JP2011251892A - InP SINGLE CRYSTAL AND METHOD FOR PRODUCING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an InP single crystal which is reduced in twin defects in an area with low carrier concentration while reducing dislocation density therein.SOLUTION: The InP single crystal 1 includes a minor diameter portion 10, a conical portion 20, and a straight body portion 30. The straight body portion 30 includes a low carrier concentration portion 31 with carrier concentration of 4.0×10cmor less and a high-carrier concentration portion 32 with carrier concentration exceeding 4.0×10cm. In a section perpendicular to the growing direction of the low carrier concentration portion 31, the low carrier concentration portion 31 includes a high dislocation density area 31B which is formed in a region including the outer periphery and has average dislocation density of 1,000 cmor more, and a low-dislocation density area 31A which is formed so as to be surrounded by the high dislocation density area 31B and has average dislocation density of 500 cmor less.

Description

  The present invention relates to an InP single crystal and a method for manufacturing the InP single crystal, and more particularly to an InP single crystal capable of suppressing the generation of twin defects while reducing the dislocation density in a region having a low carrier concentration. Is.

  In an InP (indium phosphide) single crystal, it is required to reduce the dislocation density while suppressing the generation of twin defects. In order to meet such demands, for example, in the LEC (Liquid Encapsulated Czochralski) method, by reducing the temperature gradient in the growth direction, the growth of dislocations is suppressed, and the temperature fluctuation due to gas convection is suppressed, thereby reducing twinning. There has been proposed a method for suppressing the occurrence of (see, for example, Patent Document 1).

JP-A-3-237088

  However, in the pulling method such as the LEC method, the growing crystal comes into contact with the external atmosphere. And since it is necessary to avoid the dissolution of the crystal resulting from this, there is a limit in reducing the temperature gradient in the growth direction. As a result, it is not always easy to suppress the dislocation density by reducing the temperature gradient.

  In addition, when an impurity such as sulfur or zinc is introduced into an InP single crystal, the impurity is known to inhibit dislocation propagation and reduce dislocation (impurity hardening effect). This impurity curing action becomes more prominent as the concentration of the introduced impurity is higher. Here, since sulfur and zinc have a segregation coefficient of less than 1 in InP, the concentration of sulfur and zinc contained in the melt increases as crystal growth proceeds and the amount of melt decreases. Therefore, when the temperature gradient in the crystal growth direction is constant, the dislocation density decreases as the crystal growth proceeds. As a result, it is relatively easy to reduce the dislocation density in a region having a high impurity concentration, that is, a region having a high carrier concentration. However, in a region where the carrier concentration is low, it is difficult to produce an InP single crystal having a low dislocation density by a pulling method such as the LEC method.

  On the other hand, in the vertical boat method such as the VB (Vertical Bridgeman) method or the VGF (Vertical Gradient Freeze) method for growing a crystal in a sealed crucible, the growing crystal does not come into contact with the external atmosphere. The temperature gradient in the direction can be reduced as compared with a pulling method such as the LEC method. As a result, according to methods such as the VB method and the VGF method, it is relatively easy to suppress the dislocation density by suppressing the temperature gradient even in a region where the carrier concentration is low.

  However, when a method such as the VB method or the VGF method is adopted to reduce the dislocation density, there is a problem that twin defects are likely to occur.

  Accordingly, an object of the present invention is to provide an InP single crystal in which the generation of twin defects is suppressed while reducing the dislocation density in a region where the carrier concentration is low, and a method for manufacturing the InP single crystal.

The InP single crystal according to the present invention is formed in a region including the outer periphery in a cross section perpendicular to the growth direction of a region having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less, and an average dislocation density of 1000 cm ^−2. A high dislocation density region as described above and a low dislocation density region formed so as to be surrounded by the high dislocation density region and having an average dislocation density of 500 cm ⁻² or less are provided.

