GB2078695A - Cadmium Mercury Telluride Deposition - Google Patents
Cadmium Mercury Telluride Deposition Download PDFInfo
- Publication number
- GB2078695A GB2078695A GB8115127A GB8115127A GB2078695A GB 2078695 A GB2078695 A GB 2078695A GB 8115127 A GB8115127 A GB 8115127A GB 8115127 A GB8115127 A GB 8115127A GB 2078695 A GB2078695 A GB 2078695A
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- United Kingdom
- Prior art keywords
- substrate
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- cadmium
- alkyl
- tellurium
- Prior art date
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- 229910000661 Mercury cadmium telluride Inorganic materials 0.000 title claims description 7
- MCMSPRNYOJJPIZ-UHFFFAOYSA-N cadmium;mercury;tellurium Chemical compound [Cd]=[Te]=[Hg] MCMSPRNYOJJPIZ-UHFFFAOYSA-N 0.000 title claims description 6
- 230000008021 deposition Effects 0.000 title description 3
- 239000000758 substrate Substances 0.000 claims abstract description 59
- 229910052753 mercury Inorganic materials 0.000 claims abstract description 33
- 125000000217 alkyl group Chemical group 0.000 claims abstract description 32
- 229910052793 cadmium Inorganic materials 0.000 claims abstract description 31
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 27
- 239000001257 hydrogen Substances 0.000 claims abstract description 27
- 229910052714 tellurium Inorganic materials 0.000 claims abstract description 23
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 19
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 claims abstract description 19
- 150000001875 compounds Chemical class 0.000 claims abstract description 10
- 239000002019 doping agent Substances 0.000 claims abstract description 10
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 claims abstract description 7
- YMUZFVVKDBZHGP-UHFFFAOYSA-N dimethyl telluride Chemical group C[Te]C YMUZFVVKDBZHGP-UHFFFAOYSA-N 0.000 claims abstract description 6
- ILXWFJOFKUNZJA-UHFFFAOYSA-N ethyltellanylethane Chemical group CC[Te]CC ILXWFJOFKUNZJA-UHFFFAOYSA-N 0.000 claims abstract description 6
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims abstract description 5
- VQNPSCRXHSIJTH-UHFFFAOYSA-N cadmium(2+);carbanide Chemical group [CH3-].[CH3-].[Cd+2] VQNPSCRXHSIJTH-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 4
- -1 dipropyl telluride Chemical group 0.000 claims abstract description 4
- WINDXPMAARBVOY-UHFFFAOYSA-N 1-butyltellanylbutane Chemical group CCCC[Te]CCCC WINDXPMAARBVOY-UHFFFAOYSA-N 0.000 claims abstract description 3
- XRPHHVRIJPKDOE-UHFFFAOYSA-N CCC[Cd]CCC Chemical group CCC[Cd]CCC XRPHHVRIJPKDOE-UHFFFAOYSA-N 0.000 claims abstract description 3
- UJYLYGDHTIVYRI-UHFFFAOYSA-N cadmium(2+);ethane Chemical group [Cd+2].[CH2-]C.[CH2-]C UJYLYGDHTIVYRI-UHFFFAOYSA-N 0.000 claims abstract description 3
- 229910004613 CdTe Inorganic materials 0.000 claims abstract 3
- 238000000034 method Methods 0.000 claims description 26
- 239000000203 mixture Substances 0.000 claims description 11
- 150000003498 tellurium compounds Chemical class 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 6
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 3
- 229940065285 cadmium compound Drugs 0.000 claims description 3
- 150000001662 cadmium compounds Chemical class 0.000 claims description 3
- 150000001768 cations Chemical group 0.000 claims description 2
- QUZPNFFHZPRKJD-UHFFFAOYSA-N germane Chemical compound [GeH4] QUZPNFFHZPRKJD-UHFFFAOYSA-N 0.000 claims description 2
- 229910052986 germanium hydride Inorganic materials 0.000 claims description 2
- 229910002058 ternary alloy Inorganic materials 0.000 claims description 2
- HTDIUWINAKAPER-UHFFFAOYSA-N trimethylarsine Chemical compound C[As](C)C HTDIUWINAKAPER-UHFFFAOYSA-N 0.000 claims description 2
- XCZXGTMEAKBVPV-UHFFFAOYSA-N trimethylgallium Chemical compound C[Ga](C)C XCZXGTMEAKBVPV-UHFFFAOYSA-N 0.000 claims description 2
- YWWDBCBWQNCYNR-UHFFFAOYSA-N trimethylphosphine Chemical compound CP(C)C YWWDBCBWQNCYNR-UHFFFAOYSA-N 0.000 claims description 2
