Time-resolved studies of biexcitons in GaAs

Abstract

Using time-window photoluminescence spectroscopy we have unambigously observed a transition corresponding to biexcitons in GaAs. The biexciton luminescence line was found to have a superlinear dependence of luminescence intensity vs. excitation density as well as a shorter lifetime than the polariton. The time-window spectra show the shift of the polariton and biexciton line peaks to lower and higher energy respectively, as the distributions cool with increasing time delay after the laser excitation pulses. This shift to higher energy upon cooling is characteristic of biexciton luminescence in direct gap semiconductors.