The present inventor has conducted detailed studies on a method for realizing an InP single crystal in which the generation of twin defects is suppressed while reducing the dislocation density in a region where the carrier concentration is low. As a result, even in a region having a low carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less, a high dislocation density region having an average dislocation density of 1000 cm ⁻² or more in the cross section perpendicular to the growth direction is formed on the outer peripheral portion. Thus, it was found that a low dislocation density region having an average dislocation density of 500 cm ⁻² or less can be formed in a region surrounded by the high dislocation density region while suppressing the generation of twin defects. Therefore, according to the InP single crystal of the present invention, in the region with a low carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less, the generation of twin defects is suppressed while the average dislocation density is reduced to 500 cm ⁻² or less. InP single crystal can be provided.

  The InP single crystal includes a small-diameter portion having a cylindrical shape, a conical portion having a truncated cone shape that is connected to the small-diameter portion in the axial direction of the small-diameter portion, and whose outer diameter increases as the distance from the small-diameter portion increases. A straight body portion connected to the conical portion in the axial direction and having a cylindrical shape having a diameter larger than that of the small diameter portion may be provided. And the length of the axial direction of a straight body part can be 150 mm or more.

  When an InP single crystal is manufactured by a method such as the VB method or the VGF method, a crucible having a small diameter portion, a conical portion connected to the small diameter portion, and a straight body portion connected to the conical portion is used. There are many. In this case, an InP single crystal having a small diameter portion, a conical portion, and a straight body portion corresponding to the shape of the crucible is obtained. Here, as a result of the study by the present inventors, it has been found that, according to the conventional manufacturing method, twin defects are extremely likely to occur when the straight body portion is 150 mm or more. Therefore, in the region where the carrier concentration is low, the InP single crystal of the present invention that can suppress the generation of twin defects while reducing the dislocation density is particularly effective when applied to a single crystal having a straight body portion of 150 mm or more. .

  In the InP single crystal, a region having a distance of 3 mm or less from the outer periphery may be the high dislocation density region. Thereby, the low dislocation density region in which the generation of twin defects is suppressed can be easily formed.

The InP single crystal manufacturing method according to the present invention includes a step of preparing an InP single crystal raw material, and a step of growing the InP single crystal by solidifying the raw material after melting. Then, in the step of growing the InP single crystal, the average dislocation density is 1000 cm in the region of the InP single crystal having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less and including the outer periphery of the cross section perpendicular to the growth direction. ^-2 or higher so that a high dislocation density region is formed.

As described above, a single crystal region having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less is formed so as to form a high dislocation density region having an average dislocation density of 1000 cm ⁻² or more in a region including the outer periphery. By growing, a region having a low dislocation density with an average dislocation density of 500 cm ⁻² or less can be formed in a region surrounded by the high dislocation density region while suppressing generation of twin defects. Therefore, according to the InP single crystal manufacturing method of the present invention, in the region where the carrier concentration is as low as 4.0 × 10 ¹⁸ cm ⁻³ or less, the generation of twin defects while reducing the dislocation density to 500 cm ⁻² or less. InP single crystal in which the above is suppressed can be manufactured.

  In the InP single crystal manufacturing method, in the step of growing the InP single crystal, the small diameter portion having a cylindrical shape is connected to the small diameter portion in the axial direction of the small diameter portion, and the outer diameter increases as the distance from the small diameter portion increases. An InP single crystal having a truncated cone shape and a straight body portion connected to the cone portion in the axial direction of the small diameter portion and having a cylindrical shape having a diameter larger than that of the small diameter portion. Good. At this time, the axial length of the straight body portion can be 150 mm or more.

  As described above, when an InP single crystal having a small-diameter portion, a conical portion, and a straight body portion is produced by a method such as the VB method or the VGF method, according to the conventional manufacturing method, the straight body portion is 150 mm or more. Then, twin defects are very likely to occur. This is presumably because the convection of the melt becomes stronger and the temperature of the melt tends to become unstable as the depth of the melt increases. Therefore, in the region where the carrier concentration is low, the InP single crystal manufacturing method of the present invention capable of suppressing the generation of twin defects while reducing the dislocation density can be applied to the manufacture of a single crystal having a straight body portion of 150 mm or more. Is particularly effective.

