JP2006080169A - Liquid phase growing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid phase growing apparatus capable of manufacturing a light emitting diode with less occurrence rate of failure by preventing arsenic from escaping through the rear surface of a substrate comprising gallium arsenide. <P>SOLUTION: In the liquid phase growing apparatus, a substrate holder 12 having a substrate housing/placing recess 16 formed therein for housing the substrate 1 comprising gallium arsenide, and a stock solution holder 13 having two or more of stock solution reservoirs in a sliding direction, are made relatively slidable opposed to each other, and the substrate 1 is brought into contact with the stock solutions 7, 8, 9 to grow a semiconductor layer comprising a compound semiconductor on the substrate 1. In the apparatus, the surface of the substrate housing/placing recess 16 undergoes mirror surface processing 16a to prevent arsenic from escaping from the substrate 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for preventing arsenic from escaping from a substrate made of gallium arsenide (GaAs) in a liquid phase growth apparatus.

  FIG. 2 shows an outline of a conventional liquid phase growth apparatus for epitaxially growing a semiconductor layer made of GaAlAs.

  This liquid phase growth apparatus is composed of four graphite parts, a pedestal 11, a substrate holder 12, a raw material solution holder 13, and a cap holder 14, and slides the substrate holder 12 in the horizontal direction with respect to the pedestal 11 and the raw material solution holder 13. It is comprised so that it can be made to.

  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 is formed for mounting the substrate 1 made of gallium arsenide.

  On the other hand, in the upper raw material solution holder 13, a plurality of raw material solution reservoirs 15 for storing the raw material solutions are formed in the horizontal direction (three in this case) sequentially spaced apart from the sliding surface of the raw material solution holder 13. The upper surface, which is the side surface, is airtightly covered with the cap holder 14.

  As a growth method (liquid phase growth method) using this liquid phase growth apparatus, (1) “slow cooling method” in which the temperature of the raw material solution is lowered at a constant rate as time passes, and (2) the temperature above and below the raw material solution. “Temperature difference method” in which a difference is provided, and the solute is placed on the upper part of the raw material solution at a constant temperature so as to keep it in a supersaturated state, and crystals are grown on the lower substrate, (3) “Combination method” using both There is.

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

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, a substrate grown by a liquid phase growth method is usually heated to a high temperature of 700 ° C. to 900 ° C. during the growth process. Arsenic is easily released from the substrate made of gallium arsenide at the high temperature (arsenic is easily removed). In addition, there are innumerable holes having a diameter of about 30 μm and a depth of about 10 μm on the surface of a graphite part that is normally used. Since the back surface of the substrate is exposed to a high temperature for a long time as compared with the growth surface, arsenic tends to escape from the holes in the surface of the graphite part, which adversely affects the characteristics such as the operating voltage of the element.

  Accordingly, an object of the present invention is to solve the above-mentioned problems and to prevent the arsenic from escaping from the back surface of the gallium arsenide substrate (arsenic detachment) and to manufacture a light emitting diode with few characteristic defects. It is to provide a phase growth apparatus.

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

  A liquid phase growth apparatus according to a first aspect of the present invention includes a substrate holder provided with a substrate storage mounting recess for storing a substrate made of gallium arsenide, and a raw material solution holder having two or more raw material solution reservoirs in the sliding direction; In a liquid phase growth apparatus for growing a semiconductor layer made of a compound semiconductor on the substrate by bringing the substrate into contact with a raw material solution and making the substrate slidable relative to each other. The substrate is mirror-finished to prevent arsenic from escaping from the substrate.

  According to a second aspect of the present invention, in the liquid phase growth apparatus according to the first aspect, the size of the hole in the surface of the substrate storage mounting recess is set to a diameter of 5 μm or less and a depth of 1 μm or less by the mirror finish. It is characterized by.

<Key points of the invention>
In the liquid phase growth method, the substrate holder is moved so that the position of the substrate holder on which the substrate is set (substrate housing mounting recess) is directly below the upper solution reservoir, that is, the substrate surface and the raw material solution are in contact with each other. A semiconductor layer is epitaxially grown on a substrate made of gallium arsenide while lowering the temperature of a surrounding heater.

