MBE Regrowth of AlGaAs on Ion Etched GaAs/AlGaAs Microstructures

Abstract

ABSTRACTThe combination of an ion beam assisted etching (IBAE) system and a Molecular Beam Epitaxy (MBE) growth chamber integrally connected in the same set of ultrahigh vacuum (UHV) chambers has allowed us to etch patterns defined by a strontium fluoride mask down into the underlying semiconductor wafer, and regrow monocrystalline material around these patterned structures entirely in situ. Scanning electron microscopy (SEM) analysis of the regrown structures reveals very directional deposition of the overgrown material. Cross-sectional transmission electron microscopy (TEM) reveals a smooth interface and vertical sidewalls at the boundary between the etched surfaces and the overgrowth. Material deposited on the sidewalls is shown to be monocrystalline, while that deposited over the mask is polycrystalline. The SrF2 mask material, previously shown to be an excellent IBAE mask for extremely fine nanostructures, is also shown to be compatible with the high temperatures need for overgrowth, and regrowth around structures as small as ˜200 nm in size has been demonstrated.