PARARE PELLICOLE EPITASSIALI PROCEDIMENTO ED APPARECCHIO PER PRE

Description

495804 / 78 ΗΜ / 7882S1B ?9Χ'ί PBSGR.1 ' / > ίOJNκ de31 ' irivenir· industrial j.one del, title* 'TROCBBlriBN'lO B APPARATUS FOR PREPARING TO.MOOI.B BRIf ASG1 ΑΧ·! ”f of the US company G'i-ίκ Diti '.ιιΐ;ΐ} ΒΐΛΦΚΒ OP Ali BRIGA, represented by Secretary? of the Ravy* and once again represented by the*Assistant Chief of Bava! Resoerch for PatenteSoc» of the State of Virginia» with headquarters inARl-IRGHOW - (υ.Β.Α.) o>toax*>ttìct'cooar *ηφή+ ο-ο-ό-ó- The present invention relates in general to a process for preparing epitactic films for use with infrared detectors, particularly to lead calculi epitactic films suitable for photovoltaic applications. Furthermore, the present invention relates to a simplified process for adjusting the conductivity type and carrier concentration of the semiconductor material during spitaxial development. Lead-salt alloy films have been intensively investigated recently, with particular attention to their photovoltaic properties. Special attention has been paid to their possible use as infrared radiation detectors. The exploration of vacuum deposition techniques is very recent, and for the benefit of those who may be unfamiliar with pioneering efforts in this technique, the following brief summary is given. Get ready) of Single**Crests!! Pilwi Of PbS, <53 R «B.Bchoolen and JM fcea.e], Journal of Appli©<5 Pbysics,Vo3· J5, B. 6,(June 3 96'0. peSS* 1648 - 1851* Bpitexial Beed*Conteining PfcotoconduetivG Mate¬riale, R, B. Sohooler, HR. Riec'3, and JP Davis*US patent 3-574,340 (April 1971) Method of Preparati on of Lmà SulfidG ΡΝJunction Diodes, by R.B. Schedar, patent V. 8. A ·$,716,424 (February 1975). Kethod of Varyￃ￬ug The Carrier ConoentrationOf Bead-Tin Solfi do Bpltaxiel Filtra di R*R. Schoolar,patent DSA'5.795.070* (February 1974). Photoconductive PbSo Epitaxial Filifedi R#BShoolei- and RJ Bowney, Jourrel of Vacuimi ScienceSlecbnology, Voi· ·8, N«3 (3971)· More recent efforts * b&nehè originated from a different direction* include; Propertiee Of ϊΐ>8, Se Epila.yere DepositedOnte PbS Substretee By Bot-Val,! / Epitaxy* by R. I«the H< Proiex·, Journal of Vaouùw Science Technology,pag· 3300 (1975)* PbSo Keteropitésxy By The Hot Wall Te ob.nl qug diK. Puh e EProie3·, Thi n So3 id Fi 3 m .Voi. ?7, peg · 247, :(1975). Doublé· Haterodunction Pt»S- Ifiseer Diodos ViiV> CW Opcratìòx> Dp 1'© ty&Y*» ài W. Freie* ♦ M,: Bleieher, W. Riede3 , e H« Maiar* Applied Vhyeiceli©11ere, Voi. 26,M* 13,(June 3976). Pb'J'e end Bpitaxial On Cleaved BeFg Substratoe Brepared B;y .li 3$fied Hot*Wall StechniQue, by ￎﾐ, Rasai, D. ^ ￃﾨￂﾫs*ett> and J.Horoung, Journal oi* Applied! Ruyeiefc / :-V 1* {ￃﾬai&ￃﾬo 19?Ò* Double*Bet'eroéiru.eture PbS-tpbSe'-BbS lisew·,' CW Viitb / Operat i00 Up to 120 K dii H. Prcier* Μ* B3eicho / ·W* Melò, and H. Haler, Journel Of Applied fchysics,Voi. 4? (December l9?6). Growth Of We Film» Itodé Nesr~BQUÌlibrium,by A. Bope»·* Otero* Journal of Applied Bbysioe, Voi.48 (Gennaio 1977)* It is well established that films of single crystals of PbE, PnSe, and related compounds, hereinafter referred to as lead salt alloys, can be grown epitaxy on heated alkaline dislogous metals by vacuum evaporation. It is also known that the conductivity of these bulk semiconductors can be adjusted by controlling the deviation from stoichiometry. Anion vacancies (V' Μ) make these crystals P-type, and ion vacancies make them N-type. In the past, lead diodes were produced using various diffusion techniques. These diodes, at low partial voltages, were used to generate vapor molecules during the emission and ignition process. In this case, few collisions occur between their vapor molecules. In the event of molecular collisions, a film prepared by simultaneous subimaging of a group of materials according to the principles of the present art, with the apparatus set forth and examples in the patent No. 5-716,424, would be of non-uniform conductivity and of graduated electrometry. An alternative process "with exposure of a film of lead compound to the vapor of a dopant" would provide only a slight change in the conductivity of the film and a noticeable change in its composition. The spectral response of the exposed film would be the same as that of the undoped film. In an earlier paper published in volume 41 of the “Executive of Applied Physics,” page 54, (19?0), Henry Hollowey stated that he employed a vacuum deposition technique in which the substrate <5 '(halide) and crystalline is retained and 3^°o. Subsequent efforts (for example, PropesiSes OS PbS g0ifpi lecere. ·.. .of K* hub and B, 3Rr©i©r,'psee above) * continued © maintain the temperature of the substrate© This value or ir» proximity to it. Efforts to improve the electrical properties of epitaxial layer films, prepared by vacuum deposition, such as hot-wall (HWJ) techniques, have increased the purity of the materials and the epitaxial layer development regime, resulting in unnecessarily complex equipment without providing device-quality films. These efforts have uniformly failed to recognize the opportunity to maintain a quasi-thermodynamic equilibrium at the film development surface or have thus allowed the cogen to re-evaporate from the development surface.zero and one, inclusive* and s 0.500 + 0.005, with predetermined electrical and optical properties, is prepared by equilibrium development techniques (BGT). On an alkaline dilog black substrate maintained in near-thermodynamic equilibrium with the source charges, a single discharge orifice of a furnace and two double-chamber zones are exposed in which a homogeneous vapor has been produced by simultaneous sublimation of a lead alloy in one chamber and a measured quantity of chalcogenide in an adjacent chamber. The regulation of the compositions of the lead alloy charge regulates the energy field and hence the spectral response of the sublimate. The regulation of the ratio between the metal alloy and chalcogenide vapors / auro regulates the aviations of the stoichiometries **©)sublimate © therefore its type of conductivity ' ' / 1 .its concentration of supports· DNA substitutes!Or > ne of materials allows the preparation, using this technique, of epitaxial layers and single phase of 0. <y ir · 1*0. By various means of rotating the cell-cell in the oven at a lower value up to its sub)motion temperatures or beyond, films and flat junctions of multiple successive epitaxial layers of the cells can be prepared, presenting opposite types of conductivity. Consequently, one of the proselyte inventions consists in providing a procedure and an apparatus for preparing thin polyolefin epithelial tissues of lead sulfide-selenide. A second object of the invention is to provide a process and apparatus for epitaxially preparing thin films of lead-tin silicates. Another object of the invention is to provide a process and apparatus for epitaxially developing thin films of lead-tin silicates. It is yet another object of the invention to provide a method and apparatus for controlling the stoichiometries of lead alloy films during development. Another purpose of the present invention is to provide a process and apparatus for epitaxially developing thin films of lead salt alloys with predetermined concentrations of charge carriers. Still