Short-channel AlGaN/GaN field-plated high-electron-mobility transistors for X-band high power operation

We present experimental results on the high frequency (10 GHz) operation of short-channel AlGaN/GaN field-plated high-electron-mobility transistors (FP-HEMTs). The gate-length of 0.25 μm, which is the shortest for FP-HEMTs on sapphire reported to date, has been used to extend the operation of FP-HEMTs to X-band and higher. High frequency performance of FP-HEMTs was investigated for different field-plate lengths (L_FP). For L_FP = 1 μm, the measured f_T and f_max were 28 and 51 GHz, respectively, which is suitable for X-band operation. When LFP was increased from 0 to 1.0 μm, the breakdown voltages of the FP-HEMTs increased from 64 to 111V giving a breakdown voltage improvement of more than 70%. In addition, leakage current did not limit the large-signal performance of the transistors resulting in excellent power-added-efficiency (PAE) of 45% under small heat dissipation condition. The FP-HEMT having L_FP = 1 μm showed a small-signal gain ot 11 dB and a saturated output power of 4.4 W/mm at 10 GHz.