JP3257286B2 - Light emitting diode manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light emitting diode (LED) having a high light output and a high reliability.

[0002]

2. Description of the Related Art Light emission output is the most important characteristic among LED characteristics. Therefore, the improvement of the light emission output of the LED is
The LED manufacturers are working hard to develop them.

For example, taking an AlGaAs-based LED as an example, a higher output has been promoted by improving the internal quantum efficiency from a single hetero structure to a dub hetero structure. G
By changing the conventional double hetero structure in which the light emitting layer is formed on the aAs substrate to the back reflection type structure in which the GaAs substrate on the back surface is removed, the light extraction efficiency is improved and the output is increased. Heretofore, this back-reflection type LED has the highest emission output, but it has been difficult to grow a thick epitaxial layer necessary for removing the substrate.

On the other hand, an interface reflection type LED having a high output has been developed by providing a cavity between a GaAs substrate and a light emitting layer and reflecting light at an interface between the light emitting layer and the cavity. (Eg, Japanese Patent Application No. 5-160610). This is because a large number of mesas are formed on the surface and Ga
Irregularities are formed on an As substrate, the concave portions of the GaAs substrate are filled with an AlGaAs layer serving as a sacrificial layer, an epitaxial light emitting layer is formed on the GaAs substrate including the AlGaAs layer, and AlGaAs serving as a sacrificial layer filling the concave portions is formed. The layer is etched away to form a cavity, and light is reflected at the interface between the cavity and the epitaxial layer. The interface reflection type LED has many advantages as compared with the backside reflection type LED, such as high light emission output, good in-plane uniformity, easy manufacture, and compatibility with high speed and high output.

[0005]

However, there are the following problems in manufacturing the above-mentioned interface reflection type LED.

(1) It is very difficult to effectively etch only the sacrificial layer. For example, when a sacrificial layer is grown in an undoped type, the sacrificial layer actually becomes p-type due to dopant diffusion. AlG with high mixed crystal sacrifice layer
In the case of aAs, a dilute solution of hydrofluoric acid is used to remove it by etching. However, since the p-type sacrificial layer is difficult to be etched, not only the sacrificial layer but also the periphery thereof is slightly etched. For this reason, it was difficult to form the cavity shape after etching with high accuracy.

In particular, a red LED which requires a high AlAs mixed crystal ratio of an epitaxial layer forming a light emitting layer
In such a case, the amount of etching of the cladding layer and the window layer constituting the light emitting layer becomes a problem. However, since the layers other than the sacrificial layer are also etched, the etching cannot be performed as designed, and a sufficiently high emission output is obtained. I couldn't do that.

(2) On the other hand, the interface reflection type LED constituted by removing the sacrificial layer entirely has a high light emission output as described above, but has a problem in reliability. In particular, in a low-temperature reliability test performed when the device is used outdoors, a large decrease in light emission output has occurred.

(3) In the interfacial reflection type LED, since the substrate and the epitaxial layer of the light emitting layer are only connected by the mesa portion, the heat generated in the light emitting layer is hardly dissipated. Therefore, increasing the current causes an increase in the forward voltage and a decrease in the response speed.

[0010] An object of the present invention is to provide an interface reflection type LED in which, when removing a sacrifice layer, the sacrifice layer can be etched at a larger rate than the other layers. A high-power L that can effectively etch away only the sacrificial layer without affecting the other layers by overcoming the disadvantages of the prior art.
An object of the present invention is to provide a method for manufacturing an ED.

It is another object of the present invention to provide an LED that can simultaneously satisfy high emission output and high reliability.

It is another object of the present invention to provide a method of manufacturing an LED by improving heat dissipation so that the forward voltage does not increase or the response speed does not decrease even when the current is increased. is there.

[0013]

First, in order to achieve the object of effectively removing only the sacrificial layer by etching, the present invention relates to an interfacial reflection type LED which is formed between a substrate and an epitaxial layer to be a light emitting layer. The type of the sacrificial layer thus formed is an n-type.