  The back surface of the substrate made of gallium arsenide is in contact with the bottom of the substrate holder, and in a high temperature state, arsenic is introduced through a hole having a diameter of about 30 μm and a depth of about 10 μm on the bottom surface of the substrate storage recess of the substrate holder made of graphite. It is easy to come off.

  Therefore, in the present invention, the surface of the bottom of the substrate storage mounting recess of the substrate holder is mirror-finished to reduce the graphite hole from a diameter of about 30 μm to a depth of about 10 μm to a diameter of about 5 μm and a depth of about 1 μm. Arsenic is prevented from escaping from the back surface of the substrate in contact with the bottom surface of the storage mounting recess, and a light-emitting diode with few characteristic defects can be manufactured.

  According to the present invention, the bottom surface of the substrate housing mounting recess of the substrate holder made of graphite is mirror-finished, and the holes existing on the surface are, for example, from about 30 μm in diameter to about 10 μm in depth to about 5 μm in diameter. Since the thickness is as small as about 1 μm, it is possible to prevent arsenic from escaping from the back surface of the substrate that is in contact with the bottom surface of the substrate storage mounting recess, and a light emitting diode with less characteristic defects can be manufactured.

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

  As an embodiment of the present invention, a liquid phase growth apparatus as shown in FIG. 1 was produced.

  This liquid phase growth apparatus has basically the same configuration as that of FIG. That is, it is composed of four graphite parts, the pedestal 11, the substrate holder 12, the raw material solution holder 13, and the cap holder 14, so that the substrate holder 12 can be slid in the horizontal direction with respect to the pedestal 11 and the raw material solution holder 13. It is configured. Of the raw material solution holder 13 and the substrate holder 12 that slide relative to each other, the lower substrate holder 12 is provided with the substrate 1 made of gallium arsenide 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 a recess for storing and mounting. The upper raw material solution holder 13 is formed with three raw material solution reservoirs 15 for containing the raw material solutions 7, 8, and 9 at intervals in the longitudinal direction of the apparatus. The upper surface, which is the opposite surface, is configured to be airtightly covered with the cap holder 14.

  However, since arsenic has a high vapor pressure, arsenic removal from a substrate made of gallium arsenic is likely to occur at a high temperature in this configuration.

  Therefore, unlike the conventional case, the hole on the bottom surface of the substrate storage mounting recess 16 of the substrate holder made of graphite is reduced from the usual diameter of about 30 μm to a depth of about 10 μm to a diameter of about 5 μm and a depth of about 1 μm. In other words, the mirror finishing 16a is applied to prevent arsenic from coming out from the back surface of the substrate 1 made of gallium arsenide during liquid phase growth.

  As a vapor phase growth apparatus of an example of the present invention, a vapor phase growth apparatus (FIG. 1) made of graphite parts was used, and an epitaxial wafer for a single heterostructure light emitting diode shown in FIG. As the substrate holder 12, a substrate having a mirror finish 16 a on the bottom surface of the substrate storage mounting recess 16 was used. In other words, in the mirror-finished state, a hole having a hole diameter of 5 μm and a depth of 1 μm on the bottom surface of the substrate storage placement recess 16 was used.

  The substrate 1 made of gallium arsenide is processed to a predetermined size, set in a predetermined location (substrate storage mounting recess 16) of the substrate holder, and the substrate holder is moved so that the set substrate comes directly under the solution reservoir. Then, the raw material solution is brought into contact with the substrate. After the raw material solution comes into contact with the substrate, the semiconductor layer is epitaxially grown on the substrate by lowering the ambient temperature.

  That is, the substrate 1 made of p-type GaAs is set in the substrate holder 12, and the semiconductor layer raw materials Ga, GaAs, Al, Zn, Te are set in the raw material solution holder 13, and a predetermined amount in the liquid phase growth apparatus is set. Installed at the place. The growth apparatus was heated to 900 ° C. in a hydrogen stream.

