JPS61274321A - Method for diffusing impurity into compound semiconductor - Google Patents

Abstract

PURPOSE:To obtain an impurity diffusion layer of less crystallizability deterioration by providing a step for forming a thin film containing one of the elements constituting a compound semiconductor crystal which is subject to dissociation by heating, and a step for heating the compound semiconductor crystal to diffuse an active impurity into the crystal. CONSTITUTION:A GaAsP crystal 1 consists of a first and a second N-type GaAsP layers 3, 4 which were formed on an N-type GaP substrate 2 by means of the vapor phase epitaxial process. On the surface of the GaAsP layer 4 of the GaAsP crystal 1 is formed a phosphorus containing silicon oxide film, that is, a phosphorated silica film. Then, when the GaAsP crystal 1 having the phosphorus containing thin film 5 is mounted on a quartz board 6, placed in a quartz tube 7, and heat-treated at 720 deg.C for eight days, a P-type GaAsP layer is formed due to the Zn diffusion. Thereafter, a light emitting diode chip 12 is completed through steps such as removal of the thin film 5, removal of the crystal surface region, formation of an electrode, and dicing into many chips.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to Ga
The present invention relates to a method of diffusing f) active impurities such as Zn into a compound semiconductor such as AsP.

[Conventional technology and its problems]

To obtain a Gj As P light-emitting diode, n-type Ga
It is well known that a shallow p shadow region is formed by vapor phase diffusion of Zn into an AsP crystal. This diffusion.

In a sealed tube, the vapor pressures of Zn, As, and P are controlled to
This is done while suppressing the decomposition of the aAsP crystal.

By the way, there is a strong demand for higher brightness in light-emitting diodes, and there is a need to further improve the light emitting efficiency of the chip itself, in addition to improvements in the Hara cage. For this reason, the vapor pressure of Zn, As, and P can be adjusted by selecting various amounts and types of sources (materials that generate vapor pressures of Zn, As, and P) for Zn diffusion using the sealed tube method. Efforts are being made to pursue the optimal conditions. but,
Even if Zi is diffused under optimal conditions in the conventional method, it has been difficult to significantly improve the luminous efficiency. now.

GaAsP K As mentioned above, GaAs, GaP
There are similar rJIMs in compound semiconductors such as .

Therefore, an object of the present invention is to provide a method for obtaining a good impurity diffusion layer that can solve the above-mentioned problems.

[Means for solving problems]

To achieve the above object, the present invention comprises the steps of: forming a thin film on the surface of a compound semiconductor crystal containing at least one element that is easily dissociated by °C among the constituent elements of the compound semiconductor crystal; In the presence of at least an active impurity and a vapor of an element contained in the thin film, the compound semiconductor crystal forming the thin film is heated, and the active impurity # is introduced into the 1Ilr compound semiconductor crystal through the thin IN. This relates to a method of diffusing impurities into a compound semiconductor, which includes a step of diffusing impurities into a compound semiconductor.

[For production]

Since the thin film in the above method contains an element that easily dissociates among the constituent elements of the compound semiconductor crystal, it acts to suppress the dissociation of this element.

Therefore, an impurity diffusion layer with less deterioration of crystallinity can be obtained.

〔Example〕

A Zn diffusion method for fabricating a GaAsP red light emitting diode will be described based on FIGS. JI1 to JI6.

FIG. 1 shows a wafer-shaped GaAsP crystal (υ). This GaAsP crystal (11 is a wafer-shaped GaAsP crystal (11) is a wafer-shaped GaAsP crystal (11) on which first and second n-type GaA
sP layer (31 (41) is formed.The first Ga
The AsP layer (3) has a composition ratio of As and P of GaAs 1
−z This is a region in which Pz is continuously changed from x=1.0 to x=0.65. Second GaAsP layer (4
) is a constant region of x=0.65, and the impurity concentration is 1
．． It is 5X10 cm.

Next, as shown in Figure 2, the G of GaAsP crystal (1)
K for forming a phosphorus-containing thin film (5) made of a phosphorus-containing silicon oxide film, that is, a phosphorus silica film on the surface of the aAsP layer (4) is first manufactured by Tokyo Ohka Kogyo Co., Ltd. Silica phosphide film forming solution manufactured by
P-8F solution (trade name) is dropped onto the GaAsP crystal (1), and the GaAsP crystal pile is rotated with a spinner to apply a thin layer. In addition, the solution for forming silica phosphide film (
P-8F solution) is mainly used to form an impurity base by applying it to the silicon surface when diffusing P (phosphorous) as an impurity into semiconductor silicon, and it contains about 6% by volume. Contains a silicon compound (silicate) to generate silicon oxide at a ratio of 1
mg/cm" (weight relative to the volume of the solution). Next, the GaAsP crystal (1) coated with the silica phosphide film forming solution was allowed to stand for a while, and then heated at 90°C. Heat treated for 30 minutes,
The coating film was dried, and then heated to 250°C.

