Vertical p-GaN/n-Ga2O3 heterojunction diodes enabled by PAMBE

Abstract

Vertical diodes are produced via the nitridation of (-201) β-Ga2O3 and subsequent GaN epitaxy via PAMBE. For undoped films, the mosaic block model parameters are extracted via XRD and used to calculate dislocation densities, where optimization of the nitridation and growth enabled two orders of magnitude reduction in screw dislocation density. These results validate a model relating screw dislocation formation to initial edge dislocation densities. The dislocation densities are compared to device parameters extracted from vertical Schottky barrier diodes on the same samples. The current on/off ratio, ideality, and Schottky barrier height are found to depend on screw dislocation density, edge dislocation density, and surface roughness, respectively. The Mg-dopant activation energy was measured to be 160 meV. Diode on/off ratios range between 104 and 105 with a differential specific on-resistance of 2.4 m Ω cm2 and a forward current density >1 kA/cm2 measured prior to reaching compliance. Temperature dependent I–V measurements are conducted to investigate reverse-bias leakage current, and variable-range hopping is identified as the transport mechanism. The hopping conduction follows a 3D mode at moderate temperatures, but above 100 °C transitions to a 1D mode.