That is, the method for manufacturing an LED according to the present invention comprises:
A plurality of recesses formed on the surface of the semiconductor substrate are filled with a semiconductor layer serving as a sacrificial layer, a light-emitting layer is formed over the substrate including the semiconductor layer, and the semiconductor layer serving as a sacrificial layer filling the recesses is removed by etching. In a method for manufacturing a light emitting diode in which a cavity is formed and light is reflected at an interface between the cavity and the light emitting layer, the conductivity type of the semiconductor layer filling the recess is n-type.

Further, according to the method of manufacturing an LED of the present invention, a plurality of recesses formed on the surface of a p-type GaAs substrate are filled with an AlGaAs layer having a high AlAs mixed crystal ratio as a sacrificial layer, and the AlG layer is formed.
GaAs or Al is formed on a GaAs substrate including an aAs layer.
A light emitting layer of GaAs homo-junction, single hetero-junction or double hetero-junction is formed, and the AlGaAs layer having a high AlAs mixed crystal ratio, which is a sacrificial layer filling the recess, is removed to form a cavity. A light-emitting diode for reflecting light at an interface between the light-emitting layer and the light-emitting layer, wherein the AlGa having a high AlAs mixed crystal ratio filling the recess is provided.
The conductivity type of the As layer is n-type.

Next, in order to simultaneously achieve high emission output and high reliability and achieve the object of improving heat dissipation, the present invention provides an interface reflection type LED with a substrate and a light emitting layer. The conductivity type of the sacrificial layer grown between the epitaxial layers is set to the conductivity type opposite to that of the substrate, and the sacrificial layer is partially removed instead of being entirely removed.

That is, the method for manufacturing an LED of the present invention comprises:
A plurality of recesses formed on the surface of the semiconductor substrate are filled with a semiconductor layer serving as a sacrificial layer, a light-emitting layer is formed over the substrate including the semiconductor layer, and the semiconductor layer serving as a sacrificial layer filling the recesses is removed by etching. In a method for manufacturing a light emitting diode, wherein a cavity is formed and light is reflected at an interface between the cavity and the light emitting layer, the conductivity type of the semiconductor layer filling the recess is set to a conductivity type opposite to that of the semiconductor substrate. And a semiconductor layer serving as a sacrificial layer filling the concave portion is partially left.

Further, according to the LED manufacturing method of the present invention, an epitaxial wafer in which a plurality of concave portions formed on the surface of a semiconductor substrate are filled with a semiconductor layer serving as a sacrificial layer and a light emitting layer is formed on a substrate including the semiconductor layer is provided. Forming a partial electrode on the front surface of the wafer, forming a full surface electrode on the back surface, removing a semiconductor layer serving as a sacrificial layer filling the concave portion to form a cavity, and forming the cavity and the light emitting layer. In the method for manufacturing a light emitting diode in which light is reflected at the interface of the above, the conductivity type of the semiconductor layer serving as a sacrificial layer filling the concave portion is n-type,
When the semiconductor layer serving as the sacrificial layer filling the concave portion is removed, the semiconductor layer is partially left, and the diameter of the remaining region is set to 50% to 150% of the partial electrode.

Further, according to the method of manufacturing an LED of the present invention, a plurality of recesses formed on the surface of a p-type GaAs substrate are filled with an AlGaAs layer having a high AlAs mixed crystal ratio serving as a sacrificial layer, and the AlG layer is formed.
GaAs or Al is formed on a GaAs substrate including an aAs layer.
A GaAs homojunction, single heterojunction or double heterojunction light emitting layer is formed to form an epitaxial wafer, a partial electrode is formed on the front surface of the wafer, and a full surface electrode is formed on the back surface. A method of manufacturing a light-emitting diode, comprising removing an AlGaAs layer having a high AlAs mixed crystal ratio to form a layer to form a cavity, and reflecting light at an interface between the cavity and the light-emitting layer.
Al having a high AlAs mixed crystal ratio to be a sacrificial layer for filling the concave portion
The conductivity type of the GaAs layer is n-type, and the AlGaAs layer having a high AlAs mixed crystal ratio, which is a sacrificial layer filling the concave portion, is partially left, and the diameter of the remaining region is 50% of that of the partial electrode.
From 150%. The LE of the present invention
In the method of manufacturing D, the p-type and the n-type may be reversed.

