Design of indium-free nitride-based tunnel junction by polarization engineering

Abstract

Structural design and characterization of indium-free nitride-based tunnel junctions (TJs) are investigated numerically. Specifically, polarization-engineered n- and p-type compositional-graded AlGaN layers are employed to pursue superior tunneling characteristics in the tunnel junctions under typical doping conditions. The corresponding polarization field in the undoped GaN layer that is surrounded by graded AlGaN layers is with the same direction as the doping-induced built-in electric field, which is beneficial for carrier tunneling. Moreover, the detrimental polarization fields in AlGaN layers whose direction is opposite to the built-in electric field can be effectively suppressed with the compositional-graded configuration. Simulation results indicate that, by appropriately adjusting the thickness of undoped GaN layer and n- and p-type graded AlGaN layers, voltage drop and resistivity of the proposed TJ structure can be as low as 0.045 V and 4.48 × 10−5 Ω cm2, respectively, at 1 kA/cm2. The results of this study may be of great help for the development of indium-free nitride-based tunnel junctions.