AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThP

Paper EM-ThP8
Atomic Order and Electron Affinity at AlN(0001) Surfaces

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Electronic Materials and Processing Poster Session
Presenter: C.I. Wu, Princeton University
Authors: C.I. Wu, Princeton University
A. Kahn, Princeton University
E.S. Hellman, Bell Laboratories, Lucent Technologies
D.N.E. Buchanan, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
We have used Auger electron spectroscopy (AES), low energy electron diffraction (LEED), x-ray and ultraviolet photoemission (XPS and UPS) and inverse photoemission spectroscopy (IPES) to investigate the preparation, atomic order and electron affinity of AlN(0001) surfaces. AlN films 0.2µm thick were grown by molecular beam epitaxy on Si(111) substrates. Following ambient transfer to the surface analysis chamber, repeated cycles of nitrogen sputtering (1 keV) and annealing (10 min., 1050 °C) were necessary to obtain ordered surfaces with only a few percent of a monolayer of O contaminant. The resulting surfaces exhibited sharp 1x1 LEED patterns. The UPS (HeI and HeII) spectra exhibited sharp features allowing a clear identification of the valence band maximum (E@sub v@). The position of E@sub v@ was confirmed by XPS measurements of the Al 2p core level and using the known binding energy of this level with respect to E@sub v@.@footnote 1@ The UPS-IPES combination showed the Fermi level at 4.8 eV above EV and 1.6 eV below the conduction band minimum at the surface of our AlN. Given these numbers and in spite of the concomitant observation of a sharp feature at the onset of photoemission, generally associated with the occurrence of negative electron affinity, the electron affinity was calculated to be +2.3 eV. Finally, the deposition of 1-2 monolayer of Al on the (1x1) surface followed by a 5 min. 1250°C anneal led to a structure characterized by a (@sr@3 x @sr@3)-R30° diffraction pattern. This LEED pattern is consistent with RHEED observations for increasing Al surface concentration during growth. @FootnoteText@ @footnote 1@J.R. Waldrop, and R.W. Grant, Appl. Phys. Lett. 68, 2879 (1996).