AlGaAs having a high AlAs mixed crystal ratio as described above
The n-type dopant that makes the conductivity type of the sacrificial layer n-type is Te,
Preferably, it is Sn, S, or Se. The method of growing the epitaxial layer is not limited to a liquid phase epitaxial growth method, a vapor phase growth method, or a metal organic chemical vapor deposition method.

[0021]

In the present invention, if the sacrificial layer is made n-type, only the sacrificial layer can be effectively removed while minimizing the etching of other layers. Therefore, it is possible to form the shape with high accuracy, and to manufacture the LED as designed, so that a higher output can be obtained. Further, in order to form an n-type sacrifice layer, it is only necessary to add an n-type dopant to the growth solution of the sacrifice layer, and it is easy to manufacture because the number of steps is not increased.

By the way, if all the sacrificial layers are removed, there is a problem in reliability. Therefore, in another invention, the entire sacrificial layer is not partially removed but is partially left. By doing so, reliability can be improved.

In order to leave the sacrificial layer partially, the etching may be stopped halfway. When the sacrificial layer is etched, the sacrificial layer is etched away from the periphery toward the center. Therefore, if the etching is stopped halfway, the sacrificial layer is left near the center.

However, if a current flows through the remaining sacrificial layer, the light-emitting portion is located immediately below the partial electrode and the light is blocked, so that the light extraction efficiency cannot be increased.
Therefore, the conductivity type of the sacrifice layer is set to the conductivity type opposite to that of the substrate so that no current flows through the sacrifice layer. With this configuration, it is possible to prevent the current from being concentrated directly below the partial electrode through the sacrificial layer, and it is possible to disperse the current. This makes it possible to obtain a highly reliable LED while maintaining a high light emission output.

Further, when the sacrificial layer is partially left, the epitaxial layer of the light emitting layer is connected to the sacrificial layer, so that the heat generated in the light emitting layer can be released.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the LED of the present invention will be described below with reference to the drawings.

(Embodiment 1) An embodiment 1 in which the conductivity type of the sacrificial layer is n-type will be described with reference to FIGS. FIG. 1 is a cross-sectional structural view of a 660 nm high-brightness red LED epitaxial wafer according to the present embodiment before a sacrificial layer is removed.

The structure of this epitaxial wafer is as follows. A large number of mesa portions 6 are formed in a matrix on a p-type GaAs substrate 5, and a large number of uneven portions are formed on the substrate surface. A concave portion on the p-type GaAs substrate 5 having the concave and convex portions is provided with an n-type AlGaAs having a high AlAs mixed crystal ratio.
Sacrifice layer 4 is buried. Substrate 5 including this sacrificial layer 4
A light emitting layer having a pn junction is formed thereon. The light emitting layer includes a p-type AlGaAs cladding layer 3, a p-type AlGaAs
It is composed of an active layer 2 and an n-type AlGaAs cladding layer 1 and has a double hetero structure.

Next, a method of manufacturing the epitaxial wafer will be described. As a manufacturing method, a liquid phase epitaxial method widely used for manufacturing an AlGaAs-based LED was used, and among the liquid phase epitaxial methods, a slide boat method, which is a kind of a slow cooling method, was used.

First, a p-type GaAs substrate 5 having a thickness of 350 μm and a carrier concentration of 2 × 10 ¹⁹ cm ⁻³ was used. The GaAs substrate 5 was subjected to photolithography and etching to form a mesa 6. The size of the mesa portion 6 was formed in a matrix such that the diameter was 15 μm, the height was 10 μm, and the distance between the centers of adjacent mesa portions was 40 μm.

A p-type GaAs having the mesa 6 formed on the surface
The s substrate 5 was set on the substrate holder of the slide boat. The slide boat has four solution reservoirs. First,
The solution reservoir contains metal Ga and metal A for growing an n-type sacrificial layer.
1, GaAs polycrystal, and metal Te as a dopant were set. In the second solution reservoir, metal Ga, metal Al, GaAs polycrystal, and metal Mg as a dopant were set for growing a p-type cladding layer. In the third solution reservoir, metal Ga, metal Al, GaAs polycrystal,
Metal Mg was set as a dopant. And the fourth
In the solution reservoir, metal Ga, metal Al, GaAs polycrystal, and metal Te as a dopant were set for growing an n-type cladding layer.

