Two terminal multi-band infrared radiation detector
5 claims: 1 independent, 4 dependent
- 1Conclusies 1. Stralingsdetector voor het detecteren van straling, omvattend een eerste pn-overgang tussen een eerste gebied van halfgeleidermateriaal van een eerste geleidingstype en een gemeenschappelijk tweede gebied van halfgeleidermateriaal van het aan het eerste geleidingstype tegengestelde tweede geleidingstype en een tweede pn-overgang tussen een derde gebied van halfgeleidermateriaal van het eerste geleidingstype 45 en het gemeenschappelijk tweede gebied, waarbij de eerste en tweede pn-overgang elk een heteroovergang vormen en de pn-overgangen elektrisch in onderling tegengestelde richting in serie geschakeld zijn tussen een eerste elektrisch contact voor het eerste gebied en een tweede contact, met het kenmerk, dat de hetero-overgang van de eerste pn-overgang bij het aanleggen van een spanning in de keerrichting van de eerste pn-overgang gevoelig is voor straling binnen een eerste spectraal gebied en de hetero50 overgang van de tweede pn-overgang bij het aanleggen van een spanning in de keerrichting van de tweede pn-overgang is voor straling binnen een afzonderlijk tweede spectraal gebied, het halfgeleidermateriaal van het eerste gebied een zodanige energiebandafstand heeft dat straling binnen het tweede spectrale gebied waarvoor de tweede pn-overgang gevoelig is daardoorheen kan dringen en het eerste en het tweede spectrale gebied zijn gekozen uit een groep bestaande uit IR-straling van korte golflengte (SWIR), 55 IR-straling van middengolflengte (MWIR), IR-straling van lange golflengte (LWIR) en IR-straling van zeer lange golflengte (VLWIR).
- 2Stralingsdetector volgens conclusie 1, met het kenmerk, dat het halfgeleidermateriaal van het tweede gebied een zodanige energiebandafstand heeft dat straling uit het tweede gebied waarvoor de tweede p-n overgang gevoelig is daardoorheen kan penetreren.
- 3Stralingsdetector volgens conclusie 1 of 2, gekenmerkt door een vierde gebied van halfgeleidermateriaal in serie in contact met het derde gebied van halfgeleidermateriaal, waarbij het vierde gebied van 5 halfgeleidermateriaal van het tweede geleidingstype, waarbij een derde p-n overgang is verschaft met een doorslagspanning in de keerrichting die verschilt van de doorslagspanning in de keerrichting van de eerste p-n overgang.
- 4Werkwijze voor het detecteren van straling met gebruikmaking van een stralingsdetector volgens conclusie 1 of 2, met het kenmerk, dat een eerste instelspanning van een eerste polariteit wordt gekoppeld 10 tussen het eerste elektrische contact en het tweede elektrische contact, zodanig dat de eerste p-n overgang in doorlaatrichting is en de tweede p-n overgang in keerrichting voor het verschaften van een stroomsignaal, dat gemoduleerd is als een functie van de stralingsflux binnen een eerste spectraal gebied;en de eerste instelspanning wordt ontkoppeld en een tweede instelspanning van een tweede, tegengestelde polariteit wordt gekoppeld tussen het eerste elektrische contact en het tweede elektrische contact, zodanig 15 dat de tweede p-n overgang in doorlaatrichting is en de eerste p-n overgang in keerrichting;voor het verschaffen van een stroomsignaal, dat gemoduleerd is als een functie van de stralingsflux binnen een tweede spectraal gebied.
