JP2732573B2 - Manufacturing method of compound semiconductor single crystal - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multicomponent compound semiconductor single crystal comprising at least three or more elements, and more particularly, to an improved traveling heater method (THM). In addition, strict vapor pressure control provides excellent composition controllability and stoichiometric controllability, and low-defect multi-element compound semiconductor single crystals with small deviations from completeness, especially low melting points The present invention relates to a method for producing a compound semiconductor single crystal containing an element component. 2. Description of the Related Art Group II-VI compound semiconductors are of direct transition type, and are known to produce highly efficient luminescence by excitation with ultraviolet rays and electron beams. For this reason, extensive research has been conducted in the field of optoelectronics as a device capable of realizing a light-emitting and light-receiving element in a wide liquid length range not available in III-V compound semiconductors. Hg _X Cd _{1 -X} Te (0 <
X <1) is a mixed crystal of HgTe and CdTe, and is a substance whose band gap can be changed by changing its composition value X. In particular, by obtaining a narrow bandgap, attention has been paid to the fact that a long-wavelength infrared detector conventionally obtained by adding impurities such as Hg and Ca to Ge can be obtained without adding impurities. . In recent years, multi-component compound semiconductors have attracted attention because their band gap and lattice constant can be independently changed. Also in these multi-component compound semiconductors, it is necessary to produce a single crystal having a low dislocation density and a low defect in order to produce various devices. Since these have various characteristics different from single element semiconductors such as Si, like general compound semiconductors, single crystal manufacturing technology different from single element single crystals is required. You. For example, for Si, the Czochralski method (CZ method), the floating zone method (FZ
), But strict control of the composition (and stoichiometry) is required in these multi-component compound semiconductors. In addition, the critical shear stress at high temperatures is smaller than that of Si, These methods cannot be used because there are various technical problems such as easy dislocations. That is, in the case of a multi-component compound semiconductor, even if the atomic weight ratio of the component elements is accurately measured and reacted in order to grow a high-purity single crystal, the obtained single crystal product does not necessarily have the intended stoichiometry. The composition of the ratio is not obtained. Therefore, it is necessary to devise a single crystal growth operation not only in terms of the composition in terms of chemical analysis but also in consideration of deviation from crystal integrity and stoichiometry. In the case of binary compound semiconductors, various crystal growth methods are known in order to make the grown crystal as perfect as possible.In particular, as a single crystal growth method for II-VI group compound semiconductors such as CdTe, a vapor pressure method is used. Because of easy control, the Bridgman method (vertical and horizontal Bridgman method) is widely used. Hg _X Cd _{1 -X} Te (0 <
x <1) is also a kind of the above-mentioned multi-component compound semiconductor material. However, particularly, the vapor pressure of Hg is high, and in the quasi-binary phase diagram of HgTe and CdTe, the gap between the solidus and liquidus is large. It was not possible to obtain stoichiometrically controlled crystals which were open and uniform in composition. This single crystal growth method is roughly classified into a thin film growth method and a bulk crystal growth method.
As a bulk crystal growth method, there are a Bridgman method, a traveling heater method, and the like. When HgCdTe is grown by these bulk crystal growth methods, the vapor pressure of Hg is extremely high and it is easy to segregate, so that it is extremely difficult to grow a crystal having a uniform composition and high characteristics. Also, J. Vac. Sci. Technology. A3 (1) Jan / Feb (1985) 9
According to the method proposed in 5-99, CdTe and H
After gTe is formed, Hg segregation is reduced using the traveling heater method. However, this method requires careful preparation. Problems to be Solved by the Invention There are various methods for growing a bulk single crystal of Hg _X Cd _{1 -X} Te (0 <x <1), but each has the following problems. In the Bridgman method, Hg segregation is large, and a crystal having a uniform composition cannot be formed. In the recrystallization method, a single crystal having large crystal grains cannot be formed. In addition, when using the traveling heater method, those using powder as a raw material are likely to contain impurities and contain air bubbles, and those using CdTe and HgTe as raw materials require extremely strict processing accuracy, resulting in poor production efficiency, The composition variation in the growth direction is also large. Therefore, an object of the present invention is to improve the conventional traveling heater method to provide a compound semiconductor having excellent stoichiometry, a small deviation from the crystal perfection, a uniform composition and uniform properties, and in particular, a vapor pressure control. It is an object of the present invention to provide a method for producing a bulk single crystal such as a multi-component compound semiconductor