Plasma-Grown Oxide on GaAs Semiquantitative Chemical Depth Profiles Obtained Using Auger Spectroscopy and Neutron Activation Analysis

Plasma oxidation of GaAs is a low temperature oxide growth technique with possible electronics device applications. Chemical depth profiles through 600-3000å thick plasma-grown oxides were obtained using Auger spectroscopy combined with ion milling and were calibrated using neutron activation analysis. The “bulk” compositions of these oxides were uniform with depth and equivalent to those of mixtures of Ga2O3 and As2O3. Approximately the first 200å of the oxide surfaces were always As-rich, but each oxide as a whole was As deficient and the Ga/As concentration ratio increased with oxide thickness from l.l8 at 600å to 1.45 at 2780å. The mechanism of As loss is the faster out-diffusion of As compared to Ga during oxidation and volatilization of surface As-containing species. A sheet of elemental As, amounting to about 1015 atoms/cm2/1000å of oxide growth, was found at the oxide-GaAs interface. The interface widths were <30 and <70å at oxide thicknesses of 600 and 2780å respectively.