WO2006101002A1

WO2006101002A1 - Semiconductor light emitting element, semiconductor light receiving element and method for manufacturing them

Info

Publication number: WO2006101002A1
Application number: PCT/JP2006/305232
Authority: WO
Inventors: Osamu Ishiguro
Original assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho
Priority date: 2005-03-22
Filing date: 2006-03-16
Publication date: 2006-09-28

Abstract

A semiconductor light emitting element (10) is provided with a lower side semiconductor clad layer (24) made of n-type GaN, a semiconductor active layer (30) made of InGaN, and a layer structure (26) of an upper side semiconductor clad layer made of p-type GaN. A bandgap of the semiconductor active layer (30) is formed narrower than a bandgap of the lower side semiconductor clad layer (24) and a bandgap of the upper side semiconductor clad layer (26). Furthermore, the bandgap of the semiconductor active layer (30) is characterized in that it is changed in a thickness direction.

Description

Semiconductor light-emitting device, semiconductor light-receiving device, and manufacturing method thereof

Technical field

[0001] This application claims priority based on Japanese Patent Application No. 2005-081801 filed on Mar. 22, 2005. The entire contents of that application are incorporated herein by reference.

The present invention relates to a semiconductor light emitting device having improved luminous efficiency (ratio at which excitation energy is converted to light energy). The present invention also relates to a semiconductor light receiving element having improved light receiving efficiency (ratio at which light energy is converted into electric energy).

Background art

A semiconductor light emitting device has a laminated structure of a lower semiconductor cladding layer, a semiconductor active layer, and an upper semiconductor cladding layer. In general, a GaN-based semiconductor material, a GaAs-based semiconductor material, or a ZnSe-based semiconductor material is used for this type of laminated structure.

For example, in a stacked structure using a GaN-based semiconductor material, n-type GaN is used for the lower semiconductor cladding layer, InGaN is used for the semiconductor active layer, and P-type GaN is used for the upper semiconductor cladding layer. Often used. The semiconductor active layer contains In in the crystal structure. For this reason, the band gap of the semiconductor active layer is adjusted so that both the band gap of the lower semiconductor cladding layer and the band gap of the upper semiconductor cladding layer are narrow. The semiconductor active layer provides a field in which electrons existing in the conduction band and holes existing in the valence band combine to emit light.

A laminated structure of GaN-based semiconductor materials is generally formed by crystal growth on a sapphire substrate. In this case, it is known that an internal electric field (called a piezoelectric field) is generated in the laminated structure due to lattice mismatch between the sapphire substrate and the GaN-based semiconductor material. When a GaN-based semiconductor material is grown on a sapphire substrate, the crystal surface force of the GaN-based semiconductor material generates an internal electric field in the direction of the sapphire substrate.

The internal electric field is described in detail in Reference 1 and Reference 2 below. Reference 1 is `` tj.Pozina, JP Bergman, B. Monemar, M. Iwava, S. Nitta, H. Amano, I. Akasaki, Applie. d Physics Letters, 77, 11 (2000), p.27-29 ". Reference 2 is “VEKudryashov, AE Yunovich, Journal of Experimental and Theoretical Physics, 97, 5 (2003), p. 43-47”.

Disclosure of the invention

Problems to be solved by the invention

FIG. 7 shows a band diagram of a stacked structure using a GaN-based semiconductor material. Due to the lattice mismatch, an internal electric field in the direction of force is generated from the upper semiconductor clad layer (p-GaN) side to the lower semiconductor clad layer (n-GaN) side. As a result, as shown in FIG. 7, the energy level of the conduction band of the semiconductor active layer (InGaN) and the energy level of the valence band are inclined in the thickness direction of the semiconductor active layer (the horizontal axis direction of FIG. 7). is doing. Therefore, electrons existing in the conduction band are unevenly distributed on the upper surface side (upper semiconductor clad layer side) of the semiconductor active layer. On the other hand, holes present in the valence band are unevenly distributed on the lower surface side (lower semiconductor clad layer side) of the semiconductor active layer. For this reason, in the semiconductor active layer in which the internal electric field acts, the real space distance between electrons and holes becomes longer, and the luminous efficiency decreases.

A similar problem exists in the semiconductor light receiving element. In the semiconductor light receiving layer of the semiconductor light receiving element, when the internal electric field acts, the energy level of the conduction band and the energy level of the valence band are inclined. For this reason, electrons existing in the conduction band of the semiconductor light-receiving layer and holes existing in the valence band are unevenly distributed on the upper surface side and the lower surface side in the thickness direction of the semiconductor light-receiving layer, respectively. Will fall.

The present invention relates to a semiconductor light emitting device in which the light emission efficiency is not substantially reduced even if the energy level of the conductor of the semiconductor active layer and the energy level of the valence band are inclined in the thickness direction based on the internal electric field. The purpose is to provide. The present invention also provides that the energy level of the conductor of the semiconductor light receiving layer and the energy level of the valence band are inclined in the thickness direction.