composed of at least three or more elements including a component having a melting point equal to or lower than a temperature, such as HgCdTe. Means for Solving the Problems As a result of various studies and studies, the present inventor has found that the storage chamber for the vapor pressure control component element is arranged below the crystal growth chamber, and the raw material for single crystal growth is placed above the above crystal. It has been found that the arrangement in the growth chamber, preferably in a separate container, is extremely effective for achieving the above object, and the present invention has been completed. That is, the method of the present invention for producing a multi-component compound semiconductor comprising at least three or more elements, for example, a HgCdTe single crystal, comprises an upper crystal growth chamber and a lower vapor pressure control component element storage chamber connected by communication holes. And a solvent comprising at least one of a single crystal growth raw material and a component element of the multicomponent compound semiconductor is stored in the upper crystal growth chamber, and the lower vapor pressure control component element is contained in the upper crystal growth chamber. A vapor pressure control element composed of at least one of the component elements of the multicomponent compound semiconductor is sealed in the storage chamber, and the vapor pressure is regulated by controlling the temperature of the vapor pressure control element to control the vapor pressure. Controlling the concentration of the component elements, dissolving the single crystal growth raw material in the solvent, and moving the single crystal growth material relative to the furnace in a furnace set at a temperature such that the inside of the reactor has a predetermined temperature distribution. By It is characterized in carrying out the single crystal growth. The multi-component compound semiconductor single crystal that can be produced by the method of the present invention includes at least three or more elements,
In particular, a single crystal or mixed crystal containing a low melting point element such as Hg or the like as a component so as to be in a liquid state under its synthesis temperature (growth temperature) or vapor pressure control temperature, or a dopant for the purpose of improving or controlling characteristics is included. And any of these analogs. Therefore, in the present specification, the term “single crystal” should be construed as including those containing the above mixed crystals, dopants and the like. Also, a preferred apparatus for performing the method of the invention is
A reaction tube including a storage chamber for a vapor pressure control component disposed below, a crystal growth chamber communicated with the storage chamber by communication means, and a single crystal growth raw material storage container disposed in the growth chamber. And a furnace having a heater arranged so as to surround the outside of the reaction tube, which is an improvement of the traveling heater method. The feature of this apparatus is that a storage chamber for component elements for controlling vapor pressure (partial pressure) is provided below the crystal growth chamber in the reaction tube. The crystal growth chamber and the storage chamber need to be in spatial communication with each other, and communication means such as a capillary and at least one pinhole is provided between them. The communicating means has a size that allows the vapor to pass therethrough, but reduces the vapor phase diffusion of the solvent and the raw material elements,
Shape is preferred. The crystal growth chamber is also integrated with the raw material storage to form a concentric cylindrical double pipe structure, and the space between the concentric cylindrical double pipe structures is used as the communication means to form the partial pressure control element storage chamber. It is also possible to adopt a configuration connected to In any case, it is sufficient that the storage chamber is provided below the crystal growth chamber and these are connected by a communication means, and various modes other than the above are conceivable, and all of them are within the scope of the present invention. Should be understood. When the crystal growth chamber and the raw material container are formed separately, when the container is accommodated in the crystal growth chamber, the partial pressure control element gas supplied to the growth chamber via the communicating means grows. It is necessary to provide a space or a passage so that the whole room or the space above the raw material container can freely enter and exit. At this time, the space above the raw material storage container has small holes through which steam can pass,
Alternatively, a pinhole is desirable. For this purpose, for example, at least 3