In the InP single crystal manufacturing method, in the step of growing the InP single crystal, at least a part of the region of the InP single crystal having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less is formed in the InP single crystal. The crucible in which the crystal grows may be grown while being pulled down at a speed of 6 mm / h or more. As a result, the growth rate of the InP single crystal is increased and the latent heat generated with the solidification of the melt is increased, so that the high dislocation density region is easily formed. As a result, it becomes easy to form a low dislocation density region having an average dislocation density of 500 cm ⁻² or less in a region surrounded by the high dislocation density region while suppressing the generation of twin defects.

The manufacturing method of the InP single crystal may further include a step of removing the high dislocation density region from the grown InP single crystal. As a result, an InP single crystal having a carrier concentration as low as 4.0 × 10 ¹⁸ cm ⁻³ or less and suppressing the generation of twin defects while reducing the dislocation density can be obtained.

  As is apparent from the above description, according to the InP single crystal of the present invention and the method for manufacturing the same, the InP single crystal that suppresses the generation of twin defects while reducing the dislocation density in the region where the carrier concentration is low, and the manufacturing thereof. A method can be provided.

It is the schematic which shows the structure of an InP single crystal. It is a schematic sectional drawing which shows the cross section along line segment II-II of FIG. It is a flowchart which shows the outline of the manufacturing method of an InP single crystal. It is a schematic sectional drawing for demonstrating the manufacturing method of an InP single crystal. It is a schematic sectional drawing for demonstrating the manufacturing method of an InP single crystal. It is a figure which shows the relationship between the dislocation density in the outer peripheral part of a low carrier concentration part, and the presence or absence of the generation | occurrence | production of a twin defect. It is a figure which shows the relationship between a carrier concentration and the incidence rate of a twin defect. It is a figure which shows the relationship between the length of a straight body part, and the incidence rate of a twin defect.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  First, an InP single crystal according to an embodiment of the present invention will be described. 1 and 2, InP single crystal 1 in the present embodiment is connected to small diameter portion 10 having a cylindrical shape and small diameter portion 10 in the axial direction of small diameter portion 10. A conical portion 20 having a frustoconical shape whose outer diameter increases with increasing distance, and a straight body portion 30 connected to the conical portion 20 in the axial direction of the small diameter portion 10 and having a cylindrical shape larger in diameter than the small diameter portion 10. And. The length L in the axial direction (growth direction) of the straight body portion 30 is 150 mm or more.

Further, the straight body section 30 includes a low carrier concentration 31 of the carrier concentration is 4.0 × ¹⁰ 18 ^{cm -3} or less, a high carrier concentration portion 32 in which the carrier concentration exceeds 4.0 × ¹⁰ 18 ^{cm -3} Is included. And in the cross section perpendicular | vertical to the growth direction of the low carrier concentration part 31 (cross section shown in FIG. 2), the said low carrier concentration part 31 is formed in the area | region including an outer periphery, and an average dislocation density is 1000 cm ^<-2 > or more. It has a dislocation density region 31B and a low dislocation density region 31A formed so as to be surrounded by the high dislocation density region 31B and having an average dislocation density of 500 cm ⁻² or less.

In the InP single crystal 1 according to the present embodiment, in the low carrier concentration portion 31 having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less, high dislocation having an average dislocation density of 1000 cm ⁻² or more in a region including the outer periphery. It has a density region 31B. As a result, a low dislocation density region 31A having an average dislocation density of 500 cm ⁻² or less is formed in the inner peripheral region surrounded by the high dislocation density region 31B while suppressing the generation of twin defects. As described above, the InP single crystal 1 according to the present embodiment has twin defect defects while reducing the average dislocation density to 500 cm ⁻² or less in a region where the carrier concentration is 4.0 × 10 ¹⁸ cm ⁻³ or less. It is an InP single crystal with suppressed generation.

  Next, a method for manufacturing an InP single crystal according to an embodiment of the present invention will be described. Here, as a method for manufacturing an InP single crystal, a case where the VB method is employed will be described as an example, and a method for manufacturing an InP single crystal will be described with reference to FIGS. When the VB method is employed, for example, the following crucible can be employed.

