Analysis of a Direct-Bandgap GeSn-Based MQW Transistor Laser for Mid-Infrared Applications

We propose the design and analysis of a group-IV material-based (Ge0.84Sn0.16/Si0.09Ge0.8Sn0.11) multiple quantum wells (MQW) transistor laser (TL) for mid-infrared applications. The base region incorporates Ge0.84Sn0.16/Si0.09Ge0.8Sn0.11 MQW structures pseudomorphically grown on silicon through GeSn virtual substrate, compatible with CMOS platforms for cost-effective integration of electronic and photonic circuits. With the introduction of a certain amount of tin (α-Sn) content (Sn > 6%) into germanium (Ge), GeSn alloy shows direct bandgap, thereby achieving the population inversion condition. In addition, the use of MQW structures such as the active region enhances gain due to quantum–confinement effects, and better carrier utilization over its bulk counterpart. A comparison is made between the theoretical finding for the proposed Ge0.84Sn0.16 MQW TL and the available experimental and theoretical data for currently employed InGaAs-based single quantum well (SQW) and MQW TLs. Estimated results show that a lower threshold base current of ∼ 2.65 mA and high modulation BW of ∼ 53 GHz can be achieved, which ensures the proposed GeSn-based MQW TL can be a good alternative for III–V-based TL.