another object of the invention is to provide a process and apparatus for epitaxially developing a thin film of lead salt alloy in which the ratio of salt to lead alloy in the deposited films is from 0 to 1, inclusive. A further object of the invention is to provide a lead sulfide*selenide* epithelial film of sufficient quality to perform photovoltaic operations. A further aim of the invention is to provide an epitaxial film of lead alloy 35 eoi© which will have a spectral response tuned in the positions. A further objective of the invention is to provide a thin film of lead chalcogen of regular stoichiometries suitable for photovoltaic applications. One purpose of the halo is to provide a thin film of lead chloride of uniform conductivity, suitable for photovoltaic halo applications. Another object of the invention is to provide a lead sulfide-selenide photovoltaic detector designed to operate at room temperature. A more complete understanding of the present invention and of many of its attendant advantages will readily become apparent unless it is understood by reference to the following description, taken together. The accompanying drawings, in which equal numerals denote equal or equal lines and in numbers 3 and 1, are a representative view of a section of a test apparatus in which the process according to the present invention may be carried out; and Figure 5 is a diagram of the temperatures of the air and the development along the length of the apparatus shown in Figure 1 along 1 and 2.and a logarithmic temperature scale is provided; Figure 3 is a perspective view of a photovoltaic detector prepared using the equilibrium development technique; Figure 4 is a diagram illustrating the current-voltage characteristics of a lead-on-Pfc Schbottky barrier; Figures 1 through 2 are diagrams of the response capacitance at 20°K, 19°K, and 300°K for Pbf-Be^* films of the P-type; Figure 5 is an orthogonal diagram showing measured values ​​of the Hall coefficient and Hall mobility at 20°K for three Pbf-Be^* films as a function of ambient temperature; «< io - Figure 7 is an orthogonal diagram illustrating the response characteristics of a lead Schottky barrier on films. If y=f>,OG£i xm,yy, Figures 8 through 8F are orthogonal diagrams illustrating the theoretical (solid lines) and experimental (dashed lines) response characteristics of lead Schottky barriers on films. Spite all of lu, Sr Se and ??°K; xy y Figure 9 is an orthogonal diagram showing the dependence of the mean lifetime of minority charge carriers and ??°K as a function of substrate temperature during development and Figure 10 is an orthogonal diagram illustrating the mean lifetime of minority charge carriers (solid line) and the lattice decoupling (dashed line) as a function of energy range in epitaxial films of lead-salt alloys. With reference to the drawings and in particular to Figure 1, a cross-section of a two-temperature vacuum deposition apparatus is shown, intended for the preparation of epitaxial layers of compounds IV-VI for devices using equilibrium development techniques. The apparatus shown is a conventional glass chamber with a single-hole cooling trap and a pump 54 and an oil melting point mounted thereon. on a base 50. The central component of the apparatus illustrated is a burner and two are double hinges 3' ©, known in common parlance as an "insert". A primary burner of 20 mm diameter, type C, produced with glass (1 oak), discharges through its upper ends into a basket.26 © single orifice, of larger diameter. A smaller vertical secondary furnace 10, also of 1 / 4 glass, known as a "cold tip," consists of a blind tube hung coaxially (that is, coaxially to ensure a more uniform distribution of sublimate) extending through the bottom and discharging into the primary furnace 20 © above the contents. A simple metal brace (not shown) holds the insert erect. During operation, the contents 2, 8 of the primary and secondary furnaces 20, 50 are brought to and maintained at the desired temperature by a pair of independently controlled external thermal devices 22, 52, shown as being helically wound around the lower ends of the primary and secondary furnaces 20, 50. Typically, the thermal device 22 is a resistor, such as a nickel-chromium wire coupled to a regulated current power supply.Heating by conduction and by radiant effect occurs between the primary furnace 20 and the upper third of the secondary furnace $0. Depending on the contents of the secondary furnace $0, the thermal device $2 may be a heating coil in the coil 22, or a cooling coil. If the chalcogen charge 6 is, for example, sulfur, the thermal device $2 may be a short section of pipe or duct arranged against the base 5>0 and carrying tap water, flowing at a sufficient flow rate to partially cancel the heat transfer by conduction and to maintain the sulfur charge 8 at a lower temperature than the metal alloy charge 2 in the primary furnace 20. A glass deflector 24, arranged between opposite ends in the primary furnace 20, reduces the size of the molecules !, entering the chimney26. . Directly above the chimney 26 are arranged one or more substrate collectors 40, each of which carries and maintains at a desired temperature a layer of substrate 12 held at 1% - plus voltage, with the latter exposed to the orifice of the chimney 26. A monitor 60 thick, available in sections and space permitting, is located above a port 40 in the substrate collector 40 so that its replaceable crystal glass plate 62 is exposed to the sublimate passing through the port 40. The mask and shutter mechanism 42, located between the orifice of the chimney 26 and the faces of the layers 12 of the six-layer furnace, is normally closed to prevent condensation of the charge materials. When the furnaces are not maintained at the appropriate temperatures, thermocouples 64, 66, 68 monitor the respective temperatures of the charge source, of the calculi 8 and of the substrates XP.An iodide gauge 2 is used to measure the vacuum within chamber 56, below 1.0 torr. The source material 2, consisting of the metallic alloy, is prepared by mixing weighed masses of the component elements, [Poi [e Be_ 3. r 8 3i J.**XJ « 8 [Pb, Bn 3 C8©)- , in which α = 0.60, proposed α = 1 *-jy α = 1 = 1 atomic weight] in the composition of the desired epitaxial layer, heating the mixtures in a vacuum chamber until a fully reacted melt forms, α = 14 - and cooling the melts to room temperature. The resulting polycrystalline is ground into coarse granules. The atomic strength, * a, is varied within 0.5% to make the mixed mass slightly rich in metal or cogenide, as desired.A methyl-rich mixture, e <0.500, produces a type II conductive epitaxial layer without a compensating chalcogenide dopant, while a chalcogenide-rich mixture, e <0.500, produces a type I conductive epitaxial layer. The dopant 8 is a pure six-nite (i.e., 99*9999$) choline chloride dopant (e.g., (8, Bo)). The substrates 40 are freshly cleavaged slices of a single crystal of an alkali halide such as Sa₂Pg, or K₅r. The bottom of the primary furnace 30 is charged with about 50 g of powdered granules of the metal alloy 2, such as D₂b₄CB₂Be, 3, wherein 0 s * «ni. A charge of 1*;Χ 20 g is sufficient to prepare about 50 epitaxial layers. The bottom of the cold point, i.e., secondary furnace 