CA2091053A1 - Miniband transport quantum well infrared detector - Google Patents
Miniband transport quantum well infrared detectorInfo
- Publication number
- CA2091053A1 CA2091053A1 CA002091053A CA2091053A CA2091053A1 CA 2091053 A1 CA2091053 A1 CA 2091053A1 CA 002091053 A CA002091053 A CA 002091053A CA 2091053 A CA2091053 A CA 2091053A CA 2091053 A1 CA2091053 A1 CA 2091053A1
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- Prior art keywords
- miniband
- layers
- semiconductor
- quantum wells
- transport
- Prior art date
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- 230000004888 barrier function Effects 0.000 claims abstract description 50
- 239000004065 semiconductor Substances 0.000 claims abstract description 46
- 239000000969 carrier Substances 0.000 claims abstract description 17
- 230000005281 excited state Effects 0.000 claims abstract description 17
- 230000005855 radiation Effects 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 13
- 230000005283 ground state Effects 0.000 claims abstract description 11
- 230000005684 electric field Effects 0.000 claims abstract description 7
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 claims description 12
- 238000010521 absorption reaction Methods 0.000 claims description 10
- 239000000758 substrate Substances 0.000 claims description 8
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 7
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 claims description 5
- 230000004044 response Effects 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 11
- 230000008569 process Effects 0.000 abstract description 2
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- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 3
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 238000003491 array Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 230000005641 tunneling Effects 0.000 description 2
- 241000272470 Circus Species 0.000 description 1
- 101100285518 Drosophila melanogaster how gene Proteins 0.000 description 1
- 101100156763 Schizosaccharomyces pombe (strain 972 / ATCC 24843) wos2 gene Proteins 0.000 description 1
- FTWRSWRBSVXQPI-UHFFFAOYSA-N alumanylidynearsane;gallanylidynearsane Chemical compound [As]#[Al].[As]#[Ga] FTWRSWRBSVXQPI-UHFFFAOYSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
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- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- VLCQZHSMCYCDJL-UHFFFAOYSA-N tribenuron methyl Chemical compound COC(=O)C1=CC=CC=C1S(=O)(=O)NC(=O)N(C)C1=NC(C)=NC(OC)=N1 VLCQZHSMCYCDJL-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
- H01L31/035236—Superlattices; Multiple quantum well structures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Microelectronics & Electronic Packaging (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Computer Hardware Design (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Nanotechnology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Biophysics (AREA)
- Optics & Photonics (AREA)
- Crystallography & Structural Chemistry (AREA)
- Light Receiving Elements (AREA)
Abstract
A semiconductor device for detecting radiation includes a plurality of doped quantum wells having at least two bound states which are surrounded by a plurality of superlattice barrier layers having a miniband with an average energy that is approximately equal to one of the bound states of the quantum wells. Carriers photoexcited from the ground state to the excited states of the doped quantum wells are swept into the miniband by an externally applied electric field for collection as photocurrent. As a result, a wide range of quantum well widths and barrier heights along with a variety of materials and carrier types may be used so that an easier process of fabricating the semiconductor device results while providing improved device characteristic such as lowering the dark current.
Description
2 ~
.. wos2to82so PCT/USs1/~8~0~
,. .
MINIBAND TRANSPORT QUANTUM WELL INFRARED DETECTOR
BACKGROUND OF THE INVE~TION
; The present invention is directed to a semiconductor infrared detector and a method of detecting thermai radiation and more particularly to a semiconductor infrared detector having a plurality of doped quantum wells separated by short period superlattice layers which form a miniband of energy states.
High performance de~ectors and detector arrays for detecting thermal radiation are u~ed in a wide variety Of military and commercial electro-optic system such as night visio~, military surveilance and navigation, the trackinq o missiles and aircraft and navigationa~ aids for commercial aircrafts.
Detectors in the medium wavelength infrared (MWIR) wavelength band (with wavelengths from 3 to 5 microns) have a number of detector materials that are . . available to be used. However, detectors in the long ., . . . . ~ . i . . . . .... .
,. wavelength infrared (LWIR) wavelength band (from . wavelengths of 8 to 12 microns) have only been able to be 20- fabricated with a narrow band gap semiconductor of mercury .. . . . . . ...
- cadmium telluride (MCT). Many problems with respect to ..the uniformity of optical and electrical properties and ; mechanical stability . are associated with ~CT. As a ~ ,result~ routine fabrication of ~WIR dPtec~or arrays is .. . . ... ., .. ~ .. , . . . . . . , . ,. . . . . : .
, ~;25. prevented. ,,~ , ~ ~
. .. Conventional quantum wéll infrared photo-. . , detectors ~QWIP~ dètect the presence of thermal ,. . ... ~ , .,, . ~ . .. - .. ,, .. , . . . - : ., .
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W092/08250 P~TIUS91/0800~ ~.
radiati~n by an internal photoemission of charged carriers from confined states in a quantum well which changes the electrical conductivity of the material ~or the QWIP
detectors. The materials used for the conventional QWIP
detectors are III-V compound semiconduct~rs such as gallium arsenide and aluminum gallium arsenide. Although processing technology suggests that III-V compound semiconductors may be used to fabricate detectors with very uniform detectivities, the performance oÇ such detectors are an order of magnitude of less than the performance of the MCT detectors in the ~WIR wavelength band.
One e~ample of a conventional QWIP detector is illustrated in ~igure 1. The QWIP detector of Fi~ure 1 includes a stack of quantum wells having widths and depths chosen to provide two confined states, the ground state and the e~cited state as illustrated in Figure la. The energy separation between the sround state and the e~cited state is equal to the energy of the photon to be detected. The quantum walls are doped with electron donor impurities which partially fill the lowest energy state with electrons. A barrier having a thickness o appro~imately one hundred angstroms (lOO ~) separates each of the quantum walls. When a bias is applied to the QWIP
~5 detector `as``illùstrated in Figure lb, electrons are ., i .. ~, . . ~.... . . ............. . . . ....... . .
photoe~cited i`nto the excited state and--tunnel through the barrier separating the guantum wells to bé -collected as a .~ photocurrent. However, dark current which fiows in the .absence of thermal radiation in~the` above described QWIP
detectors is unacceptàbly high~ due to` tunneling of electrons from the grou~d state through the thin barriers between ~he guantum wells.
