Anisotropic-strain-enhanced hole mobility in GaN by lattice matching to ZnGeN2 and MgSiN2

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, ZnGeN2 and MgSiN2. 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 [11¯00] by lattice matching to ZnGeN2 and MgSiN2 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 ZnGeN2 and MgSiN2 induces an increase in 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 Zn0.75Ge0.75Mg0.25Si0.25N2 would already increase the hole mobility by 160%.