Various other means can be taken, such as providing a book leg, or arranging a cylindrical member provided with a number of holes on the side as a support at the bottom of the storage section. The raw material container of the above apparatus can be formed of carbon-coated quartz, pyrolytic boron nitride (PBN), or any other known material that does not react with the raw material under crystal growth conditions. When a single crystal such as HgCdTe is grown by this apparatus, the component elements for controlling the vapor pressure and the raw material for growing a single crystal are put into each storage chamber (or storage vessel) of the reaction tube, and if necessary, exhausted, The reaction tube is sealed by filling with an inert gas. Next, the heater of the furnace is operated to fix the reaction tube at a predetermined position in the furnace set to a predetermined temperature distribution, and this state is maintained until the temperature in the reaction tube is sufficiently equilibrated. The reaction tube or the furnace is relatively moved at the speed described above to grow a single crystal. According to this method, the temperature of the component element for controlling the partial pressure is controlled, for example, by obtaining accurate temperature information by a temperature detector (such as a thermocouple) attached to the lower end of the storage chamber, and based on the obtained information. This can be realized by controlling the heater for heating, and it is also possible to connect the temperature detector and the heater to a computer, and to automatically control the heater in response to a signal from the former. Also, for the purpose of high resistivity crystal as a dopant,
A group III element, In, Al or the like, or a halogen element Br, Cl, F or the like may be added. The crystal to which these are added has an extremely high resistance, and when used as a material for detecting radiation, for example, γ-rays, has high sensitivity and excellent characteristics. Although the method of the present invention has been described above using HgCdTe as a specific example, the present invention is not limited to only HgCdTe of the present invention, and is similarly heavy, and is a component that melts at a single crystal growth temperature or a vapor pressure control temperature. At least three other types including
Multi-component compound semiconductor (HgZnTe, Hg
MnTe, III-V, II-VI, etc.) or a mixed crystal thereof, and of course, have a high dissociation equilibrium vapor pressure that does not become a melt at the above temperature. Needless to say, the same can be applied to this. When producing a binary or multicomponent compound semiconductor single crystal, strict vapor pressure control is required, but especially low melting point elements that melt at the crystal growth temperature or the vapor pressure control temperature are required. If it contains, or contains a component element having a high dissociation equilibrium vapor pressure at these temperatures, the conventional method can not be used as it is,
Various improvements need to be made. Among them, particularly when a component element having a low melting point and a high vapor pressure is involved, it is melted and vaporized during the crystal growth operation, so that it flows or vaporizes once or vaporizes from the raw material melt. As the element condenses, the area to be temperature-controlled is widened, and high-precision strict temperature control, accurate control of the vapor partial pressure in the crystal growth chamber, stoichiometry of the grown crystal, crystal integrity, etc. Adjustment becomes extremely difficult. However, the above-mentioned various problems, which have been observed in the case of performing single crystal growth by the vertical Bridgman method or the traveling heater method in particular, are almost solved by performing the single crystal growth by the method according to the present invention, and are satisfactory. The result can be obtained. According to the present invention, for example, when producing a single crystal of HgCdTe, by controlling the temperature of Hg for controlling the vapor pressure in the reactor having a closed tube structure, to control the Hg vapor pressure, thereby further
By defining the Hg concentration in the Te solvent and moving the Te solvent, the raw material CdTe is dissolved from one end and the HgCdTe crystal is recrystallized, so that the composition value X (Hg _1-X Cd _X Te) is uniform. Crystals can be obtained. At this time, the Hg pressure in the solvent can be changed by changing the Hg pressure in various ways, and the composition value X can be controlled. In that case, a dopant can be added as needed. Further, by using a Te solvent, impurities are trapped in Te, and a high-purity crystal can be obtained. In the present invention, in the improved traveling heater method, a chamber for accommodating a vapor pressure control component element is disposed below the growth chamber. As a result, it is possible to completely prevent the vapor pressure control region from expanding due to the influence of the weight, gravity, and the like of the vaporized element component, and to restrict the location of the melted component element to a certain location. Therefore, the temperature detection area and the temperature control area are always limited to a fixed narrow area, and strict temperature control is possible. This is an important factor in achieving strict partial pressure control. Thus, through the single crystal growth, the temperature control of the partial pressure control region (condensed phase) becomes strict, and for example, the saturated vapor pressure of each component element determined by the temperature of the condensed phase of Hg can be maintained in the growth chamber. As a result, the physical properties of the grown single crystal can be accurately and strictly controlled. In addition, the partial pressure control component element storage chamber and the growth chamber arranged below can preferably pass only gases of various elements,
