between the direct valley and L valleys in the n-type Ge-on-Si materials are exhibited based on its unique dual-valley transition by perturbation theory. The calculated average scattering times for phonon scattering in the cases of valley and L valleys, and for inter-valley optical phonon scattering between valley and L valleys are in agreement with experimental results, which are of significance for understanding the lattice scattering mechanism in the n-type Ge-on-Si material. The numerical calculations show that the disadvantaged inter-valley scattering of electrons from the direct valley to indirect L valleys reduces the electrons dwelling in the direct valley slightly with n-type doping concentration, while the strong inter-valley scattering from the indirect L valleys to indirect valleys increases electrons dwelling in the direct valley with n-type doping concentration. The competition between the two factors leads to an increasing electrons dwelling in the direct valley with n-type doping in a range from 1017 cm-3 to 1019 cm-3. That the electrons in the indirect L valleys are transited into the direct valley by absorbing inter-valley optical phonon modes is one of the effective ways to enhance the efficiency luminescence of Ge direct-gap laser. The results indicate that a low-threshold Ge-on-Si laser can be further improved by engineering the inter-valley scattering for enhancing the electrons dwelling in the valley.
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Keywords:
- unique dual-valley transitions /
- lattice scattering /
- Ge-on-Si /
- phonon
[1] Koerner R, Oehme M, Gollhofer M, Schmid M, Kostecki K, Bechler S, Widmann D, Kasper E, Schulze J 2015 Opt. Express 23 14815
[2] Lin G Y, Chen N L, Zhang L, Huang Z W, Huang W, Wang J Y, Xu J F, Chen S Y, Li C 2016 Materials 9 803
[3] Lin G Y, Yi X H, Li C, Chen N L, Zhang L, Chen S Y, Huang W, Wang J Y, Xiong X H, Sun J M 2016 Appl. Phys. Lett. 109 141104
[4] Kaschel M, Schmid M, Gollhofer M, Werner J, Oehme M, Schulze J 2013 Solid-State Electron 83 87
[5] Camacho-Aguilera R E, Cai Y, Patel N, Bessette J T, Romagnoli M, Kimerling L C, Michel J 2012 Opt. Express 20 11316
[6] Liu J F, Sun X C, Camacho-Aguilera R, Kimerling L C, Michel J 2010 Opt. Lett. 35 679
[7] Liu Z, Hu W X, Li C, Li Y M, Xue C L, Li C B, Zuo Y H, Cheng B W, Wang Q M 2012 Appl. Phys. Lett. 101 231108
[8] Saito S, Al-Attili A Z, Oda K, Ishikawa Y 2016 Semicond. Sci. Technol. 31 043002
[9] Huang S H, Li C, Chen C Z, Wang C, Xie W M, Lin S Y, Shao M, Nie M X, Chen C Y 2016 Chin. Phys. B 25 066601
[10] Bao S, Kim D, Onwukaeme C, Gupta S, Saraswat K, Lee K H, Kim Y, Min D, Jung Y, Qiu H, Wang H, Fitzgerald E, Tan S C, Nam D 2017 Nat. Commun. 8 1845
[11] Kurdi M E, Fishman G, Sauvage S, Boucaud P 2010 J. Appl. Phys. 107 013710
[12] Liu L, Zhang M, Hu L J, Di Z F, Zhao S J 2014 J. Appl. Phys. 116 113105
[13] Dutt B, Sukhdeo D S, Nam D, Vulovic B M, Yuan Z, Saraswat K C 2012 IEEE Photon. J. 4 2002
[14] Chow W W 2012 Appl. Phys. Lett. 100 191113
