Molecular beam epitaxy of GaAs using a mass-separated, low-energy As+ ion beam

Abstract

A new film growth technique of III-V compound semiconductors is under development where the sticking coefficient of group-V element can be increased to unity. In this technique, a group-III element is supplied to the substrate as a molecular beam, while a group-V element is supplied as a mass-separated, high-purity ion beam and implanted at low energy of about 100 eV. With this growth technique, epitaxial growth of GaAs on GaAs(100) is studied. Nondoped GaAs films are grown at the As+ ion energy of 100 and 200 eV. Single-crystal films with flat and smooth surface and free from oval defects are obtained at 220 °C or higher with the flux intensities of a Ga molecular beam and As+ ion beam at 2.0×1013 cm2 s and 2.0–4.4×1013 cm2 s, respectively. However, under Ga-rich conditions Ga droplets are observed on the grown films. The RHEED pattern shows c(2×8) structure in the former case. Photoluminescence spectra at 4 K of the films grown at 450 °C or higher show well-defined features due to bound exciton and donor-acceptor pairs at the As+ ion energy of 100 eV.