Observation of highly dispersive surface states on GaN(0001)1×1

Abstract

The electronic structure of n-type, Si-doped, wurtzite GaN͑0001͒1ϫ1 surfaces has been studied using synchrotron radiation excited angle-resolved photoemission. The GaN thin films were grown by metal-organic chemical-vapor deposition on SiC. Two previously unobserved surface bands were measured and fully characterized. One of the states is highly nonlocalized, dispersing throughout much of the valence band along the ⌫-K-M and ⌫-M directions of the 1ϫ1 surface Brillouin zone. The identification of these states as surface bands was confirmed both by their lack of dispersion perpendicular to the surface, and by the sensitivity of the states to hydrogen adsorption. The symmetry properties of the states were determined using the linear polarization of the incident synchrotron radiation. These states are quite distant from the localized nondispersive surface state previously observed on GaN. ͓S0163-1829͑99͒50824-2͔ RAPID COMMUNICATIONS R15 588 PRB 59 Y.-C. CHAO et al.

Microscopic origins of surface states on nitride surfaces

“…Nevertheless, the studies indicate that on the GaN (0001) surface a non-dispersive, occupied state is present close to the VBM. [19][20][21] The experimentalists related this state to Ga dangling bonds; theoretically, Wang et al 26 attributed it to the presence of Ga adatoms on T 4 sites (on top of sublayer N atoms and bonded to three Ga surface atoms).…”

“…2 Band-dispersion results were obtained through angle-resolved photoemission spectroscopy (ARPES) on the GaN(0001) [19][20][21][22][23] and GaN(0001) 24,25 surfaces. The reconstructions were deduced from low-energy electron diffraction measurements on clean surfaces, although the presence of coexisting Ga-and N-terminated surfaces could not be excluded.…”

“…2,[16][17][18] Band dispersion has also been investigated using photoemission. [19][20][21][22][23][24][25] Long et al 16 used photoelectron (PES) and X-ray photoemission spectroscopy (XPS) on the clean GaN(0001) surface. In the limit of low temperature and low doping concentration, E F −E v was measured to be about 2.7 eV on the surface of n-type GaN, and about 1.3 eV on the surface of p-type GaN.…”

Reconstructions of GaN and InGaN surfaces

“…Detailed work by Held et al using thermal desorption spectroscopy has provided valuable information on the gallium coverage of GaN during growth [6]. Photoemission spectroscopy has revealed the presence of well defined dangling bond states on the surface, although the geometry (and polarity) of the surfaces studied there was not clear [7,8].…”

Structure of clean and arsenic-covered GaN(0001) surfaces

“…[6] Photoemission spectroscopy has revealed the presence of well defined dangling bond states on the surface, although the geometry (and polarity) of the surfaces studied there was not clear. [7,8] 1 A major result of our prior work is that there exist two different families of reconstructions of GaN surfaces, one family associated with the (0001) surface and the other associated with the (000 ) surface. Each surface can exist in a number of different structures depending on the surface stoichiometry (ranging from N-rich to Ga-rich).…”