Hydrogen Surfactant Assisted Coherent Growth of GaN on ZnO Substrate

TL;DR

This paper introduces a hydrogen surfactant method to enable high-quality GaN film growth on ZnO substrates, overcoming surface energy barriers and improving device performance.

Contribution

The study proposes and validates a novel hydrogen surfactant strategy, supported by first principles calculations, to facilitate coherent GaN growth on ZnO substrates.

Findings

Hydrogen acts as an effective surfactant in GaN/ZnO heterostructures.

Theoretical predictions of H stability and growth conditions were achieved.

The approach potentially reduces manufacturing costs and enhances device efficiency.

Abstract

Heterostructures of wurtzite based devices have attracted great research interests since the tremendous success of GaN in light emitting diodes (LED) industry. Among the possible heterostructure material candidates, high quality GaN thin films on inexpensive and lattice matched ZnO substrate are both commercially and technologically desirable. However, the energy of ZnO polar surfaces is much lower than that of GaN polar surfaces. Therefore, the intrinsic wetting condition forbids such heterostructures. As a result, poor crystal quality and 3D growth mode were obtained. To dramatically change the growth mode of the heterostructure, we propose to use hydrogen as a surfactant, confirmed by our first principles calculations. Stable H involved surface configurations and interfaces are investigated, with the help of newly developed algorithms. By applying the experimental Gibbs free energy of H$_2$, we also predict the temperature and chemical potential of H, which is critical in experimental realizations of our strategy. This novel approach will for the first time make the growth of high quality GaN thin films on ZnO substrates possible. We believe that our new strategy may reduce the manufactory cost and improve the crystal quality and the efficiency of GaN based devices.