Ab initio calculations of excitons in AlN and Elliott's model

The optical absorption and excitonic properties of wurtzite AlN are investigated by means of an ab initio approach taking into account electron-hole correlations. This is done by solving the Bethe-Salpeter equation, using the results of density functional theory calculations as a starting point. The main focus is on the calculation of excitonic spectra near the conduction-band edge. The response is dominated by the exciton A formed out of excitations from valence Gamma(7) band. The n(-2) quantum-number dependence of the energies in Elliott's model fits rather well the ab initio calculations whereas the n(-3) decay of the intensities is less obvious for the calculated oscillator strengths.