  Referring to FIG. 4, crucible 5 used in the present embodiment includes seed crystal holding unit 51 and single crystal growth unit 52 connected on seed crystal holding unit 51. The seed crystal holding part 51 is a cylindrical region having a cylindrical cavity part that is open on the side connected to the single crystal growth part 52 and has a bottom wall formed on the opposite side. Crystals can be retained. The single crystal growth part 52 has a conical part 52A having a conical shape connected to the seed crystal holding part 51 on the small-diameter side in the axial direction, and a hollow cylindrical shape connected to the large-diameter side in the axial direction of the conical part 52A. And a straight body portion 52 </ b> B. The single crystal growth part 52 has a function of growing a single crystal by solidifying the raw material heated to be in a molten state while holding the raw material of the single crystal therein. Moreover, as a material which comprises the crucible 1, the various materials which can endure the temperature at the time of raw material melting | fusing can be employ | adopted, For example, pyrolytic boron nitride (PBN) can be employ | adopted.

  With reference to FIG. 3, in the InP single crystal manufacturing method in the present embodiment, first, a seed crystal charging step is performed as a step (S <b> 10). In this step (S <b> 10), as shown in FIG. 4, an InP single crystal seed crystal 61 is charged into the seed crystal holding part 51 of the crucible 5.

  Next, a raw material charging step is performed as a step (S20). In this step (S20), referring to FIG. 4, a plurality of cylindrical raw materials 62 made of, for example, polycrystalline InP are charged into the crucible 5 and stacked.

Next, a sealing agent arrangement | positioning process is implemented as process (S30). In this step (S30), as shown in FIG. 4, for example, a sealing agent 63 made of B ₂ O ₃ (boron oxide) is placed on the raw material 62 stacked in step (S20).

  Next, referring to FIG. 3, a single crystal growth step is performed. The single crystal growth step includes a first low-speed growth step performed as a step (S40), a high-speed growth step performed as a step (S50), and a second low-speed growth step performed as a step (S60). Contains.

  Specifically, in the single crystal growth step, the crucible 5 in which the seed crystal 61, the raw material 62, and the sealing agent 63 are arranged in the steps (S10) to (S30) is loaded into the crystal growth apparatus, Single crystal growth is performed. Here, referring to FIG. 5, crystal growth apparatus 7 used in the present embodiment surrounds high pressure vessel 71, crucible holding base 72 that holds crucible 5 in high pressure vessel 71, and crucible 5. And a heating element 73 disposed on the surface.

  Then, referring to FIG. 5, after crucible 5 is inserted into high-pressure vessel 71 so as to be held by crucible holding base 72, current is supplied to heating element 73 from a power source (not shown), and crucible 5 is heated. Is done. Thereby, the sealant 63 on the raw material 62 is melted to become the liquid sealant 83, and the raw material 62 is melted to become the raw material melt 82.

  Thereafter, referring to FIG. 3 and FIG. 5, in the step (S40), the crucible 5 is gradually pulled down toward the axially lower side (seed crystal holding part 51 side). In the direction, a temperature gradient is formed such that the temperature on the seed crystal 61 side is low and the temperature on the raw material melt 82 side is high. As a result, the raw material melt 82 in contact with the seed crystal 61 is solidified to grow a single crystal 81 made of InP. The growth of the single crystal 81 is continued until the solidification of the raw material melt 82 in the conical portion 52A is completed, for example. In this step (S40), the pulling speed when pulling down the crucible 5 can be set to 2.0 mm / h or more and 5.0 mm / h or less, for example. Thereby, a process (S40) is completed and the small diameter part 10 and the cone part 20 are formed among the InP single crystals 1 in this Embodiment (refer FIG. 1).

