Precise extraction of emitter resistance from an improved floatingcollector measurement

A distributed transistor model is developed which comprehensively explains the non-linear characteristics of floating collector measurements. The non-linearity is attributed to the fact that the intrinsic collector current is not zero when the collector terminal is opened. Based on this understanding, a new procedure to extract emitter resistance is proposed. Combining the measurements of forward and reverse current gains and intrinsic base sheet resistance, the ambiguity in the conventional floating collector measurement is diminished and hence the accuracy is significantly improved     

Electron space-charge effects on high-frequency performance ofAlGaAs/GaAs HBTs under high-current-density operation

The high-frequency characteristics of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) under high-current-density biasing condition are investigated in conjunction with the electron space charge in the collector depletion layer. A significant increase in cutoff frequency f_t and maximum oscillation frequency f_max at the early stage of the base push-out was observed in HBTs with a lightly doped n-type collector structure, and is attributed to the collector depletion layer widening and the enhancement of the velocity overshoot effect caused by the increasing electron density     

AlGaAs/GaAs HBTs fabricated by a self-alignment technology usingpolyimide for electrode separation

A self-aligned HBT (heterojunction bipolar transistor) technology using polymide for insulating the emitter contact from the base contact is described. A 1-μm emitter-width HBT with maximum oscillation frequency of 86 GHz was successfully fabricated. This processing was also applied to fabricate frequency-divider ICs. An operating frequency of 18 GHz was obtained with good reproducibility     

Ultrahigh-speed heterojunction bipolar transistormultiplexer/demultiplexer ICs

High-speed 2-b monolithic integrated multiplexer (MUX) and demultiplexer (DMUX) circuits have been developed using self-aligned AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with improved high-speed performance. Both ICs were designed using emitter-coupled logic. The 2:1 MUX was composed of a D-type flip-flop (D-FF) merging a selector gate and a T-type flip-flop (T-FF). The 1:2 DMUX consisted of two D-FFs driven at a clock of half the rate of the input data. Error-free operation with a pseudorandom pattern was confirmed up to 10 Gb/s. The rise and fall times of the output signals of both ICs were 40 and 25 ps, respectively. HBT frequency dividers were used as inputs for both ICs in order to find the maximum operation speed. Although only a few test patterns were available, the maximum operation speeds of the MUX and DMUX were found to be around 15 and 19 Gb/s, respectively     

Collector-top GaAs/AlGaAs heterojunction bipolar transistors for high-speed digital ICs

GaAs/AlGaAs collector-top heterojunction bipolar transistors with magnesium and phosphorus double-implanted external bases were fabricated. A cutoff frequency of 17 GHz and a gate delay time of 63 ps for DCTL were obtained. These results indicate the potential of collector-top HBTs for high-speed ICs.     

Transit-time reduction in AlGaAs/GaAs HBTs utilizing velocityovershoot in the p-type collector region

The effect of electron-velocity overshoot in a p-type GaAs collector on the transit-time reduction of AlGaAs/GaAs HBTs (heterojunction bipolar transistors) is investigated. A cutoff frequency improvement of about 30% over the conventional n-type GaAs collector was obtained in p-type collector HBTs for the same collector depletion-layer width. A significant increase in electron velocity in the p-type GaAs collector layer was confirmed by a simple analysis