We propose a model and an algorithm for computing the transport properties of GaN n-i-p devices. The formalism yields the band diagram and 1-V characteristics of these systems, and accounts for the effects of an external resistance in series with the diode and the generator. For the conditions considered, the device obeys essentially the ideal diode equation with deviations due to the external resistance and the transfer of charges between the different layers. Compared to n-p devices, the isolating layer enables one to decrease the external resistance and obtain more diode current for the same voltage. The external resistance allows one also to control and reduce appreciably the height of the barrier that characterizes the n-i interface. This barrier may serve as an energy discriminator, which can be important in applications for thermal management. (C) 2004 American Vacuum Society.