Tunable Band Gaps of In$_x$Ga$_{1-x}$N Alloys: From Bulk to Two-Dimensional Limit

TL;DR

This study uses first-principles calculations to explore how the band gaps of In$_x$Ga$_{1-x}$N alloys can be tuned from 6 eV to 1 eV in two-dimensional forms, highlighting stability and electronic properties relevant for optoelectronic applications.

Contribution

It demonstrates that hydrogen passivation stabilizes buckled In$_x$Ga$_{1-x}$N alloys and enables band gap tuning in 2D layers, with suppressed phase separation and preserved electronic properties.

Findings

Band gaps can be tuned from 6 eV to 1 eV in 2D alloys.

Hydrogen passivation stabilizes buckled phases.

Phase separation is suppressed in 2D systems.

Abstract

Using first-principles calculations combined with a semi-empirical van der Waals dispersion correction, we have investigated structural parameters, mixing enthalpies, and band gaps of buckled and planar few-layer In$_x$Ga$_{1-x}$N alloys. We predict that the free-standing buckled phases are less stable than the planar ones. However, with hydrogen passivation, the buckled In$_x$Ga$_{1-x}$N alloys become more favorable. Their band gaps can be tuned from 6 eV to 1 eV with preservation of direct band gap and well-defined Bloch character, making them promising candidate materials for future light-emitting applications. Unlike their bulk counterparts, the phase separation could be suppressed in these two-dimensional systems due to reduced geometrical constraints. In contrast, the disordered planar thin films undergo severe lattice distortion, nearly losing the Bloch character for valence bands; whereas the ordered planar ones maintain the Bloch character yet with the highest mixing enthalpies.