. , : ., : , ., . : . , - . .. . ~ ~ .: .
.. ~ , . . : :
.: ' .. .. , : ' ' ~W092/08250 ~ L ~ ~ ~ PCT/~S91t~004 Another e~ample of a conventional QWIP detector is illustrated in Figure 2. In this QWIP detector , the widths of the quantum wells are chosen so that only one state is bound in the quantum well a~d the virtual ~xcited state is pushed slightly above the barrier into the continuum as illustrated in Figure 2a. In these QWIP
deteckors, the barriers between the quantum wells ~re made to be relatively large, appro~imately 500 A, which reduces the dark current while still allowing ~he ~arriers to be collected because photoe~citation pushes the carriers above the barrier 4Or allowing the carriers to be swept out by an applied electric field. However, in the above described QWIP dete~tors, there is only one bound state in the ~uantum well and the first e~cited state must be close in energy to the top of the barrier because the absorption strength drops rapidly as the escited ~tate moves higher a~ove the barrier which reduces the detectiviky. As a result o these requirements, the well width and barrier height are uniquely defined and therefore cannot be varied .: 20 to optimize detector performance. Additionally, the ~~f ective mass of the carriers must be low in order ~o : provide one bound staté in the guan~um well. As a result, i the dopants in the QWIP detector must be n~type (electron donors) ~ which further limi~s; the de~i~n ~arameters.
Furthermore, the- wavelength range ~in which the QWIP
detector is sensitive .is;primarily a material parameter - :; that is determined by the wavelength dependence of the :process ~ of :absorption from -~a-S discrete .state to the ~ ~- continuum,~ and the wavelen~th.range i can only be changed by - 30 varying the energy of.the excited state above the:~arrier ~ which grea~ly decreases the:absorption strength~
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,, ; ~ , , . . ~ , . '. ,,, ~
2 ~ 0 ~ 3 WO 92J08250 PCI'/US91~0800~ ¢' . .
SUM~!LARY OF THE INVENTION
One object of the present invention îs to provide an improved semiconductor deYice for detecting thermal radiation.
It i~ a further object of the present invention to provide a miniband transport quantum well infrared semiconductor detector having a predetermined bandwidth corresponding to the range of wavelengths to which the detector is sensitive that is determined by the ~hickness and comp~sition of the semiconductor layers of the detector.
Another objec~ of the present inv~ntion is to obtain an electrically tunable peak absorption and bandwidth in response to an electric field applied to the detector.
The objects of the present in~ention are fulfilled by providing a semiconductor miniband transport quantum well infrared detector comprising a substrat~, a - multilay~r structure: disposed on the substrate, and first ` 20 and second contact layers disposed on.the top and bottom surfaces of the multilayer structure. . The multilayer ~ : stru~ture includes a plurality of doped quan~um wells and ~ superlattice barrier.-layers disposed on each iside of the ;; quantum wells.- The superlattice,barrier lay~rs comprise a :- -' 2s-`plurality-`of -alternating..~irst and second lay~rs wherein : the ~irst -layers have a:relatively low,ba~d gap and the second layers jhave~-a relatively high .band gap. The : ~ sup~rlattice-barrier -layers form a miniband of energy istates :which~:transport~ photoe~cited carriers from the : - . 3~ quantum wells for collectio~ as photocurren~.
:; . .. . .
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,.-;,w092io8250 ~ f~$ ~ PCT/US91/OB004 The semiconduc~or detector of the present invPntion comprises quantum wells having two or more bound states so that a wide range of materials and carrier types may be used for the semiconductor layers. In one embodiment of the present in~ention, the semiconductor detector comprises a GaAs/AlGaAs quan~um well system. In further embodiments, a wide range of semiconductor materials for the detector may be used such as InGaAs/InAlAs (lattice-matched to InP substrates) or InGaAs/InAlGaAs strained layer systems ~or e~ample.
The present invention additionally pro~ides a method for detecting thermal radiation by a semiconductor device comprising the s~eps of providing a plurality of doped ~uan~um well layers, forming a miniband from a plurality of strongly ~oupled superlattice barrier layers disposed on each of the quantum well layers, photoe~citing carriers from the quantum wells to the miniband and applying an electric ield aCross the superlattice barrier layers and the quantum -well layers to transport the ? 20 ~ carriers through~: the .- miniband--.for collection as a photocurrent corresponding ~o the thermal radiation.
Ac~ording to the present invention, a semiconductor detector and a method is provided which : allows the quantum wells to be ormed with more than one bound:state and ~ wide variety of well widths and barrier heights. The superlattice barrier~layers redu~e the dark --current~ and the sensitivi~y to proces~ing ~ariations by - using wider quantum~wells. B~ allowing the quantum wells ~ ' -~to contain two or more1bound states, a larger range of mat0rials and ~carrier :1.types may be used for the dëtectors. Furthermore, the bandwidth of the detector may J
b`é-selected over-a wide range :b~:varying;the coupling of the layers in the superlattace barrier ,to provide a ,~ , , .
, , :~ , ,; : ~ : , 2 ~ ~t~ 3 W092~08250 PCT/US91/~800 broader or narrower miniba~d as desired which broadens or narrows the absorption range respectively while maintaining the absorption strength.
Further scope o~ applicability of the present invention will become apparent from the detailed description given herein after. However, it should be understood that the detailed description and specific e~amples, while indicating preferred embodiments of the : present invention, are given by way o~ illus~ration only, since various changes and modi~ications within the spirit and scope o the present invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE D~AWINGS
The present invention will become more fully understood from the detailed description given herein ~elow and the accompanying drawings which are given by way ? illustration.-;only:--and thus;are not limitative of the present i~vention, and wherein:
.
-' Figures la and lb illustrate the energy states of 20 -a conventional quantum well i~frared photodetector where ' ' ''' J'; no ~ias;is applied~to the detector.in Figur~ la and a bias 'is applied to:the-detector in Figure lb; ~.
r ~Figures 2a andr2b illustrate the~energy state~ of another~conventional- quantum well inrared photodetector ~ 25 :whére no bi~as is applied to the detector in Figure 2a and . a bias is applied.to;the detector in Fi~ure 2b;.
