High performance AlGaN/GaN HEMTs with recessed gate

High performance AlGaN / GaN high electron mobility transistors with recessed gate have been successfally fabricated on sapphire substrate. The HEMT with 0.5 um gate length exhibited excellent current saturation properties without no kink effect and no current degradation. The maximum extrinsic trans-conductance was as high as 327 mS/mm. Effective electron velocity of the HEMT with 0.5um gate length calculated from intrinsic f_T (49.7GHz) was as high as 1.56 × 10⁷ cm/sec. To our knowledge, this is the fastest value of any GaN-based FETs ever reported. Moreover, the HEMTs with T shape recessed gate of 0.21um gate length was also fabricated and exhibited excellent high frequency performances. A maximum unity current cut-off frequency f_T of 57 GHz and a maximum oscillation frequency f_max of 108 GHz were obtained.