AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS1+EM-TuM

Paper SS1+EM-TuM5
Angle Resolved Photoemission Studies of the Surface Electronic Structure of GaN(0001)

Tuesday, October 26, 1999, 9:40 am, Room 606

Session: Nitrides and Compound Semiconductors
Presenter: K.E. Smith, Boston University
Authors: K.E. Smith, Boston University
Y.C. Chao, Boston University
P. Ryan, Boston University
J. Downes, Boston University
C.B. Stagarescu, Boston University
R. Singh, Boston University
T.D. Moustakas, Boston University
D. Hanser, North Carolina State University
R.F. Davis, North Carolina State University
Correspondent: Click to Email
The physical properties of GaN are under intense study due to its use in optoelectronic and high temperature semiconductor devices. However, the surface electronic structure of GaN remains poorly understood. Numerous reconstructions of GaN are observed, but very little is known about the detailed electronic structure of clean, ordered GaN surfaces. We report the results of an extensive synchrotron radiation excited angle-resolved photoemission study of n-type and p-type wurtzite GaN(0001)1x1 surfaces. GaN thin films were grown both by MOCVD on SiC, and by MBE on Al@sub 2@O@sub 2@. Surfaces were cleaned by repeated cycles of N@super 2+@ ion bombardment followed by annealing in UHV. We have observed a number of different surface states on these materials. For n-type MBE samples we find a non-dispersive surface state just below the valence band maximum that is highly sensitive to surface contamination and disorder. This state shows no dispersion perpendicular to the surface and exists across the surface Brillouin zone in a region devoid of bulk states. Polarization measurements reveal that this feature originates from a state with sp@sub z@ character. Destruction of this state only partially removes the observed band bending. For n-type MOCVD samples, cleaned in an identical fashion, we find at least two surface states. One is similar to that seen on the MBE material, while the second is a highly dispersive back bonding state, extending to the bottom of the valence band at points in the surface Brillouin zone. Removal of these states does not alter the observed band bending. For p-type MBE samples, we also find a surface state in the fundamental band gap, above the valence band maximum. Such states are not observed for the n-type material. We will discuss the surface electronic structure of GaN in the context of these measurements. @FootnoteText@ Work supported in part by NSF grant DMR 95-04948. Experiments were performed at the NSLS, which is supported by US DOE.