JPS63303885A - Method for growing compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To grow a large-area crystal having a large diameter by adding an easily evaporable element to an alloy from which the easily evaporable element is removed, packing the alloy into an ampoule, inserting an element for controlling a vapor pressure into the ampoule and heating the same to a co-existing state of a liquid phase and solid phase. CONSTITUTION:The material from which a part or the whole of easily evaporable Hg or the like of a compd. semiconductor crystal forming material 22 is removed is melted and solidified to preform the alloy. This alloy is ground and the easily evaporable element is added thereto, then the alloy is packed into the ampoule 21. The easily evaporable element material such as Hg for controlling the vapor pressure is installed in a receiving tray 25 provided in a capillary 23 of the ampoule 21. The inside of the ampoule 21 is evacuated and the end C of the capillary 23 is sealed. This ampoule 21 is inserted into a furnace core pipe 27 in a heating furnace 26 and is heated to the temp. profile of the temp. between the liquid phase temp. and solid phase temp. of the crystal, by which the material is put into the co-existing state of the liquid phase and the solid phase. The ampoule 1 is then cooled from the end and the single crystal is successively formed.

Description

[Detailed Description of the Invention] [Summary] A method for forming a compound semiconductor crystal containing mercury (Hg), an easily evaporable element such as water, cadmium, and tellurium, by the Bridgman method. After forming an alloy of both elements in advance using cadmium (Cd) and tellurium (Te), excluding (Hg), this alloy, a predetermined amount of mercury, and mercury for vapor pressure control are sealed in an ampoule. By heating the ampoule to a temperature between the solidus and liquidus lines of the alloy phase diagram of mercury, cadmium, and tellurium, a coexistence state of solid and liquid of Hg+-x Cde and Te is achieved within the ampoule. A method for easily obtaining a compound semiconductor crystal with a stoichiometric composition and a large area with a large radial dimension without increasing the internal pressure of the ampoule by solidifying a semiconductor crystal forming material from one end of the ampoule to form a single crystal. .

[Industrial application field]

The present invention relates to the production of compound semiconductor crystals, particularly mercury (H
The present invention relates to a method for manufacturing a compound semiconductor crystal having an easily evaporable element such as g).

Compound semiconductor crystals such as mercury-cadmium-tellurium (Hgl-xcdXTe), which have a narrow energy band gap and high photoelectric conversion efficiency, are used as materials for forming infrared sensing elements.

Such compound semiconductor crystals require crystals with a large area for convenience in device formation, and they also require crystals with large areas such as ng, Cd, Te, etc.
It is necessary that a desired amount of each element be contained in the grown crystal.

[Conventional technology]

Conventionally, in order to form such Hgl-x Cd, Te crystals with x = 0.2, for example, as shown in Fig. 3, after weighing Hg, Cd, and Te to predetermined weights, these are The material 1 is sealed in a quartz ampoule 2 with one end pointed, and the ampoule 2 is introduced into a furnace core tube 4 provided in a heating furnace 3. Then material 1 in ampoule 2
is melted in the heating furnace 3.

Next, regarding the subsequent operation, Hgl-xCd in FIG.
, will be explained using a phase diagram of a Te crystal.

In the figure, the horizontal axis shows mercury-tellurium (HgTe) and cadmium-tellurium (Cd), which constitute the Hgl-x Cdx Te crystal.
Te), and the contracted axis represents this Hgl-x CdxT
The growth temperature of the crystal of e is shown.

The temperature of the heating furnace 3 is the liquidus line 11 at x = 0.2.
After melting the material in the ampoule 2 and holding it for a predetermined time, the ampoule is rapidly cooled to 720° C., which is an intermediate temperature between the liquidus line 11 and the solidus line 12. , Hgt-x Cd, Te crystal, )Ig+-x
The ampoule 2 is lowered in the direction of the arrow from the state where the CdxTe melt is mixed, and the ampoule 2 is gradually cooled from the tip B to form a single crystal, thereby forming a liquidus line 11 and a solidus line 12. Even in the crystal of Hgl-,1CdXTe, where the distance is large and the difference between the liquid phase composition and the solid phase composition is large,
The present applicant has proposed in JP-A-61-146783 that crystals can be formed with a uniform composition without segregation.

