p++-GaAs/n-InGaP heterojunction structure in application to wide-gap channel field-effect transistors

p⁺⁺-GaAs/n-InGaP heterojunction field-effect transistors (HJFETs) with a highly carbon-doped gate and a wide-gap channel were reported. A self-aligned T-shaped gate HJFET exhibits a gate of 0.6 μm in length by depositing gate metal of 1.0 μm. DC characteristics including a turn-on voltage of 2.0 V at 1 mA/mm, a gate-drain breakdown voltage up to 30 V, a drain-source breakdown voltage exceeding 25 V, a maximum available transconductance of 160 mS/mm and AC performances such as a unit-current gain frequency of 16.8 GHz, and a unit-power gain frequency of 25 GHz were obtained for a non self-aligned HJFET. With a self-aligned processing structure, the transconductance and f_max were improved to 230 mS/mm and 35 GHz, respectively.