AlN/GaN HEMTs with high- Delta k ALD HfO2 or Ta2O5 gate insulation

AlN/GaN Metal-Insulator-Semiconductor High Electron Mobility Transistors (HEMTs) have been grown and fabricated which utilize a 6 nm thick atomic layer deposited film of either Ta2O5 or HfO2 for gate insulation. Drain, transfer, and gate current characteristics are compared between both structures, showing a measurable difference in threshold voltage and transconductance. The cause is highlighted by the results of capacitance-voltage analysis which showed 10 MHz dielectric constants of 8.7 and 11.7 for the HfO2 and Ta2O5 films, respectively. Furthermore, interface trap state density was extracted by Terman's method and compared between films. HEMT small signal frequency performance was representative of the different sub-micron gate lengths. Consideration of the compared electrical results suggests that at this stage in ALD development, Ta2O5 appears better suited for gate insulation of AlN/GaN HEMTs. (? 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)