Gain and current-density calculation in IV–VI quantum well lasers

In this work, a theoretical model is used to study the gain versus current-density relationship for IV–VI semiconductor quantum well lasers. The model, based on Kane’s two band theory, solves for the anisotropy in the constant energy surfaces and for the strong nonparabolicity of the bands. The system investigated is the EuSe–PbSe0.78Te0.22 quantum well structure at 77 K. The effects of nonparabolicity on the gain versus current-density relation are a reduction in the current density needed for any given gain and an increase in the gain saturation level. The nonparabolicity of the bands in the growth direction lowers the values of the confinement factor relative to parabolic bands which in turn lowers the modal gain values. Finally, the effects of nonparabolicity on the threshold current are significant for short cavity lasers and decrease with an increase in the cavity length.