J.M. McGregor

Drift hole mobility in strained and unstrained doped Si/sub 1-x/Ge/sub x/ alloys

Results of the drift hole mobility in strained and unstrained SiGe alloys are reported for Ge fractions varying from 0 to 30% and doping levels of 10/sup 15/-10/sup 19/ cm/sup -3/. The mobilities are calculated taking into account acoustic, optical, alloy, and ionized-impurity scattering. The mobilities are then compared with experimental results for a boron doping concentration of 2*10/sup 19/ cm/sup -3/. Good agreement between experimental and theoretical values is obtained. The results show an increase in the mobility relative to that of silicon. >

Measured In-plane hole drift and hall mobility in heavily-doped strained p-type Si1−xGex

Measured in-plane hole drift and Hall mobilities in heavily boron-doped strained Si1−xGex layers are reported. In the range of boron dopings examined (1.5–2.1 × 1019 cm−3), the drift mobility is seen to increase with increasing germanium fraction. The Hall mobility decreases with increasing germanium fraction.

Modified simple expression for bandgap narrowing in n-type GaAs

Abstract A simple theoretical expression which has been very successful in interpreting experiments on bandgap narrowing (BGN) in n- and p-type Si, n-type Ge and p-type GaAs is modified to fit recent optical and transistor BGN data for n-type GaAs. The impurity scattering part of the BGN in this expression is replaced by an expression obtained by a numerical fit with the results of multiple scattering theory. The modified expression is simple and describes all available luminescence and transistor data extremely well. The Fermi energy is evaluated by analyzing available luminescence data in n-type GaAs. It is found that for dopant concentrations larger than 2 × 1019 cm−3, the observed Fermi level starts becoming smaller than the calculated using the accepted value of conduction band density of states.

Output conductance of bipolar transistors with large neutral-base recombination current

Neutral base recombination current, which is negligible in most modern bipolar transistors, can affect the common-emitter output conductance quite dramatically if it dominates other sources of base current. Mathematical theory for this phenomenon is developed, applied to some simplified special cases, and compared with numerical simulation. The large output conductance of some real Si/Si/sub 1-x/Ge/sub x/ DHBTs is seen to be the result of a large neutral base recombination current. >

Bipolar transistor base bandgap grading for minimum delay

It is shown that the base delay t bb of a bipolar transistor in low-level injection is minimised when the bandgap E g in the neutral base region is a linear function of position

A simple expression for ECL propagation delay including non-quasi-static effects

Abstract A simple, analytical, expression for the emitter-coupled logic (ECL) propagation delay is useful not only in predicting the performance of ECL circuits, but as a figure of merit for use in the design and “optimisation” of bipolar transistors used in nonsaturating logic applications. A simple expression for the propagation delay time of a differential pair with an ideal, non-inverting output buffer is obtained from an analysis, in the s -domain, of its large-signal non-quasi-static equivalent circuit, and its predictions are compared with circuit simulation results for buffered differential pairs and Active Pulldown ECL (APD-ECL) inverters.

Transistor design for predictable power gain at maximum frequency

Equations which define the neutral base width, collector doping, and epitaxial collector thickness of a bipolar transistor giving a specified unilateral power gain at the highest frequency, possible are derived. Emitter-base capacitance, emitter delay, emitter stripe width, base doping, and the operating base-collector voltage are assumed to be known and fixed. The hybrid- pi equivalent circuit is assumed valid up to the transition frequency f/sub t/. Peak f/sub max/ (maximum oscillation frequency) is examined as a function of the collector doping. Maximizing f/sub max/ at all costs leads to a design with an f/sub t/ which approaches zero. In designing a transistor, the two figures of merit must be traded off against each other. A simple expression giving maximum f/sub max//f/sub t/ is derived and used to define the transistor design which gives some specified power gain at the highest possible frequency. >