- 5Werkwijze voor het detecteren van straling met gebruikmaking van een stralingsdetector volgens conclusie 3, met het kenmerk, dat een eerste instelspanning van een eerste polariteit wordt gekoppeld 20 tussen het eerste elektrische contact en het tweede elektrische contact, zodanig dat de eerste en derde p-n overgang in doorlaatrichting zijn en de tweede p-n overgang in keerrichting is voor het verschaffen van een stroomsignaal, dat gemoduleerd is als een functie van de stralingsflux binnen een eerste spectraal gebied;de eerste instelspaning wordt ontkoppeld en een tweede instelspanning van een tweede, tegengestelde polariteit, welke instelspanning kleiner is dan de hoogste van de omkeerdoorslagspanningen van de eerste 25 en derde p-n overgangen, wordt gekoppeld tussen het eerste elektrische contact en het tweede elektrische contact voor het verschaffen van een stroomsignaal, dat gemoduleerd is als een functie van de stralingsflux binnen een tweede spectraal gebied en een derde instelspanning van de tweede, tegengestelde polariteit wordt gekoppeld tussen het eerste elektrische contact en het tweede elektrische contact, zodanig dat de derde p-n overgang in keerrichting ingesteld wordt voorbij een doorslagspanning van de eerste p-n 30 overgang en voor het verschaffen van een stroomsignaal, dat gemoduleerd is als een functie van de stralingsflux binnen een derde spectraal gebied. Hierbij 4 bladen tekening RELATIEVE RESPONS/FOTON 1 2 3 4 5 6 7 β 9 10 GOLFLENGTE (MICRON)
Independent claims5
51 paragraphs in 2 sections, as filed
f
<img file="NL195040C_D0001.tif" />
Patent Board
The Netherlands © 195040 © C OCTROOI
2Ï) Application for a patent: 9100637 22) Submitted: 12.04.1991 © lnt.CI.<sup>7</sup>
H01L31 / 072, H01L31 / 0296
<td>© Laid for inspection:</td><td>© Patent holder (s):</td>
<td>01.06.2001 IE 2001/06</td><td>Raytheon Company in El Segundo, California,</td>
<td>© Daily date: 25.06.2003</td><td>United States of America (US). © Authorized representative:</td>
<td>© Issued: 01.09.2003 IE 2003/09</td><td>Drs. F. Barendregt et al., 2280 GE Rijswijk.</td>
fe4) Radiation detector.
NL C 195040
This patent has been granted in application of Article 102b of the Kingdom Act of 19 December 2002 amending the Patents Act 1995 in connection with the handling of patent applications filed under the Patents Act (Bulletin of Acts and Decrees 2003, 35)
Radiation detector
The invention relates to a radiation detector for detecting radiation, comprising a first pn junction between a first region of semiconductor material of a first conductivity type and a common second region of semiconductor material of the second conductivity type opposite to the first conductivity type and a second pn- transition between a third region of semiconductor material of the first conductivity type and the common second region, wherein the first and second pn junctions each form a hetero junction and the pn junctions are electrically connected in series in opposite directions between a first electrical contact for the first region and a second contact.
The invention also relates to a method for detecting radiation using the radiation detector.
Such a radiation detector and method for detecting radiation are known from US patent publication US-4,278,986. In the known radiation detector, the first and the second pn junction each form a hetero junction in that the composition of the semiconductor material of the common area differs from the composition of the semiconductor material of the areas connected to the contacts. The dimensions and dopant concentration of the common area are chosen such that in the absence of an external voltage no free charge carriers are present in the common area.
Radiation detectors, for example, detectors of semiconductor II-VI connections for detecting IR radiation, are generally made with such a composition of II-VI connections that the energy band distance is suitable for absorbing radiation within a single spectral region. A possibility of detecting radiation within more than one spectral region with a single detector is therefore a desirable goal. However, the technology currently available to realize this function is less than optimal. For example, two separate focal planes may be provided in conjunction with an optical device for spectrally splitting an incident radiation beam, thereby directing a portion of the bundle toward each of the focal planes. However, this approach requires relatively complicated optical devices and optical alignment and further requires the costs associated with two focal areas of radiation detectors.
It is an object of the invention to provide a single radiation detector with two electrical contacts, which is placed in a single radiation beam for separately detecting radiation within more than one spectral region of distinguishable spectral regions and in a method for using the single radiation detector. detecting radiation for more than one spectral region of the distinguished spectral regions.
To that end, a radiation detector of the type described in the preamble according to the invention is characterized in that the hetero junction of the first pn junction when applying a voltage in the reverse direction of the first pn junction is sensitive to radiation within a first spectral region and the hetero-transition of the second pn-transition when applying a reverse-voltage voltage to the second pn-transition is for radiation within a separate second spectral region, the semiconductor material of the first region has such an energy band distance that radiation within the second spectral region to which the second pn junction is sensitive can penetrate and the first and the second spectral region are selected from a group consisting of short-wavelength IR radiation (SWIR), IR wavelength of medium wavelength (MWIR), IR radiation of long wavelength (LWIR) and IR radiation of very long wavelength (VLWIR).
