Nb2O5 high-k dielectric enabled electric field engineering of β-Ga2O3 metal–insulator–semiconductor (MIS) diode

Abstract

We demonstrate an Nb2O5/β-Ga2O3 metal–insulator–semiconductor (MIS) hetero-junction diode with Nb2O5 as the high-k dielectric insulator for more efficient electric field management resulting in enhanced breakdown characteristics compared to a β-Ga2O3 Schottky barrier diode. Nb2O5 dielectric films were grown using atomic layer deposition and exhibited a high dielectric constant of 50. The high dielectric constant resulted in a 5× lower electric field at the metal/dielectric interface in the MIS diode compared to the metal/β-Ga2O3 interface in the Schottky barrier diode. With good electron conduction in forward bias enabled by the negative conduction band offset of Nb2O5 with respect to β-Ga2O3, the MIS design led to a 3× improvement in the reverse blocking voltage with a slight trade-off in the specific on-resistance. Overall, a 3.3× increase in the power figure of merit was observed (3.25 MW/cm2 for the Schottky diode and 10.8 MW/cm2 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 2D technology computer-aided design simulations.