The interaction between lithium acceptors and gallium donors in zinc oxide

Abstract

Diffusion of lithium (Li) in uniformly gallium (Ga)-doped monocrystalline bulk Zinc Oxide (ZnO) is studied over a wide temperature range (500 − 1150◦C) and is demonstrated to be dictated by the distribution of Ga. Below 800◦C, the indiffusion of Li from a Li-doped ZnO sputtered film into a n + ZnO bulk yields an abrupt and compensated Li-doped box region with the Li concentration matching the free-electron concentration, in accordance with several previous experimental and theoretical reports. However, experimental observations of Li-diffusion at higher temperatures have not previously been reported. In this study we give a detailed description of a dissociative diffusion mechanism for Li up to 1150◦C. By employing a reaction-diffusion model that accounts for the presence of both Li and Ga, a dissociation energy of 4.6 eV with an attempt frequency of 5×1015s −1 is obtained from the experimental Li diffusion data. This is in excellent agreement with theoretical results for the dissociation of (LiZnGaZn) 0 (4.8 eV) into Li+ i and (GaZnVZn) −, and strongly suggest that this neutral and stable acceptor-donor pair prevails in Li- and Ga-doped ZnO.