Breakdown Mechanism of AlGaN/GaN-based HFET With Carbon-doped GaN Buffer Layer grown on Si substrate

摘要

In this paper, we evaluated the effect of carbon doping on the breakdown mechanism of GaN buffer as well as the material and electrical properties of AlGaN/GaN HFETs. The introduction of carbon will slightly increase the surface roughness and degrade the 2DEG carrier density, while leakage current (breakdown voltage) can be suppressed (enhanced) significantly (346 V@1 μA/mm and 748 V@1 mA/mm). Leakage current of GaN can be explained using trap charge limited space-charge limited current (SCLC) model and shows an obvious dependency on carbon concentration. The transient drain current measurements demonstrate that the traps in the unintentional doped GaN buffer are mainly acceptor traps (C_N) with an energy level of EV+538 meV, while both acceptor and donor traps (C_Ga with an energy level of E_C-600 meV) coexist in the carbon doped GaN buffer layer.