30, is charged with about 1 B of choline chloride dopant 8. Before placing in furatone, insulating, recently cleavaged (III) crystalline substrates 12 are placed in the substrate heater 40. The chamber 26 is moved under vacuum to a pressure of the order of 10 ^ torr (i.e., approximately 1.2-10 ^ Pe), although only a vacuum higher than 10 ^ torr is necessary. The temperature of the substrates 12 is brought to and maintained within the range of 322 9 210 µC. The fraction of atoms of the layer 12 is dependent on the substrate temperature. The metal alloy charge 2 in the primary furnace 20 is brought to between 5 5 µC and 6 20 µC and is maintained within ± 2 µC of this range. The temperature of the dopant charge 8, if the dopant is sulfur, is maintained at a conventional ambient temperature with a tolerance of + 2°C. Before sublimation, a substrate temperature is empirically chosen to allow epitaxial development >me with a minimum of 4n defects.By varying the temperature of the φtanic alloy core 2 or the substrate 12 or both within their respective temperature ranges, the development rate of the epitaxial layer film 14 is varied within a range of φ between 2 and 20 μm per hour. The epitaxial layer is not sensitive to the development regime. However, as shown below, the average thickness of the epitaxial layer is maintained by keeping the substrate temperature increased during its development. The thickness of the developed films can be varied from about 200 μm to over 1 μm. Referring now to figure 16, of dreams» a vertical operating temperature profile of the two-temperature zone apparatus of figure 1 is plotted in orthogonal coordinates for the preparation of a Pn& So film. A logarithmic x1*x scale of the temperature starting from approximately room temperature and passing through thousand degrees Kelvin is plotted along the x-axis and a semi-profile of part of the apparatus is plotted along the right-hand ordinate with a linear x-axis scale along the left-hand ordinate.As shown, the operating temperature within the apparatus varies from 500° K (26°C; » + 5°) across the sulfur dopant charge 8, to the range of 820° - 92° K (550° - 65°) across the metal alloy charge, and to the range of 598° - 790° K (525° - 510°) across the substrates 12. With the chambers 56; The thermodynamic equilibrium can be defined (taking into account the Gibbs functions) as a condition in which an isothermal profile is maintained over all lengths of the development chambers of the apparatus. The deviation of the profile shown in figure 1 from an isothermal one ensures the transport of vapor molecules 6 as well as .},»%their condensation on the substrates l£* the need to maintain the temperatures of only two areas of the furnace chamber, namely the main furnace charge 2 and l-'.fpélratl,12S within specific ranges» provides the simplification of this development theory, almost of ' equilibrium t ee of its associated apparatus atura*. Once the selected operating pressure and temperatures have been reached, the sublimation of the source charges 2 occurs, the shutter mechanism 42 is opened and 10 molecular particles 4 and 10 rise above the deflector 44 (i.e. the molecular particles 6) and fall onto the exposed surfaces of each substrate 12. The deflector 24 is arranged so that the largest of the particles 4, 10 can pass through and so that no particle can penetrate a 2, 6 source cell up to the substrate 12. in straight lines - Without the baffle plate 24, large particles would rapidly rise through the chimney P and advance until the substrate surfaces 12 © would block and cobble together 3, Adjacent surface layer, thereby causing a pinpoint in the epitaxial layer P, or would strike and rebound from the surface, possibly thereby breaking the epitaxial layer 14.Some particles 6 pass through the light 44 and condense on the crystal layer 62 of the thick monitor 60. This condensation decreases the resonant frequency of the piezoelectric crystal 62, thereby allowing the particles 62 and the rate of growth of the epitaxial layer or the closely adjacent substrate 12 to be observed. When an epitaxial layer 14 of the desired thickness has been developed, the shutter 42 is closed, the substrate and oven heaters are turned off, and atmospheric pressure is restored to the chamber. After cooling, the lead epitaxial layer 34, as shown in Figure 3, is removed from the film 54 under vacuum, and a Schottky barrier junction 136 is formed by depositing under vacuum, on the exposed surfaces of the films 14, through a tube. ·.stainless steel electrodes, a 300 mm centered point or strip of metal (e.g., indium, bismuth, lead, or tin). The developed electrode is annealed in a vacuum at 170°C for 30 minutes and then cooled to room temperature before depositing lead barriers. This process causes oxygen desorption from the exposed surface and is performed to ensure the production of a stable device. None of the samples are superficially passivated in the following examples. In one experiment, the electrode is a narrow strip of circular holes with an arc of 3 cm and 10 cm center spacing. The metal electrode.100 inverts the semiconductor and converts part of the underlying volume of epitaxial layer 14 into a zone 117 of a second-order conductivity opposite to the conductivity of epitaxial layer 14. The deposited metal spot 100 serves as an electrical contact onto which an electrical conductor 3.1 £ for an external circuit may be attached by lead soldering or gold or silver varnish, 101. A thin metallic layer (e.g., gold or nickel) is deposited elsewhere on the exposed face of epitaxial layer 34 to form an ohmic electrode 120. An ohmic electrode is an electrode that provides a supply of charge carriers that are freely available to enter epitaxial layer 14 as required. An electrical conductor 111 may be attached to electrode 180.Typically, incident radiation 1 passes through substrate 18 and into epitaxial layer 1Λ within a single scattering length of the plane junction 117 projected onto the common surface of substrate 18 © of the epitaxial layer 14Ϊ! The material chosen for substrate 38 must be transparent at the wavelengths of interest. Balv becomes opaque at about 14μ, XBr at about ρ2μ, and Srα at an intermediate wavelength. By placing a very thin layer of metal (say, of the order of 100μ) to form electrical contact 100, the contact will be transparent in the near-intermediate and far infrared bands, and the detector can be arranged to allow radiation 21 to be seen. Indigent X enters the epitaxial layer 1l without first passing through the substrate12* Based on the general nature of the present invention, the following illustrative examples are presented as typical embodiments thereof. It is understood that the invention is not limited to these examples and is susceptible of various modifications which are within the reach of any person skilled in the art. The true values ​​of the mobility of the charge carriers given in the examples are obtained after taking into account the oxidized surface layer, by analyzing two layers of petrite, as set out in "Surface Chorge 'fransporl In ΡθΒχ^ο1;χend Pbj ^Bn^Se. Ispitaxiel filma", by JI). Joneene RB. Journal, dJT Vacuum Science 3'e- chnolog, / , Vol. 3$, No. 4ￂﾻ, '1970...