In situ optical characterization of GaAs and InP surfaces during chloride atomic layer epitaxy

Abstract

In this paper, the results of in situ surface photo-absorption (SPA) measurements on GaAs and InP surfaces under an alternating supply of GaCl and AsH 3 or InCl and tertialybutylphosphine (TBP) in chloride atomic layer epitaxy (ALE) are presented. It was found that the reflection intensity varied by several per cent, depending on the source gas supply sequence. This reflection intensity was constant during the GaCl and InCl supply from both the GaAs and InP surfaces, probably corresponding to the self-limiting mechanism of chloride ALE. Reflection spectra from a GaAs surface during and after GaCl supply were found to be similar. They showed anisotropic spectral structures according to the incidence azimuth of light. This anisotropy is considered to originate from the existence of surface dimers. Thus, a GaAs surface under GaCl supply is assumed to be covered by Ga. In contrast, the spectra from an InP surface during InCl supply were isotropic and different from the anisotropic spectra measured from an In-stabilized surface formed by P desorption. Accordingly, it is assumed the Cl adsorbs on an InP surface during InCl supply and prevents the formation of dimers. The different behavior of Cl on GaAs and InP may be due to a different reaction rate with H 2.