- 230000001939 inductive effect Effects 0.000 claims 1
- 125000001319 lambda(5)-arsanyl group Chemical group [H][As]([H])([H])([H])[*] 0.000 claims 1
- JLTRXTDYQLMHGR-UHFFFAOYSA-N trimethylaluminium Chemical compound C[Al](C)C JLTRXTDYQLMHGR-UHFFFAOYSA-N 0.000 claims 1
- 229910045601 alloy Inorganic materials 0.000 abstract description 3
- 239000000956 alloy Substances 0.000 abstract description 3
- 150000002431 hydrogen Chemical class 0.000 abstract description 3
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 150000004678 hydrides Chemical class 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000010790 dilution Methods 0.000 description 3
- 239000012895 dilution Substances 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 2
- RBFQJDQYXXHULB-UHFFFAOYSA-N arsane Chemical compound [AsH3] RBFQJDQYXXHULB-UHFFFAOYSA-N 0.000 description 2
- 229910052785 arsenic Inorganic materials 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 239000012776 electronic material Substances 0.000 description 2
- 229910052733 gallium Inorganic materials 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- VCEXCCILEWFFBG-UHFFFAOYSA-N mercury telluride Chemical compound [Hg]=[Te] VCEXCCILEWFFBG-UHFFFAOYSA-N 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910004262 HgTe Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910000070 arsenic hydride Inorganic materials 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 238000001931 thermography Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
- C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
- C23C16/45561—Gas plumbing upstream of the reaction chamber
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B19/00—Selenium; Tellurium; Compounds thereof
- C01B19/007—Tellurides or selenides of metals
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- C30B25/02—Epitaxial-layer growth
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/46—Sulfur-, selenium- or tellurium-containing compounds
- C30B29/48—AIIBVI compounds wherein A is Zn, Cd or Hg, and B is S, Se or Te
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/50—Solid solutions
- C01P2002/52—Solid solutions containing elements as dopants
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
- C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
- C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Physical Deposition Of Substances That Are Components Of Semiconductor Devices (AREA)
Abstract
A layer (20) of CdxHg1-xTe is grown on the surface of a substrate (21) by decomposing volatile compounds of cadmium and tellurium e.g. alkyls in a mercury atmosphere. The substrate (21) is placed in a vessel (16) containing a mercury bath (19) with the vessel and bath at a suitable pressure and a temperature below the alkyl decomposition temperature. Hydrogen is passed through bubblers (6, 7, 25) separately containing alkyls of cadmium, tellurium, and if required a dopant, into the vessel (16). The substrate (21) is independently heated (18) above the temperature of the vessel (16) so that the alkyls decompose on the substrate (21). The substrate may be CdTe, a II-VI compound or mixed II- VI alloy. The alkyls may be dimethyl cadmium, diethyl cadmium, dipropyl cadmium, dimethyl telluride, diethyl telluride, dipropyl telluride or dibutyl telluride, or hydrogen substituted tellurium alkyls such as hydrogen ethyl telluride. <IMAGE>
Description
SPECIFICATION
Manufacture of Cadmium Mercury Telluride
The invention relates to the manufacture of the material cadmium, mercury telluride i.e.
CdxHGl~xTe commonly referred to as CMT or
MCT.
Such a material in its semiconducting form is used as a detector of infra red radiation in thermal imaging systems. These detectors comprise small pieces of CMT cut and polished flat with electrical contacts. U.K. Patent Specification No. 859,588, published 25 January 1961, describes the production and use of CMT detectors.
