Study on possible double peaks in cutoff frequency characteristics of AlGaAs/GaAs HBTs by energy transport simulation

T. Okada, K. Horio

Research output: Contribution to journalArticle


By using an energy transport model, we simulate cutoff frequency fT- versus collector current density Ic characteristics of npn-n AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with various n--collector thickness and n--doping densities. It is found that the calculated fr characteristics show double peak behavior when the n--layer is thick enough and the n--doping is high enough to allow existence of neutral n--region. The mechanism of the double peak behavior is discussed by studying energy band diagrams, electron-energy profiles and electron-velocity profiles. Particularly, we discuss the origin of the second peak (at higher Ic) which is not usually reported experimentally.

Original languageEnglish
Pages (from-to)437-442
Number of pages6
JournalVLSI Design
Issue number1-4
Publication statusPublished - 1998 Jan 1



  • Cutoff frequency
  • Double peaks
  • Energy transport model
  • GaAs
  • Heterojunction bipolar transistor
  • Velocity overshoot

ASJC Scopus subject areas

  • Hardware and Architecture
  • Computer Graphics and Computer-Aided Design
  • Electrical and Electronic Engineering

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