Polarity control of GaN epitaxial films grown on LiGaO2(001) substrates and its mechanism

Abstract

The polarity of GaN epitaxial films grown on LiGaO₂(001) substrates by pulsed laser deposition has been well controlled. It is experimentally proved that the GaN epitaxial films grown on nitrided LiGaO₂(001) substrates reveal Ga-polarity, while the GaN epitaxial films grown on non-nitrided LiGaO₂(001) substrates show N-polarity. The growth mechanisms for these two cases are systematically studied by first-principles calculations based on density functional theory. Theoretical calculation presents that the adsorption of a Ga atom preferentially occurs at the center of three N atoms stacked on the nitrided LiGaO₂(001) substrates, which leads to the formation of Ga-polarity GaN. Whereas the adsorption of a Ga atom preferentially deposits at the top of a N atom stacked on the non-nitrided LiGaO₂(001) substrates, which results in the formation of N-polarity GaN. This work of controlling the polarity of GaN epitaxial films is of paramount importance for the fabrication of group-III nitride devices for various applications.