Tunable Band Gaps of In_xGa_{1- x}N Alloys: From Bulk to Two-Dimensional Limit

Using first-principles calculations combined with a semiempirical van der Waals dispersion correction, we have investigated structural parameters, mixing enthalpies, and band gaps of buckled and planar few-layer In_xGa_1-xN alloys. We predict that the band gaps of buckled In_xGa_1-xN alloys with hydrogen passivation can be tuned from 5.6 to 0.7 eV with preservation of direct band gap and well-defined Bloch character, making them promising candidate materials for future light-emitting applications. Unlike that in their bulk counterparts, the phase separation could be suppressed in these two-dimensional systems because of reduced geometrical constraints. 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.