Dependence of the photoreflectance of semi-insulating GaAs on temperature and pump chopping frequency

The amplitude of the photoreflectance (PR) spectra of the direct gap of semi-insulating GaAs has been studied as a function of pump chopping frequency (2-4000 Hz) and temperature (25-198°C). We have been able to deduce a temperature-dependent trap time and hence trap activation energy of 0.70±0.05 eV. Our experiment demonstrates that PR can be used as a contactless method to study deep traps in semiconductors, analogous to deep level transient spectroscopy.