Schottky barrier height and electron affinity of titanium on AlN

Abstract

Approximately 100 or 1000 Å of AlN was deposited on the (0001)Si-face of on-axis n-type 6H–SiC. The surfaces were examined by ultraviolet photoemission spectroscopy (UPS) utilizing the He I α (21.2 eV) and the He II α (40.8 eV) excitation. Experimental difficulties are discussed. Titanium was deposited on the clean surface of in situ grown AlN. The titanium–AlN interface was also characterized with UPS. Two approaches are presented to identify the valence band maximum (VBM) and the electron affinity χ of the clean surface of AlN was found to be either 0 to 1 eV depending upon the position of the valence band edge. The same assumptions were applied to the analysis of the Ti/AlN interface and, for the case of χ=0 eV, the position of the valence band maximum is 3.4 eV below the position of the Fermi level. For the case of χ=1 eV, the position of the valence band maximum is 4.4 eV below the position of the Fermi level. Therefore, the p-type Schottky barrier height of titanium on AlN is measured to be 3.4±0.2 or 4.4±0.2 eV for χ=0 eV and χ=1 eV, respectively. Independent of the selection of the valence band maximum, the observed Schottky barrier differed from that predicted by the Schottky–Mott model by 1.5±0.2 eV.