High-transconductance AlGaN/GaN high-electron-mobility transistors on semi-insulating silicon carbide substrate

Epitaxial layers of AlGaN/GaN were grown on semi-insulating (SI) silicon carbide (SiC) by metalorganic chemical vapor deposition (MOCVD) with a very high electron sheet carrier density n_s = 1.2 × 10¹³ cm^-2 and a Hall carrier mobility as high as μ_H = 1281 cm²/Vs at room temperature. High-electron-mobility transistors (HEMTs) have been demonstrated using an AlGaN/GaN heterostructure on a SI-SiC substrate. The fabricated 2.2-μm-gate-length Al_0.26Ga_0.74N/GaN HEMTs exhibited extrinsic transconductance as high as 287 mS/mm with drain-source current density as high as 857 mA/mm. This is the first report of such high transconductance achieved so far for 2.2-μm-gate-length Al_0.26Ga_0.74N/GaN HEMTs on SI-SiC substrates. A very small percentage (3%) of drain-source current density reduction at the gate voltage of +1.5 V has been observed for HEMTs on SI-SiC substrates. The observation of high extrinsic transconductance can be explained with the help of intrinsic transconductance values.