Small-Scale InGaP/GaAs Heterojunction Bipolar Transistors for High-Speed and Low-Power Integrated-Circuit Applications.

Small-scale InGaP/GaAs heterojunction bipolar transistors (HBTs) with high-speed as well as lowcurrent operation are demonstrated. To reduce the emitter size S[sub E] and the base-collector capacitance C[sub BC] simultaneously, the HBTs are fabricated by using WSi/Ti as the base electrode and by burying SiO[sub 2] in the extrinsic collector region. WSi/Ti metals simplify and facilitate processing to fabricate small base electrodes, and the buried SiO[sub 2] reduces the parasitic C[sub BC]: under the base electrode. The cutoff frequency ƒ[sub T] of 156 GHz and the maximum oscillation frequency ƒ[sub max] of 255 GHz were obtained at a collector current I[sub c] of 3.5 mA for the HBT with S[sub E] of 0.5 µm × 4.5 µm, and ƒ[sub T] of 114 GHz and ƒ[sub max] of 230 GHz were obtained at l[sub c] of 0.9 mA for the HBT with S[sub E] of 0.25 µm × 1.5 µrn. A 1/8 static frequency divider operated at a maximum toggle frequency of 39.5 GHz with a power consumption per flip-flop of 190 mW. A transimpedance amplifier provides a gain of 46.5 dB.Ω with a bandwidth of 41.6 GHz at a power consumption of 150 mW. These results indicate the great potential of our HBTs for high-speed, low-power integrated-circuit applications. [ABSTRACT FROM AUTHOR]