Next, in the step (S50), following the step (S40) in which the raw material melt 82 in the conical portion 52A is solidified, the raw material melt 82 in the straight body portion 52B is solidified. In this case, the carrier concentration in the single crystal 81 to the raw material melt 82 in the step (S50) are obtained by solidification, 4.0 × ¹⁰ 18 ^{cm -3} or less, more specifically, for example, 1.0 × ^{10 18} It is cm ⁻³ or more and 4.0 × 10 ¹⁸ cm ⁻³ or less. In this step (S50), the crucible 5 is pulled down at a speed higher than that in the step (S40), for example, 10 mm / h or more. As a result, the growth rate of the single crystal 81 is increased and the heat (latent heat) generated with the solidification of the raw material melt 82 is increased, so that the dislocation density is increased in the region including the outer periphery. As a result, in this step (S50), it is formed so as to be surrounded by a high dislocation density region 31B having an average dislocation density of 1000 cm ⁻² or more and a high dislocation density region 31B. The low carrier concentration portion 31 including the low dislocation density region 31A having a density of 500 cm ⁻² or less grows while the generation of twin defects is suppressed (see FIGS. 1 and 2). Note that the crucible is pulled down at a rate of 6 mm / h or more, preferably 8 mm / h or more, more preferably 10 mm / h or more at least part of the region where the carrier concentration is 4.0 × 10 ¹⁸ cm ⁻³ or less. By growing, the high dislocation density region 31B can be easily formed in the region.

Next, in the step (S60), subsequent to the step (S50) in which the low carrier concentration portion 31 is grown, the raw material melt 82 remaining in the straight body portion 52B is solidified. At this time, due to the progress of solidification of the raw material melt 82 in the steps (S40) and (S50), the concentration of impurities contained in the raw material melt 82 remaining in the straight body portion 52B increases, and the raw material in the step (S60) The carrier concentration of the single crystal 81 obtained by solidifying the melt 82 exceeds 4.0 × 10 ¹⁸ cm ⁻³ . When the solidification of the raw material melt 82 remaining in the straight body portion 52B is completed, the step (S60) is completed and the single crystal growth step is completed. Through the above steps, the InP single crystal 1 shown in FIGS. 1 and 2 is produced in the crucible 5, and the InP single crystal 1 in the present embodiment is obtained by taking it out. Further, when a single crystal having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less and a dislocation density of 500 cm ⁻² or less is required in the entire region, the following steps (S70) and (S80) are performed. The

That is, as the steps (S70) and (S80), a cutting step and a peripheral grinding step are performed. In these steps (S70) and (S80), the InP single crystal 1 taken out from the crucible 5 is cut to obtain the low carrier concentration portion 31 and the outer periphery of the low carrier concentration portion 31 is ground. As a result, the high dislocation density region 31B is removed. Thereby, only the low dislocation density region 31 ^</ b> A having an average dislocation density of 500 cm ⁻² or less remains in the low carrier concentration portion 31. With the above procedure, the manufacturing method of the InP single crystal in the present embodiment is completed. The obtained low dislocation density region 31A can be used as an InP single crystal substrate by being sliced to a desired thickness, for example.

In the InP single crystal manufacturing method in the present embodiment, the crucible 5 is pulled down at a high speed in the step (S50) of growing a single crystal region having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less. Then, a high dislocation density region 31B having 1000 cm ⁻² or more is formed in a region including the outer periphery of the low carrier concentration portion 31. As a result, a low dislocation density region 31A having an average dislocation density of 500 cm ⁻² or less can be formed in a region surrounded by the high dislocation density region 31B while suppressing generation of twin defects. Therefore, according to the InP single crystal manufacturing method of the present embodiment, in the region where the carrier concentration is as low as 4.0 × 10 ¹⁸ cm ⁻³ or less, the twin defects are reduced while the dislocation density is reduced to 500 cm ⁻² or less. InP single crystal 1 in which the occurrence of the above is suppressed can be manufactured.

  An experiment was conducted to confirm the effect of the method for producing an InP single crystal of the present invention. First, an InP single crystal doped with sulfur was manufactured by carrying out the steps (S10) to (S60) described in the above embodiment. Specific manufacturing conditions are as follows.

First, in steps (S10) to (S30), the crucible 5 was charged with InP single crystal as a seed crystal, 4 kg of InP polycrystal as a raw material, and 300 g of B ₂ O ₃ as a sealant. Next, in the single crystal growth step, the crucible 5 was set in the crystal growth apparatus 7, and the raw material 62 and the sealant 63 were heated and melted. At this time, the pressure in the high-pressure vessel 71 was set to 35 atm or more in order to prevent phosphorus from coming off.

