Small-signal equivalent circuit model of GaN-based nanodiodes at low temperature including trap-related low frequency dispersion

The small-signal equivalent circuit of GaN-based self-switching diodes has been obtained, which apart from the intrinsic R‖C branch, generally used to describe the diode performance, needs new elements to describe the low-frequency dispersion of the impedance originated by the presence of surface and bulk traps. The proposed model allows us to reproduce not only the high-frequency results (extracted from S-parameter measurements in the 40 MHz–43.5 GHz range) at room temperature, but also the low-frequency impedance measurements (75 kHz–30 MHz) at cryogenic temperatures down to 70 K. These new elements are a self-inductance associated to the effect of surface states (typical of a device with a high surface-to-volume ratio) and an extra series R–C branch modeling the influence of the bulk traps.