Light Emitting Transistor and Laser


This invention is the world's first light emitting transistor. The HBLET extends the capabilities of light-emitting diodes and could make this transistor the fundamental element in electronics and optoelectronics.


In a bipolar device there are two kinds of injected carriers, negatively charged electrons and positively charged holes. Some of these carriers, for example, a transistor, recombine rapidly, supported by a base current essential for normal transistor function. In the past, this base current has been regarded as a waste current that generates unwanted heat. However, this technology shows the base current creates light that can be modulated at transistor speed. This recombination process is the same (but enhanced by carrier transport) as the one used in LEDs to produce visible, rather than infared, light. The transistor laser produces infared radiation in phase with its base current, so it can be modulated at a switching speed impossible to attain with an LED. The switching speed obtained is fast enought to operate in fiber optic networks, as well as other applications.

These transistors are made with indium gallium phosphide and gallium arsenide, unlike traditional transistors which have been built from silicon and germanium. The recombination process in indium gallium phosphide and gallium arsenide materials create infared photons, the "light" in the light emitting transistor. This contributes to the device's ability to operate as both a laser and a transistor. The existence of a third port (the photon output) can interconnect optical and electric signals for display or communication purposes. Additionally, electrical and optical qualities are increased by the incorporation of quantum wells into the active region of the transistors. The transistor laser has a unique capability in signal processing and electronic-photonic integrated circuits.


  • Electronics
  • Optoelectronics
  • Displays


  • Speed: These transistors produce infared light in phase with their base current, allowing it to attain a switching speed superior to light emitting diodes (LEDs).
  • Controlled light emission: Light intensity can be controlled by varying the base current.
  • Simultaneous control of optical and electrical outputs: The addition of a third port allows greater control.
  • Utilizes base current: Once considered wasteful, the base current is used to create light.