Gain spectra of quaternary semiconductors

A simple analytical model is applied to predict gain spectra of InGaAsP quaternary alloys. Band-to-band recombination between parabolic bands with no K-selection is assumed, with contributions from both heavy and light hole bands taken into account. An effective bandgap energy varying with the carrier concentration accounts for the bandgap shrinkage effect. The gain function is calculated analytically in terms of carrier concentration via the approximations of Marinelli, Unger, and Joyce and Dixon. Comparison of calculated results with available data shows good agreement between theory and experiment. The dependence of gain spectra on carrier concentration, doping and alloy composition is discussed.