Well width dependence of gain and threshold current in GaAlAs single quantum well lasers

The optical gain of single quantum well GaAs/GaAlAs laser diodes is studied theoretically. The model uses a no k -selection rule and Fermi statistics to obtain the gain coefficient expression. Gain-current characteristics are then reported and allow comparison of structures with well widths between 50 and 400 A. Comparison is also made to previous models which use a strict k -selection rule. Then theoretical threshold current densities are calculated for typical single quantum well lasers where the optical confinement is performed using a five-layer slab waveguide. They are shown to be relatively insensitive to the well width as long as L z is larger than 80 A. Comparison between two different structures shows that optical confinement plays a critical role for optimizing the threshold Current and should be carefully studied, especially if the k -selection rule is relaxed.