JPH07232999A - Znse single crystal and its production - Google Patents

Abstract

PURPOSE:To produce a ZnSe single crystal free from twin defects with satisfactory productivity. CONSTITUTION:A melt is prepd. by adding 0.1-6mol% ZnTe and/or 0.1-5mol% BeSe to ZnSe and melting them. Crystal growth is carried out from the melt to produce the objective ZnSe single crystal contg. Zn, Se and Te and/or Be as essential components. The compsn. of this single crystal consists of, by atom, 50% Zn, (50-x)% Se and x% Te, (50-y)% Zn, y% Be and 50% Se or (50-x)% Se, (50-y)% Zn, x% Te and y% Be (0.05<=x<=3 and 0.05<=y<=2.5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-defect-free high-quality ZnSe-based single crystal used as a substrate material for growing a single crystal such as a blue semiconductor laser device and a blue light emitting diode device, and a method for producing the same.

[0002]

2. Description of the Related Art Since a blue semiconductor laser has a wavelength about half that of a currently used red semiconductor laser, it is said that the density of optical recording represented by a compact disc can be quadrupled, and other Compared with a light source, it has advantages such as compactness and low power consumption, and therefore its development is desired.

Further, if a blue semiconductor diode is realized, the three primary colors of light can be obtained in combination with the existing red and green light emitting diodes, and its application to a large high-brightness color display is considered. A so-called wide-gap semiconductor material having a bandgap corresponding to the energy of blue light is used for manufacturing these light-emitting elements. Among wide-gap semiconductor materials, ZnSe-based II-VI group compound semiconductors are regarded as the most promising. However, since a ZnSe single crystal substrate, which is a substrate for epitaxial growth necessary for device fabrication, has not been industrially manufactured at a low cost, GaAs, which has a close lattice constant, is generally used as a substrate for epitaxial growth. is doing.

However, a GaAs substrate (lattice constant: 5.6
54Å) and ZnSe (lattice constant: 5.668Å) have close lattice constants, but still have a mismatch of 0.25%,
Further, since there is a difference in thermal expansion coefficient, strain remains in the epitaxial growth layer, and defects such as dislocations occur, which inevitably leads to deterioration of device characteristics. Therefore, a high-quality ZnSe-based single crystal substrate is desired for practical use of the blue light emitting device.

[0005]

As a method for industrially growing a new bulk crystal processed on a substrate, a melt growth method of growing a crystal from a melt is advantageous from the viewpoint of productivity. Has a melting point of 1526 ° C., and when a crystal is grown by a melt growth method such as Bridgman method, 1
At around 420 ° C, a phase transition from a high temperature hexagonal system to a low temperature phase cubic system occurs, so that twin defects are introduced, resulting in the disadvantage that a good single crystal cannot be obtained (Jour.
nal of Crystal Growth, vol.86, 1988, 132-137). Further, Japanese Patent Application Laid-Open No. 63-310786 discloses a method for producing a ZnSe single crystal by the Bridgman method, and the details thereof are described in a technical paper by the inventor (Journal of C
rystalGrowth, vol.117, 1992, pp. 80-84)). Although there is no description of twinning in the publication, twinning occurs in the article.

In order to avoid twin defects due to the phase transition, in principle, it is only necessary to grow crystals at a temperature of 1420 ° C. or lower to grow a cubic crystal phase. As a method therefor, there is a low temperature growth method such as a chemical vapor deposition method or a physical vapor deposition method as disclosed in JP-A-1-264990, but the growth rate is slow and the productivity is very poor. There's a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a ZnSe-based single crystal having good productivity and containing no twin defects, and a method for producing the same.

[0008]

The ZnSe type single crystal of the present invention contains Zn, Se and Te as essential components,
The composition of each component is atomic%, Zn: 50%, Se: 50-x
%, Te: x%, where x: 0.05 to 3 or Zn, Be and Se as essential components,
The composition of each component is atomic%: Zn: 50-y%, Be: y
%, Se: 50%, but y: 0.05 to 2.5, or Zn, Se, Be and Te are contained as essential components, and the composition of each component is atomic%: Se: 50-x.
%, Zn: 50-y%, Te: x%, Be: y%, where x: 0.05-3 and y: 0.05-2.5.

