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Journal ArticleDOI

A theory of transistor cutoff frequency (f T ) falloff at high current densities

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TLDR
In this paper, it was shown that the observed falloff in the f T of a transistor at high currents is due to the spreading of the neutral base layer into the collector region of the device at high current densities.
Abstract
It is shown that the observed falloff in the f T of a transistor at high currents is due to the spreading of the neutral base layer into the collector region of the device at high current densities. The base layer spreading mechanism derives from an analysis of the effect of the current-dependent buildup of the mobile-carrier space-charge density in the collector transition layer. Calculations show that at sufficiently high collector current levels, the mobile space-charge density in the collector transition layer cannot be considered negligible in comparison to the fixed charge density of that region. The over-all effect of taking the mobile space charge into account in analyzing the collector transition region is that, at high current densities, the transition region boundary adjacent to the neutral base layer is displaced toward the collector metal contact with increasing collector current. The attendant widening of the neutral base layer results in the observed, high-current falloff in f T . The application of this theory to transistor structures of both the alloy and mesa variety yields, in each case, calculated curves of f T vs I c which are in reasonably good agreement with experiment.

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Citations
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Proceedings ArticleDOI

Laterally etched undercut (LEU) technique to reduce base-collector capacitances in heterojunction bipolar transistors

TL;DR: Laterally etched undercut (LEU) as discussed by the authors was proposed to reduce the parasitic junction capacitance of AlGaAs-GaAs heterojunction bipolar transistors by physically removing the extrinsic base-collector junction area and results in a cantilever structure.
Journal ArticleDOI

Physics of semiconductor power devices

TL;DR: In this paper, the basic principles of the operation of bipolar and field effect power transistors and thyristors are discussed, and a discussion of phenomena of special interest for power devices; junction avalanche breakdown, the effect of the current level on the current gain, dynamic and static behaviour at high currents and thermal properties and instabilities.
Journal ArticleDOI

A simulation study of high-speed silicon heteroemitter bipolar transistors

TL;DR: In this paper, the upper limit of Si homotransistor cutoff frequency was estimated under the assumed conditions of punchthrough voltage, and the optimum values of heteromaterial properties for high-speed HBT operation including energy gap, band discontinuity, and heterointerface recombination were discussed.
Patent

Multiple layer wide bandgap collector structure for bipolar transistors

TL;DR: In this article, a multiple layer wide bandgap collector structure is provided which comprises a relatively thin, highly doped layer 12 and a relatively thick, low doped or non-intentionally Doped layer 14.
Journal ArticleDOI

Analytical modeling of polycrystalline silicon emitter bipolar transistors under high-level injection

TL;DR: In this paper, the authors derived an analytical model, focused on injected charge storage, for electron current density, hole current density and current gain β, and forward transit time τ f for heavily doped base and emitter with non-uniform band structures.
References
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Journal ArticleDOI

The theory of p-n junctions in semiconductors and p-n junction transistors

TL;DR: The theory of potential distribution and rectification for p-n junctions is developed with emphasis on germanium, resulting in an admittance for a simple case varying as (1 + iωτ p )1/2 where τ p is the lifetime of a hole in the n-region.
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Mobility of Holes and Electrons in High Electric Fields

TL;DR: In this paper, the field dependence of mobility has been determined for electrons and holes in both germanium and silicon, and the observed critical field at 298\ifmmode^\circ\else\textdegree\fi{}K beyond which $\ensuremath{\mu}$ varies as ${E}^{-}\frac{1}{2}}$.
Journal ArticleDOI

The Dependence of Transistor Parameters on the Distribution of Base Layer Resistivity

TL;DR: In this article, a method of analyzing transistor behavior for any base-layer impurity distribution is presented, in particular expressions for emitter efficiency, transverse sheet resistance R, transit time, and frequency cut-off f?.
Journal ArticleDOI

Structure-Determined Gain-Band Product of Junction Triode Transistors

TL;DR: In this article, the authors compared the power gain of the junction triode with those of the field effect transistor and the analog transistor and showed that the gain-band product is nearly independent of the particular alpha cutoff frequency selected.