Study on TiAlOx as high-k dielectric for MISHEMTs

Abstract:
Ti:AlOx ternary oxides were characterized structurally and electrically with the aim of applying them as gate dielectric in metal insulator semiconductor high electron mobility transistors. The thin films were deposited on Si and GaN substrates using atomic layer deposition. With the help of the X-ray fluorescence spectroscopy it was found, that the atomic layer deposition cycle ratio actually corresponds to the atomic composition Al2O3:TiO2 of the mixed layers. X-ray diffraction measurements were carried out to analyze the crystallinity of the ternary oxides, in particular after the implementation of a post deposition annealing at 800 °C. The dielectric constant of the oxides as well as the fixed charge was determined using capacitance-voltage measurements. With an increasing Ti-content an increasingly negative oxide charge and a larger dielectric constant was observed. A high leakage current was measured for ternary oxides with a Ti-content of 50 at% and above.