Photoluminescence Spectroscopy of many-body Effects in Heavily Doped   Al$_x$Ga$_{1-x}$As
  We present an experimental investigation of heavy doping-induced many-body effects such as band gap narrowing(BGN) and Fermi edge singularity(FES) in Al$_x$Ga$_{1-x}$As using photoluminescence(PL) spectroscopy. The band-to-band transition energy shifts to lower energies and FES-like feature in PL spectra grows with increasing electron concentration. We show that FES-like feature is a nonmonotonic function of temperature and excitation intensity. Our data lead us to suggest that a small concentration of nonequilibrated holes is required to enhance the FES-like feature in the PL spectra. 
Subhasis Ghosh and Niladri Sarkar