CA2232084C - Semiconductor heterostructure radiation detector having two spectral sensitivity ranges - Google Patents
Semiconductor heterostructure radiation detector having two spectral sensitivity ranges Download PDFInfo
- Publication number
- CA2232084C CA2232084C CA002232084A CA2232084A CA2232084C CA 2232084 C CA2232084 C CA 2232084C CA 002232084 A CA002232084 A CA 002232084A CA 2232084 A CA2232084 A CA 2232084A CA 2232084 C CA2232084 C CA 2232084C
- Authority
- CA
- Canada
- Prior art keywords
- semiconductor
- photodiode
- radiation detector
- quantum well
- detector according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000004065 semiconductor Substances 0.000 title claims abstract description 80
- 230000005855 radiation Effects 0.000 title claims abstract description 50
- 230000003595 spectral effect Effects 0.000 title claims abstract description 38
- 230000035945 sensitivity Effects 0.000 title claims description 33
- 239000002800 charge carrier Substances 0.000 claims abstract description 12
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 18
- 239000000758 substrate Substances 0.000 claims description 17
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 9
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 claims description 7
- 229910005542 GaSb Inorganic materials 0.000 claims description 5
- 229910000673 Indium arsenide Inorganic materials 0.000 claims description 4
- 230000004044 response Effects 0.000 claims description 4
- RPQDHPTXJYYUPQ-UHFFFAOYSA-N indium arsenide Chemical compound [In]#[As] RPQDHPTXJYYUPQ-UHFFFAOYSA-N 0.000 claims description 3
- 230000010748 Photoabsorption Effects 0.000 claims 1
- 238000010586 diagram Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 4
- 230000005684 electric field Effects 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000001143 conditioned effect Effects 0.000 description 2
- 230000005284 excitation Effects 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000001451 molecular beam epitaxy Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- NYPYHUZRZVSYKL-UHFFFAOYSA-N 2-azaniumyl-3-(4-hydroxy-3,5-diiodophenyl)propanoate Chemical compound OC(=O)C(N)CC1=CC(I)=C(O)C(I)=C1 NYPYHUZRZVSYKL-UHFFFAOYSA-N 0.000 description 1
- NJXWZWXCHBNOOG-UHFFFAOYSA-N 3,3-diphenylpropyl(1-phenylethyl)azanium;chloride Chemical compound [Cl-].C=1C=CC=CC=1C(C)[NH2+]CCC(C=1C=CC=CC=1)C1=CC=CC=C1 NJXWZWXCHBNOOG-UHFFFAOYSA-N 0.000 description 1
- 241000282326 Felis catus Species 0.000 description 1
- 229910000661 Mercury cadmium telluride Inorganic materials 0.000 description 1
- 206010034972 Photosensitivity reaction Diseases 0.000 description 1
- JLQUFIHWVLZVTJ-UHFFFAOYSA-N carbosulfan Chemical compound CCCCN(CCCC)SN(C)C(=O)OC1=CC=CC2=C1OC(C)(C)C2 JLQUFIHWVLZVTJ-UHFFFAOYSA-N 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000036211 photosensitivity Effects 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000001931 thermography Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- 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
- H01L31/08—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
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
- H01L31/105—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PIN type
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Light Receiving Elements (AREA)
Abstract
Disclosed is a semiconductor heterostructure radiation detector leaving two adjacent semiconductor layer regions sensitive in different spectral ranges, in which regions photons having different energies respectively can be absorbed, which photons optically excite charge carriers present in the semiconductor layer regions in such a manner that a photo current can be generated in the respective semiconductor layer regions in dependence on an external electric voltage applied via electrodes provided at the semiconductor heterostructure.
The present invention is distinguished by the fact that the one semiconductor region is a photodiode and the other a quantum well intersubband photodetector.
The present invention is distinguished by the fact that the one semiconductor region is a photodiode and the other a quantum well intersubband photodetector.
Description
i Semicandu;tor Heterostructure Radiation Detector Having Two Spectral Sensitivity Ranqes ~ s c r i p t i o n Technical Field The prese~a invention relates to a semiconductor heterostrl:cture radiation detector having two spectral sensitivi'~y ranges. They two spectral sensitivity ranges result from adjacent semiconductor layer regions in which photons h~.ving differer.~t energies respectively can be absorbed. The photons optically excite charge carriers present i5~ the semiconductor layer regions in such a manner that a phc.to current can be generated in dependence on an external electric voltage applied via electrodes provided at the semicc.nductor layer structure.
State of the Art In the field of semiconductor radiation detectors, photodiod~s are known with conventional p-i-n junctions as well as so-called.quant:um well intersubband photodetectors (QWIP), w=pose spectral sensitivity properties can be set according to the selection of material layer systems, layer thickness parameters a:~ well as the selection of n-doping or p-doping. Conventional photodiodes possess spectral sensitivity in the vis:Lble to the near-infrared spectral range. Defending on ths~ selection of material, they can also detect. wa~:-elengths in t:he ~m range. The so-called quantum well i.nte~-subband photodetectors actually have spectral sensit.ivir.y ranges in i~he long wave spectral range, preferably in the range. between the 3 and 20 ~ln range, which can be see by means of the choice of material and layer thickness parameters.
In addition to performance enhancement and optimization of indivi.dua~ radiation detectors, combinations of radiation detectors with which e:Lectromagnetic radiation of different wavelengtYa can be detected are being examined. Known are so-called two=color dei~ectors, which by way of illustration are emplo~~ed in thermoc~raphy and for the optical discri.min~.tion of certain ob jects within the field detected by the rac:iation deteci;or.
The artic_.e by A. Kock et al.:" Double Wavelength Selective GaAs/AlGa~.s Infrared DE~tector Device" , Appl . Phys . Lett .
60, 2011 11992) proposE~s combining two QWIP semiconductor structure: having diffE~rent detection wavelengths. The 2-step QWIP system introduced in this article comprises alternatir:g sequences of GaAs/AlGaAs layers respectively.
Quantum will structures differing in the dimensions of the barrier hE:ight respectpvely the band gap as well as well-width res;~ectively layer thickness characteristic of the quantum wEll structure are employed for setting different spectral ~~ensitivity. ~'he QWIP structures conditioned for detecting different wavelengths, however, are separated by an add.itir;nal doped contact layer. Although the physical separa.tio_-°. attained by this means has the advantage that both ~!WIP structures can be separately optimized to their respective operating wavelength, this arrangement has the drawback ,:hat, due to t:he separation at least one additional electrode is required f:or voltage supply.
