Production of native donors in ZnO by annealing at high temperature in Zn vapor

• DOI: 10.1063/1.2117630
• Publication Date: 2005-10-20T22:00:51Z
• Authors: L. E. Halliburton; N. C. Giles; N. Y. Garces; Ming Luo; Chunchuan Xu; Lihai Bai; L. A. Boatner
• Keywords: Photoconductivity; Shallow donor; Absorption edge

Zinc oxide crystals grown by the seeded chemical vapor transport method have been annealed in zinc at 1100 °C for 30 min. These thermochemical reduction treatments produce a deep red coloration and increase their n-type electrical conductivity. Electron paramagnetic resonance (EPR), optical absorption, Hall measurements were used to monitor changes crystals. After an anneal, intense absorption band is present that extends from edge out approximately 550 nm, EPR signal near g=1.96 (due shallow donors and/or conduction-band electrons), free-carrier electron concentration are all larger. Hydrogen was not during these anneals, thus leaving oxygen vacancies interstitials as candidates added donors. Neutral produced high temperature additive-coloration mechanism, responsible broad near-edge band. The observed number of free carriers result either (1) formation or (2) having ground state neutral vacancy conduction