Valence-band photoemission from the GaN(0001) surface

A detailed investigation by one-step photoemission calculations of the GaN( 0001)-(1 X 1) surface in comparison with recent experiments is presented in order to clarify its structural properties and electronic structure. The d iscussion of normal and off-normal spectra, reveals through the identified surface states, clear fingerprints for the applicability of a surface model proposed by Smith et al. [Phys. Rev. Lett. 79, 3934 (1997)]. Especially th e predicted metallic bonds are confirmed. In the context of direct transiti ons, the calculated spectra allow us to determine the valence-band width an d to argue in favor of one of two theoretical bulk band structures. Further more, a commonly used experimental method to fix the valence-band maximum i s critically tested. [S0163-1829(99)05939-1].