Efficient carrier transport in GRIN-SCH transistor lasers

We report analytical and theoretical results of simulation of a graded-base, single quantum well (SQW) transistor laser (TL). Using an appropriate carrier transport model, device performances for different confinement structures are studies. Physical parameters including the diffusion constant and optical confinement factor are calculated, and the dependence of the optical response on both current level and structure design (e.g. base doping and cavity length) is investigated. Simulation results show that using graded index layers of Al_ξGa_1-ξAs (ξ: 0.1 → 0) in the lefthand side of the QW and Al_ξGa_1-ξAs (ξ: 0.05 → 0) in the righthand side of the QW (instead of GaAs in the base region) increases the optical output power by a factor of 3, eliminates completely the resonance peak, and most interestingly increases optical bandwidth by ~37% compared to the conventional (i.e. non-graded base) structure.