  After holding for 3 hours, the temperature was lowered to 700 ° C. at a rate of 1 ° C./min. The substrate 1 is sequentially brought into contact with the raw material solution 8 for the active layer made of p-type GaAlAs and the raw material solution 9 for the n-type cladding layer made of n-type GaAlAs while the temperature is lowered, and the active layer 3 made of p-type GaAlAs, n The n-type cladding layer 4 made of n-type GaAlAs was sequentially grown by liquid phase epitaxy to obtain an epitaxial wafer for a light emitting diode having a single heterostructure shown in FIG. However, during the temperature drop, the substrate 1 is sequentially applied to the p-type cladding layer raw material solution 7 made of p-type GaAlAs, the active layer raw material solution 8 made of p-type GaAlAs, and the n-type cladding layer made of n-type GaAlAs. The p-type cladding layer 2 made of p-type GaAlAs, the active layer 3 made of p-type GaAlAs, and the n-type cladding layer 4 made of n-type GaAlAs are brought into contact with the raw material solution 9 in this order, and shown in FIG. An epitaxial wafer for a light emitting diode can also be obtained.

  In this example, a single heterostructure was laminated on a substrate, and the obtained epitaxial wafer was evaluated by a grooving method.

  Further, as a vapor phase growth apparatus of a comparative example, a part whose surface of the bottom of the substrate storage mounting recess 16 of the substrate holder 12 is not mirror-finished is used, that is, the diameter of the hole on the bottom surface of the substrate holder is 30 μm, deep. 3 having a thickness of 10 μm was epitaxially grown on the substrate 1 made of gallium arsenide under the same conditions as described above, and the epitaxial wafer for a light emitting diode shown in FIG. 3 was produced. And the obtained epitaxial wafer was evaluated by the grooving method.

  Table 1 shows the defect occurrence rate when growth is performed using the vapor phase growth apparatus of the present embodiment and the vapor phase growth apparatus of the comparative example.

  As is apparent from this, the epitaxial wafer manufactured by the vapor phase growth apparatus of the present embodiment is more defective in the characteristics such as operating voltage than the epitaxial wafer grown by the vapor phase growth apparatus of the comparative example (defect occurrence). Rate) is as low as 1/10. This is because the bottom surface of the substrate storage placement recess of the substrate holder is mirror-finished, thereby preventing arsenic detachment in the substrate made of gallium arsenide.

  In the growth apparatus of the above-described embodiment, an example of manufacturing an epitaxial wafer for light emitting diodes having a single heterostructure has been described. However, as shown in FIG. 4, the growth apparatus of the present invention is also used for manufacturing an epitaxial wafer for light emitting diodes having a double heterostructure. And similar effects can be obtained.

  The growth apparatus of the present invention can also be used for the production of a back-reflection type light emitting diode made by removing a substrate from an epitaxial wafer having a double hetero structure.

It is sectional drawing which showed the liquid phase growth apparatus of this invention. It is sectional drawing which showed the conventional liquid phase growth apparatus. It is sectional drawing of the epitaxial wafer for light emitting diodes of the single heterostructure made into manufacture object by this invention. It is sectional drawing of the epitaxial wafer for light emitting diodes of the double hetero structure made into manufacture object by this invention.

Explanation of symbols

1 Substrate 7 Raw material solution (for p-type cladding layer) 8 Raw material solution (for active layer) 9 Raw material solution (for n-type cladding layer) 12 Substrate holder 13 Raw material solution holder 14 Cap holder 15 Raw material solution reservoir 16 Substrate storage Mounting recess 16a Mirror finish

Claims (2)

A substrate holder provided with a substrate storage mounting recess for storing a substrate made of gallium arsenide and a raw material solution holder having two or more raw material solution reservoirs in the sliding direction are made to be able to slide relative to each other. In a liquid phase growth apparatus for growing a semiconductor layer made of a compound semiconductor on the substrate by bringing the substrate into contact with a raw material solution,
A liquid phase growth apparatus characterized in that a mirror finish is applied to the surface of the substrate storage mounting recess to prevent arsenic from escaping from the substrate. In the liquid phase growth apparatus according to claim 1,
The liquid phase growth apparatus characterized in that the size of the hole in the surface of the substrate storing and placing concave portion is 5 μm or less in diameter and 1 μm or less in depth by the mirror finish.

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