- -:- : ~ Figurer?~.;3 ~illustrates -the structure for the - --~miniband ~transport-.quantum well .in rared detector for an embodiment of ~he present invention; . .
- :, " , ,,,~, " . :: ..
, ; . , ~. -~q~ J~ ~ .
wos2~o~2so PcT/US91/OgO~q Figure 4 illustrates a miniband transport quantum well infrared detector for an embodiment of the present invention which utilizes the semiconductor structure of Figure 3;
Figures 5a and 5b illustrate the energy states for the miniband ~ransport detec~or ~or the present invention where no bias is applied in Figure 5a and a bias is applied in Figure 5b;
Figure 6 illustrates the wavelength dependence of photocurrent obtained from a miniband transport detector of the present invention; and Figure 7 illustrates the bias dependence of the detectivity of the mi~iband transport detector of the present inYention.
DET~ILED DESCRIPTION OF THE PREFERRED EM~ODI~ENTS
Figure 3 is first referred to and illustrates an embodiment of the structure for a miniband transport quantùm well infrared~d~tector (her2inafter referred to as MBT detector). The MBT detector is formed of a multilayer structure:~ 40 which has alternating quantum. wells lol, - 102, . . . 10n and superlattice barrier layers 201, 202,~ . . . 20n. A - capping layer 60 and a buried - contact 70 are disposed on each.end of thP multilayer -'- structure 4~. : The-^above described structure is formed on `25 a sùbstrate 30.
Figure 4 illustrates.:an-embo~iment .of the present `- invention ~which includes an array -of d~tector elements pi~els~. Each pisel is delineated.and.the buried.`contact is; exposed by etching::away the rmaterial surrounding the pixels. Each pîxel i~cludes a layer 80 having an optical diffraction grating etched into the capping layer 60 and a - . .. . . . . .
. :. .....
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: : . ~, , ~ ., . - . : ~ ; , , . .;
. . . .. .
2 ~ ~ G3 3 WO 92/082~0 PCr/US91/08004 ( metal contact deposited on the ~urface of the optical diffraction grating. Radiation is incident through the substrate 30 and is coupled into the detector layers by the optical diffraction grating.
The quantum wells o~ the MBT detector contain two or more bound states which include at least a ground state - and an ea:cited stat~. A miniband o energy states is formed by strongly coupling the superlattice layers of the structure. The superlattice barrier layers include a plurality of thin quantum wells ~eparated by thin harrier layers. These plurality of layers correspond to alternating low band gap layers and high band gap layers which are chosen so that the lowest energy miniband is in resonance with the e~cited state o~ the quantum wells.
An esample o~ this structure is illustrated in Figure ~a where the quantum well includes a ground state and an e~cited state which fall~ between the energy l~vels of the miniband 100. Fi~ure 5b illustrates the application of an electric field to the structure wherein .1the minibahd is tilted -and-breaks up into a series of - : quasi-discrete states (not shown in the figuses) ~ e~tending through several periods of the superlattice :. :layers. The quantum.wells-are doped so that the ground states are partially-filled with carriers. The carriers 25 n in:.the ground :states-o the quantum wells may thereby be ~ v~- e~cited::into~.the -ne~t,-higher energy -~state~(or a~y odd : order energy ~tate as dictated by ~selection rules for `optical ~ransition) by infrarea photons~ ~s a result, the carriers -are-~placed in~!the,miniband which allows the : 30~i:carrier~ to.:~move ~:through ; the barrier layers with J relatively~;~ease foricollection as photscurrent in the , 3 !; coIltact ' layerS'~
'' ' , ', ' "'' '' . ' '~:' ' ` .
~ ,WO92/082so P~T/US9~/08004 , ., The superlattice barrier layers may be made of a thickness so that the probability of carriers tu~neling directly from the ground sta~e into ~he ne~t quantum well or into the continuum is substantially zero e~cept when very hi~h biases are applied to the structure. In other words, the tunneling componen~s of the dark current is appro~imately zero. Also, the energy of the superlattice barrier layers may be chosen to be sufficiently large for limiting the thermionic emission o~ carriers into the continuum at the desired operating temperature of 77 Kelvin. The precise quantum well and superlattice barrier layer geometry is determined by solving ~he Schroedinger equatio~ ~or the system in order to obtain the desired wavelength pea~ and range in the responsitivity of the detector. The number of layers in the superlattice barrier layers are chosen based on the crystal growth time ~; or other similar considerations. The quantum well layers are doped so that the ground states are partially filled with carriers where the layers are usually doped with electron donors. ` ; ~
- , The energy a~d the spatial extents of the - ~ quasi-discrete states in the miniband are strong functions of the applied électric field. As a result, properties of . the MBT detector such as the peak absorption and the responsitivity bandwidth may be electrically-tuned. :
.. .. . . ... . . ..
One e~amplé of an MBT detector that was formed by molecular béam epitaxy includes forty GaAs quan~um wells, . which have a thickness of àpproximately 78 ~ and are doped ~ - -- -17 ;-~
w~th silicon to- a level of 4xl~ Ocm~, s~parated by . 30 ~uperlattice barrier layérs having -nine Ga~s wells, .. appro~mately 20 ~ thick, and ten AlGaAs barriers, .; . ajprosimatëiy 40 ~ thick.` Doped contact layers having a thicknéss of 1 ~ m were formed above and below the active : ~ :, ", .. ..
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Wo92/08250 2 ~ b ~ ~ Pcr/us9l/080O4 ~
quantum well regions. Detector elements having various areas were thereaf~er defined hy c~emical etching in order to form ohmic metalization areas. A conventional 4 ~ m pitch triangular grating is etched into the back of the wafer in order to collect light with a polarization component perpendicular to the quantum well layers.
