JP2006173338A - Manufacturing method of epitaxial wafer for light emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To permit the manufacturing of a light emitting diode with excellent crystallinity through the reduced amount of Zn charge than before by preventing Zn diffusion of Zn dopant upon temperature rise to supply stable Zn dopant and preventing the participation of the same into an n-type layer. <P>SOLUTION: In the manufacturing method of an epitaxial wafer for light emitting diode, the epitaxial layer of a compound semiconductor is grown employing an epitaxial growing device with a substrate holder 12 for receiving a substrate 1 for growing, and a raw material solution holder 13 having two sets or more of raw material solution reservoirs 15 in the sliding direction which are opposed so as to be relatively slidable. Partitioning plates 20, 30 are inserted into one of the raw material solution reservoirs 15 to partition the raw material solution into up-and-down three layers, and the raw material solution in respective chambers is dropped into a lower layer to use the same for the epitaxial growth by pulling out the partitioning plates 20, 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an epitaxial wafer for light emitting diodes, and more particularly to a technique for improving a graphite jig used for liquid phase epitaxial growth and preventing diffusion of Zn dopant during growth.

  FIG. 4 shows an outline of a conventional liquid phase growth apparatus for liquid phase epitaxial growth of a GaAlAs thin film.

  In this liquid phase growth apparatus, four graphite parts of a pedestal 11, a substrate holder (slider) 12, a raw material solution holder 13, and a cap holder 14 are stacked up and down, and the substrate holder 12 is attached to the pedestal 11 and the raw material solution holder 13. It is comprised by the slide boat which can be made to slide in a horizontal direction.

  Among the raw material solution holder 13 and the substrate holder 12 that slide relative to each other, the lower substrate holder 12 is dug in a part of the surface on one end side in the apparatus longitudinal direction of the upper surface that is the sliding surface, A substrate storage mounting recess 16 for mounting the GaAs substrate 1 is formed.

  On the other hand, the upper raw material solution holder 13 is formed with a plurality (three in this case) of raw material solution reservoirs 15 in which the growth solution is placed in the slide direction at sequential intervals. The upper surface, which is the opposite surface, is airtightly covered with a cap holder 14.

  The growth method using this growth apparatus is as follows: (1) “Slow cooling method” in which the temperature of the molten semiconductor raw material is lowered at a constant rate as time elapses, and (2) a temperature difference is provided above and below the molten liquid. There are a “temperature difference method” in which the solute is placed at a constant temperature so as to keep the solute in a supersaturated state on the upper part of the liquid, and a crystal is grown on the lower substrate, and (3) a “combined method” in which both are used together.

  Here, when the object to be manufactured is an epitaxial wafer for a light emitting diode shown in FIG. 3, when the slow cooling method is taken as an example, first, a p-type GaAlAs cladding layer 2, a p-type GaAlAs active layer 3, and an n-type GaAlAs cladding In order to grow the layer 4, the p-type GaAlAs cladding layer material solution 7, the p-type GaAlAs active layer material solution 8, and the n-type GaAlAs cladding layer material solution 9 are placed in the three solution reservoirs 15. That is, a slide boat in which raw materials are set is put into a furnace, and the temperature is raised to a high temperature region of 700 to 900 ° C. which is a growth start temperature, and a growth solution is created in the solution reservoir 15. Thereafter, the solution reservoir 15 is moved onto the GaAs substrate 1 while gradually cooling, and the growth solution 7 is brought into contact with the GaAs substrate 1. As a result, a GaAlAs epitaxial layer 2 is grown on the GaAs substrate 1. After the thin film having a predetermined thickness is grown, the solution reservoir 15 is moved again from above the GaAs substrate 1 to stop the growth. This operation is repeated for each of the three growth solutions 7, 8, and 9 to grow the respective epitaxial layers of the light emitting diode epitaxial wafer of FIG.

A method has also been developed that enables epitaxial growth with a constant growth temperature (see, for example, Patent Document 1).
JP-A-9-115842

  However, Zn is usually used as the dopant of the p-type layer. In general, a wafer grown by a liquid phase epitaxial method is heated to a high temperature of 700 ° C. to 900 ° C. during the growth process. The Zn dopant diffuses at that high temperature. Since the diffusion amount is not quantitatively diffused, stable characteristics cannot be obtained, and a large amount of Zn is charged, so that the crystallinity is deteriorated. Further, the diffused Zn reaches the n-type layer and adversely affects the light emission characteristics such as luminance.

  Growth with a graphite jig used in the liquid phase epitaxial growth method is performed by moving the slider so that it is directly under the upper solution reservoir (so that the substrate surface comes into contact with the solution) and lowering the temperature of the surrounding heater to lower the temperature of the GaAs Grown on the substrate.

  The upper solution reservoir is in an open state, and Zn as a dopant is easily diffused when the temperature is raised. Further, the diffused Zn reaches the n-type layer and adversely affects the light emission characteristics.

