We study the origins of conductivity and low-frequency noise in GaNp-njunctions under reverse bias. Carrier hopping through defect states in the space charge region is identified as the main mechanism responsible for low bias conductivity. Threading dislocations appear the most likely source of such defect states. At higher bias hopping is supplemented with Poole–Frenkel emission. A relatively high level of1/f-like noise is observed in the diode current. The bias and temperature dependencies of the noise current are investigated.©1998 American Institute of Physics.