Title :
Frequency dependence of the unilateral gain in bipolar transistors
Author_Institution :
IBM T.J. Watson Res. Center, Yorktown Heights, NY, USA
Abstract :
The frequency dependence of the current gain and the unilateral gain in advanced bipolar transistors is analyzed. A GaAlAs/GaAs heterostructure bipolar transistor (HBT) is used as an example to show that the extrinsic parasitics still dominate the gain rolloff. Transit-time effects, even though they are a significant component of the time constants that determine the f/sub T/ and f/sub max/ of transistors, do not cause a change in the rolloff of unilateral gain with a frequency from 6 to 12 dB/octave in these advanced devices. Devices with very large transit times, and hence low f/sub T/ and f/sub max/ may, however, exhibit the rolloff change if designed to have a very low fringing capacitance and other parasitics.<>
Keywords :
III-V semiconductors; aluminium compounds; gallium arsenide; heterojunction bipolar transistors; semiconductor device models; solid-state microwave devices; GaAlAs-GaAs; HBT; current gain; device parasitics; extrinsic parasitics; f/sub T/; f/sub max/; frequency dependence; gain rolloff; heterostructure bipolar transistors; maximum frequency of oscillation; microwave transistors; models; semiconductors; transit time effects; unilateral gain; unity current gain frequency; Bipolar transistors; Delay; Electron emission; Extrapolation; Frequency dependence; Frequency estimation; Frequency measurement; Heterojunction bipolar transistors; Parasitic capacitance; Resonance;
Journal_Title :
Electron Device Letters, IEEE