An object of the present invention is to provide a semiconductor light receiving element in which the light receiving efficiency is not substantially lowered. Means for solving the problem

[0004] The present invention is characterized in that the band gap of the semiconductor active layer or the semiconductor light receiving layer is changed in the thickness direction. By changing the band gap in the thickness direction, the semiconductor An energy level region in which electrons or holes can stably exist (hereinafter referred to as a concentrated region) can be formed in at least a part of the body active layer or the semiconductor light receiving layer. The energy level of this concentration region is surrounded by the energy level of the remaining semiconductor active layer or semiconductor light receiving layer, and electrons or holes can be concentrated. Using this concentration region, electrons can be concentrated locally in a part of the conduction band and holes can be concentrated locally in a part of the valence band. The positional relationship between the concentration of electrons and holes coincides with the thickness direction of the semiconductor active layer or semiconductor light receiving layer.

The present invention uses the semiconductor active layer or the semiconductor light receiving layer having the above phenomenon to suppress the light emission efficiency or the light reception efficiency from being lowered due to the influence of the internal electric field. According to the present invention, a semiconductor light emitting device with improved luminous efficiency can be provided. In addition, according to the present invention, it is possible to provide a semiconductor light receiving element with improved light receiving efficiency. The semiconductor light emitting device of the present invention has a laminated structure of a lower semiconductor cladding layer, a semiconductor active layer, and an upper semiconductor cladding layer. The band gap of the semiconductor active layer is adjusted to be narrower than both the band gap of the lower semiconductor cladding layer and the band gap of the upper semiconductor cladding layer. Furthermore, the band gap of the semiconductor active layer changes in the thickness direction of the semiconductor active layer.

The semiconductor active layer may be constituted by a so-called multiple quantum well structure (MQW) which may be constituted by a single layer. When the semiconductor active layer has a multiple quantum well structure, it is preferable that the band gap of each layer of the polymer well structure changes in the thickness direction. When the band gap of the semiconductor active layer is changed in the thickness direction, a concentrated region in which electrons or holes can stably exist can be formed in at least a part of the semiconductor active layer. In the semiconductor active layer, electrons are concentrated locally in the concentrated region of the conduction band, and holes are concentrated locally in the concentrated region of the valence band. The energy level of the conduction band in the concentrated region is surrounded by the energy levels of the surrounding conduction bands. The energy level of the valence band in the concentrated region is surrounded by the energy level of the surrounding valence band. Even if the energy level in the concentrated region is tilted by the internal electric field acting on the semiconductor active layer, the concentrated region is surrounded by the surrounding energy levels (electrons and holes are less likely to exist than in the concentrated region). Because electrons and holes are concentrated in the concentration region Can do. Therefore, the electrons existing in the conduction band and the holes existing in the valence band are prevented from being unevenly distributed separately on the upper surface side and the lower surface side of the semiconductor active layer. In the semiconductor light emitting device of the present invention, a decrease in light emission efficiency is remarkably suppressed.

In the semiconductor light emitting device, when the operating voltage is applied, the energy level of the conduction band and the energy level of the valence band of the semiconductor active layer are tilted, and the emission wavelength is shifted due to fluctuations in the operating voltage. The phenomenon of doing is a problem. However, in the semiconductor light emitting device of the present invention, when the operating voltage is applied, the emission wavelength shifts even if the energy level of the conduction band of the semiconductor active layer and the energy level of the valence band are inclined. It is suppressed. In the semiconductor light emitting device of the present invention, even if the energy level of the conduction band of the semiconductor active layer and the energy level of the valence band are inclined, electrons and holes can be concentrated in the concentration region. . In the semiconductor light emitting device of the present invention, even if the energy level of the conduction band of the semiconductor active layer and the energy level of the valence band are inclined, the band gap of the concentrated region is stable, so that the emission wavelength is stable. Yes.

[0006] It is preferable that the energy level of the conduction band of the semiconductor active layer continuously changes in the thickness direction and has one minimum value at a substantially intermediate position in the thickness direction. In this case, the energy level of the valence band of the semiconductor active layer continuously changes in the thickness direction and has one maximum value at a substantially intermediate position in the thickness direction.

In this case, the energy level of the conduction band can draw a curve of a second order function in the thickness direction of the semiconductor active layer. The concentrated area is formed corresponding to the minimum value of the curve of the quadratic function. In the semiconductor active layer of the above aspect, electrons are locally concentrated in a region corresponding to the minimum value of the energy level of the conduction band, and holes are locally concentrated in a region corresponding to the maximum value of the valence band. is doing. As a result, it is possible to remarkably suppress a decrease in luminous efficiency by piled on an internal electric field acting on the semiconductor active layer. Furthermore, when the energy level of the conduction band draws a curve of a quadratic function, the allowed quantization energy levels are arranged at approximately equal intervals. For this reason, the quantization energy level of the conduction band can be increased as necessary. Therefore, the amount of electrons existing in the conduction band can be increased, and the light emission efficiency can be improved.

[0007] Lower semiconductor clad layer, semiconductor active layer, and upper clad layer force Al Ga In —— N (0≤X ≤1, 0≤Y≤1, 0≤1—X—Y≤l). Increasing the content of aluminum (A1) increases the band gap, and decreasing the content decreases the band gap. Increasing the indium (In) content narrows the bandgap, and decreasing the content increases the bandgap. By increasing or decreasing the contents of aluminum and Z or indium, a desired band gap size relationship can be obtained among the lower semiconductor cladding layer, the semiconductor active layer, and the upper cladding layer.

