Laser ionization mass spectrometry measurements of arsenic sticking and incorporation during GaAs(1 0 0) homoepitaxy

Abstract

Abstract The fluxes of Ga, As4 and As2 desorbed or scattered from a GaAs(1 0 0) surface are monitored with laser single-photon ionization time-of-flight mass spectrometry (SPI-TOFMS) during homoepitaxy of GaAs(1 0 0) with incident As4 and Ga molecular beams. When the Ga flux is opened to the surface under a constant incident arsenic flux, the observed decrease in the scattered As4 and As2 mass signals are a measure of the arsenic incorporation into the growing GaAs layers. Simultaneous reflection high-energy electron diffraction (RHEED) oscillations measured during epitaxy are used to quantify the arsenic and gallium fluxes. The sticking probability for As4 molecules on the GaAs surface is measured over a range of As4 and Ga incident fluxes and for the substrate temperature range 600–900 K. At substrate temperatures and under flux conditions in which RHEED specular beam intensity oscillations are observed during epitaxy, the maximum sticking probability for As4 exceeds the often-quoted value of 0.5, with values observed greater than 0.8. At higher substrate temperatures and under flux conditions in which Ga islands are present on the GaAs surface, the maximum sticking probability of As4 is 0.5. The sticking probability of As4 on the GaAs surface decreases with increasing surface temperature.