A method for detecting radiation using the radiation detector has the feature according to the invention that a first bias voltage of a first polarity is coupled between the first electrical contact and the second electrical contact such that the first pn junction is in the forward direction and the second pn junction in the reverse direction to provide a current signal, that is modulated as a function of the radiation flux within a first spectral region;
and the first bias voltage is disconnected and a second bias voltage of a second, opposite polarity is coupled between the first electrical contact and the second electrical contact such that the second pn junction is in the forward direction and the first pn junction in the reverse direction;
for providing a current signal that is modulated as a function of the radiation flux within a second spectral region.
In use, the detector is coupled to a switchable bias voltage source, which includes a source of positive bias voltage (+ Vb) and a source of negative bias voltage (-Vb). When + Vb is supplied across the detector, the first hetero junction is far in pass direction and acts as a low-resistance conductor, so that this junction does not provide a significant amount of photo current to the circuit. The second hetero-transition, however, is in a reverse state and modulates the circuit current in proportion to the photon flux of a particular spectral region or color. When vice-versa is supplied over the detector, the second hetero transition is in the forward direction and does not provide a significant photo current to the circuit, while the first hetero transition is set in the reverse direction and produces a current modulation proportional to the flux incident thereon, flux refers to a different spectral region.
In an illustrative embodiment, the detector consists of HgCdTe and contains an n-type base layer with an energy band distance, which responds to mid-wavelength IR (MWIR) radiation. Above the base layer is a highly doped p-type short-wave IR (SWIR) sensitive layer. The p-type layer forms a hetero-transition with the base layer, but does not provide significant numbers of SWIR photon-generated charge carriers, since most SWIR photons do not penetrate through the base layer. An n-type long-wave IR (LWIR) sensitive layer is provided above the SWIR layer. The LWIR layer has a thickness large enough to absorb LWIR radiation penetrated through the two underlying layers. Another hetero junction is thereby formed between the LWIR and SWIR layers, the hetero junction almost exclusively responding to LWIR radiation. A one or two-dimensional array of the detectors can be made as mesa-type or as planar-type devices. Additional regions of semiconductor material can be provided to produce additional hetero transitions, resulting in a radiation detector that is sensitive to three or more spectral regions.
The invention is explained with reference to the drawing.
Figure 1 shows a cross-sectional view of an embodiment of a radiation detector for two different spectral regions;
Figure 2 is a cross-sectional view of another embodiment of radiation detector for two different spectral regions;
Figure 3 shows a cross-sectional view of a further embodiment of a radiation detector for two different spectral regions;
Figures 3A and 3B are schematic representations of the detector of Figure 3 when applying a voltage of mutually different polarity;
Figures 3C and 3D graphical representations of various operational characteristics of the radiation detector of Figure 3;
4A, 4B and 4C show current-voltage characteristics of a radiation detector with two connections; Figure 5 shows an embodiment of a radiation detector with four consecutive regions of alternately different conductivity type;
Figure 6 shows a current voltage characteristic with the optimum set points for the radiation detector of Figure 5; and figure 7 shows a cross-sectional view of a device.
The radiation detector is described below in the context of a presently preferred embodiment of a rear-exposed radiation detector consisting of Hg<sub>(1</sub> O.<sub>X)</sub>CD<sub>X</sub>To. It will be understood, however, that the radiation detector may be formed from other III-VI materials, III-V materials, such as, for example, GaAs, GaAIAs and InP, and from silicon, such as silicon-doped platinum. In general, the radiation detector is formed from a semiconductor material in which different energy band distances are provided, for example, by selective doping or fouling of the material.
Figure 1 shows a three-layer hetero-transition (TLHJ) semiconductor radiation detector 10 with two connections. Detector 10 is constructed from Hg<sub>(1 o</sub>.<sub>X)</sub>CD<sub>X</sub>Te and contains an n-type base layer 12 with an energy band distance sensitive to medium-wavelength IR radiation (MWIR). Above layer 12 there is a highly doped p-type layer 14 with an energy band distance sensitive to IR wavelength of short wavelength (SWIR) 14. Layer 14 forms a hetero-transition 14a with the base layer 12, but does not provide significant numbers of SWIR photon-generated charge carriers, since most SWIR radiation does not penetrate through the base layer 12. In connection with this, a filter (not shown) can be used on the radiation recording back surface of the detector 10 to eliminate any SWIR-related response in the base layer 12. Thus, transition 14a is substantially only sensitive to
MWIR radiation. Above the SWIR layer 14, an n-type layer 16 with an energy band distance sensitive to IR radiation of a long wavelength (LWIR) is provided. LWIR layer has a depth large enough to absorb the LWIR radiation penetrated through the two underlying layers 12 and 14. A hetero-junction 16a is formed between layers 14 and 16, the hetero-junction 16a responding almost exclusively to LWIR radiation. As used herein, the SWIR radiation is believed to contain a spectral region ranging from about 1000 nm to about 4000 nm. MWIR radiation is assumed to contain a spectral region that extends from approximately 3000 nm to approximately 8000 nm and LWIR radiation is believed to contain a spectral region that extends from approximately 7000 nm to approximately 14000 nm. VLWIR radiation is believed to contain a spectral region ranging from about 12000 nm to about 20000 nm.