Solvents are communicated by small holes, such as capillaries and pinholes, to the extent that the vapor phase diffusion of the source element is reduced, and while sufficiently supplying the vaporization element from the partial pressure control chamber to the growth chamber, The backflow of the solvent element gas and the component element gas to the low temperature portion (that is, the partial pressure control region) is effectively prevented. This enables not only strict control of the vapor pressure but also improvement in the quality of the obtained single crystal and its yield. Further, the loss of the solvent element and the raw material can be prevented by making the space above the raw material container a small hole or a capillary. Depending on the type of element, it may be in a boiling state under the vapor pressure control temperature, but also in this case, since the storage chamber is provided below the crystal growth chamber, the existing area of the melt does not expand, and The advantage that the pressure control is sufficient at one point can be obtained. Further, according to the apparatus having the above-described structure, during the crystal growth process, volatile and heavy impurities move toward the vapor pressure control element storage chamber provided below, and the impurities are also captured in the solvent. Therefore, an effect of refining the crystal can be expected. According to a preferred embodiment of the present invention, during the crystal growth, in order to homogenize the single crystal in the radial direction, by using a means such as rotating the raw material container by rotating the reactor, the solvent and the generated single crystal Flatten the solid-liquid interface. In addition, when producing a HgCdTe single crystal, the crystal growth rate is
A range of 0.04 to 0.4 mm / hour is preferred. That is, 0.04mm /
If it is grown at a speed less than the time, productivity is poor, 0.4 mm /
If the raw material CdTe does not sufficiently dissolve and diffuse in the solvent Te when grown at a speed exceeding the time, the growth direction of the generated single crystal
A Cd concentration distribution occurs. Thus, according to the method of the present invention, since the strict control of the vapor pressure of Hg is possible, the composition value X (Hg _1-X Cd _X Te) and the conductivity type can be controlled by appropriately selecting the vapor pressure during growth. In addition, it is possible to obtain a single crystal with sufficiently controlled physical properties such as resistance value with good reproducibility, and this can be advantageously used as a material for manufacturing various semiconductor devices. Hereinafter, the method of the present invention will be described with reference to FIG.
FIG. 1 shows an example in which the method of the present invention is used for growing a HgCdTe single crystal. The above equipment uses raw materials CdTe3 and Te
Storage container 5 that stores solvent 2 and also serves as a single crystal growth chamber
And a capillary 4 having small holes 8 for introducing elemental gas into the storage container 5, a storage chamber 5 having the storage container 5 at the top and a storage chamber containing the vapor pressure control element 6 at the bottom. It consists of a sealed reactor 7. According to the method of the present invention, by controlling the Hg vapor pressure inside the reaction vessel 7, the concentration of Hg in the Te solvent 2 is regulated, and Hg _1-X Cd is again dissolved while dissolving the raw material CdTe3 in the Te solvent.
It is characterized by being grown as an _X Te crystal. The temperature distribution of the growth furnace used in the method of the present invention is Te solvent 2
There are three temperature zones: zone II which determines the zone, zone III which determines the Hg vapor pressure, and zone I which is lower in temperature than zone II and higher in temperature than zone III. As shown in the temperature distribution diagram on the right side of FIG. 1, the length of the II zone is determined so that the length of the range in which the melting point of the raw material CdTe3 of the Te solvent 2 is equal to or higher than the diameter of the Te solvent 2 is smaller. The following procedure is used to realize the method of the present invention using the above-described apparatus and growth furnace. Te solvent 2 and raw material in storage container 5
CdTe3 and dopant as needed are added, and the capillary 4 is attached. Hg6 for vapor pressure control is installed in the storage room of reactor 7.
, And the storage container 5 with the capillaries is mounted. After that, the reactor 7 is evacuated to a vacuum, and an inert gas is introduced and sealed if necessary. This reactor was placed in a growth furnace having the temperature set as shown in FIG. 1 and maintained for a sufficient time in a state before the start of growth. Then, the reactor and the growth furnace were relatively moved to grow a single crystal. Do. EXAMPLES Hereinafter, the method of the present invention will be described in more detail and specifically by way of examples. However, the scope of the present invention is not limited by the following examples. Using the apparatus shown in FIG. 1, a single crystal of Hg _1-X Cd _X Te was prepared. As raw materials, 3.31 g of 6N-purity CdTe and 2.55 Te
g and Hg of 6.02 g were weighed and placed in a raw material storage container and a vapor pressure control element storage chamber, respectively. 1 × 10 ^-6 Torr inside the reaction vessel
It was evacuated below and set in a growth furnace. The set temperatures were set at 700K for Zone I, 903K for the maximum temperature of Zone II, and 573K for the Hg temperature for vapor pressure control. The crystal was grown to a size of φ6 × 20 mm at a crystal growth rate of 0.125 mm / hour. 2A and 2B show the composition X value of the obtained single crystal in the growth direction and the composition X value of the growth cross section in the radial direction, respectively.
