Growth of Epitaxial ZnSn_xGe_(1−x)N_2 Alloys by MBE

Abstract

ZnSn_xGe_(1−x)N_2 alloys are chemically miscible semiconductor compounds with potential application as earth-abundant alternatives to In_xGa_(1−x)N. Preparation of ZnSn_xGe_(1−x)N_2 thin-films by reactive RF sputter deposition yield low-mobility, nanocrystalline films. In contrast, the growth of ZnSn_xGe_(1−x)N_2 films by molecular-beam epitaxy (MBE) on c-plane sapphire and GaN templates is described herein. Epitaxial films exhibited 3D growth on sapphire and 2D single-crystal quality on GaN, exhibiting substantial improvements in epitaxy and crystallinity relative to nanocrystalline sputtered films. Films on sapphire were n-type with electronic mobilities as high as 18 cm^2 V^(−1) s^(−1), an order of magnitude greater than the 2 cm^2 V^(−1) s^(−1) average mobility observed in this work for sputtered films. Mobility differences potentially arise from strain or surface effects originating from growth techniques, or from differences in film thicknesses. In general, MBE growth has provided desired improvements in electronic mobility, epitaxy, and crystal quality that provide encouragement for the continued study of ZnSn_xGe_(1−x)N_2 alloys.