Design and Simulation of a Mid-Infrared Quantum Cascade Laser Based on Ge-Si Superlattices

This paper presents a novel valance intersubband laser based on Si-based Si-Ge superlattices grown on a relaxed Si0.5Ge0.5 buffer layer. Effective mass theory is used to calculate the inplane valence subband dispersion of Si-Ge superlattices within 6×6 Kane model. Analysis of the inplane energy dispersion shows that the light-hole effective mass is inverted at off zone center region. The laser structure can be designed with a simple quantum cascade scheme. Our calculation shows that with the electrical pump, it is possible to achieve population inversion between the two subbands at local k space where the light-hole effective mass is inverted. Optical gain of the order 100/cm can be achieved with a pumping current density 10 kA/cm2.