RECOGNITION OF NONRADIATIVE RECOMBINATION CENTERS IN SEMIINSULATING GAAS

A novel technique, double-beam photoluminescence (DBPL), is introduced. This is used to investigate photoquenching effects of deep levels which affect near-band-edge photoluminescence (PL) in bulk-grown semi-insulating (SI) GaAs. We show that there is a remarkable increase in band-to-band radiative transition efficiency after photoquenching of near-band-edge absorption (also known as Reverse Contrast or RC) at low temperatures (less than 35 K) and associate this effect with a reduction in non-radiative recombination centres. We suggest that RC absorption does indeed map concentrations of the dominant recombination centre in SI GaAs and that the observed increase in luminescence after low-temperature illumination with light of near 1-mu-m wavelength is due to photoquenching of the RC defects.