ￂﾷ 22 -. Ks / Miip jo, The apparatus shown in Figure 1 was used to deposit epitaxial films of freshly cleaved FbSxSc'l. x^°~x BO BePg (111 ). The deposition pressures and substrate temperatures are on the order of 10* torr (i.e., 1.5 x 10 'P&) and 550 to 400°C, respectively. The primary furnace 20 is maintained at 600°C. The growth rates are in the range of 2 to µm per hour. The distance between the source 2 and the substrate 12 is 5 4 cm in diameter in the primary furnace 20. Approximately 20 g of granulated, slightly lead-rich, PbS source material 2 is placed in the upper furnace 20. This is a sufficient charge of material to obtain 35 to 20 films of constant composition. The auxiliary furnace 50 or coaxial second furnace is charged with a small amount of pure sulfur 8 during the growth of PbG Se films. (0.5-£ x <1), ì*t.A sulfur source is needed to obtain p-type, nearly gold-free conductivity films. When the pressure is lowered, the substrate heater is turned on and allowed to reach a steady-state temperature between 525 and 510°C, the sublimation temperature of the source material. The primary furnace is then set to between 600 and 610°C and the films are deposited on the Baikal substrates. The films are cooled to room temperature, exposed to the atmosphere, and placed in a second evaporator to deposit lead Efchothy barriers. Before depositing the barriers, the films are annealed in vacuum at 120°C for 10 minutes and cooled to room temperature. The films are exposed to the atmosphere and introduced into a clean vacuum system in which gold contacts are deposited at the centers of the lead contacts and fine gold wires are attached with silver-plated material.The gold plates used for resistivity and Ball's coefficient measurements serve as optical contacts for detector measurements. The detector samples are then mounted in an optical dewer with a 20° field of view, and three Bi-Optic barriers are evaluated on each film. It should be noted that exposing fresh films to the atmosphere without passivation causes oxidation of their surfaces and a concomitant reduction in their electrical characteristics. The transport property for eight samples of PbS ile, with x various ahi lex 1 - X ninth reported in table t / .hii: between Del,3 h / p 1 a 77[,K> X Λ(µΠι) i·, »3 V10 '|c« ) lHlnS) 0^0 4.6 3.1 26,000 • * 0.0 ¢.1 0.175 V 26.000 >6.1 , >$2.2* 0 V 4.100 * − o,s 3.6 0.242 1.0 3.300 >3.6 >6.0 0)0 V li2 7.900 * * 0 05 5.e 0.294 0.6 7.000 5.0 5.4 * V) 1.30 1.30 0.305 2.8 8.000 >2.4 V Ιό curve 1 - V here :I urn I want.<·. Move each curve by two degrees along the axis of the heart. ··: 1<·. The temperature at the target * i 1. prod ο Ί toi· is 5 stenx : » - ·; τ ea of ​​a 1> arrives -abr ο 1 -top; the end? q υ where fi ia ρ p 1 i chi υ a polar p. / and x. I laughed and came; adi 0.1 S1 or t 31 product of PA then its air if ohe rullab 2.1 x 10* oh η i / e ir i? and ?7°K. Po e aj iae ;it à di rj sp os ί. abarri no of Γ; hey 11 k. y of 1 ' ì Π f ! a spectrals of quattrori ο n .fi .11 ra t ? s ο η ο η o E. et re te in figures 5A up to and *?&· The measurements are carried out with a modulation frequency of 5*10Hz. All four samples have broad response curves with sharp breaks at wavelengths corresponding to the limits of each of the delegations. The shape of these curves indicates that PbBSe detectors respond like ideal quantum meters with very little self-absorption in the films. The peak detection capabilities are just below that of infrared photodetectors limited by ground noise at ??bK,K. Photovoltaic detectors made of FoS Βε- stones prepared according to the erection process. XJ· X equilibrium output are suitable for operation at room temperature. Lower modulation frequencies will provide higher response capabilities. Example 11 «AV + . > Λ ·'' "f- ''»* *- ·. ' > Several hepatic films of Pt> Sn Se· 3 -yy (0 < y < 1) on freshly flaked (iii) are prepared using the apparatus shown in Figure 3 although the furnace 50 coaxial auxiliary.» is inactive, with the pressure and temperature ranges reported in example 1. The upper primary furnace is charged with approximately 20 g of Pb Sn Se i ” yj 26 - (O * y $0%0?) 1 and a lead-rich ray. The niche is charged with 1 1 ac ￎ﾿ￏﾄￎﾷￏﾁ oaii ￎ﾿ of the ingot of the 2nd sorbent, from which the films are grown. A sorbent charge rich in 0.4% metal is furnaced and per 1 N moles of type N ingot per 1 in the stoichiometric reaction of the new furnace. P-type samples of low carrier density. The transport properties of eight sample films at 77°K, the second having an N-type conductivity or a Γ-type conductivity, are reported in Table 2.ίλ ‘ : : Λ ? 0 (ITI *0 N 10,?(c«rJl £ / Vii) l'u <ηε» o,»w <>* 0,056 1,0 »0,000 hi • 0,6 o*»o M 0,106 6,6 li,000 ·» m o,»o io,> ο,ιοβ 1,0 »0,000 - * o,m V o ,m M »2,000 6,0 hi 0,636 m»o o,m M 18,000 f M hi 0,6<0 10,t o,m M 21,000 1,6 0,60 V 0,116 M 16,000 1,6 *>* 0,6« 6,1 0,122 1,6 ' »1,000 h*. Selected samples are measured up to liquid helium temperature as a quality control of the films. The Hall coefficient and Bell mobilities of 4.2° at 500°K are shown in Figure 6 for several epitaxial layers of FbSc and Pt>. Λ_βηΛ ^r,Sc as grown. The temperature-dependent mobility for O j0(0 / compares well with the highest values ​​reported in the literature. The mobility follows Ϊ very closely between 100 and 100°K and becomes temperature-independent below about 20°K. This departure from Ϊ is compatible with estimates of size effects, assuming diffuse scattering from a surface and a mean free path of 6.à μ. Nevertheless, the maximum mobility of 5 2 4 X 1.0 erri / V-si is the highest mobility observed for Pb. O;.Bn. O8e.The corrosion factor for size effects would increase the actual mobility of sample 99 to 1.8 x 10° cm / V~ & provided that other dispersion mechanisms were negligible. The maximum mobility for the P-type Pb&n&e sample deviates by a factor of four from the mobility of the N-type sample. This is compatible with the transport property of pure FbSe which has a higher electron mobility. The coefficient ~ 26. The Hall effect is essentially independent of temperature according to the measurements of Allgaeu and Seneca. The Ball coefficient of sample 140 shows a certain temperature dependence above 90°K indicating that the sample is becoming intrinsic. The I-V curve of a BcbottVy barrier of 0.06 Sn, 0.06 A*cBe and 77°S is shown in figure ?. v\Vp;> 0.06? , ,, ' p The product' a poi » ri * za none nul 1 ana . is 2.0 ohm / cm which compares very well with values ​​reported for similar devices produced by other means reported by Hohnke, Holloway, Young, and Burley in Applied Physioe Letter» Vol. 29, page 96 (1976)* The spectral response capabilities of six Pt>8n8e Bchottby barrier samples are shown in Figures 8A through Bf. The response capability of the JPbBe sample shown in the figure corresponds to that of an ideal quantum gauge and shows no evidence of peak formation due to absorption. All other alloys show some degree of peak formation, which is maximum in the thicker samples. The peak response capabilities decrease with increasing SnSe content and decreasing energy range. This is mainly due to a decrease in the zero-polarization RA product as the energy range becomes smaller. The solid curves in Figures 8A through 8F are calculated using a model for self-filtering detectors. The peak detection capabilities of these devices are close to those of infrared photodetectors limited by background noise at ??