[Problem that the invention seeks to solve]

However, with such a method, it is necessary to raise the temperature of the ampoule to a temperature above the liquidus line, for example, x-0,2.
In the case of the Hgl-x Cdx Te crystal (applicable to a 103 m band sensing element), the liquid phase temperature is 796°C, and the internal pressure of the ampoule at this time is about 33 atmospheres, which makes the ampoule easy to break. Also, when trying to obtain a single crystal with a large cross-sectional area,
It is difficult to obtain crystals with a large cross-sectional area because it is necessary to increase the diameter of the ampoule, which lowers the withstand pressure limit of the ampoule and makes the ampoule more likely to break. Furthermore, as the X value increases, the liquidus temperature increases according to the phase diagram in Figure 4, and the internal pressure of the ampoule also increases.
-xCd+cTe crystals cannot be obtained, and elements for detecting short wavelength infrared rays (x=0.3 and 3
There is a problem in that it is not possible to obtain a 5 μm band). In such a conventional method, the value of x = 0.2 lag,−,CdXT
The diameter of the crystal of e is about 22 mm, and the value of H for x = 0.3
g + −x (: d xTe crystal diameter is approximately 18
You can only get something like a cabinet.

The present invention aims to solve the above-mentioned problems and provide a method for obtaining a compound semiconductor crystal having a large diameter and a large area without increasing the internal pressure within the ampoule.

[Means for solving problems]

In order to achieve the above object, the compound semiconductor crystal growth method of the present invention includes sealing a compound semiconductor crystal-forming material of a plurality of elements including a monomerically active element in an ampoule with a pointed end; In the method of forming a crystal by sequentially solidifying the melted crystal forming material from one end of the ampoule after melting the compound semiconductor crystal forming material,
After preliminarily forming an alloy by melting and solidifying the material from which at least a part of the easily evaporable element has been removed, the easily evaporating element is added to the alloy and sealed in an ampoule, and the ampoule is filled with the formed crystal. After heating to a temperature between the solidus line and the liquidus line to bring the material in the ampoule into a solid-liquid equilibrium state, it is cooled from one end of the ampoule to form a single crystal.

[Effect]

In the method of the present invention, an alloy is formed in advance in which the respective components are uniformly mixed in a compound semiconductor crystal-forming material excluding easily evaporable elements. In this case, since no easily evaporable elements are contained, it melts at a high temperature above the liquidus line, and the components can be mixed uniformly.

Next, Hg, which tends to cause interdiffusion, and the above-mentioned alloy are melted at a temperature below the liquidus line. Then, the internal pressure inside the ampoule will not increase, and accidents such as damage to the ampoule will be eliminated. Next, the easily vaporizable element and the previously formed alloy are mixed in the ampoule and melted at a temperature between the solidus line and the liquidus line, resulting in a state in which solid and liquid coexist. In this state, the easily evaporable Hg element can diffuse into the Cd and Te crystals sufficiently even at temperatures between the solidus and liquidus lines, and by slowly cooling this crystal-forming material, uniform chemical chemistry can be achieved over a large area. A compound semiconductor crystal with a stoichiometric composition is obtained.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

Among the Hg+-x Cdx Te crystals to be formed in the ampoule 1 having a diameter of about 30 mm, Cd and Te are each weighed and filled at predetermined weights with Hg, an easily evaporable element, removed. , evacuate the inside and seal one end. The ampoule is then inserted into a heating furnace and Cd.

After raising the temperature of the heating furnace above the melting temperature of Te and heating it for about 24 hours, nitrogen gas is blown from one end of the ampoule to rapidly cool the molten material and solidify it to form an alloy of Cd and Te. It is formed in a state where the Te element does not segregate.

Next, this alloy consisting of Cd and Te was taken out from the ampoule and crushed, and then H was placed in the ampoule 21 shown in FIG.
Hg is similarly weighed so that the composition becomes g+-x Cdl Te, and a crystal forming material 22 of Hg and an alloy of Cd and Te is filled. At this time, ampoule 2
The mercury 24 provided in the thin tube 23 extending from the tip of the ampoule 21 for controlling the vapor pressure of the mercury vapor of the crystal forming material 22 in the ampoule 21 is similarly weighed, and the receiver is placed in the pan 25. After exhausting the air, one end C of the thin tube 23 is sealed.

Next, this ampoule 21 is inserted into the furnace core tube 27 in the heating furnace 26, and the temperature of the heating furnace 26 is controlled so that the temperature profile of the heating furnace 26 becomes the curve 28 in FIG. In this state, the ampoule 21 was heated in a heating furnace 26 for three days.
After holding the Hg inside and sufficiently diffusing the Hg into the Cd and Te,
Ampoule 21 was lowered in the direction of the arrow at a speed of 5 mm/24 hr so that the temperature gradient of the ampoule near the solidus temperature of 707°C was 2°C/cm.
Single crystals are sequentially formed from the bottom of 1.

