Annealing behavior of deep-level defects in semi-insulating gallium arsenide studied by photoluminescence, infrared absorption, and resistivity mapping

Abstract

Deep-level defects in as-grown, ingot-annealed, and wafer-annealed samples of semi-insulating gallium arsenide have been investigated by spatially resolved measurements of room-temperature photoluminescence, infrared absorption, free-carrier lifetime, and resistivity. High-temperature ingot annealing mainly causes a homogenization of the EL2 distribution. Rapid cooling from a wafer annealing process at T>900 °C suppresses the formation of the previously lifetime-limiting recombination center. After wafer annealing the EL2 defect may be the dominant recombination center, while in as-grown and ingot-annealed material lifetime is limited by a different trap. There is experimental evidence that this trap is related to the 0.8-eV luminescence band and that its density is spatially anticorrelated to the EL2 distribution. Based on lifetime measurements and a correlation of EL2 and photoluminescence topographs, we developed a recombination model, which explains the relationship between defect densities, and photoluminescence. The effect of surface recombination is described by a numerical calculation.