Characterizations of recessed gate AlGaN/GaN HEMTs on sapphire

A recessed gate high electron mobility transistor (HEMT) has been fabricate d with AlGaN/GaN heterostructure on a sapphire substrate using metalorganic chemical vapor deposition, Capacitance-voltage (C-V) and Shubnikov-de Haas measurements have shown the formation of two-dimensional (2-D) electron ga s (2DEG) at Al0.11Ga0.89N/GaN heterointerface, A 2DEG mobility 12000 cm(2)/ V-s with a sheet carrier density 2.8 x 10(12) cm(-2) was measured on Al0.11 Ga0.89N/GaN heterostructure at 8.9K. The recessed gate Al0.26Ga0.74N/GaN HE MT structure showed maximum extrinsic transconductance 181 mS/mm and drain- source current 1120 mA/mm for a gate length 1.5 mum at 25 degreesC. The dev ice exhibited stable operation characteristics at 350 degreesC for long tim e (500 h), No interfacial change has been observed at metal/AlGaN interface even after 350 degreesC for 500 h treatment. The threshold voltage of devi ce does not depend very much on operating temperature (25 to 350 degreesC).