Inert gas reactive ion etching damage to GaAs using inverted heterojunctions

Abstract

Selectively doped inverted heterojunctions containing a two-dimensional electron gas were used as a sensitive vehicle for monitoring dry processing damage. We found that the electron sheet concentration, strongly dependent on the total number of carriers in the GaAs cap layer, and the mobilities were significantly depressed even for very short exposures to low-voltage helium plasmas. Argon, which caused less degradation than helium, was found to increase the sheet carrier concentration and hence the mobility after prolonged exposure. The damage mechanism responsible for the carrier loss in both cases is most likely the production of traps. The subsequent carrier increase seen for the argon case is probably attributable to the creation of a very thin donorlike damage layer on the surface of the GaAs cap layer.