Therefore, for rationalization purposes, an attempt has been made to o~:,erate the detector structure described in the aforem.ent~oned publications with a not connected, additional electrode (see the paper by K.L. Tsai et al. " Two-Color Infrared Phototodector Using GaAs/AlGaAs and Strained InGaAs/AlC=aAs Multiquantum Wells" , Appl. Phys. Letter 62, 3704, (19~~3)). Operation of detector structures of this type has revea_.ed that the relative sensitivity can be tuned with regard to the two oper~~ting wavelengths by applying suited electrica_ voltage. However, there is the disadvantage that the indiv__dual in-series-connected detectors influence each other electrically. Defending on the application of external voltage, the photosensitivity of one of the two combined detectors,can be raised, with the sensitivity of the other detector being lowered. The overall noise behavior of this detector combination is. also determined by the respective detector c:lement~not participating in photodetection.
Consequen;:ly the signa l-to-noise ratio of this detection structure is relatively poor.
Further~rno::e a two-color detector based on a single QWIP
structure having two possible intersubband junctions with wavelengths of 5~m and 10~m is known from a paper by K.
Kheng cat ~~.1. :" Two-colon GaAs/ (AlGa)As Quantum Well Infrared Detector with Voltage-Tunable Spectral Sensitivity at 3-5 and 8-12~:,:'' , Appl . Phys . Letter 61 , 666 ( 1992 ) . The selection of operating wavelengths is made possible by the fact that the Sum junction demonstrates photovoltaic and the l0~un junction photocond.uctive behavior. In this case as well, the principal disadvantage is that the noise behavior is also determined at short operating wavelengths by the noise associated with long wave detection.
Finally, electrically tunable two-color detectors formed by combining two back-to-back p-i-n photodiodes are known (see the paper by M.P. Reine et al.:" Independently Accessed Back-To-B~.ck HgCdTe Photodiodes: A New Dual-Band Infrared Detect.or'' , J. Electronic Mater. 24, 669 (1995).
Descri.pti~~n of the Inve=ntion The object. of the presE~nt invention is to improve in such a manner a ~-emiconductor heterostructure radiation detector having two; adjacent semiconductor layer regions sensitive in different spectral ranges, in which regions photons having different energies respectively can be absorbed, which photons oiaically excite the charge carriers present in the semicondur:tor layer regions in such a manner that a photo current ir. the respective semiconductor layer region can be generated in dependence on an external electric voltage applic=d v~.a electrodes provided at the semiconductor heterostrl:cture, that the spectral sensitivity ranges of both ;semi~_:onductor layer structures can be set separately without l~;stingly influencing the overall noise behavior of the two-cc_:lor detector. In particular, the noise behavior of the two-color detector should be dominated by the noise of the resper:tively active individual detector. Moreover, the spectral :sensitivity ranges of both semiconductor layer detectors are..~o be set: largely independent of each other and ca.n be optimized. The solution to the object on which the preseia invention is based is set forth in claim 1.
Other adv~.ntageous prei:erred embodiments of the inventive idea a.re :et forth in claims 2ff.
The present invention is based on understanding to design a semiconductor heterostructure radiation detector according to the ge:_eric part of claim 1 in such a manner that the two adjacent ~:emiconductor layer regions differing in their spectral :sensitivity ranges are provided by a combination of a photodic:de and a quantum well intersubband photodetector.
By com;bin:_ng a photodiode with a QWIP structure according to the preser_t invention, contrary to the hitherto attempts at realizing electrically tunable two-color detectors, the noise behe.vior of the invented two-color detector can be determ.inec~ by the noise of the respectively active individuals. detector.
Preferabl«, the individual detectors of different construction are appliE~d onto a base substrate in such a manner th~.a the layer :>equence of a p-i-n photodiode is precip~itaa.ed by means of epitaxial precipitation processes, preferabl~.~ molecular beam epitaxy, on top of which the layer sequence c.f a quantum well intersubband photodetector is applied i~_ immediate succession. Moreover, at least two electrodes are provided, of which one is contacted with the photodiode: contact layer opposite the QWIP structure and the other electrode with tree top covering layer of the QWIP
structure.
Upon appl:.cation of an external electric voltage to the electrode:.< in such a manner that the p-i-n photodiode is operated -n forward direction, the spectral sensitivity of the invented two-color detector is determined by the semiconductor layer region of the QWIP structure. The reason for this ._s that the photodiode, which is operated in forward d~.rection possE~sses a negligible differential intrinsic resistance. Consequently, it does not lastingly influence the sensitivity of the active QWIP structure.
On the other hand, if the external voltage is applied in such a manner that the photodiode is located in the block direction the sensitivity of the entire two-color detector is solely determined by the photodiode. The reason for this is that the photodiode possesses a high dark resistance compared to which the differential intrinsic resistance of the QWIP structure can be ignored.
In accordance with one aspect of the present invention there is provided a semiconductor heterostructure radiation detector having first and second adjacent semiconductor layer regions which absorb photons having different energies respectively and which are sensitive in different spectral ranges, absorbed photons optically exciting charge carriers present in said semiconductor layer regions in such a manner that a photo current can be generated in said respective semiconductor layer regions in response to an external electric voltage applied via electrodes provided at the semiconductor heterostructure, wherein said first semiconductor layer region is a photodiode; and said second semiconductor layer region is a quantum well intersubband photodetector.
In accordance with another aspect of the present invention there is provided a semiconductor heterostructure radiation detector in which absorbed photons optically excite charge carriers present therein whereby a photo current can be generated in response to an externally applied voltage, said radiation detector comprising: a first semiconductor layer region which absorbs photons having a first energy level and is sensitive in a first spectral range; a second semiconductor layer region which is adjacent said first semiconductor region, and which absorbs photons having a second energy level different from said first energy level, and is sensitive to a second spectral range different from said first spectral range;
and electrodes for applying voltage to said semiconductor heterostructure; wherein said first semiconductor layer region comprises a photodiode layer structure; and said second semiconductor layer region comprises a quantum well intersubband photodetector layer structure.
In accordance with yet another aspect of the present invention there is provided a semiconductor heterostructure radiation detector, comprising: a first semiconductor layer region forming a photodiode; a second semiconductor layer region forming a quantum well intersubband photodetector in series electrical contact with said first semiconductor layer region; and electrodes for applying a bias voltage across said first and second semiconductor layer regions.
