Optical gain in GaAs

Utilizing optical pumping techniques with the active medium excited in a stripe geometry, the amplified spontaneous emission and absorption spectra are measured monolithically at 77 K. Gain and absorption spectra are deduced from these results. It has been found that the band to band transitions (intrinsic band plus impurity band) dominate the emission and absorption spectra in heavily doped GaAs. The electronic band model described by Halperin-Lax-Hwang provides an appropriate picture for heavily doped GaAs. Also, the energy gap is shrunk by both the impurity ion cores and exchange interaction among the populated carriers.