RHEED Intensity Oscillation Studies of the Kinetics of GaAs Deposition During Chemical Beam Epitaxy(CBE)

Abstract

ABSTRACTRecently we have reported the measurement of RHEED intensity oscillations during Chemical Beam Epitaxy(CBE) of GaAs using triethylgallium(TEG) and As2 derived from an arsine cracker(Appl. Phys. Lett. 50(19), May 11,1987). The existence of RHEED intensity oscillations during CBE growth of GaAs indicates that over the range of conditions studied, growth proceeds via nucleation of islands which grow two-dimensionally as opposed to a vicinal step propagation mechanism. In the same study we observed a significant variation of the GaAs growth rate with substrate temperature at constant flux. In addition, the variation of growth rate with incident flux at constant temperature was found to be non-linear below approximately 500°C and linear above 500'C for incident fluxes yielding maximum growth rates between.2 and 1.8 monolayers/sec. Additional measurements of the dependence of the damping of RHEED intensity oscillations on V/11 ratio have indicated much less sensitivity of the growth front morphology to group V flux in CBE. This behavior is thought to reflect the role of highly mobile, partially saturated ethyl-gallium radicals in epitaxial growth by CBE. Measurements of As2 arrival rate limited intensity oscillations on gallium rich surfaces prepared by pyrolyzing TEG in the absence of As2 have shown that the pyrolysis of TEG is not self-limiting at 500°C and that excess gallium can be deposited on gallium rich surfaces. This paper also describes a simple model of the surface pyrolysis of TEG which is consistent with the above experimental observation.