At present CMT appears to be the most useful of all infra red detectors and is therefore used in the majority of high performance thermal imager systems.
CMT is a difficult material to grow and handle, partly because of the volatile nature of the components.
Present methods of manufacture can be broadly classified into bulk melt growth and epitaxial methods.
The most important melt growth methods are: the Bridgman method involving growth in a sealed container carried out in a vertical or horizontal manner; the cast quench anneal method; a cast recrystalline anneal method; and a socalled slush method. All these methods involve batch preparation that is lengthy and expensive taking weeks rather than days to complete. A further disadvantage is that the crystals produced are roughly cylindrical and need slicing, grinding, lapping, etching and dicing into small pieces for use as e.g. detectors.
Epitaxial methods of manufacturing semiconductors on the other hand are intrinsically quicker in so far as they produce thin layers of semiconductor material onto a substrate directly often in a matter of hours or minutes. In the case of materials like GaAs, InP, and GaP well developed methods are available for the growth of homoepitaxial layers of these compounds onto substrates of the parent semiconductor by either liquid or vapour phase processes. However no such well developed art is available in the case of
CMT.
In the case of the epitaxial growth of CMT from the liquid it has been reported by Harman, J.
Electronic Materials 8 (1979)191; and by Schmit and Bowers, Appl. Phys. Letters 35(1979) 457; and by Wang et al, J. Electrochem. Soc. 127 (1980) 175; and by Bowers et al, I.E.E.E. Trans.
Electron Devices ED 27 (1980) 24; and by Wang et al, I.E.E.E. Trans. Electron Devices ED 27 (1980) 154; that it is possible to grow layers of
CMT from supersaturated solutions in excess tellurium or mercury onto substrates of cadmium telluride (CdTe). Such processes demand considerable skill and a very long development period. The epitaxial layers frequently suffer from surface blemishes which can render them useless for device fabrications. Such methods also suffer a fundamental limitation in respect of composition control i.e. the value of x (in CdxHgl~xTe) cannot be independently controlled.
Thus to produce epitaxial layers having different values of x it is necessary to use differently composed solutions of CMT in Te.
A vapour phase epitaxial (VPE) process for growing CMT has been reported by Vohl 8 Wolfe (J. Electronic Materials, 7 (1978) 659).
This uses an open flow process with independently controlled sources of the elements
Cd, Hg, and Te. However, this method suffers a fundamental limitation in the inability to effect adequate control of the values of x at the low deposition temperature that is needed to produce
CMT particularly in the important range x=0.2- 0.3. Because of the low vapour pressure of Cd and Te in the region of 4000C the input vapours can suffer a capricious reduction in composition before they reach the substrate. When the substrate is held at a temperature suitable for epitaxial CMT growth the temperature gradient in the deposition chamber is not high enough to prevent condensation of CdTe upstream from the substrate.
Epitaxial layers ot CMT have also been produced by subliming sources of HgTe onto a
CdTe substrate in close proximity-socalled close-spaced epitaxy-with or without the presence of additional Hg. Examples include the work Cohen-Solal and co-workers, and Tufte and
Stelzer. References to these works can be found in J.Appl.Phys. 40 (1969).
This technique relies on the production of CMT by the interdiffusion of Cd and Hg between the substrate and the epitaxial layer. It suffers from the problem of compositional non-uniformity in the direction normal to the plane of the layer. It does not have the advantages of independent control of composition enjoyed by an open flow technique.
Epitaxial layers of GaAs have been grown successfully by VPE using gallium alkyl and arsine.
This contrasts with the situation concerning
CMT where it is common knowledge that the attempted growth of CMT using the three alkyls of the elements Cd, Hg and Te in combination has not been successfui.
Although there has been a need, since 1961, for a relatively simple method of growing CMT the existing techniques of bulk growth, and epitaxial growth have proved inadequate in terms of speed of preparation and in the versatility of growing material of the desired composition. There is a need therefore to provide an effective method of manufacturing layers of CMT which method allows independent control of the composition Cd,Hg,Te and that preferably allows for independent control of doping.
