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Nb$_{2}$O$_{5}$ high-k dielectric enabled electric field engineering of $β$-Ga$_{2}$O$_{3}$ metal-insulator-semiconductor (MIS) diode

We demonstrate an Nb$_{2}$O$_{5}$/$β$-Ga$_{2}$O$_{3}$ metal-insulator-semiconductor (MIS) hetero-junction diode with Nb$_{2}$O$_{5}$ as the high-k dielectric insulator for more efficient electric field management resulting in enhanced breakdown characteristics compared to a $β$-Ga$_{2}$O$_{3}$ Schottky barrier diode. The Nb$_{2}$O$_{5}$ dielectric films were grown using atomic layer deposition and exhibited a high dielectric constant of 50. The high dielectric constant resulted in a 5$\times$ lower electric field at the metal/dielectric interface in the MIS diode compared to the metal/$β$-Ga$_{2}$O$_{3}$ interface in the Schottky barrier diode. With good electron conduction in forward bias enabled by the negative conduction band offset of Nb$_{2}$O$_{5}$ w.r.t $β$-Ga$_{2}$O$_{3}$, the MIS design led to a 3$\times$ improvement in the reverse blocking voltage with a slight trade-off in the specific on-resistance. Overall, a 3.3$\times$ increase in the power figure of merit was observed (3.25 MW/cm$^2$ for the Schottky diode and 10.8 MW/cm$^2$ for the MIS diode). A detailed analysis of the energy band line-up, and the forward and reverse current transport mechanisms are also presented using analytical modeling and 2-D TCAD simulations.