Self-heating and polarization effects in AlGaN/AlN/GaN/AlGaN based devices

The interplay of self-heating and polarization affecting the current is studied in Al0.32Ga0.68N/AlN/GaN/Al0.1Ga0.9N Transmission Line Model (TLM) heterostructures with a scaled source-drain distance. The study is based on meticulously calibrated TCAD simulations against I-V experimental characteristics using an electro-thermal model. The electro-thermal simulations show hot-spots at the edge of the drain contact due to a large electric field affecting the device reliability. Due to the applied electrical stress, the total polarization, relative to the 18 pm heterostructure, decreases by 7 %, 10 % and 17% during a reduction of the source-to-drain distance to the 12 pm, 8 pm, and 4 pm, respectively, as a result of the additional strain induced by electrical stress. This additional stress on source/drain contacts reduces the polarization at the surface as a result of the inverse piezoelectric effect.