Small size collector-up AlGaAs/GaAs hbts fabricated using H+ implantation

Small size collector-up AlGaAs/GaAs HBTs have been developed making the entire emitter layer under the external base highly resistive by oblique H⁺ implantation from both sides of the collector normal mesa. A collector cap layer of In_0.5Ga_0.5As and a high dose base layer doped with Be of 4 × 10¹⁹ cm⁻³ are formed in a multilayer structure for the HBTs. A current gain cutoff frequency fT of 31 GHz. and a maximum oscillating frequency fmax of 50 GHz have been obtained in the HBT with a collector size of 1 × 10 μm².