Relationship between near bandedge absorption and photoluminescence efficiency in semi-insulating GaAs
We demonstrate that near bandedge photoluminescence efficiency in SI bulk GaAs can be increased by low temperature photo-quenching of native point defects in the material. These defects cause infrared absorption at photon energies just below the bandgap energy in cooled samples and their concentrations anti-correlate with those of EL2 in unannealed crystals. This absorption has been previously termed “Reverse Contrast.” The increase in PL efficiency is almost an exponential function of the photoquenching time and proportional to the Reverse Contrast absorption coefficient.