From Transistors to Lasers and Light-Emitting Diodes
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From Transistors to Lasers and LightEmitting Diodes Nick Holonyak Jr. Abstract This article is based on the 2004 Von Hippel Award address by Nick Holonyak Jr. (University of Illinois at Urbana-Champaign). Holonyak received the award for “his many contributions to research and development in the field of semiconductors, not least for the first development of semiconductor lasers in the useful visible portion of the optical spectrum.” The talk was presented on Holonyak’s behalf by Russell Dupuis on December 1, 2004, at the Materials Research Society Fall Meeting in Boston. With the discovery of the transistor by Bardeen and Brattain in 1947, and as a consequence of carrier injection and collection, the hole indeed became equal to the electron. The semiconductor took on new importance, as did the study of electron–hole recombination, first in the transistor materials Ge and Si, and then in III–V crystals (e.g., GaAs and GaP). Beyond Si and its indirect-gap and heterojunction limitations, the directgap III–V materials, particularly III–V alloys, made possible lasers and light-emitting diodes (LEDs)—and thus optoelectronics. The direct-gap III–V alloy LED after four decades of development exceeds in performance the incandescent lamp (as well as other forms of lamps) in much of the visible range. Beyond growing display applications, it has put conventional lighting under longrange threat with a semiconductor lamp—an “ultimate lamp” that promises unusual performance and energy savings. In principle, the LED or laser, basically a p–n junction, is an ultimate lamp that cannot be exceeded. Keywords: lasers, LEDs, light-emitting diodes, semiconductor lamps.
Introduction Following John Bardeen (Figure 1) and Walter Brattain’s 1947 discovery of the transistor1,2 and their identification of carrier injection,3–5 making the hole (positive, p) equal in performance to the electron (negative, n), the semiconductor took on new importance. With the transistor—a new idea, a new principle, a new device, a new name—a new electronics emerged that could not be based on or matched by the capabilities of the vacuum tube, even if we could or would be willing to cover the earth with tubes. With the emerging dominance of the semiconductor, the study of electron–hole recombination also attracted intense interest, first in the transistor materials Ge and Si, and then in III–V crystals (e.g., GaAs and GaP). Beyond Si and its indirect-gap and heterojunction limitations, the directgap III–V materials, particularly III–V alloys,
MRS BULLETIN • VOLUME 30 • JULY 2005
made possible lasers and light-emitting diodes (LEDs)—and thus optoelectronics. The first practical visible-spectrum LED, not to mention the first III–V alloy device (a first laser), began in the early 1960s with the direct-gap III–V alloy GaAs1–xPx, which is also the beginning of III–V epitaxy. Of special importance, GaAs1–xPx established the viability of III–V alloys and, with its energy-gap and wavelength “tunability,” set the direction for the construction of heterojunctions. The pr
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