IC-Oriented Self-Aligned High-Performance AlGaAs/GaAs Ballistic Collection Transistors and Their Applications to High-Speed ICs


IEICE TRANSACTIONS on Electronics   Vol.E76-C   No.9   pp.1392-1401
Publication Date: 1993/09/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Heterostructure Electron Devices)
heterojunction bipolar transistor,  self-aligned structure,  ballistic collection transistor,  launcher,  cutoff frequency,  maximum oscillation frequency,  multiplexer,  preamplifier,  selector,  frequency divider,  

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This paper describes IC-oriented high-performance AlGaAs/GaAs heterojunction bipolar transistors that were fabricated to demonstrate their great potential in applications to high-speed integrated circuits. A collector structure of ballistic collection transistors with a launcher (LBCTs) shortens the intrinsic delay time of the transistors. A novel and simple self-aligned fabrication process, which features an base-metal-overlaid structure (BMO), reduces emitter- and base-resistances and collector capacitance. The combination of the thin-collector LBCT layer structure and the BMO self-alignment technology raises the average value of cutoff frequency, fT, to 160 GHz with a standard deviation as small as 4.3 GHz. By modifying collector thickness and using Pt/Ti/Pt/Au as the base ohmic contact metal in BMO-LBCTs, the maximum oscillation frequency, fmax, reaches 148 GHz with a 114 GHz fT. A 2:1 multiplexer with retiming D-type flip-flops (DFFs) at input/output stages fabricated on a wafer with the thin-collector LBCT structure operates at 19 Gbit/s. A monolithic preamplifier fabricated on the same wafer has a transimpedance of 52 dBΩ with a 3-dB-down bandwidth of 18.5 GHz and a gain S21 OF 21 dB with a 3-dB-down bandwidth of 19 GHz. Finally, a 40 Gbit/s selector IC and a 50 GHz dynamic frequency divider that were successfully fabricated using the 148-GHz fmax technologies are described.