Many-body Coulomb effects on the gain and absorption line shapes of the electron-hole plasma in GaAs

Many-body effects due to electron-hole (e-h) attraction and self-energy corrections are investigated on gain and absorption line shapes of degenerate e-h plasma in direct-gap semiconductors. It is demonstrated for GaAs that a large enhancement in experimental gain and absorption coefficients near crossover, which is not reproduced in single-particle treatments, is accounted for by the excitonic e-h interaction. The self-energy corrections, containing the renormalization due to e-e and e-phonon interactions, reduce the direct band gap in GaAs. The fact that the absorption and gain line shapes are sensitive to the plasma density (n) and temperature (T) in a wide energy range shows that they can be used for determining n and T more accurately than can luminescence studies.