On the other hand, according to the method for producing a ZnSe-based single crystal of the present invention, 0.1 to 6 mol% of ZnTe is added to ZnSe for melting, or 0.1 to 5 mol% of BeSe is added to ZnSe for melting. Or 0.1 to ZnSe
~ 6 mol% ZnTe and 0.1-5 mol% Be
Se is added and melted, and crystals are grown from the melt. As a method for growing a crystal from a melt, a known melt growth method such as a high pressure vertical Bridgman method, a rotary pulling method, a horizontal Bridgman method can be appropriately applied.

It is to be noted that addition of a small amount of a commonly used trace element of about several tens to several hundreds ppm for controlling conduction, such as addition of an n-type dopant chlorine, to a ZnSe type single crystal is not effective in the present invention. It does not change the essence at all, and is included in the present invention.

[0011]

[Function] ZnSe is replaced with Se to replace Te, or Z
The cubic phase is stabilized by substituting a predetermined amount of Be in place of n. Although the details of the mechanism are unknown, in the grown ZnSeTe single crystal, Te atoms having a large atomic radius are substituted at Se atom positions, while in the ZnBeSe single crystal, Be atoms having a small atomic radius are substituted at Zn atom positions. , It seems that the cubic phase is stabilized by generating a stress field in the crystal. Due to the stability of the cubic phase,
The phase transition of the crystal grown from the melt during cooling is eliminated, and the generation of high-density twin crystals due to the phase transition can be avoided.

In this case, Te is a group V element that is in the same group as Se.
On the other hand, Be is a Group II element that is in the same group as Zn, so
Both of these elements are isoelectronic impurities in ZnSe,
It does not work as a donor, acceptor, etc., and is a ZnSe group
The effect on the electrical properties of the plate is negligible. Zn₅₀Se
_50-xTe_xSystem crystal, Zn_50-yBe_yTe₅₀System crystal and Z
n_50-yBe _ySe_50-xTe_xSystem crystal (however, the subscript is an atom
% Is shown. ), The content of Te that should replace Se
Is x: 0.05 to 3, while Be which should be replaced with Zn
Content of y: 0.05 to 2.5. x and y
If both are less than 0.05, the effect is insufficient and a stable action is obtained.
I can't get it. On the other hand, if x exceeds 3 and y exceeds 2.5, the group
Proper supercooling becomes remarkable and single crystal growth becomes difficult. Well
Zn₅₀Se_50-xTe_xIn the system, the lattice constant of the grown crystal is
Zn increases with increasing Te, and Zn_50-yBe _ySe₅₀
In the system, it decreases as Be increases, and in any case
However, the lattice mismatch during epitaxial growth is large.
And lose its suitability as a substrate for epitaxial growth.
become. On the other hand, Zn_50-yBe_ySe_50-xTe_xIn the system
Control the lattice constant by adjusting the ratio of x and y
It is possible, for example, a substrate lattice-matched with ZnSe
It is also possible to obtain crystals. Incidentally, as already mentioned, ZnSe
Has a lattice constant of 5.668Å, and ZnTe has a lattice constant of
Is 6.103Å, while that of BeSe is 5.13
It is 9Å.

Further, in particular, in the case of a device structure in which the junction between the substrate and the epitaxial growth layer is positively utilized, in other words, in the case of a device structure having an active layer in the substrate, the band gap of the ZnSe-based substrate increases as the substitution amount of Te increases. Although the energy decreases and the emission wavelength shifts to the long wavelength side, when x exceeds 3, the wavelength shift becomes excessive, which is not desirable for a blue light emitting element. When Be is replaced, the bandgap energy of the ZnSe-based substrate increases with an increase in the amount of replacement, and the emission wavelength shifts to the short wavelength side.
Is more than 2.5, the wavelength shift becomes too large, which is not desirable for a blue light emitting element as in the case of replacing Te.
On the other hand, in the Zn _50-y Be _y Se _50-x Te _x system, the band gap can be freely changed by adjusting the ratio of x and y, and the same band as ZnSe can be obtained on a substrate lattice-matched with ZnSe. It can also have a gap value.

