DFT modeling of wurtzite III-nitride ternary alloys

Abstract This chapter describes DFT band structure calculations that were performed in order to simulate the dielectric response of III-nitride semiconductors. The aim of this study is to improve our understanding of the features in the low-loss electron energy-loss spectra of ternary alloys, but the results are also relevant to optical and UV spectroscopy results. For these DFT calculations, the standard tools found in Wien2k software were used. The novel modified Becke–Johnson (mBJ) exchange-correlation potential was also implemented, in order to improve the band structure description of these semiconductor compounds. The results from these calculations include band structure, density of states, and complex dielectric function for the whole compositional range. When compared with standard generalized gradient approximation (GGA), the predicted band gap energies for the novel potential were found to be larger and closer to experimental values. Additionally, the dependence of the most interesting features with composition was described by applying a Vegard law to band gap and plasmon energies. For this purpose, three wurtzite ternary alloys, from the combination of binaries AlN, GaN, and InN, were simulated through the whole compositional range (i.e., Al x Ga 1 − x N , In x Al 1 − x N , and In x Ga 1 − x N , with x = [ 0 , 1 ] ). Moreover, a detailed analysis of the collective excitation mode in the dielectric response coefficients (CDF and ELF) was performed by model based analysis. This reveals their compositional dependence, which sometimes departs from a linear behavior. Finally, an advantageous method for measuring the plasmon energy dependence from these calculations was also developed.