N-type MWIR sensitive base layer 12 consists of, for example, Hg<sub>07</sub>CD<sub>03</sub>Te with a thickness of around 80000 nm. Base layer 12 is doped with an indium in a concentration of approximately 2 × 10<sup>15</sup> indium10 atoms per cm<sup>3</sup>.
P-type SWIR sensitive layer 14 consists of Hg<sub>0 6</sub>CD<sub>0 4</sub>Te with a thickness of around 3000 nm. P-type SWIR sensitive layer 16 is doped with arsenic in a concentration of approximately 1X10<sup>17</sup> arsenic atoms per cm<sup>3</sup>. The n-type LWIR sensitive layer 16 consists of Hg<sub>oe</sub>CD<sub>o2</sub>Te with a thickness of around 6000 nm. N-type LWIR sensitive layer 16 is also doped with indium in a concentration of approximately 2X10<sup>15</sup> indium atoms per cm<sup>3</sup>. The layers 12, 14 and 16 can be grown by means of LPE, VPE, MOCVD or by any other suitable process.
The multi-layer detector 10 described so far is provided with an electrical contact in the form of a nickel coating with thereon an indium lump 18 and a base contact 20 consisting of nickel or any suitable electrical conductor. Contacts 18 and 20 can be formed by conventional photolithographic processes. Typically, a large number of detectors 10 are provided as a one or two-dimensional array of detectors, such as, for example, a focal plane array (FPA), and are in use coupled to bias and readout circuits via contacts 18 and 20.
In the three-layer detector 10, the two hetero-junctions 14a and 16a are coupled in series and function electrically as two diodes connected in series in opposite directions. In use, the detector 10 is coupled to a switchable bias voltage source 22, which includes a bias bias voltage (+ Vb) and a bias bias voltage source (-Vb) 22A. Sources 22A and 22B are shown schematically as batteries for convenience. Sources 22A and 22B are each coupled to a switching device 22C such as, for example, a transistor switch, for supplying either + Vb or -Vb over the detector 10.
When the positive bias voltage + Vb is supplied across the detector 10, the np junction 16A is far in the forward direction and functions as a low resistance conductor, thereby providing no significant amount of photo current to the circuit. Transition 14A is in a reverse or reverse state and modulates the circuit current in proportion to the MWIR photon flux.
Conversely, when the negative bias voltage -Vb is supplied across the detector 10, the transition 14A in the forward direction is set and does not provide a significant photo current to the circuit.
Transition 16A is in the reverse or reverse direction and produces a current modulation proportional to the LWIR flux incident on detector 10. The modulated current is supplied in a conventional manner via the contacts 18 and 20 to a readout circuit (not shown).
Figure 4 shows the current-voltage (IV) characteristic of transition 16A, Figure 4B shows the IV characteristic of transition 14A, while Figure 4C shows the IV characteristic of the combined transition 14A and 16A. The designation A indicates one set point which is suitable for reading the photo response from transition 16A, while the transition 14A is held far in the forward direction. The designation B indicates one set point which is suitable for reading the photo response of the transition 14A, while the transition 16A is held far in the forward direction.
The embodiment described above shows the operation of a MWIR-LWIR "two-color" radiation detector device. However, other choices of semiconductor material with different energy band distances provide a different response. For example, in Figure 2 an MWIR / LWIR / MWIR detector is shown and this provides MWIR and LWIR modulated current from transition 34A and LWIR modulated current only from transition 36A. An LWIR / MWIR / VLWIR detector (not shown) provides a two-color response similar to the execution standard of Figure 1, but in other radiation bands.