[15] Huang S H, Li C, Chen C Z, Zheng Y Y, Lai H K, Chen S Y 2012 Acta Phys. Sin. 61 036202 (in Chinese)[黄诗浩, 李成, 陈城钊, 郑元宇, 赖虹凯, 陈松岩 2012 物理学报 61 036202]
[16] Ridley B K 2013 Quantum Processes in Semiconductors (Oxford:Oxford University Press)
[17] Lever L, Ikonic Z, Valavanis A, Kelsall R W, Myronov M, Leadley D R, Hu Y, Owens N, Gardes F Y, Reed G T 2012 J. Appl. Phys. 112 123105
[18] Fischetti M V, Laux S E 1996 J. Appl. Phys. 80 2234
[19] Wang X X, Li H F, Camacho-Aguilera R, Cai Y, Kimerling L C, Michel J, Liu J F 2013 Opt. Lett. 38 652
[20] Herring C, Vogt E 1956 Phys. Rev. 101 944
[21] Mak G, Driel H 1994 Phys. Rev. B 49 16817
[22] Zhou X Q, Driel H, Mak G 1994 Phys. Rev. B 50 5226
[23] Claussen S A, Tasyurek E, Roth J E, Miller D 2010 Opt. Express 18 25596
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[1] Koerner R, Oehme M, Gollhofer M, Schmid M, Kostecki K, Bechler S, Widmann D, Kasper E, Schulze J 2015 Opt. Express 23 14815
[2] Lin G Y, Chen N L, Zhang L, Huang Z W, Huang W, Wang J Y, Xu J F, Chen S Y, Li C 2016 Materials 9 803
[3] Lin G Y, Yi X H, Li C, Chen N L, Zhang L, Chen S Y, Huang W, Wang J Y, Xiong X H, Sun J M 2016 Appl. Phys. Lett. 109 141104
[4] Kaschel M, Schmid M, Gollhofer M, Werner J, Oehme M, Schulze J 2013 Solid-State Electron 83 87
[5] Camacho-Aguilera R E, Cai Y, Patel N, Bessette J T, Romagnoli M, Kimerling L C, Michel J 2012 Opt. Express 20 11316
[6] Liu J F, Sun X C, Camacho-Aguilera R, Kimerling L C, Michel J 2010 Opt. Lett. 35 679
[7] Liu Z, Hu W X, Li C, Li Y M, Xue C L, Li C B, Zuo Y H, Cheng B W, Wang Q M 2012 Appl. Phys. Lett. 101 231108
[8] Saito S, Al-Attili A Z, Oda K, Ishikawa Y 2016 Semicond. Sci. Technol. 31 043002
[9] Huang S H, Li C, Chen C Z, Wang C, Xie W M, Lin S Y, Shao M, Nie M X, Chen C Y 2016 Chin. Phys. B 25 066601
[10] Bao S, Kim D, Onwukaeme C, Gupta S, Saraswat K, Lee K H, Kim Y, Min D, Jung Y, Qiu H, Wang H, Fitzgerald E, Tan S C, Nam D 2017 Nat. Commun. 8 1845
[11] Kurdi M E, Fishman G, Sauvage S, Boucaud P 2010 J. Appl. Phys. 107 013710
[12] Liu L, Zhang M, Hu L J, Di Z F, Zhao S J 2014 J. Appl. Phys. 116 113105
[13] Dutt B, Sukhdeo D S, Nam D, Vulovic B M, Yuan Z, Saraswat K C 2012 IEEE Photon. J. 4 2002
[14] Chow W W 2012 Appl. Phys. Lett. 100 191113
[15] Huang S H, Li C, Chen C Z, Zheng Y Y, Lai H K, Chen S Y 2012 Acta Phys. Sin. 61 036202 (in Chinese)[黄诗浩, 李成, 陈城钊, 郑元宇, 赖虹凯, 陈松岩 2012 物理学报 61 036202]
[16] Ridley B K 2013 Quantum Processes in Semiconductors (Oxford:Oxford University Press)
[17] Lever L, Ikonic Z, Valavanis A, Kelsall R W, Myronov M, Leadley D R, Hu Y, Owens N, Gardes F Y, Reed G T 2012 J. Appl. Phys. 112 123105
[18] Fischetti M V, Laux S E 1996 J. Appl. Phys. 80 2234
[19] Wang X X, Li H F, Camacho-Aguilera R, Cai Y, Kimerling L C, Michel J, Liu J F 2013 Opt. Lett. 38 652
[20] Herring C, Vogt E 1956 Phys. Rev. 101 944
[21] Mak G, Driel H 1994 Phys. Rev. B 49 16817
[22] Zhou X Q, Driel H, Mak G 1994 Phys. Rev. B 50 5226
[23] Claussen S A, Tasyurek E, Roth J E, Miller D 2010 Opt. Express 18 25596
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