According to this invention a method of growing a layer of the ternary alloy cadmium mercury telluride onto a substrate comprises the steps of:
providing an atmosphere of mercury vapour at a required temperature and pressure inside a vessel;
controlling the temperature of the substrate mounted in the vessel;
providing the supply of a volatile cadmium compound into the vessel and onto the substrate;
providing a supply of a volatile tellurium compound into the vessel and onto the substrate;;
the arrangement being such that the cadmium and the tellurium compounds decompose in the region of the substrate and the cadmium and tellurium combine with mercury on the substrate to form a layer of cadmium mercury telluride whose cadmium composition is controlled by the supply of cadmium and the overall composition of the cation content is controlled by the supply of tellurium compound, the mercury vapour pressure being held greater than the decomposition pressure of the growing layer.
The grown layer may a single epitaxial layer or multiple layers. Such a layer or layers may be graded in composition. The layer or layers may also be suitably doped. For example two layers may be grown with two different values of x so that a detector, sensitive to both the 3 to 5 and 8 to 14 ym wavebands may be made. Also a passivating layer of CdTe may be grown on the.
Cd,Hg,Te layer. Suitable lI-VI compounds or mixed alloys may be grown on the layer e.g. CdTe,
ZnS, CdTex Sel~x} which may be used to make heterojunctions or form antireflection coatings, etc.
The substrate may be CdTe, a Il-VI compound or mixed lI-VI alloy. The substrate may be silicon (Si), gallium arsenide (GaAs), spinel (MgAI2O4), alumina or sapphire (AI2O3), etc.
The volatile cadmium compound may be an alkyl such as dimethyl cadmium, diethyl cadmium, or dipropyl cadmium, etc.
The volatile tellurium compound may be an alkyl such as diethyl telluride, dimethyl telluride, dipropyl telluride, or dibutyl telluride, etc., or equivalent hydrogen substituted tellurium alkyls, such as, e.g. hydrogen ethyl telluride [H(C2H5)Te].
Apparatus for growing a layer of cadmium,
mercury telluride according to the method of this
invention, comprises a vessel containing a substrate, heating means for heating the vessel, a substrate heater, a means for supplying a mercury vapour inside the vessel, means for supplying a cadmium alkyl into the vessel, and means for supplying a tellurium alkyl or hydrogen substituted tellurium alkyl into the vessel, the arrangement being such that the cadmium and tellurium compounds decompose in the mercury atmosphere to form the compound CdxHg~xTe on the surface of the substrate.
The mercury vapour may be provided by a bath of mercury inside the vessel adjacent to the substrate.
The vessel heater may be an electrical
resistance heater surrounding the vessel to heat
both the vessel and mercury bath.
The substrate may be mounted on a carbon
susceptor and heated by an RF coil surrounding part of the vessel. Alternatively resistance heaters may be used inside the vessel, or an infra red heater may be caused to illuminate the substrate surface.
The compounds of Cd and Te may be supplied by passing high purity hydrogen through two bubblers containing the appropriate compounds of Cd and Te.
The invention will now be described, by way ef example only with reference to the accompanying drawing which is a schematic flow diagram.
As shown high purity hydrogen is supplied to a hydrogen manifold 1 which maintains a supply for five mass-flow controllers 2, 3, 4, 5, and 23. Mass flow controller 2 supplies hydrogen via a bypass line 14 to a combustion chamber 31 which burns exhaust vapour in a hydrogen flame. Mass flow controllers 3 and 4 supply hydrogen to alkyl bubblers 6, and 7, which respectively contain an alkyl of cadmium such as dimethyl cadmium and an alkyl of tellurium such as diethyl telluride.
Hydrogen flow from the controllers 3 and 4 can be diverted via valves 8 and 9 to the bypass line 14 or through valves 10,11 and 12, 13 thus enabling the alkyl flows to be turned on and off.
Hydrogen bubbling through the liquid alkyl will become saturated with alkyl vapours at the ambient temperature of the liquid alkyl, typically 250C. These alkyl plus hydrogen streams are mixed in a mixer 1 5 with a further dilution flow of hydrogen supplied by the mass flow controller 5.
