## Abstract

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 language | English (US) |
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Article number | 6587527 |

Pages (from-to) | 2271-2298 |

Number of pages | 28 |

Journal | Proceedings of the IEEE |

Volume | 101 |

Issue number | 10 |

DOIs | |

State | Published - Jan 1 2013 |

## Keywords

- 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