The transistor laser: Theory and experiment

Han Wui Then, Milton Feng, Nick Holonyak

Research output: Contribution to journalArticlepeer-review


The quantum-well (QW) heterojunction bipolar transistor (HBT) laser [the transistor laser (TL)], inherently a fast switching device, operates by transporting small minority base charge densities $\sim\!\! {\hbox {10}}^{16}\ {\hbox {cm}}-3 over nanoscale base thickness ( $<$ 900 A) in picoseconds. The base QW acts as an optical 'collector,' in addition to the usual electrical collector, that selects out 'fast' recombining carriers, resulting in a short lifetime ($\ sim$29 ps) and higher differential laser gains. Charge and current continuity, together with the boundary conditions imposed by both collectors of the TL lead to a new charge control model, 'unpinning' of population inversion beyond lasing threshold, quasi-Fermi level discontinuity across base QW, and a new equivalent circuit model requiring an extension to Kirchhoff's law. With the TL, the HBT becomes more than just a charge control device, but also a photon storage and switching device. The TL, owing to fast recombination speed, its unique three-terminal configuration, and the complementary nature of its optical and electrical collector output signals, enables resonance-free base current and collector voltage modulations, and compact realization of electro-optical applications such as nonlinear signal mixing, frequency multiplication, negative feedback, and optoelectronic logic gates.

Original languageEnglish (US)
Article number6587527
Pages (from-to)2271-2298
Number of pages28
JournalProceedings of the IEEE
Issue number10
StatePublished - Jan 1 2013


  • Analog and logic optoelectronic circuits
  • Carrier-photon dynamics
  • Charge control
  • Current and voltage modulation
  • Dependent optical source
  • Differential laser gain
  • Equivalent circuit model
  • Feedback linearization
  • Frequency multiplication
  • Heterojunction bipolar transistor (HBT)
  • Laser theory
  • Light-emitting transistor (LET)
  • Optical switch
  • Quantum transitions
  • Quasi-fermi level discontinuity
  • Resonance-free response
  • Stimulated and spontaneous recombination
  • Transistor laser (TL)
  • Tunnel junction (TJ) transistor laser

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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