By control of flows through controllers 3, 4, and 5, the concentrations of cadmium and tellurium alkyls in the mixed stream can be independently determined over a wide range of values.
The alkyl plus hydrogen mixture is passed into a reactor vessel 1 6 which is heated with an electrical resistance furnace 1 7 and R.F. induction coil 1 8. Inside the reactor vessel is a mercury bath 19 and a carbon susceptor 21 carrying the substrate 20 to be coated with a layer of CMT.
The furnace maintains the temperature of the reactor vessel wall from the mercury reservoir 19 to the substrate 20 equal to or greater than the mercury reservoir temperature, the mercury reservoir being heated by thermal conduction through the reactor wall 24. The RF induction coil
18 couples into the carbon susceptor 21 thereby heating the substrate to a temperature above that of the reactor wall 24 so that the cadmium and tellurium alkyls will crack and deposit cadmium and tellurium onto the surface of the substrate 20. The temperature of the mercury reservoir 9 is determined by the requirement of an equilibrium partial pressure of mercury to be maintained at the growth interface. The hot reactor wall 24 ensures that the mercury partial pressure in the vapour stream is the same at the substrate 20 as over the mercury reservoir 1 9.
Typical conditions for growth of a layer of CMT on a CdTe substrate are:- alkyl bubbler temperature 250C; vessel wall and mercury bath temperature 220-3200C (e.g. around 3000C): substrate temperature 400-4300C (e.g. around 410"C): Hydrogen dilution flow through controller 5 is around 500 ml/min: flow through Cd alkyl bubbler around 2-200 ml/min (e.g. 40 ml/min); flow through Te alkyl bubbler around 500-1100 ml/min (e.g. 1,000 ml/min). The walls of the vessel 1 6 are sufficiently hot to prevent condensation of Hg without significant decomposition of the alkyls, whilst the temperature of the substrate 20 is sufficient to decompose the alkyls at the substrate 20 surface.
The substrate may be inclined slightly e.g. 40 to give more uniform growth along the substrate.
In one example a layer of Cdo 2Hg08Te was grown on CdTe at 20 off the [100] orientation and inclined at 40 to the gas flow under the following conditions:-- alkyl bubbler temperature 250 C; Hg temperature 2900C; substrate temperature 410"C; H2 dilution flow 400 ml/min; Cd alkyl flow 50 ml/min; Te alkyl flow 950 ml/min.
A water cooling jacket 22 at one end of the vessel 1 6 condenses out the unreacted mercury and prevents overheating of reactor vessel and plate seals. The exhaust vapour stream is then mixed with the bypass 14 stream of hydrogen and burnt in the combustion chamber 31 for safety reasons.
A vacuum pump 30 is connected to the vessel 16 via a cold trap 29 for initial purging of the vessel 1 6.
The layer of CMT grown on the substrate may include one or more dopants. Such a dopant is provided by passing hydrogen from the manifold through a mass flow controller 23 to a bubbler 25 containing an alkyl of the dopant. Alternatively a volatile hydride of the dopant in hydrogen may be used. From the bubbler the alkyl passes to the mixer 1 5 and thence to the vessel 1 6. Valves 26, 27, 28 control the flow of hydrogen and alkyl.
Examples of dopants and their alkyls are as foliows:-- Al, Ga, As, and P from the respective alkyls (C '3)3Al, (CH3)3Ga, (CH3)3As, (CH3)3P.
Examples of dopants and their hydrides are as follows: Si, Ge, As, and P from their respective hydrides SiH4, GeH4, AsH3 and Ph3. A supply of the hydrides e.g. SiH4 may be supplied direct from gas cylinders.
In a modification the cadmium and tellurium compounds may be supplied together or independently direct into the vessel 1 6 to mix above the substrate 20. These supplies may be via thermally-insulated tubes.
Using the above method and apparatus infra red detectors may be made. Such a detector may be a layer of CMT on CdTe substrate with a passivating layer of oxide or CdTe on the CMT layer surface. The detector may be in the form of a strip with electrodes on the surface at each end as described in UK Patent Specification 1,488,258.
Such a detector is photo conductive and has the image of a thermal scene scanned over its surface.