Brief Description of the Drawings The present invention is made more apparent, by way of example, in the following using preferred embodiments with reference to the drawings, depicting in:
FIG. 1 is a schematic depiction of the layer structure of a radiation detector according to the invention;
FIGS. 2(a) and (b) are band diagrams which depict two different states of operation of the two-color detector according to the invention; and FIG. 3 shows the variation of the detector sensitivity as a function of the applied external voltage.
Description of the Preferred Embodiments In FIG. l, a layer sequence of a p-i-n photodiode 1 is deposited on a substrate layer 2 with the layer sequence FIG. 3 shows the variation of the detector sensitivity as a function of the applied external voltage.
Description of the Preferred Embodiments In FIG. 1, a layer sequence of a p-i-n photodiode 1 is deposited on a substrate layer 2 with the layer sequence of an intersubband photodetector 3 applied immediately on top of the p-i-n photodiode structure. A p-doped GaAs layer (la), which serves as the p-region of the p-i-n photodiode, is applied to a base substrate layer (2) composed of GaAs. Moreover, all further layer sequences are applied on top of each other with the aid of molecular beam epitaxy. The intrinsic (i) region (1b) characteristic for a photodiode possesses a multiplicity of thin, alternating InGaAs layers in succession with GaAs layers.
An n-doped GaAs layer (lc), which is precipitated onto the so-called pared multiquantum well structure in the i-region, provides the n-region of the p-i-n photodiode. A
quantum well intersubband structure (3) having the layer sequence AlGaAs (3a) and GaAs (3b) is applied immediately on top of the n-layer, and an n-doped GaAs layer is employed as the final covering layer of the quantum intersubband structure.
The invented combination of a photodiode and a QWIP
structure is provided, according to the preferred embodiment of FIG. 1 as described there, with the electrodes E1, E2 and E3. Electrode E2, which preferably is applied to the n-region of the photodiode, is executed as a floating electrode.
FIG. 2 shows in details a and b, the band diagrams respectively of an advantageous preferred embodiment of the invented two-color detector. The parallel continuous lines represent the valance band (VB) and the conduction band (CB), respectively. The layers with smaller band gaps 20 in the p-i-n photodiode structure correspond to the InGaAs layer regions, whereas the layer regions with larger band gaps contain GaAs. The i-layer designed in this manner serves, in particular, to expand the sensitivity range to wavelengths for which the GaAs substrate is transparent. Regions with a larger band gap 21 in the QWIP structure correspond to the AlGaAs layer (5), whereas the regions with smaller band gaps respectively laying therebetween are composed of n-doped GaAs.
The quantum well structure is dimensioned in such a manner that the charge carriers L located in the potential wells assume quantized states and that the barrier height determined by the large band gap in the AlGaAs layers prevent the charge carriers from tunnelling through from one potential well to the other.
In FIG. 2(a) an external voltage applied via electrodes E1 and E3 causes the photodiode to operate in the forward direction. Under these voltage conditions, the band diagram of the QWIP structure is bent due to the extant external electrical field in such a manner that, due to optical excitation, the electrons located in the lower subbands are excited into upper states (not shown) lying near or above the conduction band edge. Due to the optical excitation, charge carriers of this type can also be partially raised into the continuum i.e., above the conduction band edge energy so that they are immediately drawn off laterally due to the external electrical field and, in this manner, are able to contribute to the photo current.
The operating state of the two-color detector according to FIG. 2(a) represents a case in which the spectral sensitivity range of the QWIP structure prevails, so that the developing photo current is solely composed of charge carriers emanating as a result of intersubband absorption processes. If however, the external voltage is applied so that the photodiode is biased in the reverse direction, the charge carriers generated inside the i-layer are separated due to the optical absorption by the electric field prevailing within the i-layer and, in this manner, contribute to the photo current.
An essential characteristic of the invented two-color detector is that the noise behavior of the entire detector is determined by that part of the detector in which the photo current is generated. This is due in particular to the fact that the photodiode biased in the block direction has an extremely high dark resistance relative to the differential intrinsic resistance of the QWIP structure, so that the latter can be ignored. Likewise the differential intrinsic resistance of the photodiode, which is biased in the forward direction, has such a low value that the noise portion from this detector region compared to the noise portion of the actively operated QWIP
structure can be ignored due to an appropriate material selection.
Preferably the two-color detector, as described in the mentioned example according to FIG. 2 is optimized to two wavelengths so that long wave radiation portions are absorbed by the QWIP structure and the short wavelength portions are absorbed by the p-i-n photodiode.
FIG. 3 is a diagram showing the dependence of the spectral sensitivity of the two-color detector of FIG. 1 on the photon energy, for two different voltage conditions. The spectral sensitivity is shown in amperes per irradiated photon power in watts along the ordinate. The photon energies are plotted on the abscissa.
If the external voltage is 2 volts in the forward direction of the photodiode, the spectral sensitivity of the QWIP structure is 0.5 A/W at a photon energy of 153 meV. If, however, a bias voltage of 1 volt is applied in the block direction of the photodiode, a spectral sensitivity of 0.18 A/W at a photon energy of 1.47 eV is yielded in the region of the photodiode.
The measured data generated by the invented two-color detector correspond to the respective detector sensitivities of separate known individual detectors.
Thus, it can be demonstrated that a combination of a radiation detector composed of a photodiode and a quantum well intersubband photodetector possesses similar detection properties as single individual detectors do.
Furthermore, FIG: 3 shows in the right bottom part of the diagram that by irradiating the two-color detector from the back side (back illum.), i.e., from the side of the base substrate, the sensitivity range breaks off at 1.5 eV, which can be explained by the great absorption of the base substrate. In contrast, the dotted line indicates the spectral sensitivity of the photodiode under forward illumination which lies considerably above the value under backside illumination.
In addition to the aforementioned preferred embodiments of the invented two-color detector, other combinations of materials or doping possibilities are feasible. Thus n-i-p photodiodes can also be employed and can be combined with a correspondingly p-doped quantum well structure. Likewise inverted layer sequences are feasible in which first the QWIP structure and then the layers of the photodiode are precipitated onto the substrate. Additional preferred embodiments are yielded, by way of illustration, when a p-doped quantum well intersubband photodetector, i.e., a QWIP structure having p-doped quantum well layers and a p-conducting contact, are employed.
Moreover, there are alternatives to the above described material system AlGaAs/GaAs/InGaAs. Thus, it is also possible to precipitate onto an InP-substrate, the base substrate, a multilayer sequence composed of InGaAs/InAlAs as the QWIP structure adapted to the lattice constant of the substrate crystal respectively slightly strained.
