Near-Edge Optical Absorption Behaviour in Weakly Damaged Ion-Implanted GaAs

The long exponential absorption tail near the fundamental absorption edge occuring in weakly damaged ion implanted GaAs is investigated in dependence on the ion species (N+, Ar+, Zn+, and Cd+ ions are used) and on the ion fluence. The results show that characteristic native defects are responsible for the observed absorption behaviour. The near edge absorption coefficient as well as the characteristic tailing energy increase with the energy density deposited in nuclear processes and reach both a maximum value for a critical energy density. From the optical measurements and considering the results of temperature dependent RBS measurements conclusions are made concerning the nature of defects in the weakly damaged GaAs layers.