W.J. Kloosterman

A new analytical diode model including tunneling and avalanche breakdown

An analytical model describing reverse and forward DC characteristics is presented. It serves as a basis for a compact model for circuit simulation purposes. The model is based on the solution of the hole continuity equation in the depletion layer of a p-n junction and incorporates the following physical mechanisms: band-to-band tunneling, trap-assisted tunneling (both under forward and reverse bias), Shockley-Read-Hall recombination, and avalanche breakdown. It contains seven parameters which can be determined at one temperature. No additional parameters are needed to describe the temperature dependence. From comparisons with both numerical simulations and measurements it is found that the model gives an adequate description of the DC characteristics in both forward and reverse modes. >

New formulation of the current and charge relations in bipolar transistor modeling for CACD purposes

New, compact analytical formulas for the current and stored charge in a vertical bipolar transistor are derived. The derivation is not based on the charge control concept, but shows how current and charge depend on minority carrier concentrations, which in turn are functions of junction voltages. In this way the influence of the built-in field, the bias-dependent transit times, and the Early effect are incorporated quite naturally. The new set of equations is the framework of a complete transistor model for computer-aided circuit design purposes.

Improved extraction of base and emitter resistance from small signal high frequency admittance measurements

The base- and emitter resistance are important parameters of bipolar transistors and can be extracted from high frequency small signal admittance (Y) parameters. The circle impedance method and the two port method are examined and improvements are presented.

Modeling of the collector epilayer of a bipolar transistor in the MEXTRAM model

A new model description for the behaviour of epitaxial collectors in bipolar transistors is given. This is part of MEXTRAM, a compact model for circuit simulation, and it gives the voltage drop and stored minority carrier charge in the collector epilayer as a function of the bias conditions. It covers (total) depletion and quasi-saturation for both ohmic and space charge conditions in the end region of the epilayer. New features are that the collector current and stored charge are given as explicit analytical functions, thus guaranteeing continuity also for their derivatives, and that collector current spreading is taken into account. >

Avalanche multiplication in a compact bipolar transistor model for circuit simulation

A simple weak avalanche model valid in a wide range of voltages and currents, is presented. The proposed model is derived by using the base-collector depletion capacitance for predicting the avalanche current. The model needs only one additional transistor parameter; the extraction method and temperature dependence of this parameter are discussed. The decrease in avalanche current for high collector current densities may originate from internal device heating, a voltage drop in the epilayer, or mobile carriers in the depleted part. From experimental results it is concluded that, below a critical hot-carrier current, the decrease in avalanche current due to mobile carriers is negligible. >

Experience with the new compact MEXTRAM model for bipolar transistors

The improved performance of the compact bipolar transistor model MEXTRAM is demonstrated by comparison with Gummel-Poon (GP) model calculations and measured DC and high-frequency data. The MEXTRAM model contains extended modeling of the collector epilayer and the inactive region of the base-collector epilayer and the parasitic pnp. It has five internal nodes, whereas the GP model has three. The advantage is a more accurate prediction of the DC behavior and the f/sub t/ fall-off at high currents. The AC small-signal behavior at frequencies >or=f/sub t/ is dominated by the inactive part of the device. If unphysical fit parameters are accepted, the GP model can obtain in the forward mode up to the top of the f/sub t/ nearly as good a fit as MEXTRAM does; the predictive capability, especially for down-scaled devices, however, will remain inferior. This is a very important point for circuit optimization MEXTRAM has been used successfully in this area, e.g. for ECL gates.<<ETX>>

A comprehensive bipolar avalanche multiplication compact model for circuit simulation

In this paper, a new comprehensive bipolar transistor avalanche multiplication model is presented that takes into account the finite thickness of the epilayer, modulation of the electric field by the collector current (Kirk effect), current spreading in the epilayer and quasi-saturation. Two parameters are needed to model the collector voltage dependency at small current levels and one parameter is required to describe high current effects. The dependency of the collector-emitter breakdown voltage BV/sub ceo/ with collector current is shown. The model will be part of the bipolar compact transistor model Mextram 504, but also can be used separately.

Efficient parameter extraction for the MEXTRAM model

A very fast, robust and accurate parameter extraction method for bipolar compact models has been developed. Using a combination of simplified expressions and selected measurements the iterative solution of the full model equations (e.g. using a circuit simulator) is avoided. The method is applied to the bipolar compact model MEXTRAM.

Explorations for high performance SiGe-heterojunction bipolar transistor integration

Presents a SiGe HBT integration-study, introducing a low-complexity integration-scheme. We demonstrate a stepped box-like SiGe base-profile designed to reduce reverse Early effects, achieving f/sub T/=55 GHz and BV/sub CEO/=2.7 V. The transistor characteristics are well modeled by Mextram 504.

MODELLA-a new physics-based compact model for lateral p-n-p transistors

A lateral p-n-p compact model, suitable for computer-aided circuit design purposes, is introduced. In this formulation, called MODELLA, the equivalent circuit topology, analytical equations, and model parameters are derived directly from the physics and structure of the lateral p-n-p. MODELLA incorporates current crowding effects, substrate effects, and a bias-dependent output conductance and it uses the approach to lateral p-n-p high injection modeling whereby the main currents and charges are independently related to bias-dependent minority-carrier concentrations. Model-specific aspects of the parameter determination strategy are discussed; the Ning-Tang resistance determination method, for example, is shown to be highly suitable for lateral p-n-p devices. The effectiveness of this strategy and the improved performance of this physics-based formulation become evident in comparisons between MODELLA and the standard SPICE Gummel-Poon model using measured device characteristics. >