JPH0247439B2 - EKISOEPITAKISHARUSEICHOHOHO - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a liquid phase epitaxial growth method, more specifically, a slide boat method.
Regarding epitaxial growth of GaAlAs layer,
This article relates to a liquid phase epitaxial growth method for preventing oxidation of a Ga solution and obtaining an epitaxial layer with good crystallinity. (Prior Art) Compound semiconductor crystals such as GaP and GaAlAs are widely used as semiconductor light emitting devices, and are manufactured by a liquid phase epitaxial growth method, a vapor phase epitaxial growth method, or the like. In particular, a liquid phase epitaxial growth method using a slide boat method is frequently used because it allows continuous multilayer epitaxial growth. However, especially when a GaAlAs layer is liquid-phase epitaxially grown by the slide boat method, there are the following problems. That is, the slide boat method uses a device in which a slider 3 having a plurality of solution reservoirs 4 and 5 is configured to be slidable on a boat 2, as schematically shown in FIG. 2 for GaAs wafers. First, the GaAs substrate 1 is placed in the substrate holder 13 provided at a predetermined location on the boat 2, and on the other hand, a predetermined amount of Ga, Al, GaAs as a raw material for the melt is placed in each solution reservoir 4, 5, and the necessary p-type Alternatively, after adjusting and charging the n-type dopant and preparing the raw materials, the temperature was raised according to a predetermined temperature program while flowing H ₂ gas into the device to obtain growth melts 6 and 7. This is followed by a step of epitaxially growing p-type and n-type GaAlAs layers on the GaAs substrate 1. However, when preparing the above raw materials,
Ga metal solution containing Al is extremely easy to oxidize.
If an oxidized solution is used, the substrate will not be wetted due to the oxide film, inhibiting epitaxial growth or causing abnormal growth, and eventually reducing the luminous efficiency and life characteristics of the obtained semiconductor crystal. etc., leading to a decrease in yield. For this reason, conventionally, when charging the above raw materials, the raw materials were charged in an inert atmosphere using a glove box, or Al (melting point 660°C) was separated from Ga and then melted immediately before epitaxial growth. Ga−GaAs
Countermeasures such as pouring it into a solution were attempted, but
Such a method requires special jigs and equipment, resulting in complicated operations and a complicated equipment configuration, which reduces productivity and is not an effective solution. (Object of the invention) The present invention is based on the slide boat method described above.
To provide a method capable of solving problems associated with liquid phase epitaxial growth of a GaAlAs layer, easily and effectively preventing oxidation of a raw material solution, and obtaining an epitaxially grown layer with good crystallinity. The purpose is to (Structure of the Invention) In order to achieve the above object, the present inventors analyzed and studied the causes of the raw material preparation step in the conventional slide boat method, and found that in the past, Al was dissolved in the Ga solution in advance during the preparation. We have determined that this is due to the fact that the liquid Ga melt containing Al must be brought into a highly oxidized state because the atmosphere is adjusted and then the epitaxial growth process begins. Based on this, we conducted further research to find a method to prevent Al from dissolving into Ga during the preparation stage.As a result, we loaded Ga metal as an ingot into the solution reservoir during the raw material preparation stage and used it as a temperature program for the epitaxial growth process. Therefore, we have discovered that it is possible to melt the material by increasing the temperature, and have developed the present invention. The present invention will be explained in detail below based on examples. In the present invention, first, prior to charging raw materials for melt into the solution reservoir of the slider, a Ga metal ingot is manufactured and prepared as follows. A predetermined amount of Ga metal is accurately weighed and melted, poured into a mold (not shown) having the same planar shape as the solution reservoirs 4 and 5 of the slider 3 (FIG. 1), and solidified by cooling to obtain an ingot. At this time, the temperature is kept below the melting point of Ga (29.8℃), the mold is made of Teflon, etc., but a mold with a coating on the inside may also be used, and the working atmosphere from melting to casting to cooling and solidification is atmospheric air. Although there is no problem even if the reaction is carried out, it is preferable to carry out the reaction in an inert gas in order to prevent oxidation. Also, Al (melting point 660℃) and GaAs (melting point 1237℃)
After performing appropriate etching, a predetermined amount is weighed. These may have any size and shape. As a dopant, for n-type GaAlAs layer,
Te, Sn, etc. are used, and for p-type GaAlAs layer
Mg, Zn, etc. are used. Next, these melt raw materials are loaded into the solution reservoirs 4 and 5 of the slider 3 as shown in FIG.
The procedure is as shown in FIG.
9 is placed on top of these, but in this case, since the Ga metal ingot is manufactured using a mold with the same planar shape as the solution reservoirs 4 and 5 at the stage before loading, as described above, the solution reservoir 4 , 5 like a lid, and in the subsequent raw material melting step, the Ga metal ingot is first melted and flows onto the Al, GaAs, and dopants, and a uniform required solution can be obtained. There is an effect. In addition, by making the Ga metal coplanar with the solution reservoir,
The thickness of the Ga metal can be minimized, and therefore the thickness of the slider can also be minimized, which is advantageous for multi-stage growth equipment. These raw material loading operations must be carried out at a temperature that does not melt the Ga metal ingot, preferably below 25°C, but since it can be carried out in the air, no special equipment is required and a normal clean bench can be used. It can be done within. Note that there is GaAs in the substrate holder 13 of the boat 2.
Needless to say, it is necessary to load the substrate 1. After loading the melt raw material into the slider 3 in this way, it is set in an epitaxial growth furnace (not shown), and the operation of evacuation → Ar gas flow → vacuum evacuation is repeated several times to replace the atmosphere in the furnace. and
Remove residual oxygen in the furnace. Finally, the temperature is raised while H ₂ is passed through the furnace,
Epitaxial growth is carried out according to the usual temperature program. During this temperature raising process, the Ga metal ingot is melted, and then Al, GaAs, dopants, etc. are dissolved, and the required solution can be obtained in each solution reservoir. Next, an embodiment of the present invention will be described. (Example) Raw materials for melt having the composition and purity shown in Table 1 were prepared. First, Ga metal was melted at 50°C, a predetermined amount of this was poured into a Teflon mold of the same shape as the solution reservoir, and solidified in a cold place to produce a Ga metal ingot. Next, a weighed amount of GaAs, Al, and Zn dopant was introduced into the bottom of one solution reservoir of the slider, and a weighed amount of GaAs, Al, and Zn dopant was added to the bottom of the other solution reservoir.
GaAs, Al, and Te dopants were introduced, and the Ga metal ingot was placed on each dopant with a lid. Meanwhile, a GaAs substrate was placed inside the substrate holder on the boat. All of these raw material loading operations were performed in a clean bench at 25°C in the atmosphere.

