Optical and electrical investigation of ion bombarded GaAs

GaAs surfaces of (100) orientation were bombarded with low-energy Ar⁺ ions at energies to 4 keV. Photoconductivity and Schottky diode studies were then performed. A striking persistent photoconductivity that was observed is attributed to an optically sensitive and temperature-sensitive metastable defect complex formed by the ion-beam etching (IBE). Optical quenching of spectral conductivity, restorable by thermal activation at temperatures above 120 K, is also attributed to this complex. Photovoltaic response of Schottky diodes is essentially destroyed by IBE damage for all ion energies. The IBE-caused damage is also seen in low-frequency capacitance dispersion; none is evident for the virgin (no IBE) case. Two electron traps resulting from IBE, at 0.32-eV and 0.52-eV energies, were detected by deep-level transient spectroscopy. The IBE-caused disappearance of the EL2 trap at 0.76 eV is consistent with the formation of EL2-IBE related complexes at lower energies in the bandgap, which can account for the persistent photoconductivity and low-frequency capacitance dispersion