TIME-RESOLVED PHOTOLUMINESCENCE STUDIES OF BIEXCITONS IN INP

The low-temperature (5 K), steady-state photoluminescence spectra of a high-quality InP sample grown by chemical-beam epitaxy, reveal a new emission band at high excitation intensities. This emission is characterized by a superlinear intensity dependence on excitation density, a lifetime shorter than that of the polariton, and an energy between those of the donor-bound exciton and the free-exciton-polariton emissions. This suggests that it is due to the biexciton recombination transition. The origin of this new emission line is confirmed by the study of time-dependent photoluminescence spectra under high excitation intensity. The time-resolved spectra show the shift of the polariton and biexciton peaks to lower and higher energy, respectively, with increasing time delay after the laser excitation pulses. The high-energy shift of this new peak is characteristic of biexciton luminescence in direct-gap semiconductors.