Effects of quasi-ballistic base transport on the high-frequency characteristics of bipolar transistors

TitleEffects of quasi-ballistic base transport on the high-frequency characteristics of bipolar transistors
Publication TypeJournal Article
Year of Publication1997
AuthorsVaidyanathan, M., and D. L. Pulfrey
JournalElectron Devices, IEEE Transactions on
Pagination618 -626
Date Publishedapr.
Keywordsballistic decay mechanism, bipolar transistors, Boltzmann equation, Boltzmann transport equation, common-base current gain, dynamic distribution function, forward characteristics, Grinberg-Luryi approach, high-frequency characteristics, intrinsic transit frequency, microwave bipolar transistors, minority carriers, minority-carrier scattering length, moving boundary condition, one-flux approach, phase angle, quasi-ballistic base transport, reverse small-signal parameters, S-parameters, scattering parameters, semiconductor device models, Thomas-Moll expressions

High-frequency transport in bipolar transistors with quasi-ballistic base widths (on the order of a minority-carrier scattering length) is examined by using the approach of Grinberg and Luryi (1992) to solve the Boltzmann transport equation (BTE). By considering the phase angle of the dynamic distribution function in wave-vector space, it is shown that the ballistic mechanism of decay in the common-base current gain becomes important even for base widths in the quasi-ballistic regime. Simple expressions, which correctly yield both the magnitude and phase of all the forward characteristics, as predicted by the BTE, up to the intrinsic transit frequency, are found by combining the results from a one-flux approach with the well-known expressions of Thomas and Moll (1958). Expressions for the reverse small-signal parameters are also found by applying a ldquo;moving boundary condition rdquo; to the basic one-flux equations of Shockley (1962)


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