Fast-response photoconductive ultraviolet light detectors fabricated using high-quality ZnO films obtained by plasma-assisted molecular beam epitaxy

ZnO films form the core of numerous ultraviolet (UV) optoelectronic devices. Herein, a ZnO buffer layer produced by thermal plasma oxidation of metallic Zn was used to grow an active ZnO layer, with Zn film and active layer growth achieved by plasma-assisted molecular beam epitaxy. Although low-temperature ZnO buffer layer and Zn film growth was mainly three-dimensional (3D) due to a large lattice mismatch between ZnO/Zn and Si, the use of thermal plasma oxidation changed the growth mode from 3D to 2D, producing a smooth ZnO active layer. The thus fabricated ZnO active layer (sample 2) exhibited a lower tensile stress than that fabricated on a ZnO buffer layer using a conventional method (sample 1). Both samples were used to fabricate UV sensors, with that based on sample 2 exhibiting a faster photoresponse.