Here, the compositions of the second to fourth solutions are the same as those used for growing the conventional DH structure red LED. For the composition of the first solution reservoir, extra Al for growing a highly mixed crystal AlGaAs layer was added. Polycrystalline Ga
As does not matter. Te was set to 0.05 mg per 1 g of Ga.

The slide boat on which the raw materials were set was set in a reaction tube, the inside of the reaction tube was replaced with hydrogen gas, and the temperature was raised to the growth temperature. Then, after maintaining at the growth start temperature for about 3 hours, slow cooling was started. After the slow cooling was started, the substrate holder on which the GaAs substrate was set was slid, and the GaAs substrate was brought into contact with the growth solution in the first solution reservoir. Due to this contact, a high mixed crystal (AlAs mixed crystal ratio of 0.
9) An n-type AlGaAs sacrificial layer was grown. About 2μm
After the growth, the substrate holder was slid, the substrate was brought into contact with the growth solution in the second solution reservoir, and the p-type AlGaAs cladding layer was grown.

Although the thickness of the sacrificial layer of 2 μm seems to be theoretically irrational with respect to the depth of the concave portion of 10 μm, the growth of the concave portion of the mesa portion and the melting of the convex portion during the growth of the sacrificial layer actually occur. Simultaneously progressing, 2 μm growth in the concave portion, 7 μm in the convex portion
There is no problem because melting occurs and after the growth is completed, the surface becomes considerably flat.

The p-type AlGaAs cladding layer is made of AlAs
The mixed crystal ratio is 0.6, the carrier concentration is 5 × 10 ¹⁷ cm ⁻³ ,
The thickness is 30 μm. Once the cladding layer has grown,
The substrate holder is moved to grow an active layer of p-type AlGaAs. The p-type AlGaAs layer has an AlAs mixed crystal ratio of 0.1.
35, the carrier concentration is 9 × 10 ¹⁷ cm ^-3 and the thickness is 1 μm
It is. After the growth of the active layer, the substrate holder was further moved to grow an n-type AlGaAs cladding layer. The n-type AlGaAs layer has an AlAs mixed crystal ratio of 0.6, a carrier concentration of 1 × 10 ¹⁸ cm ^{−3 on the surface} , and a thickness of 40 μm.
After the growth of the n-type cladding layer is completed, the substrate holder is further moved to separate the growth solution and the epitaxial wafer. When the separation was completed, the heater of the epitaxial furnace was turned off, and rapid cooling was started.

The cooled epitaxial wafer is taken out of the furnace, and a circular AuGe having a diameter of 150 μm is formed on the wafer surface.
/ Ni / Au electrodes were formed in a matrix at intervals of 350 μm vertically and horizontally. On the back surface of the wafer, an AuZn full-surface electrode was formed. Next, in order to form a chip, the circular electrode 7 is positioned so that the surface circular electrode 7 is located at the center.
Separation grooves were formed vertically and horizontally around the surface by a dicer. The formation depth of the groove is 100 μm. This grooved epitaxial wafer was subjected to an H ₂ SO ₄ -based etching treatment, and a groove cut surface by a dicer was removed by etching. Chip size is 300μm × 300μ when viewed from the surface
m.

This epitaxial wafer is immersed in a dilute solution of hydrofluoric acid (1% by volume) for 1 hour. This immersion condition is a time sufficient to completely remove the n-type sacrificial layer 4 by etching. By this immersion treatment, the highly mixed crystal n-type AlGaAs sacrificial layer 4 grown in the concave portion of the GaAs substrate 5 was removed by etching. FIG. 2 shows the epitaxial wafer from which the sacrificial layer 4 has been removed as described above.

Thereafter, the center of the groove was fully cut to separate the epitaxial wafer into chips. This chip was fixed to a stem by die bonding, wired by wire bonding, and resin-molded to produce an interface reflection type LED.

