Impact of Isolation-Feature Geometry on Self-Heating of AlGaN/GaN HFETs

Correlation between the isolation-feature geometry and average channel temperature of AlGaN/GaN heterojunction field-effect transistors (HFETs) is investigated. The reported transistors of this paper were realized on a variety of isolation-feature geometries resembling the following structures: 1) island; 2) fin; 3) comb; and 4) ladder. The average channel temperature of the devices from all categories of the fabricated AlGaN/GaN HFETs was studied using finite element analysis in ANSYS Mechanical. To check the validity of these analyses, results were compared with the experimental data. According to these studies, a less pronounced self-heating is observed in devices, which enjoyed a closer proximity between the drain-edge of the gate and side-walls of the isolation feature. Among these devices, for the same moderate dc bias power of 5 W/mm (i.e, per millimeter width of the transistor), ~60 K decrease in the average channel temperature is observed.