The ~3T detector is not restricted to this specific Ga~s-AlGaAs quan~um well system. A wide varie~y of layers, layer thicknesses and materials may be used for the M~T detector. For e~ample, InGaAs/In~lAs (la~tice matched to InP substrates) or InGaAs~InAlGaAs strained layer systems may be used. The widths of the quantum wells and the thicknesses of the superlattice barrier layers may range from one monolayer to se~eral hundred Angstroms. The wavelength sensitivity is determined by material parameters such as the effecti~e mass, band offsets and the well depths. The strueture of the present invention allows the llse of p-type acceptor doping in the quantum wells. As a result, the higher effective mass of the p-type carriers reducss the dark curren~ of the device by reducing the Fermi level and the corresponding . ~ thermionic emission.
Figures 6 and 7 illustrate the improved .. characteristics of the ~BT detector of the present invention. . Figure 6 illustrates the wavelength depende~ce . ~ . . . , , , , . . ," ...
. . ~ of.the photocurrent which has a péak response of about .. . ~ . . . , .., . , ~; . .
- .. 10.5 ~ m and.a long wavelength cutoff (a half power point) .. of 11.1 ~ m. Figure 7 illustrates the bias~dependence of ; th~ peak detectivity at a temperature of 77 Kelvin which obtains a value of lxlOlOcm ~ /W.
- The embodiments of the present invention provide .. . ..
- an...infrared detector for .collecting photocurrent by - quantum wells having a wide range of depths and widths.
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,"
: , , ,, ,, : .
- - . .
r ~092/08250 ~ PCr/US91/08004 Because the MBT detectors allow materials having more than one bound state for the guantum wells to be used, the range of materials and carrier types are greater.
Furthermore, the bandwidth of the MBT detector may be selected o~er a wide range by strongly coupling the superlattice barriers layers to provide a broader miniband which increases the absorption range while maintaining the strength of absorption in th~ quasi-bound state.
Accordingly, an e~hanced semiconductor device and a method for detecting thermal radiation is provided i~ the present invention.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departufe from he lS spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the .-follo~ing claims~
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.. wos2to82so PCT/USs1/~8~0~
,. .
MINIBAND TRANSPORT QUANTUM WELL INFRARED DETECTOR
BACKGROUND OF THE INVE~TION
; The present invention is directed to a semiconductor infrared detector and a method of detecting thermai radiation and more particularly to a semiconductor infrared detector having a plurality of doped quantum wells separated by short period superlattice layers which form a miniband of energy states.
High performance de~ectors and detector arrays for detecting thermal radiation are u~ed in a wide variety Of military and commercial electro-optic system such as night visio~, military surveilance and navigation, the trackinq o missiles and aircraft and navigationa~ aids for commercial aircrafts.
Detectors in the medium wavelength infrared (MWIR) wavelength band (with wavelengths from 3 to 5 microns) have a number of detector materials that are . . available to be used. However, detectors in the long ., . . . . ~ . i . . . . .... .
,. wavelength infrared (LWIR) wavelength band (from . wavelengths of 8 to 12 microns) have only been able to be 20- fabricated with a narrow band gap semiconductor of mercury .. . . . . . ...
- cadmium telluride (MCT). Many problems with respect to ..the uniformity of optical and electrical properties and ; mechanical stability . are associated with ~CT. As a ~ ,result~ routine fabrication of ~WIR dPtec~or arrays is .. . . ... ., .. ~ .. , . . . . . . , . ,. . . . . : .
, ~;25. prevented. ,,~ , ~ ~
. .. Conventional quantum wéll infrared photo-. . , detectors ~QWIP~ dètect the presence of thermal ,. . ... ~ , .,, . ~ . .. - .. ,, .. , . . . - : ., .
' " ..... ' ~' ' " ' """ ' ''';, ' " ' ' ' '~ ' , ' ' ' " ' ' ' '' ' " '' '. ','''~. ' " ' ' '' ' ' ,' " "' ' , - 2~Q~
W092/08250 P~TIUS91/0800~ ~.
radiati~n by an internal photoemission of charged carriers from confined states in a quantum well which changes the electrical conductivity of the material ~or the QWIP
detectors. The materials used for the conventional QWIP
detectors are III-V compound semiconduct~rs such as gallium arsenide and aluminum gallium arsenide. Although processing technology suggests that III-V compound semiconductors may be used to fabricate detectors with very uniform detectivities, the performance oÇ such detectors are an order of magnitude of less than the performance of the MCT detectors in the ~WIR wavelength band.
One e~ample of a conventional QWIP detector is illustrated in ~igure 1. The QWIP detector of Fi~ure 1 includes a stack of quantum wells having widths and depths chosen to provide two confined states, the ground state and the e~cited state as illustrated in Figure la. The energy separation between the sround state and the e~cited state is equal to the energy of the photon to be detected. The quantum walls are doped with electron donor impurities which partially fill the lowest energy state with electrons. A barrier having a thickness o appro~imately one hundred angstroms (lOO ~) separates each of the quantum walls. When a bias is applied to the QWIP
~5 detector `as``illùstrated in Figure lb, electrons are ., i .. ~, . . ~.... . . ............. . . . ....... . .
photoe~cited i`nto the excited state and--tunnel through the barrier separating the guantum wells to bé -collected as a .~ photocurrent. However, dark current which fiows in the .absence of thermal radiation in~the` above described QWIP
detectors is unacceptàbly high~ due to` tunneling of electrons from the grou~d state through the thin barriers between ~he guantum wells.
. , : ., : , ., . : . , - . .. . ~ ~ .: .
.. ~ , . . : :
.: ' .. .. , : ' ' ~W092/08250 ~ L ~ ~ ~ PCT/~S91t~004 Another e~ample of a conventional QWIP detector is illustrated in Figure 2. In this QWIP detector , the widths of the quantum wells are chosen so that only one state is bound in the quantum well a~d the virtual ~xcited state is pushed slightly above the barrier into the continuum as illustrated in Figure 2a. In these QWIP
deteckors, the barriers between the quantum wells ~re made to be relatively large, appro~imately 500 A, which reduces the dark current while still allowing ~he ~arriers to be collected because photoe~citation pushes the carriers above the barrier 4Or allowing the carriers to be swept out by an applied electric field. However, in the above described QWIP dete~tors, there is only one bound state in the ~uantum well and the first e~cited state must be close in energy to the top of the barrier because the absorption strength drops rapidly as the escited ~tate moves higher a~ove the barrier which reduces the detectiviky. As a result o these requirements, the well width and barrier height are uniquely defined and therefore cannot be varied .: 20 to optimize detector performance. Additionally, the ~~f ective mass of the carriers must be low in order ~o : provide one bound staté in the guan~um well. As a result, i the dopants in the QWIP detector must be n~type (electron donors) ~ which further limi~s; the de~i~n ~arameters.