It is known that when this semiconductor material is used, a strong internal electric field is generated in the semiconductor active layer. The present invention is a technique for reducing the influence of such an internal electric field. Therefore, the present invention is particularly useful when such a semiconductor material is used.

[0008] The lower semiconductor clad layer is formed using GaN as a main material, the semiconductor active layer is formed using InGaN as a main material, and the upper semiconductor clad layer is formed using GaN as a main material. preferable. It is preferable that the content of In in the semiconductor active layer is small on the lower side in the thickness direction and small on the upper side in the middle.

When the In content of the semiconductor active layer is adjusted slightly higher in the middle and lower in the thickness direction, the band gap of the semiconductor active layer becomes narrower in the middle and wider in the thickness direction. A wide structure can be obtained. A concentrated region is formed in the middle of the semiconductor active layer, and the semiconductor light emitting device of the present invention can be implemented.

The present invention is also useful for a semiconductor light receiving element.

That is, the semiconductor light-receiving element of the present invention comprises a semiconductor light-receiving layer, one main electrode directly or indirectly in contact with the semiconductor light-receiving layer, and the other main electrode directly or indirectly in contact with the semiconductor light-receiving layer. I have. Here, the band gap force of the semiconductor light-receiving layer changes in the thickness direction, and is characterized by that.

In this case as well, a concentrated region of energy levels where electrons or holes can stably exist is formed in at least a part of the semiconductor light receiving layer. The energy level of this concentrated region is surrounded by the energy level of the remaining semiconductor light receiving layer, and electrons or holes can be concentrated and exist. Even if the energy level of the semiconductor light-receiving layer is tilted by the internal electric field applied to the semiconductor light-receiving layer, the positional relationship in the thickness direction between the conduction band concentration region and the valence band concentration region is maintained. Therefore, the semiconductor light receiving layer is light energy. The electrons are excited to the conduction band at the shortest distance. The decrease in light receiving efficiency is remarkably suppressed. In the semiconductor light receiving element of the present invention, even if the energy level of the conduction band and the energy level of the valence band of the semiconductor light receiving layer are inclined, electrons and holes can be concentrated in the concentration region. In the semiconductor light-receiving element of the present invention, even if the energy level of the conduction band and the energy level of the valence band of the semiconductor light-receiving layer are inclined, the band gap in the concentrated region is stable, so that the light-receiving efficiency decreases. Is suppressed.

[0010] It is preferable that the energy level of the conduction band of the semiconductor light-receiving layer continuously changes in the thickness direction and has one minimum value at a substantially intermediate position in the thickness direction. In this case, the energy level of the valence band of the semiconductor light-receiving layer continuously changes in the thickness direction and has one maximum value at a substantially intermediate position in the thickness direction.

In this case, the energy level of the conduction band can draw a curve of a second order function in the thickness direction of the semiconductor light receiving layer. The concentrated area is formed corresponding to the minimum value of the curve of the quadratic function. In the semiconductor light receiving layer of the above aspect, electrons are locally concentrated in a region corresponding to the minimum value of the energy level of the conduction band, and holes are locally concentrated in a region corresponding to the maximum value of the valence band. is doing. Also, if the conduction band energy level draws a curve of a quadratic function, the allowed quantization energy levels are arranged at almost equal intervals. For this reason, the quantization energy level of the conduction band can be increased as necessary. Therefore, the amount of electrons existing in the conduction band can be increased, and the light receiving efficiency can be improved.

The inventor has also created a method for manufacturing a semiconductor light-emitting element or light-receiving element suitable for manufacturing the semiconductor light-emitting element or semiconductor light-receiving element described above.

The method for producing a semiconductor light-emitting device or semiconductor light-receiving device according to the present invention provides a semiconductor active layer or a semiconductor light-receiving device for the initial stage force and the middle stage when a semiconductor active layer or a semiconductor light-receiving layer is grown on the semiconductor layer. The first half of the process is adjusted so that the band gap of the layer becomes smaller over time. Furthermore, from the middle stage to the final stage, there is provided a second half process in which the band gap of the semiconductor active layer or the semiconductor light receiving layer is adjusted to increase with time.

When the above manufacturing method is carried out, at the timing when the first half process and the second half process are switched, Concentrated regions are formed in the conductor active layer or the semiconductor light receiving layer. The semiconductor light emitting device or semiconductor light receiving device of the present invention can be obtained.

[0012] In Ga N (0≤X≤1) is used as the main material for the semiconductor active layer or semiconductor light receiving layer.

X 1 -X

It is preferred that In this case, in the first half process, the In content in the crystal structure is adjusted from the initial stage to the middle stage, and the In content in the crystal structure is adjusted from the middle stage to the final stage in the second half process. It is preferable to adjust to the condition that the content of

In semiconductor materials with In Ga N (0≤X≤ 1), the higher the In content, the higher the band gap.

X 1 -X

The tape becomes narrower. Therefore, when the above manufacturing method is performed, a region in which the In content in the semiconductor active layer or the semiconductor light receiving layer is maximized is formed at the timing when the first half process and the second half process are switched. Thereby, a concentrated region is formed in the semiconductor active layer or the semiconductor light receiving layer, and the semiconductor light emitting device or the semiconductor light receiving device of the present invention can be obtained.