When the characteristics of the manufactured LED were measured using an integrating sphere, a high output of 8 mW was obtained at a forward current of 20 mA. This luminance is equivalent to a commercially available 3000 mcd class LED as a red LED. Such a high-brightness LED can be manufactured by using a highly mixed crystal n-type AlGaAs while minimizing the etching of other epitaxial layers.
This is because the s sacrificial layer could be removed by etching.

With respect to the interface reflection type LED, it is very important whether only the sacrificial layer can be effectively etched. Therefore, the etching rate of the high mixed crystal AlGaAs sacrificial layer was examined by changing the carrier concentration from p-type to n-type. The result is shown in FIG. Zn was used as a p-type dopant, and Te was used as an n-type dopant. The horizontal axis indicates the carrier concentration (cm ⁻³ ), and the vertical axis indicates the etching depth a (μm). The etching depth a was the diameter of the cavity 9 shown in FIG.

The composition of the etching solution was 100 parts of water and 1 part of hydrofluoric acid by volume. This composition may be thinner, but is not preferred because it requires an etching time. If the concentration of hydrofluoric acid is increased in order to shorten the etching time, the etching of the epitaxial layer, particularly the n-type AlGaAs cladding layer on the surface becomes intense, which is not preferable.

With this etching solution, n-type highly mixed crystal AlGaAs
By etching the sacrificial layer, cutting the wafer, and observing the cross section, the depth a of the sacrificial layer 4 that could be removed by etching (the depth inward from the end in the radial direction) was determined. Since the area of the sacrificial layer is 300 μm square, when the depth in the radial direction becomes 150 μm, it means that all of the sacrificial layer has been removed.

As shown in FIG. 3, in the case of the p-type sacrificial layer, the etching is several tens μm, which is very small. As the carrier concentration decreases, the etching depth also increases,
The etching amount is small. On the other hand, when the sacrificial layer becomes n-type, the amount of etching sharply increases. It can be seen that as the n-type carrier concentration increases, the etching rate also increases, and when the carrier concentration reaches 1 × 10 ¹⁷ cm ⁻³ , the sacrificial layer is completely dissolved.

When Mg or the like was used as a p-type dopant in addition to Zn, the amount of etching was small as in the case of Zn. As n-type dopants, Sn, S,
Although Se or the like was used, in this case, the etching rate was high as in the case of Te. For this reason, it was confirmed that the reason why the etching rate of the sacrificial layer was high was not due to the use of Te as the dopant, but the n-type.

As described above, according to the first embodiment, the sacrificial layer is formed of n
The use of the mold facilitated the etching of the sacrificial layer.
Further, since the sacrifice layer etching was facilitated, the yield of chip fabrication could be greatly improved.

Although the above embodiment has been described with reference to an AlGaAs-based red LED, the AlGaAs-based infrared LED can be etched without etching other epitaxial layers when etching the sacrificial layer. Could be etched cleanly, selectively and promptly.

In the above embodiment, the case where the n-type AlGaAs sacrificial layer and the epitaxial layer to be the light emitting layer are formed on the p-type GaAs substrate has been described.
The same effect was obtained when an n-type AlGaAs sacrificial layer and an epitaxial layer serving as a light emitting layer were formed on an aAs substrate.

The LED manufactured according to the present embodiment
Is a red LED for high-brightness LED for outdoor display, and a low power consumption LED for mobile phone etc. due to its high efficiency.
And so on. As for the infrared LED, since the sacrificial layer can be etched with high accuracy, the output can be further increased and the mass productivity can be improved. Since this infrared LED has high speed and high output, it can be used for spatial transmission for audio and video transmission. In addition, it can meet the demands for low power consumption and long-distance transmission in the conventional remote control area, and can be used more widely. It also has high output characteristics required for information transmission on roads and the like.

(Embodiment 2) Next, referring to FIGS.
A second embodiment in which a part of the sacrificial layer is left will be described. FIG. 4 is a sectional structural view of an epitaxial wafer for a high-output infrared LED having an emission wavelength of 850 nm. The basic structure of the epitaxial wafer is basically the same as that of the first embodiment.

