Electrochemical and Hydrothermal Synthesis of Epitaxial Arrays of Doped ZnO Nanowire Emitters for Light Emitting Diodes With Tunable Emission From Near-UV to Blue

Abstract

The bandgap control of doped-ZnO nanowires is important for tunable light emitting diodes (LEDs). Ultraviolet (UV), violet, blue and near-white LED structures based on Cu- or Ag-doped ZnO /p-GaN and Cd-alloyed ZnO (Zn1-xCdxO) nanorods or nanowires (NWs)/p-GaN heterojunction have been fabricated by epitaxial electrodeposition and hydrothermal growth at low temperatures. A single UV electroluminescence (EL) peak centered at around 397 nm was observed at room temperature for pure ZnO nanowires/p-GaN. The emission was shifted to 405-450 nm by using heterojunction between Cu or Ag-doped ZnO and Zn1-xCdxO-nanorods grown on p-GaN substrate. Moreover, the shift could be tuned by changing the dopant concentration. The electroluminescence emission threshold voltage was low at about 5.0 V and EL intensity increased with the applied forward voltage bias. In the case of Cu-doped ZnO prepared by hydrothermal growth, a near-white electroluminescence was achieved. The presented experimental results demonstrate the tunable emission from transition metal-doping in ZnO-based nanoLEDs.