Ag and N acceptors in ZnO: ab initio study of acceptor pairing, doping efficiency, and the role of hydrogen

TL;DR

This study uses ab initio calculations to analyze how Ag and N acceptors behave in ZnO, revealing pairing tendencies, effects on doping efficiency, and hydrogen's role in complex formation.

Contribution

It provides new insights into acceptor pairing mechanisms, the impact on doping efficiency, and hydrogen's influence on acceptor complexes in ZnO.

Findings

Ag-N pairs and N-Ag-N triangles tend to form in ZnO.

Acceptor pairing raises impurity energy levels, reducing doping efficiency.

Hydrogen promotes acceptor complex formation, lowering acceptor levels.

Abstract

Efficiency of ZnO doping with Ag and N shallow acceptors, which substitute respectively cations and anions, was investigated. First principles calculations indicate a strong tendency towards formation of nearest neighbor Ag-N pairs and N-Ag-N triangles. Binding of acceptors stems from the formation of quasi-molecular bonds between dopants, and has a universal character in semiconductors. The pairing increases energy levels of impurities, and thus lowers doping efficiency. In the presence of donors, pairing is weaker or even forbidden. However, hydrogen has a tendency to form clusters with Ag and N, which favors the Ag-N aggregation and lowers the acceptor levels of such complexes.