°K. The previous detailed report describes an equilibrium growth process for preparing Bchottky barrier photovoltaic detectors, which is suitable for a single-phase lead calc-cogenide epilayer device. The process allows variation of the energy range of the epilayer by changing the composition of the PbS^Sc χ alloy filler, thereby providing a process for preparing composition-tuned detectors within the bandwidth of 3 to ? μ. Similarly, variation of the PbS^Sc χ alloy filler composition allows the preparation of composition-tuned detectors within the bandwidth of 7 to 30 μ. Furthermore, the charge carrier lifetimes in a minority of layers prepared by the methods of the present procedure are extended and the number of crystal defects is reduced, while maintaining a high substrate temperature during growth, thus allowing detectors prepared from the layers to operate at room temperature. Referring now to Figure 9, a graph shows the substrate temperature increasing along the abscissa as a function of the charge carrier lifetime in the minority increasing along the ordinate. As shown, a substrate temperature higher than about 400°C during growth will result in charge carrier lifetimes longer than a nanosecond at room temperature (i.e., 20°C + 2°C) for the electrons having a spectral response cutoff of about 5 μ.Epilayers prepared from materials having a spectral response between about μ and 10 μ must be cooled during operation to increasingly lower the temperatures in order to have charge carrier lifetimes in the minority of a nanosecond, while epilayers with spectral response cut-off wavelengths between 10 and 12 μ must be cooled (with liquid nitrogen) to about 5?°h to achieve the same carrier lifetimes. Obviously, the procedure described above can be implemented with several variations. For example, selenium can be substituted for the sulfur dopant. Since selenium has a much lower vapor pressure, the "cold tip" would need to be heated to about 150°C to obtain single-phase films. Higher tip temperatures would produce P-type films, and lower tip temperatures would produce N-type layers. Similarly, tellurium could be used as a dopant. Furthermore, this process provides a method for preparing single or multiple in-plane junction devices. By periodically varying the temperature of the chalcogenide contents in the cold tip below or above its sublimation temperature, the partial vapor pressures of the chalcogenide in uniformly mixed molecular particles vary. < / aumenterà, dando come risultato un cambiamento nellala conduttività del conseguente spessore della pelli¬cola.If the alloy charge £? is slightly metal-rich and during the initial growth of the epilayer JA the temperature of the chalcogenide 8 in the cold tip 50 is kept below the sublimation temperature of the chalcogenide, the first growth will show N-type conductivity. If the temperature of the chalcogenide is 5? - increased to a) the oe] of epra of the sublime temperature to the chalcogenide, the subsequent growth of the epilayer 14 will show a type R conductivity. Returning the temperature of the chalcogenide 8 below its sublimation temperature will cause subsequent growth to show a type K conductivity. Since the procedure ensures a uniform mixing of the vapors of the metal alloy % chalcogenide 8, and therefore growth of uniform stoichiometry, subsequent layers will clearly define a junction otw> PN in plane. When reviewing the previous discussion of the executions.illustrative, it may be noted that effective diffusion lengths of minority carriers and effective lifetimes can be calculated from analysis of the response capabilities of Schottky barriers using a procedure described in Applied Physics Letters, Vol. 16, 446 (1970). It can be shown that the mean of a back-illuminated Schottky barrier on a film of thickness d, t-obscuring surface recombination, is given by: - ​​35 *(?) · |l« -» · '•“'Vm where η is the external quantum efficiency; o is the unit electronic charge; Z is the impedance of the sample and the receiving preamplifier; E is the photon energy; and R is the reflection loss at the BaF^ interface, "sample. The R coefficient is calculated using the where n and α are the refractive indices of the film and the substrate, respectively. The reflection coefficient at the interface between the film and the barrier metal is very high and is set equal to unity to simplify equation (1). The coefficient α was measured 1 * V per.PbS as a function of temperature and at 90°1 is given by: «*?.»* IO4 ♦ ,001 (oV) (3) · K30 e>p 206 (E-Ec) C <e9 ♦ .001 (cv) (4) * in cui k ed ì.* sono uni tè di elettronvolt.B These relations are used for all calculations because the optical constants of other lead salts have not been measured at 75°K but are known to exhibit a similar energy dependence at room temperature. Theoretical models do not include the exponential tails observed in the absorption edges of these semiconductors. The continuous curves in Figures 6A through 8F are calculated using equations (1) and (5) and adjusting E and K to obtain the best fit to the shapes of the response capacitance curves. Quantitative agreement is also good. The fit to the PbSe sample shown in Figure 6A is remarkably good and gives the accepted value of 0.17 eV for E at 1ί. The di- The discrepancy between the experimental and the calculated curves is mainly due to optical interference effects not included in equation (1). The values ​​obtained for L^ are listed in table 1. Lower limits are obtained only when L^ is equal to the thickness of the sample. The effective lifetime -tL of minority carriers is calculated using the well-known relation for carrier diffusion given by: where K is Boltsmann's constant; T is 2 at temperature ; and μ^ is, J at noble te of the minority carrier. The measured Hall mobilities are used in the calculations since the mobility ratio is close to unity in lead salts. The calculated values ​​of v / jj are plotted in the figure 10 as a function of the energy range, E*. The points with arrows represent lower limits and are calculated for samples where Ln is greater than d. The lifetimes reach a maximum value at a point near L > 0.175 eV corresponding to the PbSo compound. This may be due to a lower density of mismatched dislocations in the PbSe films since the lattice mismatch with respect to BaP2 is 1.5 eV and becomes larger in both alloys. The disagreement between the lattice constant of the chickens and the lattice constant of their substrates of 1 * , ·, is represented by the dotted line in Figure 10 as a function of the energy range of the fur material.*The disagreement in the lattice,òa / a, is shown1by a scale along the ordinate of the- * J'G »'. [to grow the pelvic] and on Ba Sr„ E' 2 3-a 2 substrates with matched lattice. While pure Br„ has a smaller lattice constant than that of alloy IV, pure Br„ has a larger lattice constant. Therefore, the lattice constants of Ba Br„ P„ substrates can match perfectly to both alloys IV and VI. It should be noted in Figure 10 that the two thicker Pb„ ^Be samples have longer lifetimes than thinner samples of similar composition. This may be due to a reduction in the number of mismatch points as the films become thicker.

