ELECTRONIC-STRUCTURE OF GAN MEASURED USING SOFT-X-RAY EMISSION AND ABSORPTION

The electronic structure of thin-film wurtzite GaN has been studied us ing a combination of soft-x-ray absorption and emission spectroscopies . We have measured the elementally and orbitally resolved GaN valence and conduction bands by recording Ga L and N K spectra. We compare the x-ray spectra to the partial density of states from a recent ab initi o calculation and find good overall agreement. The x-ray emission spec tra confirm that the top of the valence band is dominated by N 2p stat es whereas they reveal that there is only weak hybridization between G a 4s and N 2p states. Surprisingly,we found a weak feature in the N K emission at approximately 19.5 eV below the valence-band maximum that arises from hybridization between N 2p and Ga 3d states. X-ray absorpt ion spectra show that the bottom of the conduction band is a mixture o f Ga 4s and N 2p states, again in very good agreement with the theory.