On‐State Current Increasing Structure of Source‐Connected Polarization Superjunction Transistor

A structure is proposed for increasing the on‐state current in a polarization superjunction (PSJ) field effect transistor (FET) using gallium nitride (GaN). A PSJ FET can achieve a high breakdown voltage, but in the simplest PSJ FET structure, the PSJ structure and the gate are integrated, so the input capacitance will increase, which is disadvantageous for high‐speed switching. Therefore, a structure in which the PSJ structure is connected to the source electrode has been proposed. By connecting the PSJ structure to the source, the capacitance of the PSJ structure is on the output side, where it has little effect on switching. However, those structures suffer from reduced on‐state current. To address this issue, a structure is investigated that increases the on‐state current because the PSJ structure is etched into a comb shape, and a current path in the on‐state is provided separately from the PSJ structure. It is confirmed that the on‐state current can be improved by etching the PSJ region. The V BD · I D,sat product is calculated to evaluate the effectiveness of the comb‐shaped PSJ structure. It is possible to improve the V BD ·I D, sat product by 2.17 times compared to the PSJ FET without PSJ structure etching.