JPS6158971B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for vapor phase growth of a compound semiconductor (hereinafter referred to as "-V group semiconductor") mixed crystal epitaxial film consisting of elements of Groups and V of the periodic table. In general, infrared and visible light emitting diodes are
- Manufactured from a Group V semiconductor epitaxial film. In particular, gallium arsenide phosphide (Ga As _lx PX, O<
x<1), or gallium indium phosphide (Gay In _ly P, O<y<1), etc.
The group semiconductor mixed crystal epitaxial film can relatively freely change the peak emission wavelength in the infrared and visible regions by setting the mixed crystal ratio (x or y) to an appropriate value, so it is suitable for use in light-emitting diodes. It is often used as a material. Light-emitting diodes made of these mixed crystal epitaxial films are generally produced using a vapor phase growth method, which is characterized by the ability to easily change the constituent elements of the mixed crystal and the mixed crystal ratio.
It is manufactured by forming it on a single crystal substrate made of gallium phosphide (GaP), germanium (Ge), a group element semiconductor, or the like. However, the brightness of light emitting diodes conventionally manufactured by the vapor phase length method is lower than the theoretical value, and therefore is not satisfactory in practical applications. As a result of intensive research, the present inventors have discovered that in the case of a mixed crystal epitaxial film, the substrate and the epitaxial film are made of different materials, that is, their lattice constants are different from each other. The present invention was achieved by discovering that the main cause is non-radiative recombination of carriers caused by dislocations. An object of the present invention is to provide a novel vapor phase growth method for a - group semiconductor mixed crystal epitaxial film suitable for manufacturing light emitting devices such as high brightness light emitting diodes. Therefore, the above purpose is to produce -
a first layer (hereinafter referred to as "mixed crystal ratio changing layer") consisting of a mixed crystal consisting of two or more types of group compound semiconductors and whose mixed crystal ratio changes continuously; and a first layer on the first layer. When growing an epitaxial film consisting of a second layer made of the same - group semiconductor and having a constant mixed crystal content (hereinafter referred to as "constant mixed crystal content layer") in a vapor phase, a constant mixed crystal content layer is grown. The mixing step is performed by reducing the supply amount of either the group element or the group element to an amount that is 90% or less of the amount required for growth of the constant mixed crystal layer and is not 0. This is achieved by a method characterized in that it includes a step of reducing the growth rate of the constant crystalline layer. Examples of the group element of the periodic table constituting the - group semiconductor mixed crystal include aluminum (Al), gallium (Ga), indium (In), and the like. Examples of group elements include nitrogen (N), phosphorus (P), arsenic (As), and antimony (Sb). In the present invention, -semiconductor mixed crystal has a structure defined as a "mixed crystal" or "solid solution" in terms of crystallography, and has a structure of gallium arsenide phosphide (Ga
Gallium indium phosphide (Ga _{1-y In y} P , O<y<1), - group semiconductors consisting of two or more group elements and one group element, and gallium arsenide phosphide, indium (Ga _(1-y) InyAs _{(1- x)} Px, O<x<1, O<
It refers to a − group semiconductor consisting of two or more group elements and group elements such that y<1). That is, these mixed crystals are considered to be a mixture of two or more - group semiconductors to form a mixed crystal. Figure 1 shows - produced by the method of the present invention.
FIG. 2 is an enlarged vertical cross-sectional model diagram of a group compound semiconductor mixed crystal epitaxial film. In FIG. 1, reference numeral 1 denotes a substrate that serves as a basis for growing an epitaxial film. 2,
3, 4 and 5 were formed by vapor phase growth method.
It is a semiconductor mixed crystal epitaxial film. However, 2
3 is the mixed crystal ratio variable layer, 3 is the constant mixed crystal ratio layer, and 4 is the group element constituting the epitaxial film, or the supply amount of the group element necessary to obtain the desired mixed crystal ratio. This is a layer (hereinafter referred to as "transition layer") formed by reducing the supply amount to 90% or less of the amount and not 0. This is a constant mixed crystal ratio layer having the same mixed crystal ratio as No. 5 and No. 3. The substrate 1 may be a substrate made of a single crystal, and is usually a substrate made of a - group semiconductor single crystal such as gallium arsenide or gallium phosphide, or a group element semiconductor single crystal such as silicon (Si) or germanium (Ge). is used. In addition, the thickness of the substrate is usually preferably selected in the range of 100 μm or more and 1000 μm or less for ease of handling, etc., and 300 μm or more and 450 μm or more.
