GaN nanodiode arrays with improved design for zero-bias sub-THz detection

Abstract

GaN based self-switching diodes (SSDs) have been fabricated for the first time on SiC substrate. They have been characterized as RF power detectors in a wide frequency range up to 220 GHz, showing a cutoff frequency of about 200 GHz. At low-frequency, RF measurements exhibit a square law detection with a responsivity that well agrees with the calculations performed by means of a quasi-static model based on the shape of the I–V curve. Exploiting such a model, a simple DC characterization allows defining design rules for optimizing the practical operation of the diode arrays as RF power detectors. As strategy to improve the performance of SSDs operating as zero-bias detectors at room temperature, in terms of responsivity and noise equivalent power, we suggest: (i) the reduction of the channel width and (ii) the increase of the number of diodes in parallel in order to reduce the total device impedance to a value that coincides with 3 times that of the transmission line (or antenna) to which they are connected.