# Improved External Base Resistance Extraction for Submicrometer InP/InGaAs DHBT Models

Tom Keinicke Johansen, Viktor Krozer, Virginie Nodjiadjim, Agnieszka Konczykowska, Jean-Yves Dupuy, Muriel Riet

Research output: Contribution to journalJournal articleResearchpeer-review

## Abstract

An improved direct parameter extraction method is proposed for III–V heterojunction bipolar transistor (HBT) external base resistance $R_{\rm bx}$ extraction from forward active $S$-parameters. The method is formulated taking into account the current dependence of the intrinsic base–collector capacitance found in III–V HBTs with a fully depleted collector. It is shown that the real part of $Z_{11} - Z_{12}$ reduces to the external base resistance at the collector current $I_{c} = I_{p}/(\hbox{1} - X_{0})$, where $I_{p}$ is a characteristic current and $X_{0}$ is the zero-current distribution factor given as the ratio of the emitter to the collector area. The determination of the parameters $I_{p}$ and $X_{0}$ from experimental $S$-parameters is described. The method is applied to high-speed submicrometer InP/InGaAs DHBT devices and leads to small-signal equivalent circuit models, which accurately predicts the measured $S$-parameters as well as the maximum stable power gain/maximum available power gain in the frequency range from 40 MHz to 110 GHz.
Original language English I E E E Transactions on Electron Devices 58 9 3004-3011 0018-9383 https://doi.org/10.1109/TED.2011.2160067 Published - 2011

## Keywords

• Heterojunction bipolar transistor (HBT)
• Direct parameter extraction
• Small-signal model
• InP

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