The method of manufacturing an epitaxial wafer is the same as that of the first embodiment except for the following points. That is, the difference is that the p-type Al
The GaAs cladding layer 3 has an AlAs mixed crystal ratio of 0.3, a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ and a thickness of 50 μm. The p-type AlGaAs active layer 2 has an AlAs mixed crystal ratio of 0.05, a carrier concentration of 2 × 10 ¹⁸ cm ^-3 and a thickness of 1
μm. The n-type AlGaAs cladding layer 1 is made of AlA
s mixed crystal ratio is 0.3, carrier concentration on the surface is 1 × 10 ¹⁸ cm
^-3 , the film thickness is 30 μm.

In the second embodiment, the etching conditions are changed so that the sacrificial layer 4 is not completely removed but is partially left. The epitaxial wafer is immersed in a dilute solution of hydrofluoric acid (10% by volume) for 15 minutes. By this processing, a high-mixed crystal AlG grown in the concave portion of the GaAs substrate 5 is formed.
The peripheral portion of the aAs sacrificial layer 4 is removed by etching,
The central sacrificial layer remains. This is shown in FIG.

The light emission output of the LED manufactured from this wafer in the same manner as in Example 1 was measured by an integrating sphere. The light emission output is 18 mW at a forward current of 50 mA. Also this LE
When a reliability test was performed on D, the deterioration rate after 1000 hours was 5% or less in the room temperature current test in which 100 mA of current was supplied twice as much as the conventional one. 85 ℃, 50mA
In the high-temperature energization test, the deterioration rate after 1000 hours was 5% or less. Further, it was 5% or less in a high-temperature and high-humidity current test at 85 ° C., 85%, and 50 mA. -40 ° C, 50mA
In the low-temperature electric current test, the deterioration rate after 1000 hours was 10% at the maximum, and it was confirmed that the device could withstand a very severe environmental test.

As described above, it was found that if the etching of the sacrificial layer was stopped halfway without removing the sacrificial layer entirely, high light emission output and high reliability could be obtained at the same time.

Next, in order to examine the relationship between the remaining amount of the sacrificial layer and the reliability, LED chips were manufactured in which the amount of removal of the sacrificial layer was varied by changing the etching time of the sacrificial layer. About this LED, light emission output and relative intensity (reliability test)
I checked. The result is shown in FIG. In FIG. 5, the horizontal axis represents the diameter b (μm) of the remaining sacrificial layer. The diameter b of the sacrificial layer was measured by cutting the chip and observing the cross section. The vertical axis on the left side indicates the light emission output, and is a value obtained by evaluating the light emission output when the forward current is 50 mA using an integrating sphere. The light emission output is such that the diameter of the sacrificial layer is 120.
Up to about μm, the diameter gradually decreases as the diameter increases. When the diameter exceeds 120 μm, the light emission output decreases rapidly. Normal DH structure LED (Ga
On a As substrate, a p-type cladding layer serving as a light emitting layer, an active layer, and n
The emission output is 1.5 times larger than that of an LED manufactured from an epitaxial wafer on which a mold window layer is grown, when the diameter of the sacrificial layer is up to 220 μm.

The vertical axis on the right side of FIG. 5 shows the relative light output relative to the initial light output when a low-temperature reliability test (−40 ° C., 50 mA, 1000 hours) is performed. When the sacrificial layer is completely removed, the relative strength is reduced to 50%, indicating a large deterioration rate. On the other hand, it can be seen that as the diameter of the remaining sacrifice layer increases, the reliability is greatly improved. When the remaining diameter of the sacrifice layer exceeds 60 μm, the relative strength becomes 75% or more, and the effect of the sacrifice layer remaining becomes clear.

Therefore, the diameter of the remaining region of the sacrificial layer is
60 μm to 220 μm is preferred. This is about 5 μm of the diameter of the circular electrode because the diameter of the circular electrode is 150 μm.
It corresponds to 0% to 150%. It is preferable that the position of the remaining region of the sacrificial layer be the same as the center of the circular electrode immediately below the circular electrode.

The shape of the sacrifice layer left here is not a perfect circle but a circle close to a square. Also, although the surface electrode is circular, it need not be circular, and may be any partial electrode located approximately at the center of the chip. Further, a shape in which a cross is added to a circle may be used, and this is preferable because the current dispersion effect is enhanced.

