Fujisawa T, Arai M, Saitoh K
Opt Express. 2019 Feb 4;27(3):2457-2464. doi: 10.1364/OE.27.002457.
Threshold carrier densities of GeSn quantum well (QW) lasers and the physical reason of low-temperature lasing of current GeSn laser are investigated through the comparison of threshold carrier densities of conventional III-V QW lasers. Electrons distributed over L-band is the main cause of decreased gain for GeSn QWs. To increase the gain (and improve the laser characteristics), a modulation-doped GeSn QW is proposed and the material gain is analyzed based on many-body theory for both qualitative and quantitative simulation. Significant gain increase can be expected for n-type modulation doping QWs. The doping condition for elevated temperature lasing is discussed and it was found that material gain curve similar to III-V QW is obtained for GeSn QW with n-type modulation doping of 6 × 10 cm. It was also found that unlike III-V QW lasers, n-type modulation doping is more effective for high-speed operation in terms of differential gain than p-type modulation doping.
通过比较传统III-V族量子阱激光器的阈值载流子密度，研究了GeSn量子阱激光器的阈值载流子密度以及当前GeSn激光器低温激射的物理原因。分布在L波段的电子是GeSn量子阱增益降低的主要原因。为了提高增益（并改善激光特性），提出了一种调制掺杂的GeSn量子阱，并基于多体理论对材料增益进行了定性和定量模拟分析。对于n型调制掺杂量子阱，有望实现显著的增益增加。讨论了高温激射的掺杂条件，发现对于n型调制掺杂浓度为6×10¹⁷cm⁻³的GeSn量子阱，可获得与III-V族量子阱相似的材料增益曲线。还发现，与III-V族量子阱激光器不同，就微分增益而言，n型调制掺杂在高速运行方面比p型调制掺杂更有效。
