ANODIC-OXIDATION OF ALGAAS AND DETECTION OF THE ALGAAS-GAAS HETEROJUNCTION INTERFACE

This paper presents the results of a study of the anodic oxidation of n-type AlGaAs and AlGaAs/GaAs heterojunctions in acid-glycol-water electrolytes. Anodic oxides with thickness up to 300 nm may easily be grown under constant-current conditions if external illumination is used. Real-time derivative spectra of the anodic voltage-time data show structure that is dependent upon the thickness of the AlGaAs epitaxial layer, its doping density, and possibly band-gap energy differences. The derivative results clearly show that epitaxial layer thickness and thickness variations are readily measured. The oxide growth constant and material consumption rate are found to be 1.52 and 1.08 nm/V, respectively. Optical dispersion in the wavelength range from the near UV to the IR range is also measured and fitted to Sellmeier's equation. Composition of the AlGaAs is measured using Rutherford backscattering, which reveals an As-rich oxide.