JPH04266072A - Semiconductor light-emitting diode and its manufacture - Google Patents

Abstract

PURPOSE:To achieve an improved p-n junction and a high brightness by using the liquid phase epitaxy method in a switching element and a semiconductor light-emitting diode in a structure which can be integrated monolithically. CONSTITUTION:A p-type semiconductor layer 1 and an n-type semiconductor layer 2 with a p-n junction interface are located on a semiconductor substrate 3, dopants determining each conduction type are equal, and reduction in carrier concentration near the p-n junction interface is 1/10 or less of each carrier concentration.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting diode having a structure that can be monolithically integrated with a switching element and which can emit high-intensity light, and a method for manufacturing the same.

0002

[Prior Art] As a well-known example, Applied Physics Letters, 9(6), 1966, No. 22
Pages 1 to 223 (Appl. Phys. Lett.
, 9(6), 1966, PP221-223). In other words, the most common device structure of a semiconductor light emitting diode is composed of a p-type semiconductor layer and an n-type semiconductor layer, electrodes that connect them to each other, and a semiconductor substrate that holds them. The type semiconductor layer is conventionally manufactured using the same crystal growth method. These growth methods include liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE).
Vapor phase epitaxy (VPE) methods such as metal organic chemical vapor deposition (MOCVD) and metal organic chemical vapor deposition (MOCVD) are generally known. Among these, LPE is particularly widely used as a method for manufacturing particularly high-luminance semiconductor light-emitting diodes at low cost. As a dopant in this growth method, for example, for a gallium arsenide (GaAs) based compound semiconductor, zinc is generally used in the p-type semiconductor layer and tellurium is generally used in the n-type semiconductor layer. In this case, separate melts must be used to grow each semiconductor layer. In order to further simplify this process and reduce its cost, there is a method of using Si, which is a dopant that can form n-type and p-type semiconductor layers depending on the growth temperature, as a dopant. Si is a dopant that is highly effective in increasing the brightness of semiconductor light emitting diodes.

[0003] Furthermore, in order to monolithically integrate the conventional silicon integrated circuit and the light emitting function to realize a light emitting device with unprecedented high functionality, for example, the IEE Electron Device Letters, EDL-7
(9), 1986, pp. 500-502 (IE
EE Electron Device Let
t. , EDL-7(9), 1986, PP500-50
As described in 2), attempts have been made to use Si wafers as semiconductor substrates for semiconductor light emitting diodes.

0004

However, according to the former conventional liquid phase growth method, a region with low carrier concentration is formed in the carrier distribution near the pn junction, as shown in FIG. A sharp change in the electron and hole distribution cannot be obtained. This low carrier concentration region leads to high resistance of the diode, which hinders efficient light emission. Furthermore, gallium melt containing silicon easily reacts with carbon, which is the material of the melt reservoir for LPE, making it difficult to use two melt reservoirs to form both n-type and p-type semiconductor layers. There is a problem that.

In addition, in the latter conventional technique, a gallium arsenide (GaAs)-based compound semiconductor, which becomes a light emitting element, is directly grown on a silicon substrate by LPE, which can provide a high brightness semiconductor light emitting diode at a low cost. This is impossible because it will melt.

It is an object of the present invention to provide a semiconductor light emitting diode with a single dopant, which has a simple manufacturing process.
The present invention aims to provide a high-brightness light emitting diode in which a n-type semiconductor layer and an n-type semiconductor layer are formed. Furthermore, it is an object of the present invention to provide a semiconductor light emitting diode that can be monolithically integrated with a silicon switching element or the like, and a manufacturing method that can easily provide the same.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a p-type semiconductor layer and an n-type semiconductor layer having a pn junction interface on a semiconductor substrate, and a doped layer that determines the conductivity type of each layer. They are characterized in that the punts are the same and the decrease in carrier concentration near the pn junction interface is 1/10 or less of the respective carrier concentrations. Furthermore, in order to obtain a semiconductor light-emitting diode with even higher brightness using this structure, it is desirable that the carrier concentration of each of them is 1×10 18 /cm 3 or more. In order to realize these, specific methods for manufacturing the p-type semiconductor layer and the n-type semiconductor layer are different. As a manufacturing method, a liquid phase growth method, a vapor phase growth method, and a solid diffusion method are effective. A gallium arsenide (GaAs) based compound semiconductor is suitable for the semiconductor crystal layer forming the p-type semiconductor layer and the n-type semiconductor layer, and silicon is suitable for the dopant.

