Title | Reconciliation of methods for estimating fmax for microwave heterojunction transistors |
Publication Type | Journal Article |
Year of Publication | 1991 |
Authors | LASER, A. P., and D. L. Pulfrey |
Journal | Electron Devices, IEEE Transactions on |
Volume | 38 |
Pagination | 1685 -1692 |
Date Published | aug. |
ISSN | 0018-9383 |
Keywords | AlGaAs-GaAs, aluminium compounds, analytical expression, collector capacitance, drift-diffusion equations, effective base resistance, equivalent circuit, equivalent circuits, fT, gallium arsenide, HBTs, heterojunction bipolar transistors, hybrid- pi, III-V semiconductors, Mason's invariant gain, maximum frequency of oscillation estimation, microwave heterojunction transistors, semiconductor device models, semiconductors, solid-state microwave devices, T-equivalent circuit, transit-time effects, y-parameters |
Abstract | An attempt is made to reconcile the various approaches that have recently been used to estimate the maximum frequency of oscillation fmax in high-performance AlGaAs/GaAs HBTs. fmax is computed numerically from the full expression for Mason's invariant gain using y-parameters derived from the different approaches, i.e., the hybrid- pi; equivalent circuit, the T-equivalent circuit, and the drift-diffusion equations. It is shown that the results for fmax are essentially the same, irrespective of the source of the y-parameters, provided that the phase delays due to transit of carriers across the base and the collector-base depletion region are properly accounted for. It is also shown, for the particular device studied, that the widely used analytical expression for fmax, involving f T and effective base resistance and collector capacitance, is remarkably accurate for frequencies below those at which transit-time effects become important |
URL | http://dx.doi.org/10.1109/16.119002 |
DOI | 10.1109/16.119002 |