Correlation between DC-RF dispersion and gate leakage in deeply recessed GaN/AlGaN/GaN HEMTs

Employing deeply recessed GaN/AlGaN/GaN highelectron mobility transistors, we experimentally demonstrate the correlation between the dc-RF dispersion and the gate leakage current. It was found that both the dc-RF dispersion and the gate leakage are strongly affected by surface charging. The impact of surface charging can be controlled by using GaN/AlGaN/GaN structures with varied GaN cap thickness. In the absence of field plates, the tradeoff between the dc-RF dispersion and the gate leakage can be compromised by choosing a proper GaN cap thickness. Our optimum epistructure design yields an output power density of 5.6 W/mm with an associated power added efficiency of 72% at 28-V bias and 4-GHz frequency. The gate leakage current is as low as 30 μ A/mm at up to 40-V gate-drain bias.