In the present invention, in order to realize a highly functional optical device in which such a semiconductor light emitting diode is monolithically integrated with a switching element, etc., the semiconductor substrate of the semiconductor light emitting diode is a silicon substrate or a compound semiconductor crystal layer is already formed on a silicon substrate. It is characterized by having a substrate on which is deposited. In this case, a method other than liquid phase growth is used to form a semiconductor crystal layer deposited on a silicon substrate or a semiconductor crystal layer containing a dopant and serving as a light emitting layer. In this case, a structure in which the pn junction interface in the semiconductor light emitting diode is formed on top of the n-type semiconductor crystal layer is convenient for realizing a simple manufacturing process.

Furthermore, when the semiconductor substrate of the semiconductor light emitting diode is a silicon substrate on which a compound semiconductor crystal layer is deposited, even if both the p-type semiconductor layer and the n-type semiconductor layer are formed by liquid phase growth, a high-brightness semiconductor can be obtained. Light emitting diodes become a reality. In this case, the dopants for the p-type semiconductor layer and the n-type semiconductor layer are preferably zinc and tellurium, respectively, because they can form a good pn junction.

[0010] In a semiconductor light emitting diode in which a semiconductor substrate having a p-type semiconductor layer and an n-type semiconductor layer formed on the main surface as described above is used as a silicon substrate or a substrate on which a compound semiconductor crystal layer has already been deposited, a semiconductor substrate close to the substrate is used. There are relatively many crystal defects within the semiconductor layer that reduce luminous efficiency. Therefore, a structure in which electrodes connected to the semiconductor crystal layer having each conductivity type are formed on the surface or side surface of the semiconductor layer, in which forward current for light emission is difficult to flow through this region, is desirable for realizing high brightness of the semiconductor light emitting diode. .

[0011] In addition, the light-emitting layer contains a group III element consisting of aluminum, gallium, and indium as elements of group III of the periodic table, and nitrogen, phosphorus, arsenic, and antimony as elements of group V of the periodic table.
Group V binary compound semiconductor or these ternary or quaternary compound semiconductors
An original compound mixed crystal material is used. Group III-V compound semiconductors have a high luminous efficiency because they contain many direct transition type semiconductors, and since the band gap can change depending on the type of compound, it is possible to realize light-emitting elements with various wavelengths. Furthermore, by using not only a binary compound having a fixed energy bandgap but also a ternary or quaternary compound mixed crystal material, it is possible to obtain a luminescent material with a wavelength band that cannot be realized with a binary compound. Similarly, group II-VI binary compound semiconductors or mixed crystal materials of these, consisting of zinc, cadmium, and mercury as group II elements of the periodic table, and sulfur, selenium, and tellurium as group VI elements, and I-III-VI Alternatively, a group II-V-VII chalcopyrite compound may also be used. Many of these compound semiconductors have larger energy band gaps than III-V compound semiconductors, and most of them are direct transition type semiconductors that can be made into light-emitting devices, and can be expected to be used as visible light semiconductor light-emitting diodes.

0012

[Operation] The present invention applies different manufacturing methods including a liquid phase growth method to the manufacturing of a p-type semiconductor crystal layer and an n-type semiconductor crystal layer in a semiconductor light emitting diode. The dopants for producing the p-n of the p-type semiconductor crystal layer and the n-type semiconductor crystal layer are
We have realized a semiconductor light-emitting diode characterized by a small drop in electron and hole carrier concentration at the junction interface and a sharp change in conductivity type. Such a steep change in the distribution of electron and hole carrier concentrations at the p-n junction interface is due to this sharp change in the distribution of electron and hole carrier concentrations when applying a forward voltage to the p-n junction to emit light, compared to p-n junctions realized using conventional methods. To greatly improve the light emitting efficiency with respect to current in a semiconductor light emitting diode by reducing the diode resistance at the portion.

When a silicon substrate is used as the semiconductor substrate of a semiconductor light emitting diode, either a p-type or n-type semiconductor crystal layer cannot be directly formed on the substrate by liquid phase growth, so it is necessary to combine it with other manufacturing methods. Good. Furthermore, if the semiconductor substrate is a silicon substrate on which a compound semiconductor crystal layer has been deposited, it is not only possible to form a p-type semiconductor layer and an n-type semiconductor layer using the same dopant, but also to form liquid phase growth using the compound semiconductor crystal layer. Since the reaction between the gallium melt and the silicon substrate in the method can be prevented, it is possible to produce both p-type and n-type semiconductor crystal layers by the liquid phase growth method. In this case, it is possible to realize a semiconductor light emitting diode that has fewer crystal defects and has an excellent light emitting life compared to a semiconductor light emitting diode in which all semiconductor crystal layers are produced by the conventional vapor phase growth method.

