Low specific on-resistance GaN-based vertical heterostructure field effect transistors with nonuniform doping superjunctions**Project supported by the National Natural Science Foundation of China (Grant Nos. 61574112, 61334002, 61474091, and 61574110) and the Natural Science Basic Research Plan in Shaanxi Province, China (Grant No. 605119425012).

Abstract

A novel GaN-based vertical heterostructure field effect transistor (HFET) with nonuniform doping superjunctions (non-SJ HFET) is proposed and studied by Silvaco-ATLAS, for minimizing the specific on-resistance (RonA) at no expense of breakdown voltage (BV). The feature of non-SJ HFET lies in the nonuniform doping concentration from top to bottom in the n- and p-pillars, which is different from that of the conventional GaN-based vertical HFET with uniform doping superjunctions (un-SJ HFET). A physically intrinsic mechanism for the nonuniform doping superjunction (non-SJ) to further reduce RonA at no expense of BV is investigated and revealed in detail. The design, related to the structure parameters of non-SJ, is optimized to minimize the RonA on the basis of the same BV as that of un-SJ HFET. Optimized simulation results show that the reduction in RonA depends on the doping concentrations and thickness values of the light and heavy doping parts in non-SJ. The maximum reduction of more than 51% in RonA could be achieved with a BV of 1890 V. These results could demonstrate the superiority of non-SJ HFET in minimizing RonA and provide a useful reference for further developing the GaN-based vertical HFETs.