Dependence of (0001) GaN/AlN valence band discontinuity on growth temperature and surface reconstruction

X ray and ultraviolet photoelectron spectroscopies have been used to determine the heterojunction valence band discontinuity at the (0001) GaN/AlN interface. Type I discontinuity values of 0.5 +/- 0.2 eV were determined for GaN grown on AlN at 650 degrees C and 0.8 +/- 0.2 eV for GaN grown on AlN at 800 degrees C. These values are critically evaluated with respect to film quality, the results of other experimental studies, and theory. (C) 1998 American Institute of Physics. [S0021-8979(98)01716-2].