The Effect of Various Encapsulants on the Electrical Properties of Implanted Layers in GaAs

Abstract

Reactively sputtered silicon nitride, plasma‐enhanced CVD silicon nitride, and silox have been investigated as dielectrics for the encapsulation of for the purpose of post‐implantation anneal. The effect of several treatments on the surface prior to dielectric deposition was analyzed by Auger spectroscopy and ellipsometry to characterize the high temperature annealability of the encapsulated samples. An ammonium hydroxide‐hydrogen peroxide etchant that leaves the surface clean and damage free was found to be the most suitable. After surface treatment and dielectric deposition, Van der Pauw devices were fabricated and carrier mobilities and sheet carrier concentrations for devices annealed at 800°C were compared. In specific cases, the electrical characteristics of devices annealed at higher temperatures (850° and 900°C) were also measured. Differences in the carrier mobilities and sheet carrier concentrations obtained, using the various dielectric films, have been explained in terms of the movement of a surface depletion layer edge closer to or away from the interface.