Heat treated for 1 hour. As a result, the solvent of the phosphoric silica film forming solution is scattered, and the thickness is approximately 1,000 to 15 mm.
A thin film (5) made of 00A phosphorous silica film (phosphorus-containing silicon oxide film) is formed.

Next, as shown in the third frame, a GaAsP crystal (υ) having a phosphorus-containing thin film (5) is placed on a quartz board (6) and placed inside a quartz tube (7). 1 Vacuum sealing (IXIOtorr) with a quartz seal cap (8)
degree). Quartz tube (P (red phosphorus) for 10,000 yen) (
9) is 0.3 mg/cm' (weight per unit volume of quartz tube), and ZnAs1α is 0.35 mg/cm'.
cm” (1ff per unit volume of quartz tube) are each sealed.

In the state shown in FIG. 3, heat treatment is performed at 720° C. for 8 days. At this time, Zn is contained in the first quartz tube (7).

The vapor pressures of As and P are generated, and the sword 0 due to these vapor pressures is
Under pressure, Zn, which is a p-type impurity, forms a phosphorus-containing thin m(
5) and is diffused into the n-type GaAsP layer (4).

FIG. 4 shows the GaAsP crystal 11) after diffusion.

p-type GaAsP where aυ is formed by Zn diffusion
The depth of this p-type GaAsP Nj Qυ is 9
It is μm.

Note that since the thin film (5) comes into contact with the vapors of Zn, As, and P and is heated to 720° C., it also comes to contain Zn and As as the diffusion progresses. Therefore.

The fourth factor's thin film (5) is not exactly the same as the thin film (5) in FIG.

When forming a light emitting diode using the wafer shown in Fig. 4, there are steps such as removing the thin film (5), removing the crystal surface area, forming electrodes, and cutting m1 into a large number of chips, as shown in Fig. 5. The light emitting diode chip a2 shown is completed. In FIG. 5, (131 (141 is an electrode).

This light emitting diode chip (12+ has a peak wavelength of 63
Emit red light at 0 nm.

Figure 6 shows the luminous efficiency of one light emitting diode chip (12+) in comparison with other examples.Curve A is the data of this example.Curve B shows the thin film (5) as a simple light-emitting diode chip (12+) that does not contain phosphorus. This is the data when the silicate film is replaced.Curve C is the data when the conventional method does not form a thin film (5) on the surface of the GaAsP layer (4).As these data show, this example Light-emitting diodes have achieved significantly higher brightness.For example, forward current of 20mA
The luminous efficiency of the light emitting diode according to the embodiment shown in curve 11 is approximately 70% higher than that of the conventional case shown in curve C.

As shown in Figure 6, the reason for the significant improvement in luminous efficiency is as follows.
Although it is not necessarily clear, at present it can be estimated based on the following (a), (b), and (c), which are known as experimental facts.

Mark: The total amount of diffused Zn impurities is reduced compared to the conventional method. For example, in the case of one song @B and C, the average density is 8X
10 cm, but in the case of one curve, the joining depth is almost the same as K 2.5 x 10 cm and 17
It decreased to about 3.

C-Xj/, f”', (Xj
is the junction depth and t is the diffusion time] is small. For example, curve C is 8 μm/h', and curve IwB is 7.5 μm/h'.
rr)/h” is 6μ in the case of one curve.
m/h;

←l The surface of the GaAsP layer is prevented from developing a corrosion-like state, ie.

In the case of curve C, two lotions are likely to occur.

This did not occur in the case of curves A and B.

From the above fact (a), phosphorus in the thin film (5) acts to completely suppress the amount of Zn diffused, achieving low concentration diffusion.

It is considered that the crystallinity of the p-type GaAsP layer aυ and its vicinity is better than before. If the crystallinity is good, the diffusion length of minority carriers becomes long.

The rate at which minority carriers undergo radiative recombination increases.

In addition, the impurity concentration of the p-type GaAsP layer αD is low.

It is thought that the light absorption in the p-type GaRsP Htαυ is reduced and the light extraction efficiency is improved.

From the fact (4) above, P in the thin film (5) effectively suppresses the dissociation of P from the GaAsP layer (4), increasing the diffusion rate while minimizing the deterioration of J crystallinity. It is thought that the spread is progressing.

From the fact of e1 above, prevention of surface erosion is due to the presence of silica film, and P in the silica film is effective.
It can be said that it is not an effect brought about by.

[Modified example]

The invention is not limited to the embodiments described above.

For example, the following transformations are possible.

