MBE and ALD grown High k Dielectrics Gate Stacks on GaN

III-nitride compound semiconductors are attractive for high-temperature and high-power MOSFET applications due to their intrinsic properties of wide band gap, high breakdown field, and high saturation velocity under high fields. In this work GaN-based high k MOS diodes were fabricated using MBE-grown Ga$_{2}$O$_{3}$(Gd$_{2}$O$_{3})$, MBE-grown HfO$_{2}$ and ALD-grown HfO$_{2}$ as the gate dielectrics with dielectric constants of 14.7, 17.4 and 16.5, respectively. All MOS diodes exhibited low leakage ($<$10$^{-6}$ A/cm$^{2}$ at V$_{fb}$+1) and well behaved capacitance-voltage curves with a low interfacial density of states of $\sim $10$^{11}$ cm$^{-2}$eV$^{-1}$. Energy-band diagrams of the MOS structures have been determined by extracting valance-band offset ($\Delta $E$_{V})$ from HR-XPS and with the bandgaps of the oxides. For example, the ALD-grown HfO$_{2}$-GaN at the interfaces gave approximately $\Delta $E$_{C}$ and $\Delta $E$_{V}$ of 1.2 eV and 1.1 eV, respectively.