Another type of IR detector uses a p-n junction e.g. the junction between two differently doped, p and n doped, CMT layers to form a photo-voltaic detector. Voltage is applied by electrodes across the p-n junction and changes in current are a measure of the infra-red photons that are absorbed by the detector. Such a detector may be formed into a large array of IR detectors capable of imaging a thermal scene, without a scanning system, to form a so-called staring array system.
The materials Cd,Hg,~,Se and Cd,Hg,~,S may be grown in a manner anaiogous to that described above.
Claims (14)
1. A method of growing a layer of the ternary alloy cadmium mercury telluride onto a substrate comprising the steps of:
providing an atmosphere of mercury vapour at a required temperature and pressure inside a vessel;
controlling the temperature of the substrate mounted in the vessel;
providing the supply of a volatile cadmium compound into the vessel and onto the substrate;
providing a supply of a volatile tellurium compound into the vessel and onto the substrate;;
the arrangement being such that the cadmium and the tellurium compounds decompose in the region of the substrate and the cadmium and tellurium combine with mercury on the substrate to form a layer of cadmium mercury telluride whose cadmium composition is controlled by the supply of cadmium and the overall composition of the cation content is controlled by the supply of tellurium compound, the mercury vapour pressure being held greater than the decomposition pressure of the growing layer.
2. Apparatus for growing a layer of Cd,Hg,Te on a substrate comprising a vessel for containing the substrate, heating means for heating the vessel, a substrate heater for independent control of the substrate temperature, a means for supplying a mercury vapour inside the vessel, means for supplying a cadmium alkyl into the vessel, and means for supplying a tellurium alkyl or hydrogen substituted tellurium alkyl into the vessel, the arrangement being such that the cadmium and tellurium compounds decompose in the mercury atmosphere to form the compound Cd,Hg,Te on the surface of the substrate.
3. Apparatus according to claim 2 wherein the mercury vapour is provided by a bath of mercury inside the vessel adjacent the substrate.
4. Apparatus according to claim 2 wherein the means for heating the vessel is an electric resistance heater.
5. Apparatus according to claim 2 wherein the substrate heater is a susceptor for carrying the substrate and co-operating with an inductive heater coil surrounding part of the vessel.
6. Apparatus according to claim 2 wherein the means for supplying cadmium alkyl comprise a bubbler containing a cadmium alkyl through which bubbler hydrogen is passed to carry the alkyl into the vessel.
7. Apparatus according to claim 2 wherein the means for supplying tellurium alkyl comprise a bubbler containing a tellurium alkyl through which bubbler hydrogen is passed to carry the alkyl into the vessel.
8. Apparatus according to claim 6 comprising means for admitting hydrogen to the vessel independently of the alkyl bubbler.
9. Apparatus according to claim 2 and further comprising means for supplying a volatile dopant compound into the vessel to decompose on the substrate.
10. Apparatus according to claim 6 wherein the cadmium alkyl is selected from the group dimethyl cadmium, diethyl cadmium, and dipropyl cadmium.
11. Apparatus according to claim 7 wherein the tellurium alkyl is selected from the group, diethyl telluride, dimethyl telluride, dipropyl telluride, dibutyl telluride, or an equivalent hydrogen substituted telluride alkyl.
12. Apparatus according to claim 9 wherein the volatile dopant is selected from the alkyl group (CH3)3Al, (CH3)3Ga, (CH3)3As, (CH3)3P, or the hydride group SiH4,GeH4, AsH4 PhH4.
1 3. A device comprising a substrate having at least one layer of CdxHg1~xTe grown thereon by the method of claim 1.
14. A device according to claim 13 wherein a layer of CdxHg1~xTe includes a dopant.
1 5. A device according to claim 1 3 wherein the substrate is CdTe.