[0013] In the first half process, the crystal growth temperature should be adjusted to be lower from the initial stage to the middle stage, and in the second half process, the medium stage must be adjusted to the condition in which the crystal growth temperature is increased toward the final stage. Is preferred.

When crystal growth of InGaN (0≤X≤1) semiconductor material, the growth temperature is lower.

X 1 -X

However, the In content can be increased. Therefore, when the above manufacturing method is performed, a region in which the In content in the semiconductor active layer is maximized is formed at the timing when the first half process and the second half process are switched. As a result, a concentration region is formed in the semiconductor active layer or in the semiconductor light receiving layer, and the semiconductor light emitting device or semiconductor light receiving device of the present invention can be obtained.

[0014] When a semiconductor active layer whose band gap is changed in the thickness direction is used, a semiconductor light emitting device in which the light emission efficiency is suppressed from being reduced by the internal electric field can be obtained. In addition, when a semiconductor light-receiving layer whose band gap changes in the thickness direction is used, a semiconductor light-receiving element in which the light-receiving efficiency is suppressed from being reduced by an internal electric field can be obtained. Brief Description of Drawings

[0015] FIG. 1 is a longitudinal sectional view of an essential part of a semiconductor light emitting device of an example.

FIG. 2 (a) shows a band diagram of the semiconductor light emitting device of the example. (b) Operating voltage is marked The band diagram of the semiconductor light-emitting device of an example when it is calorified is shown.

[Fig. 3] (a) A band diagram of one modified example is shown. (B) A band diagram of another modification is shown. (C) A band diagram of another modification is shown.

IV] Shows the laminated structure of the semiconductor light emitting device of the example.

[Fig. 5] (a) Changes in the growth temperature of the semiconductor active layer. (b) shows the variation in the growth temperature of the semiconductor active layer of the comparative example.

FIG. 6 is a longitudinal sectional view of a main part of the semiconductor light receiving element of the example.

FIG. 7 shows a band diagram of a conventional semiconductor light emitting device.

[Fig. 8] (a) A band diagram before applying the operating voltage of a conventional semiconductor light emitting device is shown. (b) A band diagram when the operating voltage of a semiconductor light emitting device with a conventional structure is marked.

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] The features of the present invention will be listed.

(1) There are no particular restrictions on the type of semiconductor material used for the semiconductor active layer or semiconductor light receiving layer. If the semiconductor material generates even a small amount of internal electric field, a useful effect can be obtained by the technique disclosed in this specification.

(2) A typical example of the internal electric field is a piezo electric field. Therefore, the technology disclosed in this specification is particularly useful for a semiconductor light emitting device and a semiconductor light receiving device having a heterojunction.

(3) Since nitride-based semiconductor materials have a large piezoelectric effect, a strong piezoelectric field is likely to occur. Therefore, the technology disclosed in this specification is particularly useful in a semiconductor light emitting device and a semiconductor light receiving device that use a nitride semiconductor material.

(4) It is preferable that the energy level of the conduction band and the valence band of the semiconductor active layer or the semiconductor light-receiving layer change in a quadratic function shape, a step shape, or a sharp peak shape in the thickness direction.

Example

[0017] (First embodiment)

FIG. 1 schematically shows a longitudinal sectional view of a main part of the semiconductor light emitting device 10. The semiconductor light emitting device 10 includes a sapphire substrate 22. The semiconductor light emitting device 10 includes a lower semiconductor clad layer 24 having n-type GaN force formed on a sapphire substrate 22, a semiconductor active layer 30 having InGaN force, and an upper semiconductor clad layer also having p-type GaN force. 26 laminated structures 52 are provided. A negative electrode 42 is in contact with a part of the lower semiconductor clad layer 24. A positive electrode 44 is in contact with a part of the upper semiconductor clad layer 26. The semiconductor active layer 30 provides a field where electrons present in the conduction band and holes present in the valence band combine to emit light.

FIG. 2 (a) shows a band diagram of the stacked structure 52 of the semiconductor light emitting device 10. The horizontal axis shows the thickness direction of the laminated structure 52, and the vertical axis shows the energy level. The band gap of the semiconductor active layer 30 is narrower than both the band gap of the lower semiconductor clad layer 24 and the band gap of the upper semiconductor clad layer 26. Further, the band gap of the semiconductor active layer 30 is formed to change in the thickness direction. The energy level of the conduction band of the semiconductor active layer 30 continuously changes in the thickness direction, and has one minimum value at a substantially intermediate position in the thickness direction. The energy level of the conduction band of the semiconductor active layer 30 draws a curve of a quadratic function in the thickness direction. It can be said that the energy level of the conduction band of the semiconductor active layer 30 draws a stepless curve in the thickness direction. In addition, the energy level of the valence band of the semiconductor active layer 30 continuously changes in the thickness direction, and has one maximum value at a substantially intermediate position in the thickness direction. The energy level of the valence band of the semiconductor active layer 30 draws a curve of a nearly quadratic function that is negative in the thickness direction. The content of In in the semiconductor active layer 30 is small on the lower side in the thickness direction (lower clad layer 24 side) and slightly on the upper side (upper clad layer 26 side). Therefore, the band gap of the semiconductor active layer 30 is formed wide on the middle and narrower on the lower side in the thickness direction and wider on the upper side.

