High-f/sub max/ AlGaAs/InGaAs and AlGaAs/GaAs HBTs fabricated with MOMBE selective growth in extrinsic base regions

AlGaAs/GaAs and AlGaAs/InGaAs heterojunction bipolar transistors (HBTs) with excellent microwave performance are reported. An f/sub T/ of 102 GHz and an f/sub max/ of 224 GHz are achieved, using selective growth of heavily C-doped GaAs layers in extrinsic base regions, in combination with a 40-nm-thick compositionally graded InGaAs base structure.