Furthermore, InGaAs can be selected as the photodiode material.
Alternatively, a multilayer sequence composed of GaSb/AlGaSb can be precipitated as the QWIP structure onto a GaSb substrate on top of which InAs or a superlattice composed of GaSb-InAs or composed of AlGaSb/InGaSb can be precipitated as the photodiode layer.
By using different materials, and by a suitable selection of layer parameters and types of doping, two-color detectors can be conditioned as desired using the invented combination of a photodiode and a QWIP structure. Thus, the detector regions can be separately optimized for different spectral sensitivity ranges respectively.
A diffraction grating applied onto or under the detector structure usually employed in connection with QWIP
detectors is utilized as a further advantageous improvement of the invented semiconductor heterostructure radiation detector. The advantage of a grating of this type is that, due to the polarization selection principles for intersubband transitions, the incident light must have a component of the electric field vector along the growth direction of the semiconductor lattice. This means that the propagation direction of the light within the detector structure should occur perpendicular to respectively diagonal to the growth direction. In order to meet this demand better, the part of the radiation falling onto the structure or the part of the radiation reflected opposite the illuminated side of the detector, which lies in the spectral sensitivity range of the quantum well intersubband photodetector, are diffracted diagonal to the incidence direction.
The invented two-color detectors can be operated in single operation as well as in an array arrangement. Typical lateral dimensions of a single detector are (10-1000pm)2 with a typical overall layer thickness of a few um. In particular, two-color detectors of this type are employed in so-called focal plane array camera systems which are, by way of illustration, used in thermography.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
State of the Art In the field of semiconductor radiation detectors, photodiod~s are known with conventional p-i-n junctions as well as so-called.quant:um well intersubband photodetectors (QWIP), w=pose spectral sensitivity properties can be set according to the selection of material layer systems, layer thickness parameters a:~ well as the selection of n-doping or p-doping. Conventional photodiodes possess spectral sensitivity in the vis:Lble to the near-infrared spectral range. Defending on ths~ selection of material, they can also detect. wa~:-elengths in t:he ~m range. The so-called quantum well i.nte~-subband photodetectors actually have spectral sensit.ivir.y ranges in i~he long wave spectral range, preferably in the range. between the 3 and 20 ~ln range, which can be see by means of the choice of material and layer thickness parameters.
In addition to performance enhancement and optimization of indivi.dua~ radiation detectors, combinations of radiation detectors with which e:Lectromagnetic radiation of different wavelengtYa can be detected are being examined. Known are so-called two=color dei~ectors, which by way of illustration are emplo~~ed in thermoc~raphy and for the optical discri.min~.tion of certain ob jects within the field detected by the rac:iation deteci;or.
The artic_.e by A. Kock et al.:" Double Wavelength Selective GaAs/AlGa~.s Infrared DE~tector Device" , Appl . Phys . Lett .
60, 2011 11992) proposE~s combining two QWIP semiconductor structure: having diffE~rent detection wavelengths. The 2-step QWIP system introduced in this article comprises alternatir:g sequences of GaAs/AlGaAs layers respectively.
Quantum will structures differing in the dimensions of the barrier hE:ight respectpvely the band gap as well as well-width res;~ectively layer thickness characteristic of the quantum wEll structure are employed for setting different spectral ~~ensitivity. ~'he QWIP structures conditioned for detecting different wavelengths, however, are separated by an add.itir;nal doped contact layer. Although the physical separa.tio_-°. attained by this means has the advantage that both ~!WIP structures can be separately optimized to their respective operating wavelength, this arrangement has the drawback ,:hat, due to t:he separation at least one additional electrode is required f:or voltage supply.
Therefore, for rationalization purposes, an attempt has been made to o~:,erate the detector structure described in the aforem.ent~oned publications with a not connected, additional electrode (see the paper by K.L. Tsai et al. " Two-Color Infrared Phototodector Using GaAs/AlGaAs and Strained InGaAs/AlC=aAs Multiquantum Wells" , Appl. Phys. Letter 62, 3704, (19~~3)). Operation of detector structures of this type has revea_.ed that the relative sensitivity can be tuned with regard to the two oper~~ting wavelengths by applying suited electrica_ voltage. However, there is the disadvantage that the indiv__dual in-series-connected detectors influence each other electrically. Defending on the application of external voltage, the photosensitivity of one of the two combined detectors,can be raised, with the sensitivity of the other detector being lowered. The overall noise behavior of this detector combination is. also determined by the respective detector c:lement~not participating in photodetection.
Consequen;:ly the signa l-to-noise ratio of this detection structure is relatively poor.
Further~rno::e a two-color detector based on a single QWIP
structure having two possible intersubband junctions with wavelengths of 5~m and 10~m is known from a paper by K.
Kheng cat ~~.1. :" Two-colon GaAs/ (AlGa)As Quantum Well Infrared Detector with Voltage-Tunable Spectral Sensitivity at 3-5 and 8-12~:,:'' , Appl . Phys . Letter 61 , 666 ( 1992 ) . The selection of operating wavelengths is made possible by the fact that the Sum junction demonstrates photovoltaic and the l0~un junction photocond.uctive behavior. In this case as well, the principal disadvantage is that the noise behavior is also determined at short operating wavelengths by the noise associated with long wave detection.
Finally, electrically tunable two-color detectors formed by combining two back-to-back p-i-n photodiodes are known (see the paper by M.P. Reine et al.:" Independently Accessed Back-To-B~.ck HgCdTe Photodiodes: A New Dual-Band Infrared Detect.or'' , J. Electronic Mater. 24, 669 (1995).
Descri.pti~~n of the Inve=ntion The object. of the presE~nt invention is to improve in such a manner a ~-emiconductor heterostructure radiation detector having two; adjacent semiconductor layer regions sensitive in different spectral ranges, in which regions photons having different energies respectively can be absorbed, which photons oiaically excite the charge carriers present in the semicondur:tor layer regions in such a manner that a photo current ir. the respective semiconductor layer region can be generated in dependence on an external electric voltage applic=d v~.a electrodes provided at the semiconductor heterostrl:cture, that the spectral sensitivity ranges of both ;semi~_:onductor layer structures can be set separately without l~;stingly influencing the overall noise behavior of the two-cc_:lor detector. In particular, the noise behavior of the two-color detector should be dominated by the noise of the resper:tively active individual detector. Moreover, the spectral :sensitivity ranges of both semiconductor layer detectors are..~o be set: largely independent of each other and ca.n be optimized. The solution to the object on which the preseia invention is based is set forth in claim 1.
