An X‐Ray Photoelectron Spectroscopy Study of Native Oxides on GaAs

Abstract

The identification and distribution of chemical species comprising the native oxides of anodically and thermally grown films have been studied using XPS in conjunction with ion milling and chemical etching. Low angle electron diffraction was used to identity crystalline surface (∼150Å) layers of produced thermally from mixtures at elevated temperatures. At lower growth temperatures an amorphous modification of this product is indicated. The primary bulk constituents of all films, both anodically and chemically grown, were found to be and. In anodic films the molar ratio of was approximately unity and uniform from the surface to the interface. The anodic interface width was found to be relatively sharp (100–120Å). Water rinsing of anodic films dissolves the from the near surface (∼200Å) volume. Annealing of 2000Å anodic films at for periods from 1 to 16 hr generated a pentavalent arsenic component which was limited to the surface. A general feature of the thermal oxides was the loss of from the bulk film. In air‐grown samples (530°C, 4 hr) this loss was nearly complete and the native oxide was primarily with some addition of nonuniformly distributed elemental arsenic and unoxidized . The use of mixtures failed to produce bulk oxides with a high, uniform concentration of. Studies comparing ion milling and chemical etching demonstrated the existence of artifacts associated with argon beam reduction of in anodic films even though virtually no reduction of crystalline or vitreous control samples was observed.