Nitridation of GaAs(001) Surface Studied by Auger Electron Spectroscopy

Abstract

Auger electron spectroscopy (AES) has been used to investigate the processes taking place during the initial stages of nitridation of GaAs(001)-2×4 surface by active nitrogen species. The results of analysis of the spectral positions of the Auger electron signals from Ga, As and N, as well as their dependencies on the nitrogen exposure show that the processes taking place during nitridation greatly differ depending on the nitridation temperature. At low temperatures (≤200°C) nitridation is hindered by kinetic restrictions on the atomic migration, leading to the island growth with the formation of the disordered GaAsN phase in the subsurface region. At high temperatures (≥500°C) the process of nitridation takes place simultaneously with the etching of the surface due to decomposition of the substrate, resulting in the rough interface between the GaN and GaAs phases. However, for intermediate nitridation temperatures (300°C–400°C) AES results indicate that one monolayer of N atoms may be formed on the substrate during the initial stage of nitridation. The post-nitridation annealing of the samples nitrided at the intermediate temperatures results in the formation of a crystalline GaN layer, the line shape of the AES signals from which is identical to that for a GaN reference sample.