At the energy level of the conduction band of the semiconductor active layer 30, an energy level concentration region 32 a in which electrons stably exist is formed at a substantially intermediate position in the thickness direction of the semiconductor active layer 30. The concentrated region 32a is surrounded by the energy level of the surrounding conduction band, and electrons can be concentrated. In the energy level of the valence band of the semiconductor active layer 30, the energy in which holes exist stably at a substantially intermediate position in the thickness direction of the semiconductor active layer 30. A concentrated region 32b of ruby levels is formed. The concentrated region 32b is surrounded by the energy level of the surrounding valence band, and holes can be concentrated.

The concentrated regions 32a and 32b form a well having a narrow potential in the thickness direction. The concentration region 32a is a region where the energy level of the conduction band is surrounded by the energy level of the conduction band of the surrounding semiconductor active layer 30, and the energy level of the conduction band forms a valley. is there. In the concentrated region 32b, the energy level of the valence band is surrounded by the energy level of the valence band of the surrounding semiconductor active layer 30, and the energy level of the valence band forms a mountain. It is an area. Therefore, electrons are locally concentrated in the concentrated region 32a of the conduction band, and holes are concentrated locally in the concentrated region 32b of the valence band. The positional relationship between the conduction band concentration region 32 a and the valence band concentration region 32 b is substantially the same as the thickness direction of the semiconductor active layer 30.

Note that the band gap V between the conduction band concentration region 32a and the valence band concentration region 32b

2 is adjusted to a width that provides a desired emission wavelength.

As will be described later in the manufacturing method, the laminated structure 52 of the lower semiconductor clad layer 24, the semiconductor active layer 30, and the upper semiconductor clad layer 26 is formed by crystal growth on the sapphire substrate 22. Therefore, a strong internal electric field (piezoelectric field) is generated in the multilayer structure 52 due to lattice mismatch with the sapphire substrate 22. As shown in FIG. 2 (a), the internal electric field (piezoelectric field) is generated in the direction from the upper semiconductor clad layer 26 side toward the lower semiconductor clad layer 24 side.

In the semiconductor active layer 30 of the present embodiment, the concentration region 32a where carriers are likely to concentrate is surrounded by the energy level of the surrounding conduction band where carriers are difficult to exist. Further, in the semiconductor active layer 30 of the present embodiment, the concentrated region 32b where carriers are likely to concentrate is surrounded by the energy level of the surrounding valence band. Therefore, as compared with the band diagram of the conventional structure shown in FIG. 7, the electrons are concentrated in the conduction band concentration region 32a despite the influence of the internal electric field, and the holes are It is concentrated in the valence band concentration region 32b. The electrons existing in the conduction band and the hole force semiconductor active layer 30 existing in the valence band are prevented from being unevenly distributed on the upper surface side and the lower surface side in the thickness direction. Therefore, the real space distance between electrons and holes is the shortest, and the luminous efficiency is low. The bottom is suppressed. In the semiconductor light emitting device 10 of this example, electrons existing in the conduction band and hole forces existing in the valence band are separated and separated from the upper surface side and the lower surface side in the thickness direction of the semiconductor active layer 30. This suppresses the excitation energy from being consumed at emission wavelengths other than the desired emission wavelength. In the semiconductor light emitting device 10 of this example, it is assumed that the energy level of the conduction band of the semiconductor active layer 30 and the energy level of the valence band are inclined by the internal electric field, and the concentration region 32a of the conduction band and the concentration of the valence band are Based on the band gap V between the regions 32b, the desired emission wavelength is obtained. Semiconductor of this example

2

In the body light emitting element 10, a decrease in luminous efficiency is suppressed.

The semiconductor light emitting device 10 has the following characteristics.

When the semiconductor light emitting element 10 is operated, a positive voltage is applied to the positive electrode 44 more than the negative electrode 42. When an operating voltage is applied, 30 holes in the semiconductor active layer are supplied from the upper semiconductor clad layer 26, and electrons are supplied from the lower semiconductor clad layer 24 to the semiconductor active layer 30. In the semiconductor active layer 30, the supplied electrons and holes combine to generate light having a wavelength based on the band gap.

Here, the case of the semiconductor light emitting device of the comparative example shown in FIG. 8 will be described. In the semiconductor light emitting device of this comparative example, the energy of the conduction band of the semiconductor active layer of InGaN is formed constant in the thickness direction. Figure 8 (a) is a band diagram before applying an operating voltage to the semiconductor light emitting device. Figure 8 (b) is a band diagram when an operating voltage is applied to the semiconductor light emitting device.

When a positive voltage is applied to the upper semiconductor cladding layer (p-GaN) to operate the semiconductor light emitting device, the energy level of the conduction band and the energy level of the valence band are determined based on the applied voltage. Tilts. When the energy level of the conduction band and the energy level of the valence band are tilted, the band gap of the semiconductor active layer changes from V to V.

8a 8b

. For this reason, there is a problem that the emission wavelength of the semiconductor light emitting element shifts based on the applied voltage.

On the other hand, the semiconductor light emitting device of this example can significantly suppress the shift of the emission wavelength. FIG. 2 (b) shows a band diagram of the laminated structure when operating voltage is applied to the semiconductor light emitting device 10 of this example. In addition, the broken line in the figure is before applying the operating voltage. It is a band diagram of a laminated structure.

