Improved DC and RF performance of AlGaN/GaN HEMTs grown by MOCVD on sapphire substrates

High-quality AlGaN/GaN high electron mobility transistor (HEMT) structures were grown by metalorganic chemical vapor deposition (MOCVD) on 2-in. sapphire substrates. Two-dimensional electron gas (2DEG) mobility of 1410 cm2/V s and concentration of 1.0 × 1013 cm−2 are obtained at 295 K from the HEMT structures, whose average sheet resistance and sheet resistance uniformity are measured to be about 395 Ω/sq and 96.65% on 2-in. wafers, respectively. AlGaN/GaN HEMTs with 0.8 μm gate length and 0.2 mm gate width were fabricated and characterized using the grown HEMT structures. Maximum current density of 0.9 A/mm, peak extrinsic transconductance of 290 mS/mm, unity cutoff frequency (fT) of 20 GHz and maximum oscillation frequency (fmax) of 46 GHz are achieved. These results represent significant improvements over the previously fabricated devices with the same gate length, which are attributed to the improved performances of the MOCVD-grown HEMT structures.