Preparation and Stabilization of Anodic Oxides on GaAs

Abstract

Anodic oxidation of is examined and a technique for growing full surface oxides ≈ 8600Å thick is reported. Anodization in a hot, concentrated (30%) electrolyte of using self‐anodizing metal contacts is found to yield uniform oxides with a refractive index of 1.8 and a growth rate ranging from 22 to 50 Å/V. The as‐grown oxide will etch in and . Chemical stability of this oxide is enhanced with baking in dry nitrogen and after 2 hr at 250°C, will no longer etch the oxide; after 1 hr at 600°C, , ,, will not etch the oxide but hot will etch the oxide. The oxide is an amorphous, vitreous film which crystallizes to after several hours at 800°C. A thin (<100Å) graded, interface was found to grow at anodization potentials >100V and for heat‐treatment at temperatures greater than 400°C for 1 hr. The oxide exhibits excellent adherence to the substrate, has good match with the thermal coefficient of expansion of, and forms a relatively strain‐free interface. Since is consumed during anodization, this provides a technique for surface cleaning using an oxide growth‐strip step. Enhanced device reliability is expected to result by utilization of the oxide growth‐strip‐regrowth cycle during device fabrication, since this will remove contamination from the surface. The findings here enumerated, coupled with ease of oxide growth, suggest ready implementation to a planar technology.