According to this manufacturing method, the semiconductor crystal layer that contributes to light emission can be made from group III elements and group V elements of the periodic table without worrying about the reaction between the melt and the silicon substrate in the liquid phase growth method. Group III-V binary compound semiconductors or mixed crystal materials of these ternary or quaternary compounds, and furthermore, II-V
Group I compound semiconductor, I-III-VI or II-V
A visible light emitting diode made of a group VII chalcopyrite compound can be formed by a liquid phase growth method.

As described above, when a silicon substrate different from the light-emitting layer or a substrate on which a compound semiconductor is deposited in advance is used as the semiconductor substrate of the semiconductor light-emitting diode, the semiconductor light-emitting diode may be formed on the same silicon substrate on which the semiconductor light-emitting diode is formed. A switching circuit and an amplifier circuit for driving a light emitting element can be formed, and a more compact light emitting device that is monolithically integrated can be obtained.

[0016]

[Embodiment] (Embodiment 1) An embodiment of the present invention will be explained with reference to FIG. The figure shows an n-type semiconductor crystal layer 2 on a semiconductor substrate 3.
This is a semiconductor light emitting diode in which a p-type semiconductor crystal layer 1 is formed on the p-type semiconductor crystal layer 1 and a p-n junction interface is formed on the top of the n-type semiconductor crystal layer 2.
are the surface of the p-type semiconductor crystal layer 1 and the semiconductor substrate 3, respectively.
It is formed on the back side. In this embodiment, in this structure, phosphorus-doped low-resistance gallium arsenide (GaAs) is used as the semiconductor substrate 3, and 2.0 x 1018 cm3 of silicon-doped gallium arsenide (GaAs) is used as the n-type semiconductor crystal layer 2.
GaAs) was grown to a thickness of 4 μm using the molecular beam epitaxy method, and silicon was further grown to a thickness of 2.0 μm as a p-type semiconductor crystal layer 1.
×1018cm3 Doped gallium arsenide (GaAs)
A pn junction was formed by growing a crystal to a thickness of 4 μm using a liquid phase epitaxy method. In the molecular beam epitaxy method, a Knunsen cell was used as an evaporation source for gallium, arsenic, and silicon, and the substrate temperature during growth was 600°C. A slide board method was used for the liquid phase epitaxy method. The growth temperature was 750° C., and the cooling rate of the gallium melt during growth was maintained at 10° C./min. For the p-type and n-type electrodes 41 and 42, a three-layer metal film was formed by a vacuum evaporation method and molded by a lift-off method using photoresist. Gold-zinc alloy/nickel/gold was used for the p-type electrode 41, and gold-germanium alloy/nickel/gold was used for the n-type electrode 42. After molding, these are 400
An ohmic junction was formed by heat treatment at .degree. C. for 10 minutes.

The carrier concentration distribution along the thickness direction of this semiconductor light emitting diode was investigated by electrochemical current-capacitance measuring method. As shown in FIG. 3, the p-type and n-type carrier concentrations were both about 2.0×10 18 cm 3 , and a steep carrier concentration change was observed without any decrease in carrier concentration near the pn junction. As a result of examining the light emitting characteristics of this structure, it was possible to fabricate a high-brightness light emitting diode with a high external quantization efficiency of over 10%.

(Embodiment 2) The next embodiment of the present invention is shown in FIG. In this embodiment, silicon is used for the semiconductor substrate 1, and the structural difference from that in FIG. 1 is that both p-type and n-type electrodes 41 and 42 are formed on their respective semiconductor crystal layers. The method for manufacturing the p-type semiconductor crystal layer 1 and the n-type semiconductor crystal layer 2 and the electrode formation process are almost the same as in Example 1. The difference is that the silicon dome that becomes the n-type semiconductor crystal layer 2
When growing gallium arsenide (GaAs) by the molecular beam epitaxy method, the initial thickness of 0.2 μm is due to the fact that the remaining layer was grown at 600°C after being grown at a low temperature of 350°C, and that the p-type semiconductor crystal layer 1 and the thickness of the n-type semiconductor crystal layer 2 is 3
The reason is that it was μm.