[Table] After that, it was set in an epitaxial growth furnace, and after gas replacement with Ar, H ₂ was added at 3/min.
The temperature was started to rise while flowing at a flow rate of . The temperature program for epitaxial growth is
As shown in Figure 3, each melt is
After heating to 820°C (A in the figure) and holding at 820°C for 60 minutes, slide the slider to cover the GaAs substrate with p-melt and heat to 795°C (A) while cooling at a cooling rate of 0.3°C/min. When it reaches C), slide the slider further and cover it with n-melt, and heat it to 750℃ (D).
Wipe off was performed by sliding the slider. On the other hand, as a comparative example, the only difference from this example is in the preparation of the melt raw material. In the case where Ga was melted and charged and then directly set in the epitaxial growth furnace (Comparative Example 2), epitaxial growth was performed according to the same temperature program. FIG. 4 shows the results of examining the relative luminous efficiency of the GaAlAs epitaxial wafer produced by the above procedure. As can be seen from the figure, molten Ga
Comparative example 1 in which melt raw materials were prepared in the atmosphere using
Compared to this, Comparative Example 2 and this example have excellent luminous efficiency and are at the same level. (Effects of the Invention) As described in detail above, the present invention prevents Ga metal from being melted during the preparation stage of melt raw materials, so that oxidation in the Ga-Al solution can be suppressed during the preparation stage, and moreover, For this purpose, there is no need for complicated special jigs or equipment, so the operation is simple and not complicated, and as a result,
It has great practical effects, such as improving various properties (brightness, etc.) of GaAlAs epitaxial wafers.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views illustrating the preparation of melt raw materials in the slide boat method, and
Fig. 1 shows the case of the present invention, Fig. 2 shows the case of the conventional method, Fig. 3 shows the temperature program in one embodiment of the present invention, and Fig. 4 shows the relative luminescence of the obtained wafer. It is a figure showing efficiency. 1... GaAs substrate, 2... Boat, 3... Slider, 4, 5... Solution reservoir, 6, 7... Growth solution, 8, 9... Ga metal ingot, 11...
...Al, 12...GaAs and dopant.

Claims (1)

[Claims] 1. A GaAlAs liquid phase epitaxial growth method using a slide boat method, characterized in that solid Ga having the same planar shape as the solution reservoir of the slider, Al, GaAs metal, and dopant are used as raw materials for the growth solution. A liquid phase epitaxial growth method. 2. The liquid phase epitaxial growth method according to claim 1, wherein solid Ga is placed on top of Al, GaAs, and dopants in the solution reservoir.