The interplay of self-heating and polarization affecting resistance is studied in AlGaN/GaN transmission line model (TLM) heterostructures with a scaled source-to-drain distance. This paper is based on meticulously calibrated TCAD simulations against I-V experimental data using an electro-thermal model. The electro-thermal simulations show hot-spots (with peak temperature in a range of ~566 K-373 K) at the edge of the drain contact due to a large electric field. The electrical stress on Ohmic contacts reduces the total polarization, leading to the inverse/converse piezoelectric effect. This inverse effect decreases the polarization by 7%, 10%, and 17% during a scaling of the source-to-drain distance in the 12 μm, 8 μm, and 4 μm TLM heterostructures, respectively, when compared with the largest 18-μm heterostructure.
