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This study presents TiO2/GaN/AlGaN/GaN/Si metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs). The measured direct current, microwave, and power characteristics of the MOS-HEMT are better than for identical geometry HEMT devices. Furthermore, the effects of postdeposition annealing (PDA) in an oxygen environment on the electrical properties of the MOS-HEMTs are investigated. This is the first report of effect of PDA on TiO2 GaN-based MOS-HEMTs. The quality of the TiO2/GaN interface shows significant improvement after annealing. These results clearly establish the potential of annealed TiO2 AlGaN/GaN MOS-HEMTs for high power microwave devices.

This paper reports on improved AlGaN/GaN metal oxide semiconductor high-electron mobility transistors (MOS-HEMTs). TiO2 is used to form the dielectric and passivation layers. The TiO2 film is characterized using X-ray photoemission spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM). The quality of the gate oxide is improved by annealing at 300 °C in N2. Experimental results indicate that the annealed MOS structure effectively reduces the gate leakage current. The high performance of the annealed MOS-HEMTs and their stable operation at elevated temperatures up to 450 K is demonstrated. Furthermore, annealing improves their output power characteristics.

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