Claims

1. U? -XWP10A? Fiom 1. Process for preparing epitaxy films of stoichiometry so close to a. Ms'l 3e chosen subjects of :. cost group, removed from Pbf> Se. v X I ** X and Pb. Βω Se, you deposit crystals on a substrate. · * V? ^ / j no insulating under a vacuum of at least 10 torr ". That process includes the operations of:" ••• fcajsteft <>? * "; the substrate at a raging temperature of the sublimation temperature of the potency! the subii but sic ne temperature of the drogar, te: and will expose the substrate simultaneously with the material {. > · And and! dopant "2 Process according to claim 1, also including the fact that the aiomic fraction a varies between aero cd 1 inclusive, and the ioneatomic y varies between aero and 1 inclusive 2" Process according to claim o " and 1, comprising maintaining the substrate at a temperature greater than 350 ° C.

4. Proceedings according to the resell basket 1, accomplishing the fact of maintaining the sol- [. I I! layer and a temperature greater than 370 ° C. 3 * Czech process "giving them back to X" further comprising maintaining the substrate and a temperature greater than * 100.

6. Process according to claim 3 wherein the dopant is selected from the group consisting of sulfur, selenium or tellurium. 7Procedure © © cordova claims only 6, whereby the said material is kept at a temperature between 330 and 630 ° C.

8. Process according to resale 1 * in which. the substrate ori et © 13 ino insulating is an alloy dl '• Λ., ν. 9 ·. Process © © by the sale of house 8, further comprising the fact of varying the atomic frame size js, between sero and 3 inclusive.

10. Procedure for preparing epitaxial films. of a material chosen from the group consisting of PbB Be, .... and Pb, Bn 8c. in which x varies between x Λ · 'Χ 1-y y * sero and 3 inclusive * and y various between and 1 Hindus * which are then placed on an insulating crystalline substrate under the vacuum of © Hymen10 torr * which procedure includes the ogerations of: keeping the substrate at a temperature between 3306C ί I 39 - and the temperature ¢ 3 underwent i.mazi ο »© del mai eri eie; but« Yesterday 13 never erred at e <5 hitting tempera ture higher than its temperature of sublimation, ie, a source of a dopant; selected from the group consisting of sulfur, selenium, tellurium, or ro m.iecugJi, at its sublimation temperature; and expose the substrate simultaneously to the material ··· and the dopant * 11. Product, obtained by the process claimed in claim 10. Process for regulating carrier concentrations in epitaxial films of PbS .6 © -, in cu: i>. it varies between zero and 1 inclusive, which ver ". are deposited on an isolated crystalline substrate, maintained at a temperature between 550 ° C and the sublimation temperature of the films, under ~ 5 a vacuum of at least 10 °, starting from a source of material maintained at a temperature above its sublutation temperature, which process comprises the step of simultaneously exposing said substrate to a source of. substance capable of altering the etecbig »meters of the pel! ico3 ©, kept in a vacuum at its sublimation temperatures - 13. Process according to claim 12, / j ο * "wherein the insulating substrate is where 0 g z jg 1 * 1A * Process according to claim 1.4" further comprising the fact of. that the mesh constant of the substrate corresponds to the mesh constant of the epitaxial film. Process according to claims 10 and 14, further comprising maintaining the source of material and a temperature between f> 0% and 610 ° 0.

