Maintaining atomically smooth GaAs surfaces after high-temperature processing for precise interdiffusion analysis and materials engineering

Abstract

Arsenic's high vapor pressure leads to thermal instability during high-temperature processing (>370 °C) of GaAs, contributing to the performance degradation of subsequently fabricated devices. The resulting surface damage also obfuscates the exact quantitative characterization of the diffusion process, a critical step in device manufacturing. In this experiment, an encapsulant-and-sacrificial-layer procedure is employed to reduce arsenic sublimation and preserve a smooth surface. A capped GaAs/InGaAs/GaAs quantum well structure is subjected to rapid thermal annealing, and AFM, SEM, and energy-dispersive x-ray spectroscopy are used to compare the surface qualities of the postannealed encapsulated GaAs against the reference GaAs. For the encapsulated substrate, a smooth surface with an average root-mean-squared value of 6.5 Å is achieved after high-temperature processing. SIMS analysis is used to obtain the diffused indium atomic concentration profiles for a smooth and roughened GaAs surface and their corresponding diffusion parameters. The interdiffusion characterization process demonstrates in a GaAs/InGaAs system how precise diffusion parameter extraction requires preserving an atomically smooth surface when using surface-sensitive techniques.