As in Example 1, the carrier concentration distribution along the thickness direction of this semiconductor light emitting diode was investigated by electrochemical current-capacitance measuring method, and as a result, almost the same as shown in FIG. No decrease in carrier concentration was observed at , but a steep change in carrier concentration was observed. For comparison, an attempt was made to grow a p-type semiconductor crystal layer 1 and an n-type semiconductor crystal layer 2 directly on a silicon semiconductor substrate 1 by a liquid phase epitaxy method (slide boat method), but during the growth, the substrate was exposed to gallium. It reacted with the melt and melted. Therefore, it can be said that this diode structure using silicon as a substrate is a structure realized by the present invention. Therefore, for comparison, a light emitting diode having the structure shown in FIG. 4 was fabricated in which both the p-type semiconductor crystal layer 1 and the n-type semiconductor crystal layer 2 were grown by the molecular beam epitaxy method. In this case, beryllium and silicon were used as dopants for the p-type and n-type semiconductor crystal layers. As a result of comparing the light emitting intensities of this light emitting diode and the light emitting diode of this example, it was found that the light emitting diode of this example has a higher luminance by about 50% in terms of relative intensity.

(Embodiment 3) FIG. 5 shows the structure of a semiconductor light emitting diode shown in this embodiment. The semiconductor substrate 1 in this embodiment is a silicon wafer on which undoped high-resistance gallium arsenide (GaAs) is grown in advance as a buffer semiconductor crystal layer 5 by molecular beam epitaxy. What is particularly different from Example 2 is that both the p-type semiconductor crystal layer 1 and the n-type semiconductor crystal layer 2 are formed by liquid phase epitaxy.
It lies in the fact that it has grown through the law. In this case, zinc and tellurium were used as dopants for the p-type and n-type semiconductor crystal layers, respectively, and the p-type was doped with 5.0×10 18 cm 3 and the n-type was doped with 1.5×10 18 cm 3 . The light emitting diode forming process is the same as in Example 2.

The emission intensity of the semiconductor light emitting diode thus prepared was compared with that of the molecular beam epitaxy used for comparison in Example 2.
We obtained an intensity equivalent to that of a light-emitting diode grown by the method. In particular, the feature of the light emitting diode of this example is that, as shown in FIG. 6, the light emitting intensity is excellent in stability over time. That is, the light emitting intensity of the light emitting diode grown by the molecular beam epitaxy method decreases over time when a current of 100 mA is applied, and becomes less than 50% in 5 hours, whereas the light emitting diode of this example decreases by about 80%. remains. As described above, a more stable semiconductor light emitting diode has been realized by the present invention.

[0022]

Effects of the Invention According to the present invention, a semiconductor light emitting diode can produce high-brightness light by forming a p-type semiconductor layer and an n-type semiconductor layer with a single dopant using a simple liquid phase epitaxy process. A diode can be provided. Furthermore, a semiconductor light emitting diode that can be monolithically integrated with a silicon switching element or the like can be realized.

In particular, it is possible to realize a stable light emitting diode whose luminous intensity deteriorates by half or less over time compared to a light emitting diode manufactured by the conventional vapor phase growth method. Furthermore, when silicon is used as a substrate, it has good thermal conductivity, so it is possible to use light emitting diode arrays and matrices arranged more densely than ever before.
Furthermore, arrays and matrices of semiconductor lasers can also be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a light emitting diode structure that is the basis of the invention.

FIG. 2 is a carrier concentration distribution diagram in the thickness direction of p-type and n-type semiconductor crystal layers of a conventional example.

FIG. 3 is a carrier concentration distribution diagram in the film thickness direction of p-type and n-type semiconductor crystal layers of the present invention.

FIG. 4 is a sectional view showing another embodiment of the present invention.

FIG. 5 is a sectional view showing another embodiment of the present invention.

FIG. 6 is a diagram showing changes over time in the emission intensity of the light emitting diode of the present invention.

