Characterization of p-GaN$_{1−x}$ As$_{x}$/n-GaN PN junction diodes

Abstract

The structural properties and electrical conduction mechanisms of p-type amorphous GaN$_{1−x}$ As$_{x}$ /n-type crystalline GaN PN junction diodes are presented. A hole concentration of 8.5 × 10$^{19}$ cm$^{-3}$ is achieved which allows a specific contact resistance of 1.3 × 10$^{-4}$ Ω cm$^{2}$. An increased gallium beam equivalent pressure during growth produces reduced resistivity but can result in the formation of a polycrystalline structure. The conduction mechanism is found to be influenced by the crystallinity of the structure. Temperature dependent current voltage characteristics at low forward bias (<0.35 V) show that conduction is recombination dominated in the amorphous structure whereas a transition from tunneling to recombination is observed in the polycrystalline structure. At higher bias, the currents are space charge limited due to the low carrier density in the n-type region. In reverse bias, tunneling current dominates at low bias (<0.3 V) and recombination current becomes dominant at higher reverse bias.This work was undertaken with support from the EPSRC (EP/K014471/1)