Application of AlGaAs/GaAs ballistic collection transistors to multiplexer and preamplifier circuits

Ballistic collection transistors with a ´launcher´ (L-BCTs) are applied to the fabrication of high-speed/broadband ICs. The L-BCTs, in which base widening is suppressed and the ballistic transport of electrons is utilized to reduce transit time without an increase in base collector capacitance, are combined with a novel self-alignment process technology that makes it possible to enlarge the cutoff frequency f/sub T/ to around 160 GHz with excellent uniformity. A 19-Gb/s operation has been demonstrated in a fabricated 2:1 multiplexer with a retiming function at the input/output stages. A fabricated monolithic preamplifier exhibits a transimpedance of 52 dB Omega with a 3-dB-down bandwidth of 18.5 GHz and a gain of S/sub 21/ of 21 dB with a 3-dB-down bandwidth of 19 GHz. These results demonstrate that the L-BCTs are very promising for ICs such as those used in ultrahigh-speed digital transmission systems.<>