1-mm gate periphery AlGaN/AlN/GaN HEMTs on SiC with output power of 9.39 W at 8 GHz

Abstract

AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures with high mobility GaN channel layer were grown on 50 mm diameter semi-insulating (SI) 6H-SiC substrates by metalorganic chemical vapor deposition and large periphery HEMT devices were fabricated and characterized. High two-dimensional electron gas mobility of 2215 cm 2/V s at room temperature with sheet electron concentration of 1.044 × 10 13/cm 2 was achieved. The 50 mm diameter HEMT wafer exhibited a low average sheet resistance of 251.0 Ω/square, with the resistance uniformity of 2.02%. Atomic force microscopy measurements revealed a smooth AlGaN surface with a root-mean-square roughness of 0.27 nm for a scan area of 5 μm × 5 μm. The 1-mm gate width devices fabricated using the materials demonstrated a very high continuous wave output power of 9.39 W at 8 GHz, with a power added efficiency of 46.2% and power gain of 7.54 dB. A maximum drain current density of 1300 mA/mm, an extrinsic transconductance of 382 mS/mm, a current gain cutoff frequency of 31 GHz and a maximum frequency of oscillation 60 GHz were also achieved in the same devices.