Thereafter, in steps (S40) and (S60), the pulling rate is set to 2.0 to 5.0 mm / h, while a single crystal having a carrier concentration of 3.0 to 4.0 × 10 ¹⁸ cm ⁻³ grows ( In S50), a single crystal was grown at a pulling rate of 10 mm / h. Then, after the step (S60) was completed, the InP single crystal 1 in which the diameter D of the straight body portion 30 was 61 mm was taken out from the crucible 5 (Example). The InP single crystal 1 was manufactured five times by the procedure of this example, and five InP single crystals 1 were manufactured.

  On the other hand, for comparison, in the same manufacturing method as in the above example, a single crystal was grown at a pulling-down rate in steps (S40) to (S60) of 2.0 to 5.0 mm / h and taken out from the crucible. (Comparative example). The InP single crystal was manufactured three times by the procedure of this comparative example, and three InP single crystals were manufactured.

The InP single crystals obtained in the examples and comparative examples were examined for the average dislocation density and the presence or absence of twin defects. As a result, in the InP single crystal 1 of the example, with reference to FIG. 1, the low carrier concentration portion 31 having a carrier concentration of 3.0 to 4.0 × 10 ¹⁸ cm ⁻³ grown at a pulling-down rate of 10 mm / h. Among these, the region where the distance t from the outer periphery was within 3 mm was a high dislocation density region 31B having a dislocation density of 1000 cm ⁻² or more. A region surrounded by the high dislocation density region 31B is a low dislocation density region 31A having a dislocation density of 500 cm ⁻² or less, and generation of twin defects was not confirmed in the region. About these investigation results, it was the same about the five InP single crystals 1 of an Example.

On the other hand, in the three InP single crystals of the comparative example, it was confirmed that twin defects were generated in a low carrier concentration portion having a carrier concentration of 3.0 to 4.0 × 10 ¹⁸ cm ⁻³ . Further, when the average dislocation density was investigated for the region immediately before the occurrence of twin defects, the average dislocation density in the region having a distance of 3 mm or less from the outer periphery was less than 1000 cm ⁻² .

  From the above results, according to the InP single crystal and the manufacturing method thereof of the present invention, it is possible to provide an InP single crystal that suppresses the generation of twin defects while reducing the dislocation density in a region where the carrier concentration is low, and the manufacturing method thereof. Was confirmed.

In addition, when peripheral grinding was performed on the InP single crystal 1 of the example so as to have a diameter of 2 inches, the high dislocation density region 31B was removed, and the InP single crystal consisting only of the region having a dislocation density of 500 cm ⁻² or less. Crystals were obtained.

In the InP single crystal of the example, two of the five were single crystals having no twin defects. On the other hand, in three of the five, the generation of twin defects was confirmed only in the region where the solidification rate exceeded 0.9. This is presumably because the impurity concentration is high in the region where the solidification rate exceeds 0.9, and the dislocation density is remarkably lowered due to the increased impurity curing action. However, the carrier concentration in the region where the solidification rate exceeds 0.9 exceeds 8.0 × 10 ¹⁸ cm ⁻³ and is not used for manufacturing a general semiconductor device. Therefore, for example, when the InP single crystal of the example is used as a raw material for an InP substrate for a semiconductor device, it is considered that the generation of twin defects does not affect the yield.

In addition, an InP single crystal produced by crystal growth may be annealed in a temperature range of 800 ° C. to 1000 ° C. for the purpose of relaxing strain. Then, annealing which heated to 800 to 1000 degreeC was implemented with respect to the InP single crystal of the said Example and comparative example, and the presence or absence of the change of the dislocation density by annealing was investigated. As a result, no dislocation growth was observed in the InP single crystal of the example. On the other hand, in the InP single crystal of the comparative example, the growth of dislocation was observed in the region where the carrier concentration was 4.0 × 10 ¹⁸ cm ⁻³ or less, and the average dislocation density was only in the region within 3 mm from the outer periphery. However, it was more than 1000 cm ⁻² in the entire radial direction. This is considered to be caused by the fact that dislocations already exist at a high density in the outer peripheral portion in the InP single crystal of the example, and new dislocations are hardly generated. That is, it can be said that the InP single crystal of the present invention is an InP single crystal in which the growth of dislocations due to annealing after crystal growth is suppressed.