Other adv~.ntageous prei:erred embodiments of the inventive idea a.re :et forth in claims 2ff.
The present invention is based on understanding to design a semiconductor heterostructure radiation detector according to the ge:_eric part of claim 1 in such a manner that the two adjacent ~:emiconductor layer regions differing in their spectral :sensitivity ranges are provided by a combination of a photodic:de and a quantum well intersubband photodetector.
By com;bin:_ng a photodiode with a QWIP structure according to the preser_t invention, contrary to the hitherto attempts at realizing electrically tunable two-color detectors, the noise behe.vior of the invented two-color detector can be determ.inec~ by the noise of the respectively active individuals. detector.
Preferabl«, the individual detectors of different construction are appliE~d onto a base substrate in such a manner th~.a the layer :>equence of a p-i-n photodiode is precip~itaa.ed by means of epitaxial precipitation processes, preferabl~.~ molecular beam epitaxy, on top of which the layer sequence c.f a quantum well intersubband photodetector is applied i~_ immediate succession. Moreover, at least two electrodes are provided, of which one is contacted with the photodiode: contact layer opposite the QWIP structure and the other electrode with tree top covering layer of the QWIP
structure.
Upon appl:.cation of an external electric voltage to the electrode:.< in such a manner that the p-i-n photodiode is operated -n forward direction, the spectral sensitivity of the invented two-color detector is determined by the semiconductor layer region of the QWIP structure. The reason for this ._s that the photodiode, which is operated in forward d~.rection possE~sses a negligible differential intrinsic resistance. Consequently, it does not lastingly influence the sensitivity of the active QWIP structure.
On the other hand, if the external voltage is applied in such a manner that the photodiode is located in the block direction the sensitivity of the entire two-color detector is solely determined by the photodiode. The reason for this is that the photodiode possesses a high dark resistance compared to which the differential intrinsic resistance of the QWIP structure can be ignored.
In accordance with one aspect of the present invention there is provided a semiconductor heterostructure radiation detector having first and second adjacent semiconductor layer regions which absorb photons having different energies respectively and which are sensitive in different spectral ranges, absorbed photons optically exciting charge carriers present in said semiconductor layer regions in such a manner that a photo current can be generated in said respective semiconductor layer regions in response to an external electric voltage applied via electrodes provided at the semiconductor heterostructure, wherein said first semiconductor layer region is a photodiode; and said second semiconductor layer region is a quantum well intersubband photodetector.
In accordance with another aspect of the present invention there is provided a semiconductor heterostructure radiation detector in which absorbed photons optically excite charge carriers present therein whereby a photo current can be generated in response to an externally applied voltage, said radiation detector comprising: a first semiconductor layer region which absorbs photons having a first energy level and is sensitive in a first spectral range; a second semiconductor layer region which is adjacent said first semiconductor region, and which absorbs photons having a second energy level different from said first energy level, and is sensitive to a second spectral range different from said first spectral range;
and electrodes for applying voltage to said semiconductor heterostructure; wherein said first semiconductor layer region comprises a photodiode layer structure; and said second semiconductor layer region comprises a quantum well intersubband photodetector layer structure.
In accordance with yet another aspect of the present invention there is provided a semiconductor heterostructure radiation detector, comprising: a first semiconductor layer region forming a photodiode; a second semiconductor layer region forming a quantum well intersubband photodetector in series electrical contact with said first semiconductor layer region; and electrodes for applying a bias voltage across said first and second semiconductor layer regions.
Brief Description of the Drawings The present invention is made more apparent, by way of example, in the following using preferred embodiments with reference to the drawings, depicting in:
FIG. 1 is a schematic depiction of the layer structure of a radiation detector according to the invention;
FIGS. 2(a) and (b) are band diagrams which depict two different states of operation of the two-color detector according to the invention; and FIG. 3 shows the variation of the detector sensitivity as a function of the applied external voltage.
Description of the Preferred Embodiments In FIG. l, a layer sequence of a p-i-n photodiode 1 is deposited on a substrate layer 2 with the layer sequence FIG. 3 shows the variation of the detector sensitivity as a function of the applied external voltage.
Description of the Preferred Embodiments In FIG. 1, a layer sequence of a p-i-n photodiode 1 is deposited on a substrate layer 2 with the layer sequence of an intersubband photodetector 3 applied immediately on top of the p-i-n photodiode structure. A p-doped GaAs layer (la), which serves as the p-region of the p-i-n photodiode, is applied to a base substrate layer (2) composed of GaAs. Moreover, all further layer sequences are applied on top of each other with the aid of molecular beam epitaxy. The intrinsic (i) region (1b) characteristic for a photodiode possesses a multiplicity of thin, alternating InGaAs layers in succession with GaAs layers.
An n-doped GaAs layer (lc), which is precipitated onto the so-called pared multiquantum well structure in the i-region, provides the n-region of the p-i-n photodiode. A
quantum well intersubband structure (3) having the layer sequence AlGaAs (3a) and GaAs (3b) is applied immediately on top of the n-layer, and an n-doped GaAs layer is employed as the final covering layer of the quantum intersubband structure.
The invented combination of a photodiode and a QWIP
structure is provided, according to the preferred embodiment of FIG. 1 as described there, with the electrodes E1, E2 and E3. Electrode E2, which preferably is applied to the n-region of the photodiode, is executed as a floating electrode.
FIG. 2 shows in details a and b, the band diagrams respectively of an advantageous preferred embodiment of the invented two-color detector. The parallel continuous lines represent the valance band (VB) and the conduction band (CB), respectively. The layers with smaller band gaps 20 in the p-i-n photodiode structure correspond to the InGaAs layer regions, whereas the layer regions with larger band gaps contain GaAs. The i-layer designed in this manner serves, in particular, to expand the sensitivity range to wavelengths for which the GaAs substrate is transparent. Regions with a larger band gap 21 in the QWIP structure correspond to the AlGaAs layer (5), whereas the regions with smaller band gaps respectively laying therebetween are composed of n-doped GaAs.
The quantum well structure is dimensioned in such a manner that the charge carriers L located in the potential wells assume quantized states and that the barrier height determined by the large band gap in the AlGaAs layers prevent the charge carriers from tunnelling through from one potential well to the other.