As shown in FIG. 2 (b), in the semiconductor light emitting device 10 of this example, even when the energy level of the conduction band and the energy level of the valence band are inclined by applying an operating voltage, the conduction band The energy level of the valence band and the energy level of the valence band change while maintaining a parallel relationship. Accordingly, the band gap V between the conduction band concentration region 32a and the valence band concentration region 32b does not substantially change even when an operating voltage is applied. Semiconductor

2

In the light-emitting element 10, the emission wavelength is stable even when an operating voltage is applied.

Therefore, by adopting the semiconductor active layer 30 in the semiconductor light emitting device 10, it is possible to suppress a decrease in light emission efficiency against the influence of the internal electric field. Furthermore, by adopting the semiconductor active layer 30 for the semiconductor light emitting device 10, the shift of the emission wavelength can be suppressed against the influence of the operating voltage.

[0022] When the energy level of the conduction band draws a curve of a quadratic function, the quantization energy level of the conduction band can be increased or decreased depending on the curvature of the curve of the quadratic function. become. Decreasing the curvature of the quadratic function curve can increase the quantization energy level of the conduction band. In this case, the amount of electrons existing in the conduction band can be increased, and the light emission efficiency can be improved.

FIG. 3 shows a modified example of a useful semiconductor active layer. Figure 3 shows the energy levels of the conduction band and the valence band of the semiconductor active layer of the modification.

Fig. 3 (a) is an example in which the energy level of the conduction band and the energy level of the valence band of the semiconductor active layer change in steps in the thickness direction of the semiconductor active layer. Concentrated regions 32a and 32b are formed approximately in the middle of the semiconductor active layer, so that electrons and holes can be concentrated. This semiconductor active layer can suppress a decrease in luminous efficiency against the influence of the internal electric field.

Fig. 3 (b) is an example in which the energy level of the conduction band of the semiconductor active layer and the energy level force of the valence band change so that a sharp peak is formed in the thickness direction of the semiconductor active layer. . A steep peak is formed approximately in the middle of the semiconductor active layer, and the peaks become the concentration regions 32a and 32b. This semiconductor active layer can concentrate electrons and holes in the concentrated regions 32a and 32b. This semiconductor active layer has a luminous efficiency against the influence of internal electric field Can be suppressed.

Fig. 3 (c) shows an example where the conduction band energy level of the semiconductor active layer and the energy level force of the valence band are continuously lowered from the lower edge force to the upper edge in the thickness direction of the semiconductor active layer. The In this case, concentrated regions 32a and 32b are formed at the upper end of the semiconductor active layer, and can be trapped in electrons and holes. This semiconductor active layer can suppress a decrease in light emission efficiency against the influence of the internal electric field.

FIG. 4 shows a detailed configuration of the laminated structure 52 used in the semiconductor light emitting device 10. In FIG. 1, the force illustrated by simply showing the laminated structure 52 is actually preferably provided with a plurality of layers as shown in FIG. 4.

Next, a manufacturing method of the laminated structure 52 will be described with reference to FIG. The laminated structure 52 can be obtained by using the following manufacturing method. Note that the manufacturing method described below is an example, and other manufacturing methods may be adopted.

First, a sapphire substrate 22 that has been subjected to organic cleaning and acid cleaning is prepared, and the sapphire substrate 22 is placed in a MOCVD apparatus. The a-surface is selected as the reaction surface.

Next, while maintaining the temperature of the sapphire substrate 22 at 1100 ° C, hydrogen gas (H) was supplied to the reaction chamber at a flow rate of 10 liters Zmin at normal pressure, and the surface of the sapphire substrate 22 was etched.

2

To

Next, after the temperature of the sapphire substrate 22 is lowered to 420 ° C., hydrogen gas (H 2) is added to 20

2 liters Zmin, ammonia gas (NH) a 15 l Zmin, the TMA at 2 X 10 ^_5 molZmin

Three

A buffer layer 21 made of aluminum nitride (A1N) having a thickness of 500 A is supplied to the reaction chamber and formed on the sapphire substrate 22.

Next, a lower semiconductor clad layer 24 having a thickness of 4 m and an impurity (Si) concentration of 3 ^× 10 ¹⁸ cm ^_3 is formed on the buffer layer 21 while maintaining the temperature of the sapphire substrate 22 at 1130 ° C. .

Next, while maintaining the temperature of the sapphire substrate 22 at 850 ° C., hydrogen gas (H 2) or nitrogen gas

2

(N) 10 liters Zmin, ammonia gas (NH) 12 liters Zmin, TMG 1.93 X

twenty three

10 ^_5 molZmin, fed to the reaction chamber of TMI with 1. 93 X 10 ^_5 molZmin, the first lower semiconductor layer 31 thickness is from I n Ga N of 0. 1 m on the lower semiconductor cladding layer 24 Form.

0.05 0.95

Next, while maintaining the temperature of the sapphire substrate 22 at 885 ° C., hydrogen gas (H 2) or nitrogen gas (N) 10 liters / min, ammonia gas (NH) 25 liters Zmin, TMG 1.3 X 1

twenty three

0 ^_5 supplied at m _O lZmin, to form the second lower semiconductor layer 32 which thickness is even GaN force of 70A on the first lower semiconductor layer 31.

