Journal of Vacuum Science & Technology B, Vol.18, No.4, 2082-2087, 2000
Schottky barrier height and electron affinity of titanium on AIN
Approximately 100 or 1000 Angstrom of AlN was deposited on the (0001)Si-face of on-axis n-type 6H-SiC. The surfaces were examined by ultraviolet photoemission spectroscopy CUPS) utilizing the He I alpha (21.2 eV and the He II alpha (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 chi 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 chi = 0 eV, the position of the valence band maximum is 3.4 eV below the position of the Fermi level. For the case of chi = 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 chi = 0 eV and chi = 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.