Enhancement of Breakdown Voltage in p-GaN Gate AlGaN/GaN HEMTs With a Stepped Hybrid GaN/AlN Buffer Layer

A novel p-GaN gate AlGaN/GaN high electron mobility transistor (HEMT) structure with a stepped hybrid GaN/AlN buffer layer (S-HEMT) is proposed and simulated by the Sentaurus TCAD in this paper. A stepped hybrid GaN/AlN buffer layer is adopted and the step is near the interface of the gate and drain. First, the breakdown voltage (
BV
) of the proposed S-HEMT is significantly improved with the introduction of a stepped hybrid GaN/AlN buffer layer, which can effectively modulate the electric field distributions along the channel. Second, the AlN buffer layer below the stepped GaN buffer has a large band offset and a strong polarization, which results in a much lower leakage current and a better carrier confinement. Consequently, the
BV
of the proposed S-HEMT will be improved at no expense of the specific on-resistance (
${R} _{\mathrm{ on,sp}}$
). Compared with those of the conventional p-GaN gate AlGaN/GaN HEMT on the same gate-to-drain distance of
$12 ~\mu \text{m}$
, a higher
BV
of 1781 V and FOM of 0.72 GW/cm
²
are obtained for the proposed S-HEMT, which are both about five times. The proposed S-HEMT exhibits the potential and advantage in high power electronic applications.