In FIG. 2(a) an external voltage applied via electrodes E1 and E3 causes the photodiode to operate in the forward direction. Under these voltage conditions, the band diagram of the QWIP structure is bent due to the extant external electrical field in such a manner that, due to optical excitation, the electrons located in the lower subbands are excited into upper states (not shown) lying near or above the conduction band edge. Due to the optical excitation, charge carriers of this type can also be partially raised into the continuum i.e., above the conduction band edge energy so that they are immediately drawn off laterally due to the external electrical field and, in this manner, are able to contribute to the photo current.
The operating state of the two-color detector according to FIG. 2(a) represents a case in which the spectral sensitivity range of the QWIP structure prevails, so that the developing photo current is solely composed of charge carriers emanating as a result of intersubband absorption processes. If however, the external voltage is applied so that the photodiode is biased in the reverse direction, the charge carriers generated inside the i-layer are separated due to the optical absorption by the electric field prevailing within the i-layer and, in this manner, contribute to the photo current.
An essential characteristic of the invented two-color detector is that the noise behavior of the entire detector is determined by that part of the detector in which the photo current is generated. This is due in particular to the fact that the photodiode biased in the block direction has an extremely high dark resistance relative to the differential intrinsic resistance of the QWIP structure, so that the latter can be ignored. Likewise the differential intrinsic resistance of the photodiode, which is biased in the forward direction, has such a low value that the noise portion from this detector region compared to the noise portion of the actively operated QWIP
structure can be ignored due to an appropriate material selection.
Preferably the two-color detector, as described in the mentioned example according to FIG. 2 is optimized to two wavelengths so that long wave radiation portions are absorbed by the QWIP structure and the short wavelength portions are absorbed by the p-i-n photodiode.
FIG. 3 is a diagram showing the dependence of the spectral sensitivity of the two-color detector of FIG. 1 on the photon energy, for two different voltage conditions. The spectral sensitivity is shown in amperes per irradiated photon power in watts along the ordinate. The photon energies are plotted on the abscissa.
If the external voltage is 2 volts in the forward direction of the photodiode, the spectral sensitivity of the QWIP structure is 0.5 A/W at a photon energy of 153 meV. If, however, a bias voltage of 1 volt is applied in the block direction of the photodiode, a spectral sensitivity of 0.18 A/W at a photon energy of 1.47 eV is yielded in the region of the photodiode.
The measured data generated by the invented two-color detector correspond to the respective detector sensitivities of separate known individual detectors.
Thus, it can be demonstrated that a combination of a radiation detector composed of a photodiode and a quantum well intersubband photodetector possesses similar detection properties as single individual detectors do.
Furthermore, FIG: 3 shows in the right bottom part of the diagram that by irradiating the two-color detector from the back side (back illum.), i.e., from the side of the base substrate, the sensitivity range breaks off at 1.5 eV, which can be explained by the great absorption of the base substrate. In contrast, the dotted line indicates the spectral sensitivity of the photodiode under forward illumination which lies considerably above the value under backside illumination.
In addition to the aforementioned preferred embodiments of the invented two-color detector, other combinations of materials or doping possibilities are feasible. Thus n-i-p photodiodes can also be employed and can be combined with a correspondingly p-doped quantum well structure. Likewise inverted layer sequences are feasible in which first the QWIP structure and then the layers of the photodiode are precipitated onto the substrate. Additional preferred embodiments are yielded, by way of illustration, when a p-doped quantum well intersubband photodetector, i.e., a QWIP structure having p-doped quantum well layers and a p-conducting contact, are employed.
Moreover, there are alternatives to the above described material system AlGaAs/GaAs/InGaAs. Thus, it is also possible to precipitate onto an InP-substrate, the base substrate, a multilayer sequence composed of InGaAs/InAlAs as the QWIP structure adapted to the lattice constant of the substrate crystal respectively slightly strained.
Furthermore, InGaAs can be selected as the photodiode material.
Alternatively, a multilayer sequence composed of GaSb/AlGaSb can be precipitated as the QWIP structure onto a GaSb substrate on top of which InAs or a superlattice composed of GaSb-InAs or composed of AlGaSb/InGaSb can be precipitated as the photodiode layer.
By using different materials, and by a suitable selection of layer parameters and types of doping, two-color detectors can be conditioned as desired using the invented combination of a photodiode and a QWIP structure. Thus, the detector regions can be separately optimized for different spectral sensitivity ranges respectively.
A diffraction grating applied onto or under the detector structure usually employed in connection with QWIP
detectors is utilized as a further advantageous improvement of the invented semiconductor heterostructure radiation detector. The advantage of a grating of this type is that, due to the polarization selection principles for intersubband transitions, the incident light must have a component of the electric field vector along the growth direction of the semiconductor lattice. This means that the propagation direction of the light within the detector structure should occur perpendicular to respectively diagonal to the growth direction. In order to meet this demand better, the part of the radiation falling onto the structure or the part of the radiation reflected opposite the illuminated side of the detector, which lies in the spectral sensitivity range of the quantum well intersubband photodetector, are diffracted diagonal to the incidence direction.
The invented two-color detectors can be operated in single operation as well as in an array arrangement. Typical lateral dimensions of a single detector are (10-1000pm)2 with a typical overall layer thickness of a few um. In particular, two-color detectors of this type are employed in so-called focal plane array camera systems which are, by way of illustration, used in thermography.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
Claims (22)
1. A semiconductor heterostructure radiation detector having first and second adjacent semiconductor layer regions which absorb photons having different energies respectively and which are sensitive in different spectral ranges, absorbed photons optically exciting charge carriers present in said semiconductor layer regions in such a manner that a photo current can be generated in said respective semiconductor layer regions in response to an external electric voltage applied via electrodes provided at the semiconductor heterostructure, wherein:
said first semiconductor layer region is a photodiode; and said second semiconductor layer region is a quantum well intersubband photodetector.
said first semiconductor layer region is a photodiode; and said second semiconductor layer region is a quantum well intersubband photodetector.
2. A semiconductor radiation detector according to claim 1, wherein:
said quantum well intersubband photodetector is n-doped;
said photodiode has a p-doped region and an n-doped region which is adjacent to said quantum well intersubband photodetector; and for applying an external voltage to said radiation detector, a first electrode is applied to the p-doped region of said photodiode and a second electrode is applied to said quantum well intersubband photodetector.
said quantum well intersubband photodetector is n-doped;
said photodiode has a p-doped region and an n-doped region which is adjacent to said quantum well intersubband photodetector; and for applying an external voltage to said radiation detector, a first electrode is applied to the p-doped region of said photodiode and a second electrode is applied to said quantum well intersubband photodetector.