In the Zn ₅₀ Se _50-x Te _x system, the preferable content of Te to replace Se is 0.05 to 1.5 at%.
(X: 0.05~1.5) a is, Zn _50-y Be y Se
_{In the 50} system, the preferable content of Be to be replaced with Zn is
It is 0.05 to 1.25 at% (y: 0.05 to 1.25). This is because the lattice mismatch of the epitaxial growth substrate is within the same range (0.25% or less) as that of the conventional GaAs substrate. On the other hand, Zn _50-y Be _y Se _50-x T
In the e _x system, | 0.435x-0.529y | ≦ 0.7
As long as the relationship of is satisfied, Te: 0.05 to 3 at%, Be:
It becomes possible to make the lattice mismatch with ZnSe to be 0.25% or less in the range of the content of 0.05 to 2.5 at%.

When manufacturing an actual device, Zn
(Se, S), (Zn, Cd) Se, (Zn, Cd)
In some cases, it is necessary to grow a mixed crystal thin film such as (Se, S), and the content of Te and Be to be replaced should be Te: 0.05 so that the content should be close to the lattice constant of these mixed crystal materials. ~ 3
at% (x: 0.05 to 3), Be: 0.05 to 2.5 at
It can be appropriately selected within the range of% (y: 0.05 to 2.5).

Zn (Se, Te) single crystal, (Zn, Be) Se single crystal and (Zn, Be) (S) according to the present invention
e, Te) As a method for producing a single crystal, a predetermined single crystal can be obtained with good productivity by melting a melt having a predetermined composition and growing the single crystal from the melt. .
Regarding melting of the melt, ZnSe is added to ZnSe in an amount of 0.1 to 0.1
6.0 mol% or / and BeSe 0.1-5.0 mol
%, And melted to obtain a Zn (Se, Te), (Zn, Be) Se or (Zn, Be) (Se, Te) melt having a predetermined single crystal composition.

[0017]

EXAMPLES The present invention will be described below with reference to specific examples. Example A For 6N (Nine) grade ZnSe polycrystals, Table 1
As shown in (4), various mol% of 6N grade ZnTe was added to prepare a raw material so that the total amount was 200 g.

This raw material was placed in a growth container (crucible),
The crystal was grown in a high pressure vertical Bridgman furnace. The growth vessel is made of P-BN material and has a cylindrical shape with a diameter of 25 mm, and a capillary portion (capillary portion) with a diameter of 2 mm and a length of 40 mm for nucleation is provided at the bottom thereof. After the Ar gas pressure in the furnace was set to 10 MPa and the raw material part was heated to 1550 ° C. to melt the raw material, 10
After lowering the container at a speed of mm / h so that the capillary is out of the heater to generate crystal nuclei as seed crystals in the capillary part, the container is subsequently lowered at a speed of 5 mm / h to When the upper end reached 1450 ° C and the crystallization of the raw material was completed, the temperature of the entire container was lowered at 200 ° C / h.
The state of the obtained crystals is also shown in Table 1.

[0019]

[Table 1]

From the table, the content range of Te substituting for Se is 0.05 to 3 at% corresponding to the present invention, Sample No. 1
In ~ 6, 70% or more of twin-free crystals were obtained,
In particular, it can be seen that at 0.5 to 1.5 at%, no twins or polycrystals are formed. Next, FIG. 1 shows the results of measuring the lattice constant in the central portion of the crystals of Sample Nos. 1 to 7. The broken line in the figure indicates the theoretical value according to Vegard's law. From the figure, it was confirmed that the value of the lattice constant is proportional to the added amount of ZnTe and complies with Vegard's law, and that the added ZnTe is completely dissolved in ZnSe within the scope of the present invention. . Example B To a 6N grade ZnSe polycrystal, various mol% of 6N grade BeSe was added as shown in Table 2,
The raw material was prepared so that the total amount would be 200 g. Using this raw material, crystals were grown by the high pressure vertical Bridgman method under the same conditions as in Example A. Table 2 shows the state of the obtained crystals.
Are also shown.

[0021]

[Table 2]

From the table, the content range of Be substituting for Zn is 0.05 to 2.5 at% of the sample N which corresponds to the present invention.
In o. 11 to 14, single crystals with 75% or more of twin-free crystals were obtained, and it was found that twin crystals and polycrystals were not formed at 0.5 to 1.25 at% in particular. Next, sample No. 1
FIG. 2 shows the results of measuring the lattice constant in the central portion of the crystals of Nos. 1 to 15 in the same manner as in Example A.
The broken line in the figure indicates the theoretical value according to Vegard's law. From the figure, it was confirmed that the value of the lattice constant is proportional to the addition amount of BeSe and complies with Vegard's law, and that the added BeSe is completely dissolved in ZnSe within the scope of the present invention. .