Thereafter, it is slowly cooled to room temperature to form a single crystal.

Here, the heating temperature Ta of the ampoule 21 in the region containing the crystal forming material 22 is heated to a temperature of 750"C as shown in the temperature profile curve 28, and the thin tube containing the mercury 24 for vapor pressure control is heated to a temperature of 750"C as shown in the temperature profile curve 28. The heating temperature Tb of 23 is 615° C. as shown by curve 28.

Note that by using mercury for vapor pressure control in this way, the amount of Hg filled in the crystal forming material 22 of the ampoule 21 can be reduced, and an increase in the internal pressure of the ampoule can be prevented accordingly.

In addition, if the temperature of the vapor pressure control area where the thin tube 23 is installed is Tb, and the temperature of the vapor pressure control area eI where the crystal forming material 22 is installed is Ta, the relationship between Ta and Tb is expressed as (1). The relationship is as shown in the formula.

Ta≧Tb≧7149/(1,064+7149/Ta
)..." (1) Here, the liquid phase temperature of Cdo, zTe is about 780 ° C, and if it is done as in the present invention, the internal pressure of the ampoule will be as low as about 1 atm. Also) Igo, mcd
o, the temperature inside the ampoule during crystal growth of zTe is 7
Assuming 50°C, the internal pressure of the ampoule at this time is 25 atm, compared to 35 atm in the conventional method of heating Hgo, 5Cdo, and tTe above the liquidus temperature. The pressure can be reduced by about 10 atmospheres, and therefore a large-area Hg+-x CdXTe crystal with a large diameter can be obtained.

Also, since the internal pressure of the ampoule does not increase, H
Since it is possible to obtain a crystal of g+-x CdX Te and a crystal whose X value is controlled to a desired value, a high-performance infrared detection element with a widened wavelength range to be detected can be obtained. Further, by adjusting the amount of mercury for vapor pressure control, it is possible to eliminate the precipitation of Te in the formed crystals.

〔Effect of the invention〕

As described above, according to the method of the present invention, a stoichiometric compound semiconductor crystal with a large x value and a large cross-sectional area can be obtained, and if this crystal is used to form an infrared sensing element, it can be detected. This has the effect of providing a high-performance infrared sensing element with a wide range of wavelengths.

[Brief explanation of drawings]

Fig. 1 is a detailed explanatory diagram of the present invention, Fig. 2 is a diagram showing the temperature profile of the heating furnace used in the method of the present invention, Fig. 3 is an explanatory diagram of the conventional method, and Fig. 4 is a diagram illustrating the conventional method. It is a figure which shows the temperature profile of the heating furnace used. In the figure, 21 is an ampoule, 22 is a single crystal forming material, 23 is a thin tube, 24 is mercury for vapor pressure control, 25 is a saucer, 26 is a heating furnace, 27 is a furnace core tube, and 28 is a temperature profile. , where Ta is the heating area of the ampoule and Tb is the water for controlling vapor pressure.
The heating area, C is one end of the ampoule, and D is an arrow indicating the direction of movement of the ampoule. Half-lived
'0 Feel Figure 1 Figure 2 I'll give up! Moetan Fig. 3Hyr-y:CdxTe

Claims (1)

[Claims] A compound semiconductor crystal forming material (22) of a plurality of elements including an easily evaporable element is sealed in an ampoule (21), and after melting the crystal forming material (22), the ampoule (21) is sealed. In the method of forming a crystal by sequentially solidifying the molten crystal forming material (22) from one end, part or all of the easily vaporizable element in the compound semiconductor crystal forming material (22) is After the removed material is melted and solidified to form an alloy in advance, an easily evaporable element is added to the alloy and filled into an ampoule (21), and a thin tube (23) connected to the ampoule is filled with a material for vapor pressure control. The ampoule is filled and sealed with a material of an easily evaporable element, and the material in the ampoule is heated to a temperature between the liquidus line (11) and the solidus line (12) of the crystal to be formed. A method for growing a compound semiconductor crystal, which comprises bringing the crystal forming material (22) into a state in which a liquid phase and a solid phase coexist, and then cooling the crystal forming material (22) from one end of an ampoule (21) to form a single crystal.