An experiment was conducted to investigate the relationship between the average dislocation density and the occurrence of twin defects in a region within 3 mm from the outer periphery in a region having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less.

Specifically, the carrier concentration is adjusted to 3.0 to 4.0 × 10 ¹⁸ cm by adjusting the pulling-down speed of the crucible 5 in the step (S50) in the same procedure as that of the example in the first example. An InP single crystal in which the average dislocation density in the outer peripheral portion of the low carrier concentration portion 31 which is ⁻³ was changed was produced. Then, the average dislocation density in the region having a distance of 3 mm or less from the outer periphery in the low carrier concentration part 31 was investigated, and the occurrence of twin defects in the low carrier concentration part 31 was investigated.

  Next, experimental results will be described with reference to FIG. In FIG. 6, the horizontal axis represents an EPD (Etch Pit Density) average value corresponding to the average dislocation density, and the vertical axis represents the presence or absence of twin defects.

As shown in FIG. 6, the average dislocation density is less than 1000 cm ^-2 distance from the outer periphery in a low carrier concentration unit 31 is the region within 3 mm, more specifically when it 876Cm ^-2 or less, twin defects occur contrast was the average dislocation density of 1000 cm ^-2 or more, and more specifically if it is 1025 cm ^-2 or more, twin defects did not occur. Therefore, in the InP single crystal, a high dislocation density region having an average dislocation density of 1000 cm ⁻² or more is formed in a region including the outer periphery of the region having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less. Thus, it was confirmed that the generation of twin defects in the region can be suppressed.

  In the above embodiments and examples, the InP single crystal doped with sulfur and the method for manufacturing the same were described as an example of the InP single crystal of the present invention and the method for manufacturing the InP single crystal. The crystal and the manufacturing method thereof are not limited to this. For example, the same effect can be obtained by applying to an InP single crystal doped with zinc and the manufacturing method thereof. Further, in the above embodiments and examples, the case where the VB method is adopted as the method for producing the InP single crystal of the present invention has been described. However, the adoptable production method is not limited to this, for example, the VGF method is adopted. The same effect can be obtained.

Further, in the above embodiment and examples, the case where the shape shown in FIG. 1 is adopted as the shape of the InP single crystal of the present invention has been described. However, the InP single crystal of the present invention is different from single crystals of various shapes. Can be applied. In addition, the high dislocation density region in the present invention has a predetermined effect by being formed in a region including the outer periphery of the region having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less. A region within 3 mm, more preferably a region within 5 mm from the outer periphery, and more preferably a region within 10 mm from the outer periphery is a high dislocation density region, thereby more reliably suppressing the generation of twin defects. However, a low dislocation density region can be formed.

The relationship between the carrier concentration and the occurrence rate of twin defects when an InP single crystal was grown without forming the high dislocation density region was investigated. Specifically, the carrier concentration is 1.0 × 10 ¹⁸ cm ⁻³ using a crucible having a shape similar to that of the above embodiment (the length of the straight body portion is 150 mm or more) without forming the high dislocation density region. An InP single crystal having a size of ˜10.0 × 10 ¹⁸ cm ⁻³ was grown to prepare a plurality of samples, and an experiment was conducted to investigate the presence or absence of twin defects in the sample. The experimental results are shown in FIG.

Referring to FIG. 7, it can be seen that when the carrier concentration is low, the occurrence rate of twin defects is high. When the carrier concentration was 4 × 10 ¹⁸ cm ⁻³ or less, twin defects were generated with a probability of 100%. This confirms the effectiveness of the present invention capable of suppressing the generation of twin defects in the region where the carrier concentration is 4.0 × 10 ¹⁸ cm ⁻³ or less.