  Accordingly, an object of the present invention is to solve the above-mentioned problems and to prevent the Zn diffusion of the Zn dopant at the time of temperature rise and to supply a stable Zn dopant by making the upper solution reservoir of the p-type layer have a triple structure. It is another object of the present invention to provide a method for manufacturing a light-emitting diode having good crystallinity with a Zn charge amount smaller than that of the prior art by preventing entry into the n-type layer.

  In order to achieve the above object, the present invention is configured as follows.

  According to a first aspect of the present invention, there is provided a method of manufacturing an epitaxial wafer for a light emitting diode, wherein a substrate holder for accommodating a growth substrate and a raw material solution holder having two or more raw material solution reservoirs in a sliding direction are opposed to each other and relatively slid. In a method of manufacturing an epitaxial wafer for a light-emitting diode in which an epitaxial layer of a compound semiconductor is grown using a movable epitaxial growth apparatus, a partition plate is inserted into one of the raw material solution reservoirs to divide the raw material solution into upper and lower layers. By pulling out the partition plate, the raw material solution in each chamber is dropped to the lower layer and used for epitaxial growth.

  According to a second aspect of the present invention, in the method for manufacturing an epitaxial wafer for a light-emitting diode according to the first aspect, the partition plate is provided for a p-type dopant raw material solution reservoir, and the p-type dopant from the raw material solution during the growth is provided. It is characterized by preventing diffusion.

  According to a third aspect of the present invention, in the method of manufacturing an epitaxial wafer for a light emitting diode according to the second aspect, a GaAs substrate is used as a growth substrate and Zn is used as the p-type dopant.

  According to the present invention, a partition plate is inserted into one of the raw material solution reservoirs to divide the raw material solution into three upper and lower layers, and by pulling out the partition plate, the raw material solution in each chamber is dropped to the lower layer and used for epitaxial growth. Therefore, before the partition plate is pulled out, diffusion of p-type dopants such as Zn can be prevented.

  That is, according to the present invention, the upper solution reservoir portion of the p-type layer has a triple structure, thereby preventing Zn diffusion of the Zn dopant at the time of temperature rise, supplying a stable Zn dopant, and supplying the n-type layer to the n-type layer. Thus, a light-emitting diode with good crystallinity can be manufactured with a smaller amount of Zn charge than in the past.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  This liquid phase epitaxial growth apparatus has basically the same configuration as that of FIG. That is, the base 11, the substrate holder 12, the raw material solution holder 13, and the cap holder 14 (see FIG. 4) are stacked up and down, and the substrate holder 12 is attached to the base 11 and the raw material solution holder 13. It can be slid horizontally. Of the raw material solution holder 13 and the substrate holder 12 that slide relative to each other, the lower substrate holder 12 accommodates and places the GaAs substrate 1 on one end side in the apparatus longitudinal direction of the upper surface that is the sliding surface. A substrate storage mounting recess 16 is formed which is formed of a recess. The upper raw material solution holder 13 includes a plurality of two raw material solution reservoirs 15 in the longitudinal direction of the apparatus (here, for manufacturing the single heterojunction light emitting diode of FIG. 2). In this case, the p-type GaAlAs active layer solution 8 and the n-type GaAlAs clad layer solution 9 are formed at intervals. In addition, the upper surface which is the surface opposite to the sliding surface of the raw material solution holder 13 is configured to be airtightly covered with a cap holder 14 (see FIG. 4) as necessary.

  Here, Zn is used as the p-type dopant. However, since Zn has a high vapor pressure, it tends to sublimate and diffuse at high temperatures.

  Therefore, in the present embodiment, in the liquid phase epitaxial growth method, the two partition plates 20 and 30 are inserted into the liquid reservoir 15 containing the p-type GaAlAs active layer solution 8 to divide the raw material solution 8 into upper and lower three layers, By making the solution reservoir portion located above the p-type layer have a triple structure, Zn diffusion is prevented and Zn is prevented from entering the n-type layer. As a result, a light-emitting diode with good crystallinity is manufactured with a smaller amount of Zn charge than before.

  Specifically, the first partition plate 20 and the second partition plate 30 are inserted in parallel into the raw material solution reservoir 15 of the p-type GaAlAs active layer solution 8 from the operation side, and the raw material solution reservoir is placed in the lower chamber, the middle The raw material solution 8 is divided into three upper and lower layers by dividing into three upper and lower chambers consisting of a chamber and an upper chamber. Openings 21 and 31 are provided in the partition plates 20 and 30, respectively. When necessary, by pulling the partition plate 20 and the partition plate 30 with the operation rods 22 and 32 as operation means, the openings 21 and 31 are moved to the position of the raw material solution reservoir 15 of the p-type GaAlAs active layer solution 8. The melt is dropped to the lower layer through the openings 21 and 31. Then, the substrate holder 12 is slid by the operation rod 10, and the p-type GaAlAs active layer solution 8 is brought into contact with the p-type GaAs substrate 1 positioned in the substrate storage placement recess 16.

