Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 29: III-V Semiconductors I (mainly Nitrides)

HL 29.3: Vortrag

Dienstag, 27. März 2012, 10:00–10:15, EW 201

Surface states and band alignment of polar and nonpolar InN films studied by in-situ photoelectron spectroscopy — •Marcel Himmerlich, Anja Eisenhardt, and Stefan Krischok — Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, PF 100565, 98684 Ilmenau, Germany

The chemical and electronic properties of (0001), (0001), (1100) and (1120) InN surfaces are analysed for stoichiometric and metal-rich growth conditions. Thin InN films were grown by PAMBE on GaN/Al₂O₃(0001), GaN/6H-SiC(0001) and m/a-plane bulk GaN substrates, respectively, and characterised in-situ using XPS and UPS. The energy distance between surface valence band maximum and Fermi level (VBM-E_F) as well as the work function are dependent on crystal orientation. In general, In-rich growth leads to the formation of In adlayers which reduce VBM-E_F and result in the existence of a broad band of electron states inside the band gap. For stoichiometric (0001), (1100) and (1120) InN surfaces, the band bending is strongly reduced compared to the (0001) configuration, pointing to nearly flat band conditions. The InN(0001) surface exhibits an In-induced (2×2) reconstruction and a surface state at the Fermi edge is detected, while for the growth on the other crystallographic orientations, no superstructure was formed and the occupied surface states are located at the valence band edge. The trends of variation of the surface band alignment as well as the observed occupied states agree with results of DFT calculations by D. Segev and C. G. Van de Walle (Europhys. Lett. 76, 305 (2006) & J. Appl. Phys. 101, 081704 (2007)).