Luminescence properties of heavily carbon doped GaAs

Carbon-doped GaAs epilayers with concentrations as high as 1.8X10(20) cm(-3) were studied by photoluminescence (PL) spectroscopy. A shoulder is observed at 1.495 eV in 17 K PL spectrum of the heavily C-doped sample grown on semi-insulating substrate. But the shoulder occurs at different energies when the substrate conductivity is changed. The shoulder is found to originate from the substrate luminescence. Identifying the origin of the shoulder, the true Fermi level of p(+)-GaAs is determined and the band gap narrowing due to heavy doping is quantified. (C) 1996 American Institute of Physics.