Furthermore, the- wavelength range ~in which the QWIP
detector is sensitive .is;primarily a material parameter - :; that is determined by the wavelength dependence of the :process ~ of :absorption from -~a-S discrete .state to the ~ ~- continuum,~ and the wavelen~th.range i can only be changed by - 30 varying the energy of.the excited state above the:~arrier ~ which grea~ly decreases the:absorption strength~
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2 ~ 0 ~ 3 WO 92J08250 PCI'/US91~0800~ ¢' . .
SUM~!LARY OF THE INVENTION
One object of the present invention îs to provide an improved semiconductor deYice for detecting thermal radiation.
It i~ a further object of the present invention to provide a miniband transport quantum well infrared semiconductor detector having a predetermined bandwidth corresponding to the range of wavelengths to which the detector is sensitive that is determined by the ~hickness and comp~sition of the semiconductor layers of the detector.
Another objec~ of the present inv~ntion is to obtain an electrically tunable peak absorption and bandwidth in response to an electric field applied to the detector.
The objects of the present in~ention are fulfilled by providing a semiconductor miniband transport quantum well infrared detector comprising a substrat~, a - multilay~r structure: disposed on the substrate, and first ` 20 and second contact layers disposed on.the top and bottom surfaces of the multilayer structure. . The multilayer ~ : stru~ture includes a plurality of doped quan~um wells and ~ superlattice barrier.-layers disposed on each iside of the ;; quantum wells.- The superlattice,barrier lay~rs comprise a :- -' 2s-`plurality-`of -alternating..~irst and second lay~rs wherein : the ~irst -layers have a:relatively low,ba~d gap and the second layers jhave~-a relatively high .band gap. The : ~ sup~rlattice-barrier -layers form a miniband of energy istates :which~:transport~ photoe~cited carriers from the : - . 3~ quantum wells for collectio~ as photocurren~.
:; . .. . .
, : ,: , :
: .: ' ' ' . ,:
,.-;,w092io8250 ~ f~$ ~ PCT/US91/OB004 The semiconduc~or detector of the present invPntion comprises quantum wells having two or more bound states so that a wide range of materials and carrier types may be used for the semiconductor layers. In one embodiment of the present in~ention, the semiconductor detector comprises a GaAs/AlGaAs quan~um well system. In further embodiments, a wide range of semiconductor materials for the detector may be used such as InGaAs/InAlAs (lattice-matched to InP substrates) or InGaAs/InAlGaAs strained layer systems ~or e~ample.
The present invention additionally pro~ides a method for detecting thermal radiation by a semiconductor device comprising the s~eps of providing a plurality of doped ~uan~um well layers, forming a miniband from a plurality of strongly ~oupled superlattice barrier layers disposed on each of the quantum well layers, photoe~citing carriers from the quantum wells to the miniband and applying an electric ield aCross the superlattice barrier layers and the quantum -well layers to transport the ? 20 ~ carriers through~: the .- miniband--.for collection as a photocurrent corresponding ~o the thermal radiation.
Ac~ording to the present invention, a semiconductor detector and a method is provided which : allows the quantum wells to be ormed with more than one bound:state and ~ wide variety of well widths and barrier heights. The superlattice barrier~layers redu~e the dark --current~ and the sensitivi~y to proces~ing ~ariations by - using wider quantum~wells. B~ allowing the quantum wells ~ ' -~to contain two or more1bound states, a larger range of mat0rials and ~carrier :1.types may be used for the dëtectors. Furthermore, the bandwidth of the detector may J
b`é-selected over-a wide range :b~:varying;the coupling of the layers in the superlattace barrier ,to provide a ,~ , , .
, , :~ , ,; : ~ : , 2 ~ ~t~ 3 W092~08250 PCT/US91/~800 broader or narrower miniba~d as desired which broadens or narrows the absorption range respectively while maintaining the absorption strength.
Further scope o~ applicability of the present invention will become apparent from the detailed description given herein after. However, it should be understood that the detailed description and specific e~amples, while indicating preferred embodiments of the : present invention, are given by way o~ illus~ration only, since various changes and modi~ications within the spirit and scope o the present invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE D~AWINGS
The present invention will become more fully understood from the detailed description given herein ~elow and the accompanying drawings which are given by way ? illustration.-;only:--and thus;are not limitative of the present i~vention, and wherein:
.
-' Figures la and lb illustrate the energy states of 20 -a conventional quantum well i~frared photodetector where ' ' ''' J'; no ~ias;is applied~to the detector.in Figur~ la and a bias 'is applied to:the-detector in Figure lb; ~.
r ~Figures 2a andr2b illustrate the~energy state~ of another~conventional- quantum well inrared photodetector ~ 25 :whére no bi~as is applied to the detector in Figure 2a and . a bias is applied.to;the detector in Fi~ure 2b;.
- -:- : ~ Figurer?~.;3 ~illustrates -the structure for the - --~miniband ~transport-.quantum well .in rared detector for an embodiment of ~he present invention; . .
- :, " , ,,,~, " . :: ..
, ; . , ~. -~q~ J~ ~ .
wos2~o~2so PcT/US91/OgO~q Figure 4 illustrates a miniband transport quantum well infrared detector for an embodiment of the present invention which utilizes the semiconductor structure of Figure 3;
Figures 5a and 5b illustrate the energy states for the miniband ~ransport detec~or ~or the present invention where no bias is applied in Figure 5a and a bias is applied in Figure 5b;
Figure 6 illustrates the wavelength dependence of photocurrent obtained from a miniband transport detector of the present invention; and Figure 7 illustrates the bias dependence of the detectivity of the mi~iband transport detector of the present inYention.
