Recessed gate AlGaN/GaN modulation-doped field-effect transistors on sapphire

A recessed gate AlGaN/GaN modulation-doped field-effect transistor (MODFET) has been grown on a sapphire substrate by metalorganic chemical vapor deposition. The two-dimensional electron gas mobility as high as 9260 cm²/Vs with the sheet carrier density 4.8× 10¹²cm^-2 was measured at 4.6 K for the AlGaN/GaN heterostructure on the sapphire substrate. The recessed gate device showed the maximum extrinsic transconductance 146 mS/mm and drain-source current 900 mA/mm for the AlGaN/GaN MODFET with a gate length 2.1 μm at 25 °C. At an elevated temperature of 350 °C, the maximum extrinsic transconductance and drain-source current were 62 mS/mm and 347 mA/mm, respectively.