In the second embodiment, since the amount of etching of the sacrificial layer is reduced, the fabrication is easier than in the case where the sacrificial layer is entirely removed. When the sacrificial layer was completely removed, a luminous intensity of 3000 mcd was obtained at a forward current of 20 mA.
An emission intensity of 2600 mcd was obtained. The reason why such a high luminous intensity was obtained was that the conductivity type of the sacrificial layer 4 was changed to p-type G
This is because current is prevented from flowing through the remaining sacrificial layer 4 by using the n-type, which is the opposite conductivity type to the aAs substrate 5 and the p-type AlGaAs cladding layer 3.

In the second embodiment, as for the low-temperature reliability, the relative intensity is reduced to 50% in the interface reflection type LED from which the sacrificial layer is completely removed.
(Relative strength is 98%), but a relative strength of 80% or more was obtained.

As described above, the development of the infrared LED having the structure of the second embodiment makes it possible to manufacture a highly reliable interface reflection type LED having a high light emission output. For this reason, LEDs that could only be used for indoor information transmission in the past were
It can be widely used for outdoor traffic information transmission and information transmission between buildings. In addition, this applies not only to the infrared LED but also to the red LED, and the reliability has been greatly improved, so that the LED can be used from an indoor display to an outdoor display.

As described above, according to the second embodiment,
For the interfacial reflection type LED, the growth solution for growing the sacrificial layer is n
High emission output and high reliability can be obtained at the same time simply by adding the type dopant and stopping the etching of the sacrificial layer halfway, and in this case, a significant increase in the number of steps is not required. When the sacrifice layer is completely removed, the other epitaxial layers are also etched. On the other hand, in the second embodiment, only the surroundings where etching is fast are etched, so that the other epitaxial layers are removed in a short time. Work can be done without etching.

Here, the sacrifice layer need only be of the conductivity type opposite to that of the substrate, so that the sacrifice layer does not necessarily have to be of the n-type. In particular, when the sacrifice layer is of the n-type as in the second embodiment. As described in the first embodiment, etching of another epitaxial layer can be effectively avoided, and etching can be performed more easily.

Further, by leaving a part of the sacrificial layer, the low-temperature reliability, which has particularly been a problem in reliability, can be significantly improved without causing a significant decrease in light emission output. Also, an interface reflection type L of a type in which the sacrifice layer is entirely removed.
In the ED, the escape of heat was poor because the substrate and the epitaxial layer were connected only by the mesa portion, but in the case of Example 2, the escape of heat was increased because the sacrificial layer was left, and the current was increased. Even if it is performed, the increase in the forward voltage is small, and the response speed does not decrease.

[0064]

According to the first and second aspects of the present invention, the sacrifice layer filling the concave portion of the substrate is an n-type layer which is easily etched, so that only the sacrifice layer can be effectively removed by etching. LED with high dimensional accuracy can be manufactured with good yield,
High output can be realized.

According to the third aspect of the present invention, the sacrifice layer filling the concave portion of the substrate is partially left, and the remaining sacrifice layer is formed of a conductivity type opposite to that of the substrate. , While significantly improving reliability. Further, since the light emitting layer is also connected to the remaining sacrificial layer, heat can be effectively released and the LED characteristics can be greatly improved.

According to the fourth and fifth aspects of the present invention, the sacrifice layer is left with a predetermined size, so that a high luminous output and a relative intensity can be obtained at the same time.

According to the sixth aspect of the present invention, since the sacrifice layer can be made n-type only by adding the n-type dopant to the growth solution for the sacrifice layer, the number of steps is not increased and the LED can be easily manufactured. I can do it.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an LED epitaxial wafer for explaining Example 1 of an LED manufacturing method according to the present invention.

FIG. 2 is a cross-sectional view of a final structure of the epitaxial wafer for LED manufactured according to Example 1 from which all the sacrificial layers have been removed.

FIG. 3 is a graph showing the dependence of the amount of etching on the carrier concentration of a sacrifice layer according to the first embodiment.

FIG. 4 is a cross-sectional view of an epitaxial wafer for LED for explaining Example 2;

FIG. 5 is a diagram showing the dependence of the light emission output and the relative intensity on the diameter of the remaining sacrificial layer according to Example 2.

