Surface And Bulk Electronic Structures Of Unintentionally And Mg-Doped In0.7ga0.3n Epilayer By Hard X-Ray Photoelectron Spectroscopy

The surface and bulk electronic structures of In0.7Ga0.3N epilayers are investigated by angle-resolved hard X-ray photoelectron spectroscopy (HX-PES) combined with soft X-PES. The unintentionally and Mg-doped In0.7Ga0.3N (u-In0.7Ga0.3N and In0.7Ga0.3N:Mg, respectively) epilayers are grown by radio-frequency plasma-assisted molecular beam epitaxy. Here three samples with different Mg concentrations ([Mg] - 0, 7 x 10(19), and 4 x 10(20) cm(-3)) are chosen for comparison. It is found that a large downward energy band bending exists in all samples due to the formation of a surface electron accumulation (SEA) layer. For u-In0.7Ga0.3N epilayer, band bending as large as 0.8 +/- 0.05 eV occurs from bulk to surface. Judged from the valence band spectral edge and numerical analysis of energy band with a surface quantum well, the valence band maximum (VBM) with respect to Fermi energy (E-F) level in the bulk is determined to be 1.22 +/- 0.05 eV. In contrast, for In0.7Ga0.3N:Mg epilayers, the band bending increases and the VBM only in the bulk tends to shift toward the E-F level owing to the Mg acceptor doping. Hence, the energy band is considered to exhibit a downward bending structure due to the coexistence of the n(+) SEA layer and Mg-doped rho layer formed in the bulk. When [Mg] changes from 7 x 10(19) to 4 x 10(20) cm(-3), the peak split occurs in HX-PES spectra under the bulk sensitive condition. This result indicates that the energy band forms an anomalous downward bending structure with a singular point due to the generation of a thin depleted region at the n(+) p interface. For In0.7Ga0.3N:Mg epilayers, the VBM in the bulk is assumed to be slightly lower than E-F level within 0.1 eV. Published by AIP Publishing.