16. Process according to the riveted siphon 15 in which the dopant is selected from the group consisting of sulfur, anium and tellurium. 17 * Process for depositing an epitaxial film of a material chosen by the group co ** established by POS Se. and Pò, Su Se »ir which x various y> l-y J ~ y y * between aero and 1 included» ed. y varies between fcero and 1included, on a. insulating crystalline substrate, the process comprises the steps of: maintaining the substrate at a temperature above 10% and below the surface temperature of the material to be deposited, under a vacuum of at least 10% is to expose the substrate to a ￂ ﾩ e source, which has totally chemically reacted, of the material and ila deposition, tare "having about the same composition Ó'J that, 3" of the leathers of deposit "and that you keep it at a temperature above its time?, retare di sub! imesiope * 18. A method as claimed in claim 17 wherein the source of me tors de is maintained between 550 ° C? 0 ° 0.

19. Process according to claim 17, further comprising © le; operations of: maintaining a source of a dopant capable of altering the stoichiometry of the film and the sublimation temperature of the dopant; and exposing the substrate of the source of the dopant simultaneous to the operation of exposing the substrate to a source of the material which reacted to the substance 20 Process according to claim 14, in. where the insulating crystalline substrate is a leg of Bs Br., P-, where 0 <% <1, which procedure also includes the fact of choosing the atomic fraction "z" in Biodo that the network constant of the substrate corresponds to the lattice constant of the epitaxial film. 2.1- Process according to claim PO »Μ2 - further comprising the operation of exposing the skin during the growth, and a source of ut». A rogant maintained at a temperature not lower than the sublime temperature of the dopant. and at a temperature greater than the dopant sublimation temperature. <? 3 * Process for depositing a PbB Se- epitaxial film, where x varies between sero * x; 1- · χ ed 1 inoli ». Yes, on. an insulating crystalline substrate ",", ";"; - V _ which process you will buy the operations of; maintaining the substrate at a temperature below the temperature of. Eternal sublime of FbtS Se. r · 3Γ ^ ì, Ψ I jf under a vacuum of at least 10 'tori ·; and exposing the substrate simultaneously to a rise of PbR Se ... it underwent 5th? ion. 2Λ * Process according to claim? 3 »in which the temperature of the substrate is between 330 © 3: toc-c.

25. A process according to claim 24, wherein the temperature of the. material to be deposited is between 600 and 650 ° C.

26. Process according to claim 25, wherein said cogonide is constituted by sulfur calcide.

28. Process for depositing an epitaxial film of a material selected from the group consisting mainly of PbS Se. and Pb1 Sn Se, in which x varies phrases and 1 inclusive, and $ varies between serum and 1 inclusive, on an insulating crystalline material, under a vug _l | of at least 10 torr, which procedure includes the operations of: maintaining the substrate at a temperature higher than 550 * 0 and lower than the sublimation temperature of the material to create an oven, having a single orifice spaced at above the source of the material which has totally chemically reacted, a first vapor maintaining the material above its sublimation temperature and spore: the substrate eli'ori.fi zio 28, comprising forwarding the spy works to create an e and cord vapor while maintaining a tedium source, capable of altering the stoichiometry of the film, the sublimation temperature of the eogteitt.Be $ and redirecting the second vapor into the atom below its orifice *. %> * Process according to claim ￂ ﾣ 3 ￂ ﾻ in which the second steam is introduced into the oven like the helmets and the first steam "for eu: i the co-layer is subjected to uniform heating of the first and second steam * 51 Process according to claim 26, wherein the substrate is maintained and a temperature greater than $ 00 ￂ ﾰ C. 5 ?. Process here is the reseller 51 ￂ ﾻ in which it is sustained ￃ ﾨ chosen from the group consisting of sulfur ￂ ﾻ selenium or tellurium * 55 * Process according to Biotte 5? "In which the material is kept at a temperature between 556 and 650ft0 * y \. Process according to claim 28 wherein the crisis-like substrate is an alloy of 5 Ba Siv J '% J ~? * 35 "Second method further comprising the atomic Mz atomic fraction" between "and 36. Process according to claims 34, of varying the function including. to obtain a correspon dence between the grating constant of the substrate and the grating cost of the film. dense © between the grating constant of the substrate and the grating constant of the film.

38. Process for preparing epixial films having a constant stoichiometry and a first type of conductivity "from a material chosen from the group consisting of CPo] [6 Se, 1, ef a y JL" "X 1-a Oh., 8n 1 [SelL, where Ο <χ <1 »0 <y <1, after sited on an insulating crystalline substrate below. .., is a vacuum of at least 10 torr, which procedure includes the operations of: maintaining the substrate at a temperature above 3.50 ° 0 and below a temperature of sublimation of the material; create underneath an orifice which is spaced apart.

46. In a source of the mateniel o © has totally chemically reegi'ed, a first vapor keeping the material at a temperature below its sublimation temperatures; and expose the ether to the east fi «I * • 39- Withdrawal to regulate the type of conflictivity of an epitaxy film! e from prepares j, _ · _. As indicated in the relevant section 36, which procedure comprises the fact of varying the atomic frequency MeM of the material * 40, according to the resell 39, in which the atomic fraction "a" of the material is equal to 0.300 + 0.003%.

41. Process according to claim 40, further comprising the operation of creating a second vapor below the orifice, maintaining at its sublimation temperature a source of a substance capable of altering the stoichiometry of the film. 4; or. Process according to claim 41, further comprising the operation of discharging a homogeneous mixture of the first and second steam in the orifice.