Next, while changing the temperature of the sapphire substrate 22, hydrogen gas (H 2) or nitrogen gas (N

twenty two

) 10 liters Zmin, ammonia gas (NH) 25 liters Zmin, 3 X 10 ^_6 molZ the TMG

Three

min, supplying TMI into the reaction chamber at 2 X 10 ^_5 molZmin, thickness to form a semiconductor active layer 30 of 40 A on the second lower semiconductor layer 32.

The specific temperature change is shown in Fig. 5 (a).

When the semiconductor active layer 30 is grown on the second lower semiconductor layer 32, the crystal growth temperature decreases with time from the initial stage (0 seconds) to the middle stage (100 seconds) in the first half process. Adjust to the conditions. In this example, the temperature is continuously changed from 750 ° C to 720 ° C. In the latter half of the process, the crystal growth temperature is adjusted to increase with time from the middle stage (100 seconds) to the final stage (200 seconds). In this example, the temperature is continuously changed from 720 ° C to 750 ° C.

The lower the crystal growth temperature, the greater the In content. Therefore, when the above manufacturing method is performed, a region in which the In content in the semiconductor active layer 30 is maximized is formed at the timing (100 seconds) at which the first half process and the second half process are switched. As a result, a region where the In content is maximized is formed at a substantially intermediate position in the thickness direction of the semiconductor active layer 30. As in this embodiment, by continuously controlling the increase / decrease in temperature change, the energy level of the conduction band of the semiconductor active layer 30 can draw a curve of a quadratic function in the thickness direction. The composition of the semiconductor active layer 30 is represented by InGaN, and its X is from 0.25 to 0.5.

X 1 -X

It fluctuates in range.

Next, while maintaining the temperature of the sapphire substrate 22 at 885 ° C., hydrogen gas (H 2) or nitrogen gas

2

(N) 10 liters Zmin, ammonia gas (NH) 12 liters Zmin, TMG 1.3 X 1

twenty three

The upper semiconductor layer 34 having a thickness of 250 A and having a GaN force is formed on the semiconductor active layer 30 by supplying at 0 ^_5 mol / min.

Next, while maintaining the temperature of the sapphire substrate 22 at 1000 ° C., hydrogen gas (H 2) or nitrogen gas

2

(N) 20 liters Zmin, ammonia gas (NH) 15 liters Zmin, TMG 3 X 10_ ⁶ mol / min, TMA 1. OX 10 "mol / min, Cp Mg 1.2 x 10 molZmin in the reaction chamber

2

The upper semiconductor clad layer 26 having a thickness of 400 A and a p-type Al Ga N force

0.1 0.9

It is formed on the conductor layer 34.

2

(N) 20 liters Zmin, ammonia gas (NH) 15 liters Zmin, TMG 3.2 X 1

twenty three

0 ^_5 molZmin, fed to the reaction chamber Cp Mg in 1. 5 X 10 ^_7 molZmin, upper semiconductor cladding

2

A contact layer 28 having a thickness of 250 A and a p-type GaN force is formed on the conductive layer 26.

Through these steps, a laminated structure used for the semiconductor light emitting device 10 can be formed.

[0032] When the semiconductor light emitting device 10 having the laminated structure obtained by the above manufacturing method was operated, the light emission efficiency was 274 W. On the other hand, as shown in FIG. 5 (b), in the comparative example in which the semiconductor active layer was formed at a constant reaction temperature, the luminous efficiency was 202 W. It was confirmed that the luminous efficiency of the semiconductor light emitting device 10 of this example was significantly improved.

Furthermore, the value obtained by subtracting PL (photo-luminescence: emission wavelength observed when excited by light) from EL (electro-luminescence: emission wavelength observed when voltage is applied) of the semiconductor light-emitting element 10 is obtained. The measured value was 21. On the other hand, in the comparative example, it was 30 °. In the semiconductor light emitting device 10 of this example, it was confirmed that the shift of the emission wavelength was remarkably suppressed.

Furthermore, it was confirmed that the response speed was also improved in the semiconductor light emitting device 10. The response speed was 40mA for the maximum forward current, and the rising speed (output 10% -90%) and falling speed (output 90% -10%) were measured. The rising speed of the semiconductor light emitting device 10 was 4.1 nsec (nanosecond). The falling speed of the semiconductor light emitting device 10 was 7.6 nsec (nanoseconds). On the other hand, in the semiconductor light emitting device of the comparative example, the rising speed was 5.2 nsec (nanosecond) and the falling speed was 7.9 nse _C (nanosecond). In the semiconductor light emitting device 10 of this example, it was confirmed that the response speed was improved.

[0033] (Second embodiment)

FIG. 6 schematically shows a longitudinal sectional view of the main part of the semiconductor light receiving element 100.

The semiconductor light receiving element 100 includes a sapphire substrate 122. Semiconductor photo detector 100 Has a laminated structure of an insulating layer 124 made of i-type GaN formed on a sapphire substrate 122, a semiconductor light-receiving layer 130 made of InGaN, and a cap layer 126 also having an i-type GaN force. The positive electrode 144 is indirectly in contact with a part of the semiconductor light receiving layer 130 through the cap layer 126. The negative electrode 142 is indirectly in contact with the other part of the semiconductor light receiving layer 130 through the cap layer 126.