1 6. A device according to claim 1 5 wherein a passivating layer of CdTe is grown on the CdxHg1~xTe layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8115127A GB2078695B (en) | 1980-05-27 | 1981-05-18 | Cadmium mercury telluride deposition |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8017334 | 1980-05-27 | ||
| GB8115127A GB2078695B (en) | 1980-05-27 | 1981-05-18 | Cadmium mercury telluride deposition |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2078695A true GB2078695A (en) | 1982-01-13 |
| GB2078695B GB2078695B (en) | 1984-06-20 |
Family
ID=26275648
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8115127A Expired GB2078695B (en) | 1980-05-27 | 1981-05-18 | Cadmium mercury telluride deposition |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2078695B (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0068652A2 (en) * | 1981-06-24 | 1983-01-05 | The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and | Photo diodes |
| EP0135344A1 (en) * | 1983-09-13 | 1985-03-27 | The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and | Manufacture of cadmium mercury telluride |
| EP0140625A1 (en) * | 1983-10-19 | 1985-05-08 | The Marconi Company Limited | Tellurides |
| FR2608637A1 (en) * | 1986-12-18 | 1988-06-24 | Raytheon Co | PROCESS FOR THE GROWTH OF SEMICONDUCTOR MATERIALS BASED ON GROUP II AND VI ELEMENTS BY CHEMICAL DEPOSITION OF ORGANOMETALLIC COMPOUNDS IN VAPOR PHASE, WITH IMPROVED COMPOSITION UNIFORMITY |
| US4920068A (en) * | 1986-04-02 | 1990-04-24 | American Cyanamid Company | Metalorganic vapor phase epitaxial growth of group II-VI semiconductor materials |
| GB2263708A (en) * | 1992-01-31 | 1993-08-04 | Fujitsu Ltd | Ii-vi epitaxial layer on (111) substrate |
-
1981
- 1981-05-18 GB GB8115127A patent/GB2078695B/en not_active Expired
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0068652A3 (en) * | 1981-06-24 | 1985-05-02 | The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And | Photo diodes |
| EP0068652A2 (en) * | 1981-06-24 | 1983-01-05 | The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and | Photo diodes |
| EP0135344A1 (en) * | 1983-09-13 | 1985-03-27 | The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and | Manufacture of cadmium mercury telluride |
| GB2146663A (en) * | 1983-09-13 | 1985-04-24 | Secr Defence | Manufacture of cadmium mercury telluride |
| US4566918A (en) * | 1983-09-13 | 1986-01-28 | The Secretary Of State For Defence In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland | Utilizing interdiffusion of sequentially deposited links of HgTe and CdTe |
| EP0140625A1 (en) * | 1983-10-19 | 1985-05-08 | The Marconi Company Limited | Tellurides |
| US4920068A (en) * | 1986-04-02 | 1990-04-24 | American Cyanamid Company | Metalorganic vapor phase epitaxial growth of group II-VI semiconductor materials |
| FR2608637A1 (en) * | 1986-12-18 | 1988-06-24 | Raytheon Co | PROCESS FOR THE GROWTH OF SEMICONDUCTOR MATERIALS BASED ON GROUP II AND VI ELEMENTS BY CHEMICAL DEPOSITION OF ORGANOMETALLIC COMPOUNDS IN VAPOR PHASE, WITH IMPROVED COMPOSITION UNIFORMITY |
| GB2199594A (en) * | 1986-12-18 | 1988-07-13 | Raytheon Co | Vapor deposition growth of group II-VI semiconductor materials |
| GB2199594B (en) * | 1986-12-18 | 1991-08-07 | Raytheon Co | Vapor deposition growth of group ii-vi semiconductor materials |
| GB2263708A (en) * | 1992-01-31 | 1993-08-04 | Fujitsu Ltd | Ii-vi epitaxial layer on (111) substrate |
| US5302232A (en) * | 1992-01-31 | 1994-04-12 | Fujitsu Limited | (111) Group II-VI epitaxial layer grown on (111) silicon substrate |
| GB2263708B (en) * | 1992-01-31 | 1995-01-18 | Fujitsu Ltd | II-VI Epitaxial layer on (111) substrate and method |
| US5394826A (en) * | 1992-01-31 | 1995-03-07 | Fujitsu Limited | Method of (111) group II-VI epitaxial layer grown on (111) silicon substrate |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2078695B (en) | 1984-06-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PE20 | Patent expired after termination of 20 years |
Effective date: 20010517 |