Dynamic behavior of hot-electron-hole plasma in highly excited GaN epilayers

The room-temperature spontaneous luminescence of electron-hole plasma was investigated in GaN epilayers under extremely high quasi-steady-state photoexcitation. The photoluminescence spectra were measured for excitation power densities up to 200 MW/cm(2) both under quasiresonant and off-resonant excitation conditions. High carrier temperatures up to 1000 K were observed under off-resonant excitation. A nonmonotonous dependence of the luminescence band peak position E-p on the excitation power density was observed. We attribute this nonmonotonous behavior of E-p to two competing mechanisms: (i) band-gap shrinkage due to carrier screening effects (redshift); and (ii) nonequilibrium carrier heating (blueshift). The obtained results are in a good agreement with finite-temperature theory of the band-gap renormalization. (C) 2000 American Institute of Physics. [S0003-6951(00)02017-9].