Abstract
In this study, AlGaN/GaN Metal-Oxide-Semiconductor High Electron Mobility Transistors (MOSHEMT) on a silicon substrate were fabricated. The purpose is to use a recessed-gate structure to achieve enhance mode operation, since the recessed-gate structure blocks the formation of two dimensional electron gas under the gate. Al2O3 was used as the gate dielectric, and two surface treatments were compared using atomic layer deposition. From the results we found that the recessed-gate MOSHEMT with the H2SO4/H2O2 treatment prior to depositing ALD aluminum oxide shows a threshold voltage of 5V, a subthreshold swing of 467mV/decade, and a field effect mobility of 125cm2/V-s. The interface state density between oxide and semiconductor was 7.93x1013 cm-2eV-1 extracted using the conductance method. However, the recessed gate MOSHEMT shows significant current collapse effect due to high interface state density. About the off-state breakdown characteristics, we found that the one which shows the highest breakdown voltage was a MOSHEMT with aluminum oxide as the gate oxide using H2SO4/H2O2 treatment. For devices with a Lgd=20μm, breakdown voltage can reach 1565V. With a on-resistance of 7.18mΩ-cm2, the BFOM is 341 MW/ cm2.