Modeling and Extraction of the Specific Contact Resistance of GaN p-i-n Diodes up to 40 GHz

In this article, we propose a high-frequency model taking into account the series resistance of pseudo-vertical gallium nitride (GaN)-based p-i-n diodes. This model relies on the specific contact resistance on p-type GaN and the sheet resistance of the bottom n-type GaN. Those two quantities are obtained while fitting the RF experimental data and are slightly different from the dc values. The interest of this model is that the effective values, at the working frequency instead of “only” the dc values, are extracted using only a few devices. The novelty of the work resides in the consideration of the geometrical dimensions of the diode (anode radius and distance between anode and cathode) in the model. Furthermore, the model allows the determination of the most limiting geometrical parameters and can predict the series resistance of other topologies. In the present case, we show the most limiting factor is the radius of the anode due to the difficulties of achieving low specific contact resistance on p-type GaN. The parasitic capacitance is also extracted using the measured devices, allowing the modeling of the effective capacitance as a function of the frequency.