LOCAL ELECTRONIC STRUCTURE OF N ATOMS IN Ga(In)AsN BY SOFT-X-RAY ABSORPTION AND EMISSION: OPTICAL EFFICIENCY

The local electronic structure of N atoms in Ga(In)AsN diluted alloys (N concentration of 3%) is determined by soft-X-ray emission and absorption spectroscopies as element specific probes. The experimental spectra reflect the local 2p orbital-projected density-of-states of N impurities, the main recombination centers in Ga(In)AsN, which appears to deviate dramatically from crystalline GaN in both valence and conduction bands. In particular, we observe a N local charge transfer from the valence band maximum to deeper valence states, which fundamentally limits the optical efficiency of Ga(In)AsN, unless different N local environments are formed. The incorporation of In in large concentrations forms In-rich N local environments such as In4N, which become the main recombination centers in Ga(In)AsN due to a local decrease of the band gap. A k-conserving process of resonant inelastic X-ray scattering is discovered, which allows probing of the k-character of valence and conduction states despite the random alloy nature of Ga(In)AsN.