InGaP/GaAs Sub-Square-Micron Emitter HBT with fmax＞100 GHz

Abstract

InGaP/GaAs heterojunction bipolar transistors (HBTs) with a sub-square-micron emitter have been fabricated using a novel self-aligned emitter etching process with low damage and good lateral and vertical controllability. HBTs with an emitter size of 0.4 x 1.7 μm fabricated using this process exhibited a current gain of 44 which is comparable to that of AlGaAs/GaAs HBTs. Furthermore, the HBTs exhibited excellent microwave performance. For an HBT with an emitter size of 0.4 x 2.2 μm, a cutoff frequency (f T ) of 55 GHz and a maximum oscillation frequency (f max ) of 100 GHz were reached at a collector current (I C ) as low as 1.0 mA, and a peak f T of 62 GHz and a peak f max of 105 GHz were obtained at I C = 2.3 mA. As far as we know, this f max is the highest reported for GaAs-based HBTs with an emitter area of less than 1μm 2 . This process is thus promising for fabrication of high-speed HBT ICs with low power consumption.