Performance Optimization of Multiple Quantum Well Transistor Laser

A comprehensive physical model that emphasizes carrier tunneling between quantum wells (QWs) in the base of transistor lasers (TLs) is developed. This model relies on a set of multilevel coupled rate equations solved by computationally efficient numerical methods for simulating both steady state and transient TL operations. Our approach also features the explicit dependence of the structure design on device parameters such as optical confinement factor and carrier density-dependent gain. It also accounts for operation behaviors such as bandwidth roll-off and critical base width not yet addressed in the literature. Simulation results show significant enhancement in optical bandwidth as well as threshold current reduction when multiple QWs are incorporated within the base region. It predicts the dominance of tunneling transport of carriers for barriers thinner than 13.5 nm in a system with 7-nm QWs. However, the optimum QW number depends on the structure design as well as TL biasing conditions. For this purpose, we define a performance parameter as a TL figure of merit that can be maximized by optimizing both the base and the cavity designs.