[Explanation of symbols]

1 P-type semiconductor crystal layer 2 N-type semiconductor crystal layer 3 Semiconductor substrate 5 Buffer semiconductor crystal layer 41 p-type electrode 42 N-type electrode

Claims (10)

[Claims] 1. A semiconductor crystal layer formed by joining at least a p-type semiconductor crystal layer and an n-type semiconductor crystal layer, a semiconductor substrate having the semiconductor crystal layer formed on its main surface, and a semiconductor crystal layer having each conductivity type. A dopant for producing a p-type semiconductor crystal layer and an n-type semiconductor crystal layer in a semiconductor light emitting diode that uses light emitted by passing a forward current between these electrodes. are made of the same element, the drop in carrier concentration of electrons and holes at the pn junction interface between the p-type semiconductor crystal layer and the n-type semiconductor crystal layer is small, less than 1/10 of the respective carrier concentrations, and the conductivity type is steep. A semiconductor light-emitting diode characterized by change. 2. The semiconductor light emitting diode according to claim 1, wherein the p-type semiconductor crystal layer and the n-type semiconductor crystal layer each have hole and electron concentrations of 1×10 18 /cm 3 or more. diode. 3. The semiconductor light emitting diode according to claim 1, wherein the element serving as a dopant for forming p-type and n-type conductivity is silicon. 4. The semiconductor light emitting diode according to claim 1, wherein the semiconductor substrate forming the light emitting diode is a silicon substrate or a substrate in which a compound semiconductor is deposited on a silicon substrate. light emitting diode. 5. The semiconductor light emitting diode according to claim 1, wherein the pn junction interface is formed above the n-type semiconductor crystal layer. 6. A semiconductor crystal layer formed by joining at least a p-type semiconductor crystal layer and an n-type semiconductor crystal layer, a silicon substrate on which a compound semiconductor is deposited with the semiconductor crystal layer formed on the main surface, and each conductivity type. A semiconductor light-emitting diode is an element consisting of an electrode connected to a semiconductor crystal layer having a p-type semiconductor crystal layer, which utilizes light emitted by passing a forward current between the electrodes. type semiconductor crystal layer and n-type semiconductor crystal layer
A semiconductor light emitting diode characterized in that the punt is tellurium and zinc. 7. In the semiconductor light emitting diode according to claim 4, when the electrodes connected to the semiconductor crystal layer having each conductivity type emit light by flowing a forward current between the electrodes. A semiconductor light emitting diode characterized in that it is arranged and formed so that the current does not flow through an interface between a silicon semiconductor and a semiconductor crystal layer. 8. A semiconductor crystal layer formed by joining at least a p-type semiconductor crystal layer and an n-type semiconductor crystal layer, a semiconductor substrate having the semiconductor crystal layer formed on the main surface, and a semiconductor crystal layer having each conductivity type. A semiconductor light-emitting diode that uses light emitted by passing a forward current between these electrodes, and is a semiconductor light-emitting diode that utilizes light emitted by passing a forward current between these electrodes. - The punts are made of the same element, the drop in carrier concentration of electrons and holes at the pn junction interface between the p-type semiconductor crystal layer and the n-type semiconductor crystal layer is small, less than 1/10 of the respective carrier concentrations, and the conductivity type is A method for manufacturing a semiconductor light emitting diode that changes abruptly, characterized in that the methods for manufacturing each of the p-type and n-type semiconductor crystal layers constituting the semiconductor light-emitting diode are different. 9. A semiconductor crystal layer formed by joining at least a p-type semiconductor crystal layer and an n-type semiconductor crystal layer, a semiconductor substrate having the semiconductor crystal layer formed on the main surface, and a semiconductor crystal layer having each conductivity type. A semiconductor light-emitting diode that uses light emitted by passing a forward current between these electrodes, and is a semiconductor light-emitting diode that utilizes light emitted by passing a forward current between these electrodes. - It is composed of the element Si, which acts as a punt, and the drop in carrier concentration of electrons and holes at the pn junction interface between the p-type semiconductor crystal layer and the n-type semiconductor crystal layer is small, less than 1/10 of the respective carrier concentrations, and the conductivity type is small. A method for manufacturing a semiconductor light emitting diode that changes abruptly, characterized in that a p-type semiconductor crystal layer is manufactured by a liquid phase growth method, and an n-type semiconductor crystal layer is manufactured by a vapor phase growth method. 10. A semiconductor crystal layer formed by joining at least a p-type semiconductor crystal layer and an n-type semiconductor crystal layer;
This device consists of a silicon substrate with a compound semiconductor deposited on its main surface, and electrodes connected to semiconductor crystal layers of each conductivity type.The device uses light emitted by passing a forward current between these electrodes. In a method for manufacturing a semiconductor light emitting diode, the semiconductor crystal layer is a gallium arsenide (GaAs)-based compound semiconductor, and the dopants in the p-type semiconductor crystal layer and the n-type semiconductor crystal layer are tellurium and zinc. A method for manufacturing a semiconductor light emitting diode, characterized in that a type semiconductor crystal layer and an n-type semiconductor crystal layer are manufactured by a liquid phase growth method.