Most preferably, it is within the range of m or less. Furthermore, if necessary, a homoepitaxial layer of gallium arsenide, gallium phosphide, or the like may be formed on the surface of the substrate. Further, the mixed crystal ratio changing layer 2 is a layer in which the mixed crystal ratio is continuously changed. For example, if gallium arsenide is used as the substrate 1, and as the constant mixed crystal ratio layer 3, the mixed crystal ratio x=
0.4 and gallium arsenide phosphide (GaAs _1-x Px, x
=0.4), a layer in which the mixed crystal ratio x is continuously changed from 0 to 0.4 is provided as the mixed crystal ratio changing layer 2. That is, when there is a mismatch in lattice constant between the constant mixed crystal content layer 3 and the substrate 1, the mixed crystal percentage variable layer 2 minimizes distortion due to the mismatch in the lattice constant, and improves the crystallinity. This is provided in order to obtain a layer with a good constant mixed crystal ratio. The thickness of the mixed crystal ratio changing layer 2 is usually selected to be 10 μm or more, preferably 30 μm or more. After the mixed crystal percentage of the mixed crystal percentage change layer 2 reaches a desired mixed crystal percentage, a constant mixed crystal percentage layer 3 having a constant mixed crystal percentage is formed. The thickness of the constant mixed crystal ratio layer 3 is preferably 10 μm or more, but may be less than that. The amount of supply of the transition layer 4, that is, the group element constituting the constant mixed crystal content layer 3, or the group element, which is continuous to the constant mixed crystal content layer 3, is required to form the layer 3. After forming a layer 4 obtained by reducing the supply amount to 90% or less and not 0, more preferably 50% or more and 1% or more, the supply amount of the element is increased to keep the mixed crystal ratio constant. A constant mixed crystal content layer 5 having the same mixed crystal content as layer 3 is grown. When the supply amount of a group element is to be changed, or when the group element is composed of two or more elements, the supply amount of all elements belonging to the same group must be changed. As mentioned above, when the supply amount is reduced, the growth rate of the constant mixed crystal ratio layer decreases, and the growth rate decreases markedly especially below 20%. The thickness of the transition layer 4 is 1 μm or less, preferably
Selected to be 0.2 μm or less. Further, the thickness of the constant mixed crystal ratio layer 5 is desirably 10 μm or more, more preferably 20 μm or more. A p-n junction or the like is formed in the constant mixed crystal ratio layer 5,
Forms an operating region for elements such as light emitting diodes. The gas phase epitaxial reaction apparatus used in carrying out the method of the present invention may be any apparatus as long as it is capable of adjusting the supply amount of at least one of the elements constituting the mixed crystal. Further, the reactive gas may have a composition that allows the supply amount of at least one of the elements constituting the mixed crystal to be changed independently with respect to other elements. Each Example, each Comparative Example, Table 1 and Table 2 described below
As shown in the table, the brightness of the light emitting diode manufactured using the - group semiconductor mixed crystal epitaxial film with the transition layer 4 formed by the method of the present invention is higher than that of the conventional method, that is, the luminance of the epitaxial film without the transition layer 4. Compared to the brightness of the light emitting diode used,
This is a remarkable improvement of approximately 1.5 to 1.6 times under the same light emission conditions, and has extremely high industrial utility value. The method of the present invention will be explained in more detail below based on Examples and Comparative Examples. Example 1 Experiment 1 In a horizontal quartz epitaxial reactor with an inner diameter of 80 mm and a length of 100 cm, chemically polished gallium arsenide with a surface having a deviation of 2 degrees in the <110> direction from the (100) plane was placed. Load the single crystal substrate. Additionally, a quartz container filled with metallic gallium (Ga) is placed in a predetermined location of the reactor. After replacing the air in the reactor with argon (Ar), the temperature of the substrate charging part of the epitaxial reactor was set to 810°C, and the temperature of the metal gallium charging part was set to 790°C, and the mixed crystal ratio was We started vapor phase growth of an epitaxial film consisting of ₄₀ % gallium arsenide phosphide (GaAs _0.6 P _0.4 ) _. From the start of the vapor phase growth of the epitaxial film, diethyl tellurium ((C ₂ H ₅ ) ₂ Te) diluted with hydrogen gas to a concentration of 10 ppm (volume ratio, same hereinafter) was introduced at a flow rate of 20 ml/min. Hydrogen chloride (HCl) gas 25ml/
The resulting gallium chloride (GaCl) was supplied to the substrate loading section of the reactor. In order to form the mixed crystal ratio change layer 2, hydrogen gas containing 12% arsine (AsH ₃ ) (same by volume) was initially supplied at a flow rate of 280 ml/min, and then gradually supplied at a flow rate of 220 ml/min for 90 minutes. Feed amount of hydrogen gas containing 12% phosphine ( _PH3 ) reduced to min.
Gradually increase from 0 to 60 ml/min over 90 minutes. Then, for 40 minutes, 20 ml/min of hydrogen gas containing 10 ppm diethyl tellurium, 25 ml/min of hydrogen chloride,
220ml/min of hydrogen gas containing 12% arsine,
and 60ml/hydrogen gas containing 12% phosphine.
A constant mixed crystal content layer of a gallium arsenide phosphide epitaxial film with a mixed crystal content of 40% was formed. After that, for 10 minutes, the hydrogen chloride supply rate was reduced to 5 ml/min to form a transition layer, and then the hydrogen chloride supply rate was returned to 25 ml/min, and a further 60 ml/min was added.