The energy level of the conduction band of the semiconductor light-receiving layer 130 continuously changes in the thickness direction and has one minimum value at a substantially intermediate position in the thickness direction. The energy level of the conduction band of the semiconductor light receiving layer 130 draws a curve of a quadratic function in the thickness direction. In addition, the energy level of the valence band of the semiconductor light-receiving layer 130 continuously changes in the thickness direction and has one maximum value at a substantially intermediate position in the thickness direction. The energy level of the valence band of the semiconductor light-receiving layer 130 describes a negative quadratic function in the thickness direction. The band gap between the minimum value of the energy level of the conduction band and the maximum value of the energy level of the valence band is adjusted so as to obtain a desired light receiving wavelength.

In this case as well, as in the case of the first embodiment, carriers are more likely to exist at approximately the intermediate position in the thickness direction of the semiconductor light receiving layer 130 than the energy levels of the surrounding conduction band and the energy level of the valence band. A concentrated region of energy levels is formed. Even though the concentration region of the conduction band and the concentration region of the valence band are inclined by the internal electric field (piezoelectric field) acting on the semiconductor light-receiving layer 130, the thickness of the concentration region of the conduction band and the concentration region of the valence band The positional relationship of direction is maintained. Therefore, when the semiconductor light receiving layer 130 receives light energy, electrons are excited to the conduction band at the shortest distance. A decrease in light receiving efficiency is remarkably suppressed. In the semiconductor light-receiving element 100, even if the concentration region of the conduction band and the concentration region of the valence band are inclined by the internal electric field (piezoelectric field), the band between the concentration region of the conduction band and the concentration region of the valence band. The size of the gap is maintained, and the conversion of electrical energy to a received wavelength other than the desired received wavelength is suppressed. In the semiconductor light receiving element 100, a desired light receiving wavelength is obtained based on the band gap between the concentrated region of the conduction band and the concentrated region of the valence band. In the semiconductor light receiving element 100, a decrease in light receiving efficiency is suppressed.

In addition, since the conduction band energy level draws a curve of almost quadratic function, it is possible to increase the quantization energy level. Therefore, it exists in the conduction band The amount of electrons can be increased, and the light receiving efficiency is greatly improved.

Similar effects can be obtained by adopting a pn junction type, Schottky junction type, heterojunction type, avalanche photodiode type, or pin photodiode type instead of the semiconductor light receiving element 100 described above. .

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in this specification or the drawings can achieve a plurality of purposes at the same time, and has technical usefulness by achieving one of them.

Claims

The scope of the claims

[1] A laminated structure of a lower semiconductor clad layer, a semiconductor active layer, and an upper semiconductor clad layer. The band gap of the semiconductor active layer is either the band gap of the lower semiconductor clad layer or the band gap of the upper semiconductor clad layer. A semiconductor light emitting device characterized by being narrower and changing in the thickness direction.

[2] The semiconductor according to claim 1, wherein the energy level of the conduction band of the semiconductor active layer continuously changes in the thickness direction and has one minimum value at a substantially intermediate position in the thickness direction. Light emitting element.

[3] The lower semiconductor cladding layer, the semiconductor active layer, and the upper cladding layer are made of Al Ga In N (0≤X

X Υ 1 -Χ-Υ

3. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is formed using ≤ι, ο≤γ≤ι, ο≤ι—χ—γ≤ι) as a main material.

[4] The lower semiconductor cladding layer is made of GaN as the main material.

The semiconductor active layer is made of InGaN as the main material,

The upper semiconductor cladding layer is made of GaN as the main material,

4. The semiconductor light-emitting element according to claim 3, wherein the content of In in the semiconductor active layer is small in the middle and small in the upper side in the thickness direction.

[5] A semiconductor light-receiving layer comprising: a semiconductor light-receiving layer; one main electrode directly or indirectly in contact with the semiconductor light-receiving layer; and the other main electrode directly or indirectly in contact with the semiconductor light-receiving layer. A semiconductor light-receiving element characterized in that the gap changes in the thickness direction.

6. The semiconductor according to claim 5, wherein the energy level of the conduction band of the semiconductor light-receiving layer continuously changes in the thickness direction and has one minimum value at a substantially intermediate position in the thickness direction. Light receiving element.

[7] A method of manufacturing a semiconductor light emitting device or a semiconductor light receiving device,

A first half step of adjusting the band gap of the semiconductor active layer or the semiconductor light receiving layer to be gradually reduced toward the middle stage when the semiconductor active layer or the semiconductor light receiving layer is grown on the semiconductor layer;

The bandgap of the semiconductor active layer or semiconductor light-receiving layer from the middle to the final stage A manufacturing method characterized by comprising a second half step of adjusting the conditions so that the size of the substrate increases with time.

[8] In Ga N (0≤X≤1) is used as the main material for the semiconductor active layer or semiconductor light receiving layer.

X 1 -X

And

In the first half process, the initial stage force is adjusted to the condition that the In content in the crystal structure increases toward the middle stage,

8. The manufacturing method according to claim 7, wherein in the latter half process, the medium stage force is adjusted to a condition in which the content of In in the crystal structure decreases toward the final stage.

[9] In the first half step, the initial stage force is adjusted to the condition where the crystal growth temperature is lowered toward the middle stage,

9. The manufacturing method according to claim 8, wherein, in the latter half process, the medium-stage power is adjusted to a condition in which the crystal growth temperature increases toward the final stage.