DET~ILED DESCRIPTION OF THE PREFERRED EM~ODI~ENTS
Figure 3 is first referred to and illustrates an embodiment of the structure for a miniband transport quantùm well infrared~d~tector (her2inafter referred to as MBT detector). The MBT detector is formed of a multilayer structure:~ 40 which has alternating quantum. wells lol, - 102, . . . 10n and superlattice barrier layers 201, 202,~ . . . 20n. A - capping layer 60 and a buried - contact 70 are disposed on each.end of thP multilayer -'- structure 4~. : The-^above described structure is formed on `25 a sùbstrate 30.
Figure 4 illustrates.:an-embo~iment .of the present `- invention ~which includes an array -of d~tector elements pi~els~. Each pisel is delineated.and.the buried.`contact is; exposed by etching::away the rmaterial surrounding the pixels. Each pîxel i~cludes a layer 80 having an optical diffraction grating etched into the capping layer 60 and a - . .. . . . . .
. :. .....
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. . . .. .
2 ~ ~ G3 3 WO 92/082~0 PCr/US91/08004 ( metal contact deposited on the ~urface of the optical diffraction grating. Radiation is incident through the substrate 30 and is coupled into the detector layers by the optical diffraction grating.
The quantum wells o~ the MBT detector contain two or more bound states which include at least a ground state - and an ea:cited stat~. A miniband o energy states is formed by strongly coupling the superlattice layers of the structure. The superlattice barrier layers include a plurality of thin quantum wells ~eparated by thin harrier layers. These plurality of layers correspond to alternating low band gap layers and high band gap layers which are chosen so that the lowest energy miniband is in resonance with the e~cited state o~ the quantum wells.
An esample o~ this structure is illustrated in Figure ~a where the quantum well includes a ground state and an e~cited state which fall~ between the energy l~vels of the miniband 100. Fi~ure 5b illustrates the application of an electric field to the structure wherein .1the minibahd is tilted -and-breaks up into a series of - : quasi-discrete states (not shown in the figuses) ~ e~tending through several periods of the superlattice :. :layers. The quantum.wells-are doped so that the ground states are partially-filled with carriers. The carriers 25 n in:.the ground :states-o the quantum wells may thereby be ~ v~- e~cited::into~.the -ne~t,-higher energy -~state~(or a~y odd : order energy ~tate as dictated by ~selection rules for `optical ~ransition) by infrarea photons~ ~s a result, the carriers -are-~placed in~!the,miniband which allows the : 30~i:carrier~ to.:~move ~:through ; the barrier layers with J relatively~;~ease foricollection as photscurrent in the , 3 !; coIltact ' layerS'~
'' ' , ', ' "'' '' . ' '~:' ' ` .
~ ,WO92/082so P~T/US9~/08004 , ., The superlattice barrier layers may be made of a thickness so that the probability of carriers tu~neling directly from the ground sta~e into ~he ne~t quantum well or into the continuum is substantially zero e~cept when very hi~h biases are applied to the structure. In other words, the tunneling componen~s of the dark current is appro~imately zero. Also, the energy of the superlattice barrier layers may be chosen to be sufficiently large for limiting the thermionic emission o~ carriers into the continuum at the desired operating temperature of 77 Kelvin. The precise quantum well and superlattice barrier layer geometry is determined by solving ~he Schroedinger equatio~ ~or the system in order to obtain the desired wavelength pea~ and range in the responsitivity of the detector. The number of layers in the superlattice barrier layers are chosen based on the crystal growth time ~; or other similar considerations. The quantum well layers are doped so that the ground states are partially filled with carriers where the layers are usually doped with electron donors. ` ; ~
- , The energy a~d the spatial extents of the - ~ quasi-discrete states in the miniband are strong functions of the applied électric field. As a result, properties of . the MBT detector such as the peak absorption and the responsitivity bandwidth may be electrically-tuned. :
.. .. . . ... . . ..
One e~amplé of an MBT detector that was formed by molecular béam epitaxy includes forty GaAs quan~um wells, . which have a thickness of àpproximately 78 ~ and are doped ~ - -- -17 ;-~
w~th silicon to- a level of 4xl~ Ocm~, s~parated by . 30 ~uperlattice barrier layérs having -nine Ga~s wells, .. appro~mately 20 ~ thick, and ten AlGaAs barriers, .; . ajprosimatëiy 40 ~ thick.` Doped contact layers having a thicknéss of 1 ~ m were formed above and below the active : ~ :, ", .. ..
: . . , . : . -.. .,; ~;
.. .,, ,.. ,. - . , ., .... , . . : .. ::: . . , : ;
Wo92/08250 2 ~ b ~ ~ Pcr/us9l/080O4 ~
quantum well regions. Detector elements having various areas were thereaf~er defined hy c~emical etching in order to form ohmic metalization areas. A conventional 4 ~ m pitch triangular grating is etched into the back of the wafer in order to collect light with a polarization component perpendicular to the quantum well layers.
The ~3T detector is not restricted to this specific Ga~s-AlGaAs quan~um well system. A wide varie~y of layers, layer thicknesses and materials may be used for the M~T detector. For e~ample, InGaAs/In~lAs (la~tice matched to InP substrates) or InGaAs~InAlGaAs strained layer systems may be used. The widths of the quantum wells and the thicknesses of the superlattice barrier layers may range from one monolayer to se~eral hundred Angstroms. The wavelength sensitivity is determined by material parameters such as the effecti~e mass, band offsets and the well depths. The strueture of the present invention allows the llse of p-type acceptor doping in the quantum wells. As a result, the higher effective mass of the p-type carriers reducss the dark curren~ of the device by reducing the Fermi level and the corresponding . ~ thermionic emission.
Figures 6 and 7 illustrate the improved .. characteristics of the ~BT detector of the present invention. . Figure 6 illustrates the wavelength depende~ce . ~ . . . , , , , . . ," ...
. . ~ of.the photocurrent which has a péak response of about .. . ~ . . . , .., . , ~; . .
- .. 10.5 ~ m and.a long wavelength cutoff (a half power point) .. of 11.1 ~ m. Figure 7 illustrates the bias~dependence of ; th~ peak detectivity at a temperature of 77 Kelvin which obtains a value of lxlOlOcm ~ /W.
