AVS 52nd International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP22
Measurement of Surface States Above the Valence Band Maximum in n-type GaN(0001) Using Angle-Resolved Photoemission Spectroscopy

Tuesday, November 1, 2005, 4:00 pm, Room Exhibit Hall C&D

Session: Surface Science Poster Session
Presenter: L. Plucinski, Boston University
Authors: L. Plucinski, Boston University
L. Colakerol, Boston University
S. Bernardis, Boston University
Y. Zhang, Boston University
K.E. Smith, Boston University
I. Friel, Boston University
T.D. Moustakas, Boston University
Correspondent: Click to Email
We have performed a high resolution angle-resolved photoemission study of N-polar GaN(000-1).@footnote 1@ We have observed sharp dispersive surface states extending approximately 2 eV above the valence band maximum (VBM). These states agree with those predicted for a N-polar Ga-adlayer GaN(000-1) 1x1 reconstructed surface. Samples were grown by plasma-assisted molecular beam epitaxy on c-plane sapphire. They were doped with Si and the free-carrier concentration was 3 x 10@super 18@ cm @super -3@ which resulted in a slightly degenerate n-type material at room temperature. Experiments were performed at the U5UA undulator beamline at the NSLS, using a Scienta SES100 electron energy analyzer. Clean surfaces were prepared in situ by sputtering with nitrogen ions and annealing in UHV. Samples were held at 120 K when recording spectra. We have found a full width at half maximum for the surface state feature of 400 meV at K-point of surface Brillouin zone. The width is limited by surface imperfections and the existence of reconstructions on the surface other than a simple 1x1. Our results are similar to those obtained for p-type GaN.@footnote 2@ However, in case of p-type GaN the surface likely contained 30 degree rotated domains.@footnote 3@ We show that in the case of n-type GaN the surface is free of domains. @FootnoteText@ @footnote 1@ Supported in part by the NSF DMR-0311792, by U.S. ARO 40126-PH, and by U.S. AFOSR. Our spectrometer system is funded by U.S. ARO DAAD19-01-1-0364. Experiments performed at the NSLS which is supported by the U.S. DOE, Divisions of Materials and Chemical Sciences.@footnote 2@ P. Ryan, Y. C. Chao, J. Downes, C. McGuinness, K. E. Smith, A. V. Sampath, and T. D. Moustakas, Surf. Sci. 467, L827 (2000).@footnote 3@ F.-H. Wang, P. Krueger, and J. Pollmann, Surf. Sci. 499, 193 (2002).