The absorption, emission, and gain spectra of In0.72Ga0.28As0.6P0.4(&lgr;g=1.3 &mgr;m), which lattice matches InP, is calculated using a Gaussian fit to Halperin‐Lax band tails and Stern’s matrix element. The calculation is done both forp‐ andn‐type material at various impurity concentrations. The spectral width of emission increases both with increasing doping and impurity concentration. All results are for 297 K. The gain‐versus‐excitation rate is given by the equationg (cm−1)=0.057 (Jnom−2400), whereJnomis the nominal current density in the active layer expressed in A/cm2 &mgr;m. Also, the photon energy at maximum gain increases with increasing excitation rate.