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

Abstract

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 cm 2/V s and concentration of 1.0 × 10 13 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 ( f T) of 20 GHz and maximum oscillation frequency ( f max) 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.