  In the above, the Zn dopant is set and placed in an intermediate layer (intermediate chamber between the partition plates 20 and 30), and the time during which the Zn dopant is exposed to the growth atmosphere after dissolution is shortened to prevent Zn diffusion. By preventing the diffusion of Zn and preventing the Zn from entering the n-type layer, an epitaxial wafer having the same characteristics as the conventional one can be manufactured with a smaller amount of Zn than the conventional one. .

  An embodiment in which the single heterojunction light emitting diode of FIG. 2 is manufactured will be described.

  As the growth jig, a carbon graphite jig shown in FIG. 1 was used. This was installed at a predetermined location in the liquid phase epitaxial growth apparatus, and the growth apparatus was heated to 900 ° C. in a hydrogen stream, held for 3 hours, and then cooled to 700 ° C. at a rate of 1 ° C./min.

  After the liquid layer epitaxial growth apparatus reaches 900 ° C. and is held for 3 hours, the partition 20 and the partition 30 are pulled, the melt is dropped to the lower layer, and the slider (so that the set GaAs substrate 1 comes directly under the growth solution reservoir 15. The solution 8 is brought into contact with the GaAs substrate 1 by moving the substrate holder 12). After the solution 8 comes into contact with the GaAs substrate 1, the epitaxial layer is grown on the GaAs substrate 1 by lowering the ambient temperature.

  In the case of this example, the charge amount of Zn dopant was usually 0.25 μg / Ga1g (Zn amount in Ga1g) to 0.5 μg / Ga1g (Zn amount in Ga1g).

  Then, a wafer obtained by laminating the single hetero LED structure of FIG. 2 on the epitaxial wafer for growth is manufactured, and the quality of the obtained epitaxial wafer for LED is adjusted to the film thickness, grooving method, surface and carrier concentration, and polaron. And evaluated.

  For comparison, using a conventional jig in which the upper solution reservoir does not have a triple structure, epitaxial growth is performed on a GaAs substrate, and the obtained epitaxial wafer for LED is used for quality, thickness, grooving method and It was evaluated with Polaron.

    Table 1 shows the evaluation (film thickness, luminance, carrier concentration) results of the grown epitaxial wafer.

  As is apparent from Table 1, the characteristics of the epitaxial wafer grown by the method of the above-described embodiment are not much different in characteristics as compared with the wafer grown for comparison although the amount of Zn is half that of the conventional one. This is because the upper solution reservoir of the p-type layer has a triple structure, and the amount of Zn diffused at the time of temperature rise is prevented, so that Zn dopant can be supplied stably and the entry into the n-type layer can be prevented. This is because.

  In the above-described embodiments, description has been made in the form of an epitaxial wafer having a single heterostructure, but the present invention can be similarly applied to the manufacture of an epitaxial wafer having a double heterostructure shown in FIG.

  The present invention can also be applied to the production of a back-reflection type light emitting diode made by removing the GaAs substrate 1 from an epitaxial wafer having a double hetero structure.

It is a longitudinal cross-sectional view of the liquid phase epitaxial growth jig | tool used for the Example of the manufacturing method of this invention. It is a longitudinal cross-sectional view of the epitaxial wafer of the single hetero structure manufactured with the method of this invention. It is a longitudinal cross-sectional view of the epitaxial wafer of the double hetero structure manufactured with the method of this invention. It is sectional drawing which showed the conventional liquid phase epitaxial growth jig | tool.

Explanation of symbols

1 p-type GaAs substrate 2 p-type GaAlAs clad layer 3 p-type GaAlAs active layer 4 n-type GaAlAs clad layer 7 p-type GaAlAs clad layer raw material solution 8 p-type GaAlAs active layer raw material solution 9 n-type GaAlAs clad layer raw material solution 12 substrate holder 13 Raw material solution holder 15 Raw material solution reservoir 16 Substrate storage mounting recess 20, 30 Partition plate 21, 31 Opening

Claims (3)

An epitaxial layer of a compound semiconductor is grown using an epitaxial growth apparatus in which a substrate holder for accommodating a growth substrate and a raw material solution holder having two or more raw material solution reservoirs in the sliding direction are opposed to each other and are slidable relative to each other. In the manufacturing method of the epitaxial wafer for the light emitting diode to be made,
A partition plate is inserted into one of the raw material solution reservoirs to divide the raw material solution into upper and lower three layers, and by pulling out the partition plate, the raw material solution in each chamber is dropped to the lower layer and used for epitaxial growth. Manufacturing method of epitaxial wafer for light emitting diode. In the manufacturing method of the epitaxial wafer for light emitting diodes described in Claim 1,
A method for producing an epitaxial wafer for a light-emitting diode, wherein the partition plate is provided for a p-type dopant raw material solution reservoir to prevent diffusion of the p-type dopant from the raw material solution during growth. In the manufacturing method of the epitaxial wafer for light emitting diodes described in Claim 2,
A method for producing an epitaxial wafer for a light-emitting diode, wherein a GaAs substrate is used as a growth substrate and Zn is used as the p-type dopant.

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