When the InP single crystal was grown without forming the high dislocation density region, the relationship between the length of the straight body portion and the occurrence rate of twin defects was investigated. Specifically, a plurality of samples can be obtained by growing an InP single crystal using a crucible having a shape similar to that of the above embodiment (the length of the straight body portion is 30 mm to 300 mm) without forming the high dislocation density region. Was made. And about each sample, the experiment which investigates the presence or absence of the generation | occurrence | production of the twin defect in the area | region whose carrier concentration is 4 * 10 < ¹⁸ > cm < ^-3 > was conducted. The experimental results are shown in FIG.

  Referring to FIG. 8, it can be seen that the occurrence rate of twin defects increases as the length of the straight body increases. And when the length of the straight body part was 150 mm or more, twin defects occurred with a probability of 100%. This confirms the effectiveness of the present invention that can suppress the generation of twin defects even when the length of the straight body portion is 150 mm or more.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The InP single crystal and the manufacturing method thereof of the present invention are particularly advantageously applied to an InP single crystal and a manufacturing method thereof that are required to suppress the generation of twin defects while reducing the dislocation density in a region where the carrier concentration is low. obtain.

  1 InP single crystal, 5 crucible, 7 crystal growth apparatus, 10 small diameter part, 20 conical part, 30 straight body part, 31 low carrier concentration part, 31A low dislocation density region, 31B high dislocation density region, 32 high carrier concentration part, 51 seed crystal holding part, 52 single crystal growing part, 52A conical part, 52B straight body part, 61 seed crystal, 62 raw material, 63 sealant, 71 high pressure vessel, 72 crucible holding base, 73 heating element, 81 single crystal, 82 Raw material melt, 83 Liquid sealant.

Claims (7)

A high dislocation density region having an average dislocation density of 1000 cm ⁻² or more formed in a region including the outer periphery in a cross section perpendicular to the growth direction of the region having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less;
An InP single crystal comprising a low dislocation density region formed so as to be surrounded by the high dislocation density region and having an average dislocation density of 500 cm ⁻² or less. A small diameter portion having a cylindrical shape;
A conical portion having a truncated cone shape that is connected to the small diameter portion in the axial direction of the small diameter portion and has an outer diameter that increases with distance from the small diameter portion;
A straight body portion connected to the conical portion in the axial direction of the small diameter portion and having a cylindrical shape having a diameter larger than the small diameter portion;
The InP single crystal according to claim 1, wherein the length of the straight body portion in the axial direction is 150 mm or more.   The InP single crystal according to claim 1 or 2, wherein a region within a distance of 3 mm from the outer periphery is the high dislocation density region. Preparing an InP single crystal raw material;
A step of growing the InP single crystal by solidifying after melting the raw material,
In the step of growing the InP single crystal, the area of the InP single crystal having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less is changed to an average dislocation density of 1000 cm in a region including the outer periphery of the cross section perpendicular to the growth direction. ^A method for producing an InP single crystal, which is grown so that a high dislocation density region of ⁻² or more is formed. The step of growing the InP single crystal has a small-diameter portion having a cylindrical shape, and a truncated cone shape that is connected to the small-diameter portion in the axial direction of the small-diameter portion and whose outer diameter increases as the distance from the small-diameter portion increases. Growing the InP single crystal comprising a conical portion and a straight body portion connected to the conical portion in the axial direction of the small diameter portion and having a cylindrical shape having a diameter larger than that of the small diameter portion,
The method for producing an InP single crystal according to claim 4, wherein the length of the straight body portion in the axial direction is 150 mm or more. In the step of growing the InP single crystal, at least a part of the region of the InP single crystal having a carrier concentration of 4.0 × 10 ¹⁸ cm ⁻³ or less is formed with a crucible in which the InP single crystal grows at 6 mm / The method for producing an InP single crystal according to claim 4 or 5, wherein the growth is performed while pulling down at a rate of h or more.   The method for producing an InP single crystal according to any one of claims 4 to 6, further comprising a step of removing the high dislocation density region from the grown InP single crystal.

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