[Explanation of symbols]

 Reference Signs List 1 n-type GaAs cladding layer 2 p-type AlGaAs active layer 3 p-type AlGaAs cladding layer 4 n-type AlGaAs sacrificial layer 5 p-type GaAs substrate 6 mesa 7 n-side electrode 8 p-side electrode 9 cavity

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-137679 (JP, A) JP-A-59-23579 (JP, A) JP-A-7-193275 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) H01L 33/00

Claims (6)

(57) [Claims] A semiconductor layer serving as a sacrificial layer, a light emitting layer is formed on the substrate including the semiconductor layer, and the semiconductor layer filling the recess is removed by etching. A method for manufacturing a light emitting diode, wherein a cavity is formed and light is reflected at an interface between the cavity and the light emitting layer, wherein the conductivity type of the semiconductor layer filling the recess is n-type. A method for manufacturing a light emitting diode. 2. A plurality of recesses formed on the surface of a p-type GaAs substrate are filled with an AlGaAs layer having a high AlAs mixed crystal ratio serving as a sacrificial layer, and a G layer is formed on the GaAs substrate including the AlGaAs layer.
forming a homojunction, single heterojunction or double heterojunction light emitting layer of aAs or AlGaAs;
A method for manufacturing a light emitting diode, wherein a cavity is formed by removing an AlGaAs layer having a high AlAs mixed crystal ratio filling the recess and a light is reflected at an interface between the cavity and the light emitting layer. Fill Al with high AlAs mixed crystal ratio
A method for manufacturing a light emitting diode, wherein the conductivity type of the GaAs layer is n-type. 3. A plurality of recesses formed on a surface of a semiconductor substrate are filled with a semiconductor layer serving as a sacrificial layer, a light emitting layer is formed on a substrate including the semiconductor layer, and the semiconductor layer filling the recesses is removed by etching. In a method for manufacturing a light emitting diode, wherein a cavity is formed and light is reflected at an interface between the cavity and the light emitting layer, the conductivity type of the semiconductor layer filling the recess is set to a conductivity type opposite to that of the semiconductor substrate. A method of manufacturing a light-emitting diode, wherein a portion of the semiconductor layer filling the recess is removed by etching. 4. An epitaxial wafer having a light emitting layer formed on a substrate including the semiconductor layer by filling a plurality of recesses formed on the surface of the semiconductor substrate with a semiconductor layer serving as a sacrificial layer. Manufacturing of a light emitting diode in which an electrode is formed on the back surface, a semiconductor layer filling the recess is removed to form a cavity, and light is reflected at an interface between the cavity and the light emitting layer. In the method, the conductivity type of the semiconductor layer that fills the recess is set to the conductivity type opposite to that of the semiconductor substrate, and when the semiconductor layer that fills the recess is removed, the semiconductor layer is partially left, and the diameter of the remaining region is reduced. Is from 50% to 150% of the partial electrode. 5. A plurality of recesses formed on the surface of a p-type GaAs substrate are filled with an AlGaAs layer having a high AlAs mixed crystal ratio serving as a sacrificial layer, and G is formed on the GaAs substrate including the AlGaAs layer.
An epitaxial wafer having a homo-junction, single-hetero-junction or double-hetero-junction light-emitting layer formed of aAs or AlGaAs is formed. A partial electrode is formed on the front surface of the wafer, and a full-surface electrode is formed on the back surface. In a method for manufacturing a light emitting diode, wherein a cavity is formed by removing an AlGaAs layer having an AlAs mixed crystal ratio and light is reflected at an interface between the cavity and the light emitting layer, a high AlAs mixed crystal filling the recess is provided. AlGaAs ratio
The conductivity type of the layer is n-type, the AlGaAs layer having a high AlAs mixed crystal ratio filling the recess is partially left, and the diameter of the remaining region is 50% to 150% of the partial electrode. A method for manufacturing a light emitting diode. 6. An n-type dopant in which the conductivity type of the AlGaAs layer having a high AlAs mixed crystal ratio is n-type is Te, Sn,
The method for manufacturing a light emitting diode according to claim 2, wherein the light emitting diode is S or Se.