Ballistic Collection Transistors Research Articles

InGaP/GaAs ballistic collection transistors withburied polycrystallineGaAs under base electrode

InGaP/GaAs ballistic collection transistors, with buried polycrystalline GaAs under the base electrode, have been fabricated by using gas-source molecular beam epitaxial growth on SiO2-patterned GaAs substrates. Heavy C-doping in the base led to a high maximum oscillation frequency of 170 GHz while maintaining a high cutoff frequency of 170 GHz. Owing to the reduction in base-collector capacitance, maximum stable gain was increased by 2.3 dB compared to that of transistors without polycrystalline GaAs.

BALLISTIC COLLECTION TRANSISTORS AND THEIR APPLICATIONS

We describe the design, fabrication and application of ballistic collection transistors (BCTs) in which electron velocity overshoot is introduced in the collector of a GaAs-based heterojunction bipolar transistor. The guideline for the BCT design is the effective confinement of electrons to the Γ-valley, as simulated by Monte Carlo analysis, and the control of electron energy is accomplished basically with an i-p+-n+ doping profile. Microwave characterization demonstrates the existence of significant overshoot and cutoff frequencies higher than 100 GHz at collector current densities in the mid 104 A/cm 2 range for a typical BCT structure. Some high speed integrated circuits implemented with BCTs include a selector circuit that operates at bit rates up to 40 Gb/s, a dynamic frequency divider with divide-by-four function up to 50 GHz and a broadband preamplifier having an S21 bandwidth as high as 40 GHz.

Ultrahigh-speed AlGaAs/GaAs ballistic collection transistors using carbon as p -type dopant

Ultrahigh-speed performance is demonstrated in AIGaAs/GaAs ballistic collection transistors with a launcher (L-BCTs) grown by MOCVD using carbon (C)-doping of both a uniform base layer and a p+-layer for a potential cliff in the collector layer. A selfalignment fabrication technology characterised by a base-metal overlaid structure results in superior high-frequency performances of 100 and 144GHz for ftand fmax respectively.

Monte Carlo analysis of the space-charge effect in AlGaAs/GaAs ballistic collection transistors (BCTs) under high current injection

AlGaAs/GaAs ballistic collection transistors (BCTs) are investigated by self-consistent Monte Carlo simulation, focusing on the space-charge effect in the collector region. In addition to the conventional BCT collector structure (i-p/sup +/-n/sup +/), modified collector structures which have n/sup -/-p/sup +/-n/sup +/ and p/sup -/-p/sup +/-n/sup +/ doping profiles are examined. By taking account of the fact that the collector delay time is composed of transit time and capacitance charging time, it is shown that the n/sup -/-p/sup +/-n/sup +/ collector structure is effective for the suppression of the base-widening effect (Kirk effect) compared to the i-p/sup +/-n/sup +/ or p/sup -/-p/sup +/-n/sup + /structure. Donors in the n/sup -/ layer compensate for the negative space charges produced by near-ballistic electrons. For a simulated BCT with an n/sup -/-p/sup +/-n/sup +/ collector, the smaller collector capacitance charging time leads to improvement in current-gain cutoff frequency under high current injection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ultrahigh speed 2 bit MUX and DEMUX ICs using AlGaAs/GaAs L-BCT technology

A 2 bit multiplexer (MUX) and demultiplexer (DEMUX) with DFFs for input and output retiming were developed. The ICs were designed using two-level series-gated ECL and realised by AlGaAs/GaAs ballistic collection transistors with launcher (L-BCT) technology. The maximum operating speeds of the ICs were 19 Gbit/s for the MUX and 17 Gbit/s for the DEMUX. These error free operating speeds are the fastest in MUXs and DEMUXs with DFFs for input and output retiming.

Hot electron injection in InAlGaAs/InGaAs ballistic collection transistors

Hot electron transport in InAlGaAs/InGaAs ballistic collection transistors (BCTs) is simulated using a self-consistent Monte Carlo method. The authors analyse the effects of hot electron injection on the device performance of BCTs with various injection energies. The simulation has shown that the base and collector transit times in BCTs have conspicuous dependences on the energy of hot electrons in the base region.

18.5 GHz bandwidth monolithic preamplifier using AlGaAs/GaAs ballistic collection transistors

A circuit technique for improving the transimpedance flatness and output matching characteristics in a preamplifier is proposed. An 18.5 GHz bandwidth monolithic preamplifier with a transimpedance of 52dBΩ has been fabricated with AlGaAs/GaAs ballistic collection transistors.