Wavelength-Tunable Ultraviolet Electroluminescence from Ga-Doped ZnO Microwires.

The usage of ZnO as active layers to fabricate hybrid heterojunction light-emitting diodes is expected to be an effective approach for ultraviolet light sources. Individual ZnO microwires with controlled gallium (Ga) incorporation (ZnO/Ga MWs) have been fabricated via a chemical vapor deposition method. It is found that with the increasing Ga-incorporated concentration, the near-band-edge (NBE) photoluminescence of the ZnO MWs blue-shifted gradually from 390 to 370 nm. Heterojunction diodes comprising single ZnO/Ga MWs and p-GaN have been fabricated. With increasing injection currents, the interfacial emissions can be suppressed effectively and the typical NBE emission dominates the electroluminescence (EL). In particular, with increasing Ga-doping concentration, the dominant EL emission wavelengths of the ZnO/Ga MW-based heterojunction diodes blue-shifted from 384 to 372 nm, and the blue shift can be ascribed to the Burstein-Moss effect induced by the Ga incorporation. The present work demonstrates the feasibility of optical band gap engineering of ZnO MWs and the potential application for wavelength-tuning ultraviolet light sources.