Example C For 6N grade ZnSe polycrystals, as shown in Table 3, various mol% of 6N grade ZnTe and BeSe.
Was added to prepare a raw material so that the total amount was 200 g. Using this raw material, crystals were grown by the high pressure vertical Bridgman method under the same conditions as in Example A. The state of the obtained crystals is also shown in Table 3.

[0024]

[Table 3]

From the same table, it can be seen that the sample N corresponding to the embodiment in which the content range of Te substituting for Se is 0.05 to 3 at% and the content range of Be substituting for Zn is 0.05 to 2.5 at%
It can be seen that, in o. 31 to 38, a single crystal containing 75% or more of twin-free crystal was obtained. Next, sample Nos. 31 to 38 of the example.
FIG. 3 shows the result of measuring the lattice constant in the central portion of the crystal of Example 1 in the same manner as in Example A. In the figure, the numbers on the horizontal axis indicate the sample No., and the alternate long and short dash line indicates the value of the lattice constant of ZnSe, while the thin line indicates Z.
The value of the lattice constant of nSe ± 0.25% is shown. From the figure, it was confirmed that the lattice constant of the single crystal of each example was within the range of the lattice constant of ZnSe ± 0.25%. FIG. 4 shows (Zn, Be) based on Table 3 and FIG.
The content range of Te and Be within which the lattice constant of a (Se, Te) single crystal is within the lattice constant of ZnSe ± 0.25% is shown in FIG.
The boundary line was determined by plotting the contents of e and Be. When the region between the diagonal lines of the boundary line is expressed by a mathematical formula, | 0.435x−0.529y | ≦ 0.7, and the shaded region in the figure is the inequality, Te:
0.05-3.0 at% and Be: 0.05-2.5 at%
Shows the region that satisfies. Further, in FIG. 4, the broken line is Z
It means a composition that is lattice-matched with nSe.

[0026]

As described above, according to the present invention, Z
Since Se of nSe is contained by substituting a predetermined amount of Te or Zn by a predetermined amount of Be, the cubic phase becomes stable, and even if crystals are grown by the melt growth method, twin crystals are formed. Is suppressed, and a high-quality ZnSe-based single crystal can be easily manufactured with high productivity.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of ZnTe added and the crystal lattice constant.

FIG. 2 is a graph showing the relationship between the amount of BeSe added and the crystal lattice constant.

FIG. 3 is a graph showing a relationship between each composition point and a lattice constant of an example sample in Example C.

FIG. 4 shows that the lattice constant of a (Zn, Be) (Se, Te) single crystal falls within the range of ± 0.25% of the lattice constant of ZnSe.
It is a graph which shows the content range of e and Be.

Claims (9)

[Claims] 1. Zn, Se and Te are contained as essential components, and the composition of each component is atomic%: Zn: 50%, Se:
ZnSe-based single crystal with 50-x%, Te: x%, where x: 0.05-3. 2. The ZnSe-based single crystal according to claim 1, wherein x: 0.05 to 1.5. 3. ZnSe of 0.1 to 6 mol% in ZnSe
ZnS in which e is added and melted, and crystals are grown from the melt
Method for producing e-type single crystal. 4. Zn, Be and Se are contained as essential components, and the composition of each component is Zn: 50-y%, B in atomic%.
e: y%, Se: 50%, but y: 0.05 to 2.5 ZnSe-based single crystal. 5. The method according to claim 5, wherein y is 0.05 to 1.25.
The ZnSe-based single crystal described in 1. 6. ZnSe 0.1 to 5 mol% BeS
ZnS in which e is added and melted, and crystals are grown from the melt
Method for producing e-type single crystal. 7. Zn, Se, Te and Be are contained as essential components, and the composition of each component is Se: 50-x in atomic%.
%, Zn: 50-y%, Te: x%, Be: y%, where ZnS is x: 0.05-3 and y: 0.05-2.5.
e-based single crystal. 8. | 0.435x−0.529y | ≦ 0.
7. The ZnSe-based single crystal according to claim 7, which is 7. 9. ZnSe of 0.1 to 6 mol% in ZnSe
A method for producing a ZnSe-based single crystal in which e and 0.1 to 5 mol% of BeSe are added and melted, and crystal growth is performed from the melt.