The structural properties and electrical conduction mechanisms of p-type amorphous GaN As /n-type crystalline GaN PN junction diodes are presented. A hole concentration of 8.5 × 10$\mathrm{<mrow\; data-mjx-texclass="ORD">19</mrow>}$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-3</mrow>}$ is achieved which allows a specific contact resistance of 1.3 × 10$\mathrm{<mrow\; data-mjx-texclass="ORD">-4</mrow>}$ Ω cm$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$. 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.