1 Characterization of p-GaN 1-xAsx / nGaN PN Junction Diodes

The structural properties and electrical conduction mechanisms of p-type amorphous GaN1-xAsx/n-type crystalline GaN PN junction diodes are presented. A hole concentration of 8.5×10 cm is achieved which allows a specific contact resistance of 1.3×10 Ω-cm. 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.