Raman scattering from anodic oxide-GaAs interfaces

Abstract
The nature of the interface between anodically grown oxide films and gallium arsenide substrates was studied using Raman backscattering. Room‐temperature spectra of GaAs covered with as‐grown anodic films as well as anodized samples dried under nitrogen at 250°C showed only the first‐order longitudinal (LO) and transverse (TO) optical modes and the less‐intense two‐phonon features of the GaAs substrate. Heating the films at 450°C and above results in the appearance of intense LO (257 cm−1) and TO (198 cm−1) bands due to crystalline arsenic and the structurelessRaman scattering near 200–250 cm−1 due to amorphous arsenic. Polarized Raman spectra indicate that elemental arsenic is not an intrinsic oxidation product of the room‐temperature anodization. We suggest that the thermally induced solid‐state interfacial reaction, As2O3+2GaAs→Ga2O3+4As, is responsible for the presence of arsenic at the oxide‐semiconductor interface following annealing.