Electronic states and effective negative electron affinity at cesiated p-GaN surfaces

C. I. Wu, A. Kahn

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The electronic structure of, and the effects of cesium (Cs) and oxygen (O) adsorption on, the p-GaN(001) surface are investigated via photoemission spectroscopy. Bulk- and surface-sensitive photoemission measurements, and oxygen exposure of clean surfaces, demonstrate the existence of filled surface states which extend ∼0.6 eV above the valence band maximum. The valence band maximum measured after the removal of the surface states gives a downward band bending and electron affinity equal to 1.2±0.2 and 3.3±0.2 eV, respectively. The surface dipole layer induced by exposure to oxygen followed by Cs deposition lowers the vacuum level by 2.8±0.3 eV with respect to the valence and conduction band edges. Under these conditions, the vacuum level is approximately 0.7 eV below the conduction band minimum of the bulk, corresponding to the effective negative electron affinity at this surface.

Original languageEnglish (US)
Pages (from-to)3209-3212
Number of pages4
JournalJournal of Applied Physics
Issue number6
StatePublished - Sep 1999

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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