Correlation Between AlGaN/GaN MISHFET Performance and $\hbox {HfO}_{2}$ Insulation Layer Quality

HfO₂ films of 15 nm were deposited using atomic layer deposition at temperatures varying from 110°C to 200°C and then to 300°C on AlGaN/GaN HEMT structures. Devices with 300°C HfO₂ show dramatically better ON and OFF-state characteristics under dc biases than those with HfO₂ deposited at lower temperatures. High-resolution X-ray diffraction, together with X-ray reflectivity measurements, confirms the superior film quality of the 300°C HfO₂ in comparison to the lower temperature grown films.