Observation of RHEED intensity variations during ALE-Growth of CdTe-Epilayers

Abstract

We present the first reflected-high-energy electron diffraction (RHEED) observations during atomic layer epitaxy (ALE) growth of CdTe on GaAs substrates. The evolution of the RHEED pattern in the initial growth stages shows that, regardless of the large lattice mismatch, growth becomes two-dimensional after the deposition of a few monolayers. We have observed intensity variations of two RHEED spots under surface resonance conditions which make the spots sensitive to either Cd- or Te-deposition. We show that this new approach is superior to the observation of the specular spot for the measurement of surface coverages and adsorption kinetics. The Cd- and Tespots have been monitored during CdTe-ALE. The observed intensity variations can be explained by simple adsorption models. From the change in the spot intensities with substrate temperature during a permanent Cd- or Teexposure of the sample we deduce a drop in the Cd- and Te-surface coverage from 1 to 0.5 at substrate temperatures higher than 315 °C.