Negative luminescence
Encyclopedia
Negative luminescence is a physical phenomenon by which an electronic device emits less thermal radiation
when an electric current
is passed through it than it does in thermal equilibrium
(current off). When viewed by a thermal camera, an operating negative luminescent device looks colder than its environment.
s. Incoming infrared
radiation is absorbed in the material by the creation of an electron–hole pair. An electric field
is used to remove the electrons and holes from the region before they have a chance to recombine and re-emit thermal radiation. This effect occurs most efficiently in regions of low charge carrier density.
Negative luminescence has also been observed in semiconductors in orthogonal electric and magnetic fields. In this case, the junction of a diode is not necessary and the effect can be observed in bulk material. A term that has been applied to this type of negative luminescence is galvanomagnetic luminescence.
Negative luminescence might appear to be a violation of Kirchhoff's law of thermal radiation
. This is not true, as the law only applies in thermal equilibrium
.
Another term that has been used to describe negative luminescent devices is "Emissivity
switch", as an electric current changes the effective emissivity.
(Ge) and indium arsenide (InAs) by workers in West Germany
, Ukraine
(Institute of Semiconductor Physics, Kiev
), Japan
(Chiba University
) and the USA. It was first observed in the mid-infrared (3-5 µm wavelength
) in the more convenient diode
structures in InSb heterostructure diodes by workers at the Defence Research Agency
, Great Malvern
, UK
(now QinetiQ
). These British workers later demonstrated LWIR band (8-12 µm) negative luminescence using mercury cadmium telluride diode
s.
Later the Naval Research Laboratory, Washington DC, started work on negative luminescence in mercury cadmium telluride (HgCdTe). The phenomenon has since been observed by several university groups around the world.
Thermal radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation....
when an electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
is passed through it than it does in thermal equilibrium
Thermal equilibrium
Thermal equilibrium is a theoretical physical concept, used especially in theoretical texts, that means that all temperatures of interest are unchanging in time and uniform in space...
(current off). When viewed by a thermal camera, an operating negative luminescent device looks colder than its environment.
Physics
Negative luminescence is most readily observed in semiconductorSemiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
s. Incoming infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
radiation is absorbed in the material by the creation of an electron–hole pair. An electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
is used to remove the electrons and holes from the region before they have a chance to recombine and re-emit thermal radiation. This effect occurs most efficiently in regions of low charge carrier density.
Negative luminescence has also been observed in semiconductors in orthogonal electric and magnetic fields. In this case, the junction of a diode is not necessary and the effect can be observed in bulk material. A term that has been applied to this type of negative luminescence is galvanomagnetic luminescence.
Negative luminescence might appear to be a violation of Kirchhoff's law of thermal radiation
Kirchhoff's law of thermal radiation
In thermodynamics, Kirchhoff's law of thermal radiation, or Kirchhoff's law for short, is a general statement equating emission and absorption in heated objects, proposed by Gustav Kirchhoff in 1859, following from general considerations of thermodynamic equilibrium and detailed balance.An object...
. This is not true, as the law only applies in thermal equilibrium
Thermal equilibrium
Thermal equilibrium is a theoretical physical concept, used especially in theoretical texts, that means that all temperatures of interest are unchanging in time and uniform in space...
.
Another term that has been used to describe negative luminescent devices is "Emissivity
Emissivity
The emissivity of a material is the relative ability of its surface to emit energy by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature...
switch", as an electric current changes the effective emissivity.
History
This effect was first seen by Russian physicists in the 1960s in A.F.Ioffe Physicotechnical Institute, Leningrad, Russia. Subsequently it was studied in semiconductors such as indium antimonide (InSb), germaniumGermanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....
(Ge) and indium arsenide (InAs) by workers in West Germany
West Germany
West Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
, Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
(Institute of Semiconductor Physics, Kiev
Kiev
Kiev or Kyiv is the capital and the largest city of Ukraine, located in the north central part of the country on the Dnieper River. The population as of the 2001 census was 2,611,300. However, higher numbers have been cited in the press....
), Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
(Chiba University
Chiba University
is a national university in the city of Chiba, Japan. It offers Doctoral degrees in education as part of a coalition with Tokyo Gakugei University, Saitama University, and Yokohama National University.-Faculties:*Letters*Education*Law and Economics*Science...
) and the USA. It was first observed in the mid-infrared (3-5 µm wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
) in the more convenient diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
structures in InSb heterostructure diodes by workers at the Defence Research Agency
Defence Research Agency
The Defence Research Agency , was an executive agency of the UK Ministry of Defence from April 1991 until April 1995. At the time the DRA was Britain's largest science and technology organisation...
, Great Malvern
Great Malvern
Great Malvern is an area of Malvern, Worcestershire, England. It is the historical centre of the town, and the location of the headquarters buildings of the of Malvern Town Council, the governing body of the Malvern civil parish, and Malvern Hills District council of the county of...
, UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
(now QinetiQ
QinetiQ
Qinetiq is a British global defence technology company, formed from the greater part of the former UK government agency, Defence Evaluation and Research Agency , when it was split up in June 2001...
). These British workers later demonstrated LWIR band (8-12 µm) negative luminescence using mercury cadmium telluride diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
s.
Later the Naval Research Laboratory, Washington DC, started work on negative luminescence in mercury cadmium telluride (HgCdTe). The phenomenon has since been observed by several university groups around the world.