Abstract
The optical gain coefficient is calculated as a function of the nominal current density for In0.72Ga0.28As0.6P0.4g=1.3 μm) using a Gaussian fit to the Halperin‐Lax band tails and Stern’s matrix element. The calculation is done for p‐type, n‐type and undoped material at 297 and 350 K respectively. The results show that n‐type layers may give lower threshold currents than do comparable p‐type layers. The gain or loss at the lasing frequency is found to be a nonlinear function of the injected carrier density so that regions of strong carrier depletion may act as saturable absorbers. The results show that the effect of the Fermi factors alone cannot explain the observed temperature dependence of threshold.