3. A semiconductor radiation detector according to claim 1, wherein:
said quantum well intersubband photodetector is p-doped;
said photodiode has an n-doped region and a p-doped region which is adjacent to said quantum well intersubband photodetector; and for applying an external voltage to said radiation detector, a first electrode is applied to the n-doped region of said photodiode and a second electrode is applied to said quantum well intersubband photodetector.
said quantum well intersubband photodetector is p-doped;
said photodiode has an n-doped region and a p-doped region which is adjacent to said quantum well intersubband photodetector; and for applying an external voltage to said radiation detector, a first electrode is applied to the n-doped region of said photodiode and a second electrode is applied to said quantum well intersubband photodetector.
4. A semiconductor radiation detector according to claim 1, wherein a layer sequence of a photodiode is precipitated onto a base substrate, and the layer sequence of a quantum well intersubband photodetector is applied on the layer sequence of the photodiode.
5. A semiconductor radiation detector according to claim 1, wherein a layer sequence of a quantum well intersubband photodetector is precipitated onto a base substrate, and the layer sequence of a photodiode is applied thereon.
6. A semiconductor radiation detector according to claim 1, wherein by varying the external voltage, the spectral sensitivity ranges of both said semiconductor regions can be selected.
7. A semiconductor radiation detector according to claim 1, wherein said photodiode is a p-i-n photodiode.
8. A semiconductor radiation detector according to claim 7, wherein another electrode is provided at an n-region of said p-i-n photodiode.
9. A semiconductor radiation detector according to claim 7, wherein said photodiode is composed of the following layers:
p-layer: p-doped GaAs;
i-layer: InGaAs/GaAs alternating layer sequence;
n-layer: n-doped GaAs; and said quantum well intersubband photodetector is applied immediately onto said n-layer of said photodiode, and has alternating layers of AlGaAs and GaAs respectively.
p-layer: p-doped GaAs;
i-layer: InGaAs/GaAs alternating layer sequence;
n-layer: n-doped GaAs; and said quantum well intersubband photodetector is applied immediately onto said n-layer of said photodiode, and has alternating layers of AlGaAs and GaAs respectively.
10. A semiconductor radiation detector according to claim 1, wherein intersubband gaps contributing to photoabsorption are smaller within said quantum well intersubband photodetector than within corresponding band gaps of said photodiode.
11. A semiconductor radiation detector according to claim 1, wherein, with an application of an external voltage to said radiation detector in a forward direction, said photodiode has a differential intrinsic resistance which is negligible in comparison to said quantum well intersubband photodetector.
12. A semiconductor radiation detector according to claim 1, wherein, with an application of an external voltage to said radiation detector in a reverse direction, a dark resistance which is negligible in comparison to differential intrinsic resistance of said quantum well intersubband photodetector.
13. A semiconductor radiation detector according to claim 1, wherein said photodiode has a short wavelength sensitivity, and said quantum well intersubband photodetector has a long wavelength sensitivity range.
14. A semiconductor radiation detector according to claim 1, wherein individual layer sequences of said photodiode and said quantum well intersubband photodetector are applied successively epitaxially onto a substrate.
15. A semiconductor radiation detector according to claim 1, wherein said two semiconductor layer regions have the following spectral sensitivity ranges:
visible spectral range or near-infrared and 3-5 µm or 1 µm or 3-5 µm and 8-12 µm.
visible spectral range or near-infrared and 3-5 µm or 1 µm or 3-5 µm and 8-12 µm.
16. A semiconductor radiation detector according to claim 1, wherein:
said photodiode comprises InGaAs on a InP-substrate;
and said quantum well intersubband photodetector comprises alternating layers of InGaAs and InAlAs respectively.
said photodiode comprises InGaAs on a InP-substrate;
and said quantum well intersubband photodetector comprises alternating layers of InGaAs and InAlAs respectively.
17. A semiconductor radiation detector according to claim 1, wherein on a GaSb substrate, InAs is used as the photodiode material or a GaSb/InAs superlattice or an AlGaSb/InGaSb superlattice can be used and said quantum well intersubband photodetector has alternating layers of GaSb and AlGaSb respectively.
18. A semiconductor radiation detector according to claim 1, wherein a diffraction grating is provided on or under said semiconductor heterostructure radiation detector, which diffracts diagonally to the incidence direction the part of the radiation lying in the spectral sensitivity range of said quantum well intersubband photodetector falling onto the structure, or the part of the radiation laying in the spectral sensitivity range of said quantum well intersubband photodetector reflected opposite the illuminated side of said detector.
19. A semiconductor heterostructure radiation detector in which absorbed photons optically excite charge carriers present therein whereby a photo current can be generated in response to an externally applied voltage, said radiation detector comprising:
a first semiconductor layer region which absorbs photons having a first energy level and is sensitive in a first spectral range;
a second semiconductor layer region which is adjacent said first semiconductor region, and which absorbs photons having a second energy level different from said first energy level, and is sensitive to a second spectral range different from said first spectral range; and electrodes for applying voltage to said semiconductor heterostructure; wherein said first semiconductor layer region comprises a photodiode layer structure; and said second semiconductor layer region comprises a quantum well intersubband photodetector layer structure.
a first semiconductor layer region which absorbs photons having a first energy level and is sensitive in a first spectral range;
a second semiconductor layer region which is adjacent said first semiconductor region, and which absorbs photons having a second energy level different from said first energy level, and is sensitive to a second spectral range different from said first spectral range; and electrodes for applying voltage to said semiconductor heterostructure; wherein said first semiconductor layer region comprises a photodiode layer structure; and said second semiconductor layer region comprises a quantum well intersubband photodetector layer structure.
20. A semiconductor radiation detector according to claim 19, wherein:
said quantum well intersubband photodetector is n-conductive;
said photodiode has a p-doped region and an n-doped region, which is adjacent to said quantum well intersubband photodetector; and in order to apply an external voltage, a first electrode is applied to the p-doped region of said photodiode and a second electrode is applied to said quantum well intersubband photodetector.
said quantum well intersubband photodetector is n-conductive;
said photodiode has a p-doped region and an n-doped region, which is adjacent to said quantum well intersubband photodetector; and in order to apply an external voltage, a first electrode is applied to the p-doped region of said photodiode and a second electrode is applied to said quantum well intersubband photodetector.
