Reaction mechanisms of tertiarybutylarsine on GaAs (001) surfaces and its relevance to atomic layer epitaxy and chemical beam epitaxy

Abstract

We explore the use of tertiarybutylarsine (TBAs) as an alternative arsine source in atomic layer epitaxy (ALE) of GaAs. X-ray photoelectron spectroscopy (XPS), reflection high energy electron diffraction (RHEED), and reflectance difference spectroscopy (RDS) are used to characterize the surface reactions of TBAs on GaAs (001) Ga-rich surfaces. At a substrate temperature of 320° C and an exposure level of 90 L of TBAs, AsH_x (x = 1 or 2) is thought to be the adsorbed arsenic species. As the substrate temperature increases, As-rich surfaces are readily obtained with improved RHEED 2 x 4 patterns. No carbon related species are observed throughout the TBAs exposure experiments between 320° C and 540° C. It is suggested that AsH_x is the adsorbed species after TBAs decomposes on surface Ga atom. Interactions between AsH_x pairs form arsenic atoms by H₂ release. RDS allows anin-situ real time study of TBAs on GaAs (001) Ga-rich surfaces. It is found that the RDS results are consistent with those obtained from XPS and RHEED investigations and can provide information on the rates of reactions and the extent of surface reconstruction simultaneously. Implications for the growth of GaAs by atomic layer epitaxy and chemical beam epitaxy using TBAs are discussed.