Surface electronic structure of p-type GaN(0001)

The surface electronic structure of p-type wurtzite GaN(0001) 1 x 1 grown b y molecular beam epitaxy has been investigated using synchrotron radiation excited angle: resolved photoemission spectroscopy. Four discrete surface s tates were clearly identified and characterized. All the states were remove d by exposure of the surface to atomic hydrogen. Three of the states were o f p(z) orbital character, while the fourth is derived from s orbitals. Thre e of the surface states lie below the bulk valence band maximum throughout the surface Brillouin zone, and one surface state was observed to disperse into the bulk optical band gap. Comparison with theory suggests that this s urface state is Ga-derived, consistent with a model of Ga-terminated, but N polar, GaN. The other three surface states compare well with states observ ed earlier from n-type GaN. (C) 2000 Elsevier Science B.V. All rights reser ved.