Design optimization of a high-breakdown-voltage GaN-based vertical HFET with composite current-blocking layer

Abstract

This work proposes a GaN-based vertical heterostructure field-effect transistor with composite insulated current-blocking layer (GaN CCBL-VHFET) to improve the breakdown voltage (BV) of the current aperture vertical electron transistor (CAVET) and obtain high CBL performance. When utilizing a composite current-blocking layer, the electric field (E-field) discontinuity at the CBL/low-k dielectric interface results in a more uniform E-field distribution along the GaN buffer layer, significantly improving the BV. Simulation results show that the BV and ON-resistance ($$R_{\mathrm{ON}}$$RON) of the device with two low-k dielectric layers are 1744 V and 0.91 m$$\Omega \,\mathrm{cm}^{2}$$Ωcm2, respectively. Furthermore, the average breakdown E-field is extremely high, reaching 291 V/$${\upmu }$$μm. Compared with the conventional GaN CAVET, the BV of the GaN CCBL-VHFET increases by about 94 % while retaining low $$R_{\mathrm{ON}}$$RON. Furthermore, the challenge of activating Mg in the CBL is avoided for this device structure.