Carrier localization and the origin of luminescence in cubic InGaN alloys

The electronic structure and optical properties of cubic (nonpiezoelectric) InGaN are investigated using large scale atomistic empirical pseudopotential calculations. We find that (i) strong hole localization exists even in the homogeneous random alloy, with a preferential localization along the [1,1,0] In–N–In–N–In chains, (ii) even modest sized $\text{(<50\hspace{0.05em}Å)}$ indium rich quantum dots provide substantial quantum confinement and readily reduce emission energies relative to the random alloy by 200–300 meV, depending on size and composition, consistent with current photoluminescence, microscopy, and Raman data. The dual effects of alloy hole localization and localization of electrons and hole at intrinsic quantum dots are responsible for the emission characteristics of current grown cubic InGaN alloys.