Spectral Observation of As-Stabilized GaAs Surfaces in Metal-Organic Chemical Vapor Deposition Using Surface Photo-Absorption

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Abstract
The spectral dependencies of As-stabilized (001) GaAs surfaces in metal-organic chemical vapor deposition (MOCVD) are measured using the surface photo-absorption (SPA) method and compared them with those obtained in molecular beam epitaxy (MBE). The SPA spectrum of an As-stabilized surface at 600°C is anisotropic in regards to the perpendicularly intersecting incidence azimuths, [110] and [1̄10], of the monitoring light. It is also very similar at a arsine partial pressure of 4 Pa, which is a common MOCVD growth condition, to the spectrum obtained for an MBE As-surface having a c(4×4) reconstruction pattern in reflection high-energy electron diffraction (RHEED) observation, though not to the spectrum corresponding to a(2×4) pattern. Below 500°C, an isotropic signal appears and overlaps with the anisotropic spectrum of a c(4×4)-like surface, indicating that As species adsorbs excessively on a c(4×4)-like surface, which reduces its anisotropy. It is shown that by using different wavelengths, the dynamics of As desorption from each As-stabilized surface can be measured separately.