The surface structure of GaAs(100) studied by RHEED and REM

Abstract

Three GaAs( 100) samples, each grown on a differently misoriented GaAs( 100) substrate, were prepared using molecular beam epitaxy (MBE) and characterized by in situ reflection high energy electron diffraction (RHEED) and ex situ RHEED and reflection electron microscopy (REM): A: the substrate is 2° off the (100) toward [011] (A misorientation),B: the substrate is 2° off the (100) toward (B misorientation), andC: the substrate is within 0.1° of (100) (Fig. 1).The goals were to compare the effects of MBE growth and oxidation on the different types of steps formed on these surfaces. Understanding the processes involved in promoting ordering of terrace lengths, and reduction of meandering and step bunching is crucial to current attempts to fabricate quantum wire structures.Samples were prepared by chemically etching the substrates and then growing 0.2μm of GaAs at 600°C, at a rate of 0.4μm/h, and using a 3:1 As:Ga flux ratio. Shapes of the in situ RHEED spots were used to measure the step configuration while the oscillation of RHEED intensities was used to determine the thickness of the grown film.