- The embodiments of the present invention provide .. . ..
- an...infrared detector for .collecting photocurrent by - quantum wells having a wide range of depths and widths.
.
. ..
,"
: , , ,, ,, : .
- - . .
r ~092/08250 ~ PCr/US91/08004 Because the MBT detectors allow materials having more than one bound state for the guantum wells to be used, the range of materials and carrier types are greater.
Furthermore, the bandwidth of the MBT detector may be selected o~er a wide range by strongly coupling the superlattice barriers layers to provide a broader miniband which increases the absorption range while maintaining the strength of absorption in th~ quasi-bound state.
Accordingly, an e~hanced semiconductor device and a method for detecting thermal radiation is provided i~ the present invention.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departufe from he lS spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the .-follo~ing claims~
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, '
Claims (32)
1. A semiconductor miniband-transport quantum well infrared detector, comprising:
a substrate;
a multilayered structure disposed on said substrate including a plurality of doped quantum wells comprising ground states and excited states at varying levels, and a plurality of superlattice barrier layers disposed on each of said quantum wells, said plurality of superlattice barrier layers forming a miniband having an average energy which is continuous for each miniband formed throughout the detector and bounds each of said excited states at the varying levels in said plurality of doped quantum wells; and first and second contact layers disposed on the top and bottom surfaces respectively of said multilayered structure.
a substrate;
a multilayered structure disposed on said substrate including a plurality of doped quantum wells comprising ground states and excited states at varying levels, and a plurality of superlattice barrier layers disposed on each of said quantum wells, said plurality of superlattice barrier layers forming a miniband having an average energy which is continuous for each miniband formed throughout the detector and bounds each of said excited states at the varying levels in said plurality of doped quantum wells; and first and second contact layers disposed on the top and bottom surfaces respectively of said multilayered structure.
2. A semiconductor miniband-transport quantum well infrared detector according to claim 1, wherein the width of said miniband comprises a range between 50 meV and 70 meV.
3. A semiconductor miniband-transport quantum well infrared detector according to claim 1, wherein the varying levels of said excited states form a predetermined pattern.
4. A semiconductor miniband-transport quantum well infrared detector according to claim 3, wherein said predetermined pattern of the varying levels of said excited states comprises a first level corresponding to a low level of said miniband, a second level corresponding to a middle level of said miniband, and a third level corresponding to a high level of said miniband.
5. A semiconductor miniband-transport quantum well infrared detector according to claim 1, wherein said quantum wells comprise a plurality of first band gaps.
6. A semiconductor miniband transport quantum well infrared detector according to claim 5, wherein said superlattice barrier layers comprise a plurality of alternating first and second layers, said first layer corresponding to said plurality of first band gaps and said second layers corresponding to a plurality of second band gaps greater than said first band gaps.
7. A semiconductor miniband-transport quantum well infrared detector according to claim 6, wherein said quantum wells comprise GaAs.
8. A semiconductor miniband-transport detector according to claim 7, wherein said first layers of said superlattice barrier layers comprise GaAs and said second layers of said superlattice barrier layers comprise AlGaAs.
9. A semiconductor miniband-transport detector according to claim 6, wherein said quantum wells comprise InGaAs.
10. A semiconductor miniband-transport detector according to claim 9, wherein said first layers of said superlattice barrier layers comprise InGaAs and said second layers of said superlattice barrier layers comprise InAlAs.
11. A semiconductor miniband-transport detector according to claim 6, wherein said quantum wells comprise InGaAs.
12. A semiconductor miniband-transport detector according to claim 11, wherein said first layers of said superlattice barrier layers comprise InGaAs and said second layers of said superlattice barrier layers comprise InAlGaAs.
13. A semiconductor miniband-transport detector according to claim 1, further comprising means for applying an electric field between said first and second contact layers to develop a series of quasi-discrete states in said superlattice layers.
14. A semiconductor structure for a miniband transport quantum well infrared detector, comprising:
a substrate; and a mutilayered structure disposed on said substrate, said multilayered structure including, a first plurality of doped quantum wells comprising ground states and excited states at varying levels, and a first plurality of superlattice barrier layers disposed of each of said quantum wells, said plurality of superlattice barrier layers forming a miniband having an average energy which is continuous for each miniband formed throughout the detector and bounds each of said excited states at the varying levels in said plurality of said doped quantum wells.
a substrate; and a mutilayered structure disposed on said substrate, said multilayered structure including, a first plurality of doped quantum wells comprising ground states and excited states at varying levels, and a first plurality of superlattice barrier layers disposed of each of said quantum wells, said plurality of superlattice barrier layers forming a miniband having an average energy which is continuous for each miniband formed throughout the detector and bounds each of said excited states at the varying levels in said plurality of said doped quantum wells.
15. A semiconductor structure according to claim 14, wherein said quantum wells comprise a plurality of first band gaps.
16. A semiconductor structure according to claim 15, wherein said superlattice barrier layers comprise a plurality of alternating first and second layers, said first layers corresponding to said plurality of first band gaps and said second layers corresponding to a plurality of second band gaps greater than said first band gaps.
17. A semiconductor structure according to claim 15, wherein said quantum wells comprise GaAs.
18. A semiconductor structure according to claim 17, wherein said first layers of said superlattice barrier layers comprise GaAs and said second layers of said superlattice barrier layers comprise AlGaAs.
19. A semiconductor structure according to claim 16, wherein said quantum wells comprise InGaAs.
20. A semiconductor structure according to claim 19, wherein said first layers of said superlattice barrier layers comprise InGaAs and said second layers of said superlattice barrier layers comprise InAlAs.
21. A semiconductor structure according to claim 16, wherein said quantum wells comprise InGaAs.
22. A semiconductor structure according to claim 21, wherein said first layers of said superlattice barrier layers comprise InGaAs and said second layers of said superlattice barrier layers comprise InAlGaAs.
23. A semiconductor miniband-transport quantum well infrared detector according to claim 14, wherein the width of said miniband comprises a range between 50 meV and 70 meV.