(A) Ga expressed as GaAs s -z Px
The composition ratio of the A s P layer (4) is t-x=0-85 and 1
Amount of P (9) sealed in quartz tube (7) circle t O-15m
g7 cm”K changed, otherwise the same process,
When an orange light emitting diode chip with a peak wavelength of 590 nm was exploded, a significant improvement in luminous efficiency was achieved as shown in FIG.

Note that the same effect can be obtained even if the value of X is varied within the range of 0.60 to 0.85.

(Bl Thin M(5) in Figure 2 is made into a silica film containing both P and As and Zn is diffused therein.

A luminous efficiency equal to or slightly higher than that of curve A in FIG. 6 was obtained. In addition, when Zn was diffused by adding 71ti to thin i (51KAs) in Figure 2, curve A in Figure 6 showed that although no significant effect was strengthened, it was 1 compared to curves B and C. An improvement in luminous efficiency was observed.As mentioned above, the effect is more pronounced when the thin film (5) contains pt- than when it contains As.

GaAsP (7) It is thought that this is because As dissociates more easily than P. It is also believed that the fact that the composition ratio of P is larger than that of As, and that the behavior of Zn that tries to pass through the thin film (5) is stronger due to As and P is also considered to be an influence.

It is also applicable to compound semiconductors other than IcI GaAsP. For example, a thin Flit silica film containing IcAs to diffuse Zn into S crystals into Ga).
- May be provided. In addition, a thin M (silica film) containing KP was used to diffuse Zn into the GaP crystal.
The setup is very good.

1 Instead of the thin film +51 in Figure 2, p
It may be a thin film such as the P-containing 5ins glass film formed.

[F]l It is standard to proceed with Zn diffusion under pressure of Zn, As, and P vapor, but when the composition ratio of As is small, As is difficult to dissociate by heating compared to P. , Zn diffusion may be performed using only the vapor pressures of Zn and P.

[F] The temperature when forming the thin film (5) in Figure 2 is preferably changed in the range of 200 to 350°C, and the heating temperature in the diffusion step in Figure 3 is preferably in the range of 700 to 800°C. You can change it with .

〔Effect of the invention〕

As is clear from the above, according to the present invention, it is possible to diffuse impurities while maintaining good crystallinity. Therefore.

When a light emitting diode is entirely manufactured using impurity-diffused crystals according to the present invention, a light emitting diode with high luminous efficiency can be obtained.

[Brief explanation of drawings]

1 to 5 show a light emitting diode according to an embodiment of the present invention in order of process. 1- is a cross-sectional view showing a GaAsP crystal. The second factor is a cross-sectional view showing the crystal that formed the P-containing thin film. Figure 3 is a cross-sectional view showing the entire diffusion device. FIG. 4 is a cross-sectional view showing the crystal after diffusion. FIG. 5 is a sectional view showing a light emitting diode. FIG. 6 is a characteristic diagram showing the luminous efficiency of the light emitting diodes of Examples and Comparative Examples.

Claims (8)

[Claims] (1) Forming a thin film on the surface of a compound semiconductor crystal containing at least one element that is easily dissociated by heating among the constituent elements of the compound semiconductor crystal; and at least an active impurity contained in the thin film. impurity diffusion into a compound semiconductor, the step of heating the compound semiconductor crystal in which the thin film has been formed in the presence of a vapor of an element that has caused the active impurity to diffuse into the compound semiconductor crystal through the thin film. Law. (2) The compound semiconductor is GaAsP (gallium arsenide phosphide), and the element contained in the thin film is P (phosphorus).
A method for diffusing impurities into a compound semiconductor according to claim 1. (3) Forming the thin film involves applying a phosphoric silica film forming solution containing a silicon compound and phosphorus to the GaA
A method for diffusing impurities into a compound semiconductor according to claim 2, which comprises coating the surface of an sP crystal and subjecting it to a heat treatment. (4) The heat treatment in the process of forming the thin film is 200°C ~
4. The method for diffusing impurities into a compound semiconductor according to claim 3, wherein the heating is performed at 350°C, and the heating in the diffusion step is performed at 700°C to 800°C. (5) The method for diffusing impurities into a compound semiconductor according to claim 2, 3, or 4, wherein the vapor is pressurized vapor in a sealed tube. (6) The vapor contains the active impurities, P (phosphorus) and A
A method for diffusing impurities into a compound semiconductor according to claim 2 or 3 or 4 or 5, wherein the vapor contains s (arsenic). (7) The method for diffusing impurities into a compound semiconductor according to claim 2 or 3 or 4 or 5 or 6, wherein the active impurity is Zn (zinc). (8) The elements contained in the thin film are As (arsenic) and P.
(phosphorus), a method for diffusing impurities into a compound semiconductor according to claim 2.