43. Procedure for adjusting the type of. all conductors of films to be prepared as indicated in Kit 47 3.8 shores 58, whereby 13 material selected is a second opposite type of conductivity which process comprises the operation of creating a second vapor and d: i below 13. ' orifice deserving © 31 «its sublimation temperature ime so £ Shiite of a © stop *: ·» © capable of altering the steob.ig.metri © of the film. * 4¾. Process for preparing pitesetelic films of unique properties and optical properties from ur »material chosen from the group consisting of * xev * * Sn 8e, dowry O 4 X <1 and 6" <y <1, deposited on a , insulating crystalline substrate, under a vacuum of at least 10 torr, to which the procedure includes the operations of: maintaining between a source of the material and a monster, spaced above them, a thermal agent that varies from at least 1® sublimation plowing of the material in correspondence of the source up to a value between 550 * 0 and the sublimation temperature of the material-! in correspondence with the substrate and expose the substrate to the source of the eie motors. 45 · Process according to the * "i.vendfossio" and 44, further comprising the operations of: maintaining just © 1 of. above its sublimation temperature a sorbent of a tired substance capable of altering the stoichiometry of the films; Expose the substrate simultaneously to the sorbents of the material and the soetersa. AS * Process for preparing epi-woven films! multiple junction »of a material chosen from the group consisting of Pt> B Be. 4 * "4Ì and H> Be Bo, where 0 £ x <1" and 0 <y <1 "after si *" V v tate on an insulating eoetr & to © ristailino "under a vacuum of at least 10 torr" which procedure it involves the operations and allows to maintain the substrate and a temperature between> 50 6C and the temperature of the surface of the material; to maintain the material and impact temperature greater than its temperature of increase; "manie" to periodically be a source of a -tired, choices of the group made up of © elf, ejeIonio θ teli shouted "Aia corri sponde" © at its temperature of sublimating hours; and exposing its substrate simultaneously to the material and supporting it · ·,; ΰ, A / "Prooedime »T © then · prepare films © pi-taceteli having alternate layers of conductivity of opposite type» from a material chosen from the group consisting of ÌPb'JjB Se,) Ί and [IV BrO [Bel, Λ a> .Vot l ~ a x-y a l-a., 49 - clave Ο <χ <3 and Ο <y <1, deposited on an insulating crystalline substrate, under a vacuum of. ej,, J \ minus 3.0 mice: ·, il. ment includes the workings> 5 of: maintaining the substrate at uro temperatures above 350 ° G and · below the temperatures above ’ibi ima"! time © of the Material; ^ create a first steam under your star orifice. " I am © 3 above a source of the Rete¬rà al and that he tote? merle reacted chemicamertey mcntemute and a temperature and to sopire of his'teurperetura of underwent. ima si hours; expose the substrate and X11 o ri ti. ? I ; and periodically create a second vapor at the 4th spit of the gold while maintaining at its temperature of subii maKion ￂ ﾩ a source of su sten? ￂ ﾷ capable of altering the stoichiometry of chickens cola * 48, Procedure for regulating the type of conductivity of my epitaxial film to be prepared as indicated rolla rivendieasiore 4 ·? ». which process includes varying the atomic phrases * 'and "of the material.

49. Process according to claim?! 48 hours, in which the irosis of the atoms C and V of the material is equal 0 0.5 * 00 * 0.003% * I i>! ; THE 50. Product obtained by means of the fle curing process, £. Xe reclamation 49 * 51 * Plumbing according to claim 47 * in which IX said orifice is constituted by the upper opening of a vertical primer furnace having a constant ratio between heated length and diameter, throughout its length. ? j: - proceeding according to claim 47 * 1 ". wherein said orifice is constituted by the upper part of a primary vertical furnace having a single isotherm along its entire length. primary furnace between the said source and the doctor layer * within the range of 14 to? 54 was per ° 0. Process according to claim 51 further comprising a product of area and temperature gradient along the length of the primary tube between the source tube and said substrate, within the range of? Θ to 236 cm for ° 0 * 55. A method according to claim 51, further comprising a. produced between heresis and temperature predictor.,. between the lower extremities of the primary foil and the substrate flex, less than 163 cm @ 51 ° C / 56 ° C per sediment according to claim 51 including ino. three a. product between area and temperature greener, between the lower ends of the primary furnace and said substrate, lower than 10 mm per ° C * 5. Process according to claim 51, further comprising a product between area and temperature gradient, between the lower end of the primary furnace and the said substrate, lower and. 50 cr «per ° C * 56. Process according to claim 51 "wherein the substance is in a vertical secondary kiln, coaxially hanging from the lower end of said primary kiln and extending above it.

59. Process according to claim 58" further comprising a product between area and temperature gradient, between the lower end of the said secondary form and the iron end of the said primary furnace, within a range of 2? up to 50 cn> per ° C, 60 ° yield according to resell reason, 58, also comprising a product between area and temperature gradient between the lower end t: »- $ 2 - A of the secondary hole 0 and 11 lower end of the primary furnace * lower ￂ ﾩ ￎ ﾯ ￏ ﾄ ￢ ﾀ ﾙ 3 , 6 I was for% '* 61. Hiveletòro photoelectric sensitive infrared, the. troubles and I will buy e: a substratum or iste! insulating linen *, and an epitaxial layer of Ρ & 8χβ © ^ (χ having a duration of charge carriers of minora »« ai tìag & ìhours of m n-second at 26 '*, * 0, deposited on the substrate. rivén dicaalone'61, in which 0 <x <l. 6J, Hiv © photoelectric detector according to 1 © shores ", say &" and 6?, in which the layer has a conductivity of type jK 61. Photoelectric detector according to shores " 6p, wherein the b layer is a K-type conductivity. Vj, dicanone Photoelectric detector according to the bank. ,L* 66. Photoelectric detector according to the case and 6P, further comprising: said epitaxial layer with a first type of. conductivity; and m is a region of a second type conductivity located in said epitaxial layer; V5 «· for which it is supplied a pi unction of type p.Ji from the super! contiguous of the epitaxial age and the 3rd learned region. 16 ?. i'ceer a super et ero junction p © r produce a laser comi; Ina io having a good deli "gòometrioa station and which can be oriented in the" pa "io" which laser comprises: numerous epitaxial layers of a methyl chalcogeuride alloy, alternate layers of. they having a first type of conductive which is opposite to the type of conductivity of the interposed layers, whereby the adjacent frames form P ~ N m and partial mirror junctions which cover at least a part of the exposed surface of said numerous layers; voltage source at veriehile frequency, higher than the fener voltages of said junctions, electrically coupled to the axial ends of said numerous layers to cause injection current to flow through P ~ K 'connections, whereby the directly polarized junctions produce a laser output beam which complies with its source and junction in such a way that the stack combinations of single laser output beams form a "combined" laser beam spin; 5-.1 · - il) which i.3 the said current signal as a saloon produced by the said voltage source can be varied in wavelengths to progressively modify the phase of the injection current signal in correspondence with each of the said P-N joins in order to carry out an orion of a narrow combined beam * 68 * Laser according to claim 6, wherein said alloy is selected from the group constituted by PbS ^ SCjj ^ and 'Fb Sn ^ Se * where Ó ^ x & l and O ^ v.fi * 69 ·. Laser according to claim 68, in which each of the numerous epitaxial layers having a thickness of less than 10 μp.p. Tim IMT & b STATUS # 01 AMERICA represented by the Secretar ^ 'od tbe tTevy, and in turn represented by Assistants Ohiefof Nevai Research for Patente