Band-gap renormalization and band filling in Si-doped GaN films studied byphotoluminescence spectroscopy

We have studied band-gap renormalization and band filling in Si-doped GaN f ilms with free-electron concentrations up to 1.7 x 10(19) cm(-3), using tem perature-dependent photoluminescence (PL) spectroscopy. The low-temperature (2 K) PL spectra showed a line-shape characteristic for momentum nonconser ving band-to-band recombination. The energy downshift of the low-energy edg e of the PL line with increasing electron concentration n, which is attribu ted to band-gap renormalization (BGR) effects, could be fitted by a n(1/3) power law with a BGR coefficient of -4.7 x 10(-8) eV cm. The peak energy of the room-temperature band-to-band photoluminescence spectrum was found to decrease as the carrier concentration increases up to about 7 x 10(18) cm(- 3), followed by a high-energy shift upon further increasing carrier concent ration, due to the interplay between the BGR effects and band filling. The room-temperature PL linewidth showed a monotonic increase with carrier conc entration, which could be described by a n(2/3) power-law dependence. (C) 1 999 American Institute of Physics. [S0021-8979(99)07819-6].