As can be seen, the X value of the crystal periphery tended to increase slightly in the radial direction, but the composition in the growth direction was:
It was very uniform. The crystal just after the growth is p-type and the carrier concentration is 3 × 10
^It shows a sufficiently low value of ¹⁵ / cm ³ , indicating that the extraction of impurities with the Te solvent is being performed. Effects of the Invention As described in detail above, according to the method of the present invention,
A storage chamber for component elements for vapor pressure control (partial pressure control) is provided below the crystal growth chamber, and these are communicated by communication means having small holes. Thus, a uniform single crystal of Hg _1-X Cd _X Te can be easily prepared, and the conventional problems can be completely solved. That is, first, even if the vapor pressure control element is melted or boiled at that temperature, the region where the condensed phase (or the molten phase) exists does not expand, and therefore, the temperature of only a narrow region is detected and the temperature control is performed with high accuracy. Since the vapor pressure can be controlled, a low-defect single crystal with good stoichiometry can be produced. In addition, because accurate vapor pressure control is possible,
By maintaining this at a predetermined partial pressure, a single crystal of a specific conductivity type and resistance value can be freely formed, and the composition of the crystal can be controlled. Becomes According to the method of the present invention, it is possible to reduce the incorporation of impurities into the solvent during the growth of the crystal, and to produce a high-purity single crystal. Thus, the produced high-purity, high-quality single crystal can improve the characteristics of various devices produced using the same, and can greatly improve the reliability thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing an example of an apparatus for carrying out the method of the present invention, and also shows a temperature distribution curve in the reactor; FIG. 2a shows Hg _1-X Cd _X Te produced by the method of the present invention.
Fig. 2b is a graph showing the composition X value of the single crystal in the radial direction, Fig. 3 is a graph showing the composition X value of the single crystal in the radial direction, and Fig. 3 is a graph showing good quality HgCdTe by the conventional method. It is a schematic diagram showing the shape of the raw material required when producing a single crystal. (Main reference numbers) 1 ... single crystal, 2 ... solvent, 3 ... raw material element, 4 ... capillary, 5 ... storage container, 6 ... element for controlling vapor pressure, 7 ... reaction vessel, 8 …… a small hole,

Claims (1)

(57) [Claims] In a method for producing a multicomponent compound semiconductor single crystal comprising at least three or more elements, a crystal growth on an upper part of a reactor having an upper crystal growth chamber and a lower vapor pressure control component element storage chamber connected by a communication hole. A single crystal growth raw material containing at least two kinds of component elements of the multi-component compound semiconductor and a solvent containing at least one kind of component elements of the multi-component compound semiconductor are housed in the chamber, and the vapor pressure control of the lower part is carried out. A vapor pressure control element composed of at least one of the component elements of the multicomponent compound semiconductor is sealed in a component element storage chamber, and the vapor pressure is regulated by controlling the temperature of the vapor pressure control element to form the solvent. The length of a portion having a temperature distribution that is equal to or higher than the melting point of the single crystal growth raw material of the solvent becomes smaller than the diameter of the solvent while controlling the concentration of the component elements therein. A single crystal growth raw material is dissolved in the solvent by performing a relative movement with respect to the furnace in a furnace set at a temperature of at least three, and a multi-element comprising at least three or more types of elements. Method for producing single crystal based semiconductor. 2. At least one of at least three or more elements constituting the multicomponent compound semiconductor is an element which becomes liquid at a vapor pressure control temperature of the vapor pressure control component element storage chamber. A method for producing a multicomponent compound semiconductor single crystal comprising at least three or more elements according to claim 1. 3. 3. The method according to claim 2, wherein the multi-component compound semiconductor is a HgCdTe compound semiconductor. 4. 4. The method for producing a multicomponent compound semiconductor single crystal comprising at least three or more elements according to claim 3, wherein the element which becomes a liquid under the vapor pressure control temperature is Hg. 5. 5. A multi-component compound semiconductor single crystal comprising at least three or more elements according to claim 3 or 4, wherein the crystal growth rate is in the range of 0.04 to 0.4 mm / hour. Law. 6. The liquid crystal growth chamber is rotated during crystal growth to flatten a solid-liquid interface, and is made of at least three or more elements according to any one of claims 1 to 5. A method for producing a multicomponent compound semiconductor single crystal. 7. The temperature distribution in the reactor is characterized by being a middle temperature part for preheating the single crystal growth raw material in order from the top of the reactor, a high temperature part where the solvent is in a liquid phase, and a low temperature part for controlling the vapor pressure. A method for producing a multicomponent compound semiconductor single crystal comprising at least three or more elements according to any one of claims 1 to 6.