The radiation detector for mutually different radiation bands can be designed with an npn or a pnp polarity. The choice of an npn structure is nowadays a preferred embodiment and has the advantage that substantially all exposed surfaces of the detector are preferably passivated with a broad band gap group II-VI passivation layer, such as, for example, the partially displayed layers 24 (Figure 1) and 42 (Figure 2) consisting of CdTe. A CdTe passivation layer also tends to have a positive solid charge. The critical n-type detector surfaces are thus kept in accumulation, which is a desirable condition for these less strongly doped layers. The intermediate p-type layer (14 to 34) is preferably doped to a relatively high level, the positive charge of the passivation layer 24 or 42 lying thereon not significantly affecting the operation. If a negatively charged passivation layer is used, then a pnp structure may be more desirable. Such a pnp structure is shown in Figures 3, 3A and 3B and is described in detail below.
Figure 3 shows another embodiment of a three-layer hetero-transition detector 50, which includes a first color LWIR-SWIR pn junction 56A and a second color MWIR-SWIR pn junction 54A. By reversing the polarity or by changing the magnitude of the supplied bias voltage, one transition in reverse direction (active) and the other transition in forward direction (inactive) is set. The signal output from the detector 50 is thus alternated between the two colors when the polarity of the bias voltage is reversed. This aspect of the operation of detector 50 is shown in the simplified diagrams of Figures 3A and 3B.
The sensitivity to two spectral bands or colors is obtained with a single radiation detector and with only one indium node per detector element or pixel. That is, a multi-color detector is provided in which each detector element functions electrically as a relatively simple device with two terminals. Thus, for a series of radiation detectors for two spectral band or colors, productivity is increased, resulting in a higher yield and reduced cost of the devices.
Figure 3C is a diagram of the spatial energy band of an embodiment of the detector 50, while Figure 3D shows a desired combined spectral response.
Additional semiconductor regions or lower can be added to the radiation detector described above. Figure 5 shows a pnpn radiation detector 70 with np transition and two pn transitions coupled in series. Discrimination between the two pn junctions is achieved by providing one of the pn junctions with a relatively low breakdown voltage for the reverse or reverse direction, while the other pn junction is provided with a relatively higher breakdown voltage for the reverse or reverse direction.
By setting to a voltage smaller than the last breakdown voltage, the photo current of the highest impedance transition is read. When set above the last breakdown voltage, only the transition with the higher voltage modulates the photo current.
This is illustrated in Figure 6, in which the set points A and B of Figure 4C are shown in addition to a set point C. The set points A and C are each related to one of the two pn transitions and make the differentiation between them possible.
The radiation detector has so far been described in the context of a mesa-type device. The radiation detector can also be designed as a planar-type structure. A planar-type npn device 80 is shown in cross-section in Figure 7 and can be manufactured, for example, by a diffusion or an implantation / annealing process for forming a large number of series-connected hetero-transitions between a first electrical connection 82 and a second electrical connection 84. If desired, the detector 80 can be made as a pnp device.
Contents2
5 sheets
Sheet 1 Sheet 2 Sheet 3 Sheet 4 Sheet 5
5 members in 3 offices
Priority claims8
| Document | Office | Kind | Date |
|---|---|---|---|
| 45289189 | United States of America | A | |
| 45289189 | United States of America | A | |
| 9100637 | Netherlands (Kingdom of the) | A | |
| 10250398 | Japan | A | |
| 10250398 | Japan | A | |
| JP19980102503 | – | – | – |
| NL19910000637 | – | – | – |
| US19890452891 | – | – | – |
Members5
| Document | Office | Kind | |
|---|---|---|---|
| US5113076A | United States of America | A | |
| JPH11295145A | Japan | A | |
| JP3005674B2 | Japan | B2 | |
| NL9100637A | Netherlands (Kingdom of the) | A | |
| NL195040CThis record | Netherlands (Kingdom of the) | C |
3 legal events, as the office reported them to INPADOC
Over the term
Point at a mark for the eventEvents
| Event | Code | |
|---|---|---|
| Lapsed because of non-payment of the annual feeLapsedV1 | V1 | |
| Patent granted (not automatically)GrantedNP1 | NP1 | |
| A request for examination has been filedA1C | A1C |
Numbers
- Publication, DOCDB
- 195040
- Publication, EPODOC
- NL195040C
- Application
- 9100637
- Application, DOCDB
- 9100637
- Application, EPODOC
- NL19910000637
Titles2
- Dutch
- Stralingsdetector.
- English
- Radiation detector.
Classification
- CPC, 4
- H10F30/24
- H10F39/107
- H10F77/1237
- H10F30/26
- IPC, 6
- G01N27 416
- G01J1 02
- H01L27 144
- H01L31 0296
- H01L31 11
- H01L31 111
