FULLY SELF-ALIGNED ALGAAS GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS FOR HIGH-SPEED INTEGRATED-CIRCUITS APPLICATION

Structure optimization, uniformity, and high-speed circuit performance of an AlGaAs/GaAs heterojunction bipolar transistor (HBT) are described. The HBT is fabricated in a fully self-aligned manner using only a single photoresist mask to achieve submicrometer-dimension devices with extremely reduced parasitic elements. The fabricated HBTs exhibit excellent threshold voltage deviation σVBE = 2 mV on a 2-in. wafer, a current-mode logic (CML) gate propagation delay time τpd = 9.5 ps, and a toggle frequency ftog = 13.3 GHz for a CML divide-by-two frequency divider. These results show the applicability of the device to high-speed integrated circuits.