24. A semiconductor miniband-transport quantum well infrared detector according to claim 14, wherein the varying levels of said excited states form a predetermined pattern.
25. A semiconductor miniband-transport quantum well infrared detector according to claim 24, wherein said predetermined pattern of the varying levels of said excited states comprises a first level corresponding to a low level of said miniband, a second level corresponding to a middle level of said miniband, and a third level corresponding to a high level of said miniband.
26. A method for detecting thermal radiation by a semiconductor device, comprising the step of:
providing a plurality of doped quantum wells comprising ground states and excited states at varying levels;
forming a miniband having an average energy which is continuous for each miniband formed throughout the device and bounds each of said excited states at varying levels in said plurality of doped quantum wells from a plurality of strongly coupled superlattice barrier layers disposed on each of said quantum wells;
photoexciting carriers from said ground states of said quantum wells to said excited states within said miniband; and applying an electric field across said superlattice barrier layers and said quantum wells to transport the carriers through said miniband to be collected as a photocurrent corresponding to the detection of the thermal radiation.
providing a plurality of doped quantum wells comprising ground states and excited states at varying levels;
forming a miniband having an average energy which is continuous for each miniband formed throughout the device and bounds each of said excited states at varying levels in said plurality of doped quantum wells from a plurality of strongly coupled superlattice barrier layers disposed on each of said quantum wells;
photoexciting carriers from said ground states of said quantum wells to said excited states within said miniband; and applying an electric field across said superlattice barrier layers and said quantum wells to transport the carriers through said miniband to be collected as a photocurrent corresponding to the detection of the thermal radiation.
27. A method according to claim 26, further comprising the step of selecting a predetermined energy difference between said ground states and said one excited state of said quantum wells corresponding to a desired peak wavelength response for detecting the thermal radiation.
28. A method according to claim 26, further comprising the step of selecting thickness and composition parameters of said superlattice barrier layers to obtain a desired bandwidth for detecting the thermal radiation.
29. A method according to claim 28, further comprising the step of tuning the peak absorption and the bandwidth of the thermal radiation in response to varying said electric field.
30. A method for detecting thermal radiation by a semiconductor device according to claim 26, wherein said miniband is formed to a width of a range between 50 meV and 70 meV.
31. A method for detecting thermal radiation by a semiconductor device according to claim 26, wherein the varying levels of said excited states in said quantum wells form a predetermined pattern.
32. A method for detecting thermal radiation by a semiconductor device according to claim 31, wherein said predetermined pattern formed of the varying levels of said excited states comprises a first level corresponding to a low level of said miniband, a second level corresponding to a middle level of said miniband, and a third level corresponding to a high level of said miniband.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US60628590A | 1990-10-31 | 1990-10-31 | |
| US606,285 | 1990-10-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2091053A1 true CA2091053A1 (en) | 1992-05-01 |
Family
ID=24427344
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002091053A Abandoned CA2091053A1 (en) | 1990-10-31 | 1991-10-24 | Miniband transport quantum well infrared detector |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0555402A1 (en) |
| JP (1) | JPH06502743A (en) |
| AU (1) | AU9030791A (en) |
| CA (1) | CA2091053A1 (en) |
| IL (1) | IL99855A0 (en) |
| WO (1) | WO1992008250A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IL106130A (en) * | 1992-06-30 | 1996-10-19 | Martin Marietta Corp | Semiconductor miniband transport quantum well detector and a method for detecting electromagnetic radiation |
| US5477060A (en) * | 1993-06-25 | 1995-12-19 | The United States Of America As Represented By The Secretary Of The Army | Infrared hot electron transistor with a superlattice base |
| FR2729789B1 (en) * | 1993-09-10 | 1998-03-20 | Thomson Csf | QUANTUM WELL DETECTOR AND METHOD FOR PRODUCING THE SAME |
| GB2298735A (en) * | 1995-03-08 | 1996-09-11 | Sharp Kk | Semiconductor device having a miniband |
| US5539206A (en) * | 1995-04-20 | 1996-07-23 | Loral Vought Systems Corporation | Enhanced quantum well infrared photodetector |
| SG68636A1 (en) * | 1997-09-27 | 1999-11-16 | Univ Singapore | Dual band infrared detector using step multiquantum wells with superlattice barriers |
| US6054718A (en) * | 1998-03-31 | 2000-04-25 | Lockheed Martin Corporation | Quantum well infrared photocathode having negative electron affinity surface |
| JP5282361B2 (en) * | 2007-02-19 | 2013-09-04 | 富士通株式会社 | Quantum well type photodetector and manufacturing method thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0821748B2 (en) * | 1985-09-04 | 1996-03-04 | 株式会社日立製作所 | Semiconductor laser device |
| US4894526A (en) * | 1987-01-15 | 1990-01-16 | American Telephone And Telegraph Company, At&T Bell Laboratories | Infrared-radiation detector device |
| US5047822A (en) * | 1988-03-24 | 1991-09-10 | Martin Marietta Corporation | Electro-optic quantum well device |
| CA1314614C (en) * | 1988-06-06 | 1993-03-16 | Clyde George Bethea | Quantum-well radiation detector |
| DE69023932D1 (en) * | 1989-01-31 | 1996-01-18 | Ibm | Photodetector with resonant tunnel effect for use at long wavelengths. |
-
1991
- 1991-10-24 CA CA002091053A patent/CA2091053A1/en not_active Abandoned
- 1991-10-24 EP EP92902033A patent/EP0555402A1/en not_active Withdrawn
- 1991-10-24 AU AU90307/91A patent/AU9030791A/en not_active Abandoned
- 1991-10-24 JP JP4500854A patent/JPH06502743A/en active Pending
- 1991-10-24 WO PCT/US1991/008004 patent/WO1992008250A1/en not_active Application Discontinuation
- 1991-10-25 IL IL99855A patent/IL99855A0/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| WO1992008250A1 (en) | 1992-05-14 |
| AU9030791A (en) | 1992-05-26 |
| IL99855A0 (en) | 1992-08-18 |
| EP0555402A1 (en) | 1993-08-18 |
| JPH06502743A (en) | 1994-03-24 |
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