ABSTRACT
Abstract. We present the results of first-principles pseudopotential calculations for the defect properties of group-I elements such as Li and Na in ZnO. Although substitutional dopants behave as a shallow acceptor, these acceptors are known to be mostly compensated by coexisting interstitials. We find that an intentional codoping with hydrogen suppresses the concentration of interstitial donors, and greatly enhances the solubility of group-I dopants through the formation of hydrogenacceptor complexes. We propose that hydrogen passivated acceptors are electrically reactivated by post-annealing, leading to p-type ZnO. 1
1. Introduction Recently, zinc oxide (ZnO) has attracted much attention because of its wide applications for various optoelectronic devices [1,2]. For practical applications for optoelectronic devices based on p-n junctions, both n-and p-type ZnO are needed. However, it is difficult to obtain low resistivity p-type ZnO, while undoped ZnO exhibits intrinsic ntype conductivity with electron concentrations as high as 1021cm‘3. Among group-V elements, N is considered to be a good p-type dopant [3,4]. Recent experiments also demonstrated that ZnO can be p-type with P and As dopants [5,6]. On the other hand, although substitutional group-I elements behave as an acceptor, these dopants tend to occupy the interstitial region, resulting in self-compensation [7,8].
