Nitride-based GaN/In0.12Ga0.88N heterostructure field effect transistors (HFETs) with semi-insulating Mg-doped GaN current blocking layers were successfully fabricated. The as-grown layers exhibited a very smooth surface. The DC characteristics of these HFETs were substantially improved over those previously reported. Devices with a 0.75 μm gate length showed a maximum drain current (IDS) of 421 mA/mm, and a maximum gm of about 85.6 mS/mm at VGS between -0.5 and -3V. The device which had a very good pinch-off with source-drain (S-D) leakage current was negligibly small, in the range of 10-1-10-2mA/mm. The RF characteristic of devices showed the current gain cutoff frequency, f T, was 7.45 GHz and the maximum oscillation frequency, f MAX, was 12.36 GHz.
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