21. A semiconductor radiation detector according to claim 19, wherein:
said quantum well intersubband photodetector is p-doped;
said photodiode has an n-doped region and a p-doped region which is adjacent to said quantum well intersubband photodetector; and in order to apply an external voltage, a first electrode is applied to the n-doped region of said photodiode and a second electrode is applied to said quantum well intersubband photodetector.
said quantum well intersubband photodetector is p-doped;
said photodiode has an n-doped region and a p-doped region which is adjacent to said quantum well intersubband photodetector; and in order to apply an external voltage, a first electrode is applied to the n-doped region of said photodiode and a second electrode is applied to said quantum well intersubband photodetector.
22. A semiconductor heterostructure radiation detector, comprising:
a first semiconductor layer region forming a photodiode;
a second semiconductor layer region forming a quantum well intersubband photodetector in series electrical contact with said first semiconductor layer region; and electrodes for applying a bias voltage across said first and second semiconductor layer regions.
a first semiconductor layer region forming a photodiode;
a second semiconductor layer region forming a quantum well intersubband photodetector in series electrical contact with said first semiconductor layer region; and electrodes for applying a bias voltage across said first and second semiconductor layer regions.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19538650.7 | 1995-10-17 | ||
| DE19538650A DE19538650C2 (en) | 1995-10-17 | 1995-10-17 | Semiconductor heterostructure radiation detector, with two spectral sensitivity ranges |
| PCT/DE1996/001983 WO1997017719A2 (en) | 1995-10-17 | 1996-10-16 | Semiconductor heterostructure radiation detector, with two spectral sensitivity regions |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2232084A1 CA2232084A1 (en) | 1997-05-15 |
| CA2232084C true CA2232084C (en) | 2004-05-04 |
Family
ID=7775084
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002232084A Expired - Fee Related CA2232084C (en) | 1995-10-17 | 1996-10-16 | Semiconductor heterostructure radiation detector having two spectral sensitivity ranges |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0856201B1 (en) |
| CA (1) | CA2232084C (en) |
| DE (2) | DE19538650C2 (en) |
| WO (1) | WO1997017719A2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19723177A1 (en) * | 1997-06-03 | 1998-12-10 | Daimler Benz Ag | Voltage controlled wavelength selective photodetector |
| DE19814125C1 (en) * | 1998-03-30 | 1999-10-28 | Martin Streibl | Controllable light detector |
| DE10228309A1 (en) * | 2002-06-25 | 2004-01-22 | Sick Ag | Light sensor colour receiver for area monitoring has semiconductor photo diode surfaces arranged adjacent or along path at receive pupil with unfocussed or collimated objective |
| IL155536A0 (en) * | 2003-04-21 | 2003-11-23 | Yissum Res Dev Co | Voltage tunable integrated infrared imager |
| DE102007006211B3 (en) * | 2007-02-08 | 2008-07-17 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Hetero-junction pin photodiode data transmission i.e. high-speed optical data transmission, has doped window layer made of p-doped indium aluminum arsenide with high band gap, and protective coating made of n or p-doped indium phosphide |
| CN111886704B (en) * | 2018-03-22 | 2024-04-12 | Iee国际电子工程股份公司 | Photodetector |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5023685A (en) * | 1988-06-06 | 1991-06-11 | Bethea Clyde G | Quantum-well radiation-interactive device, and methods of radiation detection and modulation |
-
1995
- 1995-10-17 DE DE19538650A patent/DE19538650C2/en not_active Expired - Fee Related
-
1996
- 1996-10-16 EP EP96945510A patent/EP0856201B1/en not_active Expired - Lifetime
- 1996-10-16 WO PCT/DE1996/001983 patent/WO1997017719A2/en active IP Right Grant
- 1996-10-16 DE DE59610134T patent/DE59610134D1/en not_active Expired - Lifetime
- 1996-10-16 CA CA002232084A patent/CA2232084C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE59610134D1 (en) | 2003-03-20 |
| EP0856201B1 (en) | 2003-02-12 |
| DE19538650A1 (en) | 1997-04-24 |
| WO1997017719A3 (en) | 1997-07-03 |
| DE19538650C2 (en) | 1997-08-28 |
| WO1997017719A2 (en) | 1997-05-15 |
| EP0856201A2 (en) | 1998-08-05 |
| CA2232084A1 (en) | 1997-05-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5581084A (en) | Simultaneous two color IR detector having common middle layer metallic contact | |
| EP0518243B1 (en) | Two-color radiation detector array and method of fabricating same | |
| US6455908B1 (en) | Multispectral radiation detectors using strain-compensating superlattices | |
| EP0820106B1 (en) | Image conversion panel and associated methods | |
| US5959339A (en) | Simultaneous two-wavelength p-n-p-n Infrared detector | |
| US5559336A (en) | Integrated LPE-grown structure for simultaneous detection of infrared radiation in two bands | |
| US7687871B2 (en) | Reduced dark current photodetector | |
| US8022390B1 (en) | Lateral conduction infrared photodetector | |
| US7755079B2 (en) | Strained-layer superlattice focal plane array having a planar structure | |
| US5721429A (en) | Self-focusing detector pixel structure having improved sensitivity | |
| US6130466A (en) | Semiconductor heterostructure radiation detector having two spectral sensitivity ranges | |
| US5510627A (en) | Infrared-to-visible converter | |
| US6734452B2 (en) | Infrared radiation-detecting device | |
| JPH10326906A (en) | Photodetection element and image-pickup element | |
| US20140217540A1 (en) | Fully depleted diode passivation active passivation architecture | |
| US5296720A (en) | Apparatus and method for discriminating against undesired radiation in a multiple quantum well long wavelength infrared detector | |
| CA2232084C (en) | Semiconductor heterostructure radiation detector having two spectral sensitivity ranges | |
| JPH0766980B2 (en) | Quantum well radiation detector | |
| KR101099105B1 (en) | Reduced dark current photodetector | |
| US6798001B2 (en) | Semiconductor device having photo diode with sensitivity to light of different wavelengths | |
| US7619240B2 (en) | Semiconductor photodetector, device for multispectrum detection of electromagnetic radiation using such a photodetector and method for using such a device | |
| US10090426B2 (en) | Dark current mitigation with diffusion control | |
| US5115295A (en) | Photodetector device | |
| EP3693997B1 (en) | Photo-detector array with barrier with pixellation by local depletion | |
| JPH02238677A (en) | Photodetector,long wave light detector,and electron filter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20141016 |