Anisotropic-strain-enhanced hole mobility in GaN by lattice matching to ZnGeN$_2$ and MgSiN$_2$

TL;DR

This study demonstrates that lattice matching of GaN to specific II-IV nitride materials under anisotropic strain can significantly enhance its hole mobility, with potential implications for GaN electronic devices.

Contribution

It introduces a novel approach of using lattice matching to ZnGeN$_2$ and MgSiN$_2$ to improve GaN hole mobility through strain engineering, supported by ab initio calculations.

Findings

Hole mobility increases by 50% with ZnGeN$_2$ matching.

Hole mobility increases by 260% with MgSiN$_2$ matching.

Lattice matching to a hypothetical solid solution could boost mobility by 160%.

Abstract

The key obstacle toward realizing integrated gallium nitride (GaN) electronics is its low hole mobility. Here, we explore the possibility of improving the hole mobility of GaN via epitaxial matching to II-IV nitride materials that have recently become available, namely ZnGeN$_2$ and MgSiN$_2$. We perform state-of-the-art calculations of the hole mobility of GaN using the ab initio Boltzmann transport equation. We show that effective uniaxial compressive strain of GaN along the $[1\bar{1}00]$ by lattice matching to ZnGeN$_2$ and MgSiN$_2$ results in the inversion of the heavy hole band and split-off hole band, thereby lowering the effective hole mass in the compression direction. We find that lattice matching to ZnGeN$_2$ and MgSiN$_2$ induces an increase of the room-temperature hole mobility by 50% and 260% as compared to unstrained GaN, respectively. Examining the trends as a function of strain, we find that the variation in mobility is highly nonlinear; lattice matching to a hypothetical solid solution of Zn$_{0.75}$Ge$_{0.75}$Mg$_{0.25}$Si$_{0.25}$N$_2$ would already increase the hole mobility by 160%.