TiO thin films on GaN(0001)

Physical features of titanium monoxide layers deposited on p-GaN( 0001) substrate are reported in this paper. TiO was deposited under ultrahigh vacuum at room temperature. As revealed by scanning tunneling microscopy (STM) the deposit had grainy structure. The X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) studies have shown that, depending on the altered by annealing morphology of the TiO-based film, work function of the system underwent changes and electronic structure of the deposit displayed metallic character. The formation of specific Ti-N and O-N bonds is confirmed by spectroscopic techniques. Electrical conductance of the TiO-based/p-GaN interface has been studied by current-sensing atomic force microscopy (CS-AFM) with Au-covered tip. Formation of ohmic nano-contacts on p-GaN surfaces was observed over whole probed surface. The contacts were homogeneous in contrast to the grainy structure of TiO-based film. The results suggest that TiO may be considered as an intermediate semiconducting layer (ISL) useful for p-GaN electrical contact engineering. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim