Experimental study of passivating ion-beam-induced distributed energy levels in n-GaAs by hydrogen species from boiling water

Moderately doped n-GaAs substrates were etched by a 250 eV Ar+-ion beam and subsequently immersed up to 80 min in boiling distilled water, to remove the radiation damage. Comparative studies of the remaining damage to the GaAs surface region, benefiting from both alternating current (capacitance DLTS, high-frequency C-V) and time-domain (charge DLTS, feedback-charge C-V) techniques, were conducted. Prior to the passivation in water, there was a spectrum of deep levels distributed in energy, responsible for a large capacitance dispersion in AlGaAs Schottky junctions at ambient temperatures. Apart from significant differences between the responses to pulsed excitation in the frequency and time domains, the damage due to the ion beam is effectively reduced by hydrogenation. In contrast to the case of a discrete energy level, efficiency of passivating distributed levels is difficult to assess as a scalar quantity. Long-term stability of the deep-level neutralization over a period of 16 months has been confirmed.