The reaction was completed by forming a layer with a constant mixed crystal ratio of 40% per minute. The formed epitaxial film has a thickness of 35 μm in which the mixed crystal concentration changes sequentially from the substrate side, a thickness of the first constant mixed crystal concentration layer of 14 μm, and a thickness of the transition layer of 0.1 μm.
m, and the thickness of the second constant mixed crystal ratio layer was 21 μm. Experiments 2 to 5 To check the reproducibility of Experiment 1 above, an epitaxial film made of gallium arsenide phosphide (GaAs _0.6 P _0.4 ) with a mixed crystal ratio of ₄₀ % was grown in the vapor phase under the same conditions _. was carried out four times. Example 2 Experiment 1 In an epitaxial reactor similar to that used in Example 1, a chemically polished phosphide film having a surface having a 4° deviation in the <110> direction from the (100) plane was placed. A gallium single crystal substrate was charged. Furthermore, a quartz container filled with metallic gallium was placed in a predetermined position within the reactor. After replacing the air in the reactor with argon (Ar) gas, add 2000ml/h of hydrogen gas.
After stopping the supply of argon gas, the temperature was raised, and the temperature was set at 860℃ for the substrate charging area and 760℃ for the metal gallium charging area. We started vapor phase growth of an epitaxial film consisting of (GaAs _{0.14 P 0.86 ) .} That is, 20 ml/min of hydrogen gas containing 500 ppm of hydrogen sulfide (H ₂ S) and 40 ml/min of hydrogen chloride were introduced into the epitaxial reactor. Further, hydrogen gas containing 12% phosphine was supplied at 310 ml/min for 15 minutes to form a homoepitaxial layer from gallium phosphide. After that, the supply amount of hydrogen gas containing phosphine was increased from 310 ml/min to 260 ml/min for 60 minutes.
The supply rate of hydrogen gas containing 12% arsine was gradually increased from 0 to 40 ml/min to form a mixed crystal ratio change layer. After the supply amounts of arsine and phosphine reached the above amounts, they were kept constant and a layer with a constant mixed crystal ratio was formed for an additional 40 minutes. Next, the hydrogen chloride feed rate was reduced to 4 ml/min and the reaction was continued for 15 minutes to form a transition layer. After 15 minutes, the hydrogen chloride supply rate was returned to 40 ml/min, and a constant mixed crystal ratio layer was grown for another 50 minutes. After that, without changing the supply amount of each component mentioned above, ammonia (NH ₃ ) was further introduced into the reactor at 180 ml/min, and the reaction was carried out by growing a nitrogen-doped layer as an isoelectronic layer for 45 minutes. finished. The epitaxial film obtained in this example was
11 μm gallium phosphide homoepitaxial layer from the substrate surface, 34 μm mixed crystal ratio variable layer, 30 μm
It was determined by a chemical corrosion method that the layer consisted of a layer with a constant mixed crystal content of , a transition layer of 0.11 μm, a constant mixed crystal layer with a thickness of 34 μm, and a nitrogen doped layer of 20 μm. Experiments 2 to 4 To check the reproducibility of Experiment 1 above, an epitaxial film made of gallium arsenide phosphide (GaAs _0.14 P _0.86 ) with a mixed crystal _ratio of ₈₆ % was grown in the vapor phase under the same conditions as above. was carried out three times. Comparative Example 1 An epitaxial film made of gallium arsenide phosphide ( _{GaAs 0.6} P _0.4 ) with a mixed crystal content of 40% without a transition layer was prepared under the same conditions as in Example 1 except for the process of forming the transition layer _. was formed. This experiment was repeated five times. Comparative Example 2 Epitaxy made of gallium arsenide phosphide (GaAs _0.14 P _0.86 ) with a mixed crystal content of ₈₆ % without a transition layer was performed under the same conditions as in Example 6 except for the process of forming _the transition layer. A membrane was formed. This experiment was performed four times. Table 1 shows the brightness of red light emitting diodes (peak emission wavelength 660 nm±10 nm) manufactured from the epitaxial films manufactured in Example 1 and Comparative Example 1. Note that the brightness was measured at a current density of 10 A/cm ² . Furthermore, a yellow light emitting diode (peak emission wavelength 590nm±10nm) was manufactured using the epitaxial film manufactured in Example 2 and Comparative Example 2.
The brightness is shown in Table 2. Note that the brightness was measured at a current density of 20 A/cm ² .

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal sectional view of a mixed crystal epitaxial film produced by the method of the present invention. DESCRIPTION OF SYMBOLS 1...Substrate, 2... Layer with variable crystal content, 3... Layer with constant mixed crystal content, 4... Transition layer, 5... Layer with constant mixed crystal content.

Claims (1)

[Claims] 1. On a single crystal substrate, a first layer consisting of a mixed crystal consisting of two or more compound semiconductors consisting of a group element and a group V element of the periodic table and in which the mixed crystal percentage continuously changes, and the first layer A second layer, which is made of the same compound semiconductor as the first layer and has a constant mixed crystal percentage, is formed on the layer.
In vapor phase growing an epitaxial film consisting of a layer of 90 of the amount needed
%, but not zero, thereby reducing the growth rate of the second layer.