JP2001156402A - Light-emitting semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting semiconductor device that has double hetero junction structure, high light emission efficiency, and a low operating voltage. SOLUTION: The light-emitting semiconductor device having a double hetero junction is provided with at least the sandwich structure of an n-type clad layer 4, an active layer 5, and a p-type clad layer 6 and is formed of a material that the band gap energy of the active layer is smaller than that of both the clad layers. The material of both clad layers is selected so that the band gap energy of the n-type clad layer becomes smaller than that of the p-type clad layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor light emitting device. More specifically, the present invention relates to a semiconductor light emitting device capable of emitting light with high luminance by lowering the operating voltage.

Here, a semiconductor light emitting device is a light emitting diode (hereinafter, referred to as an LED) having a double hetero junction such as a pn junction or a pin, a superluminescent diode (SLD), or a semiconductor laser diode (hereinafter, referred to as an LED).
LD).

[0003]

2. Description of the Related Art Conventionally, a blue LED has low luminance compared to red and green, and has been difficult to put into practical use. However, in recent years, a low-resistance p-type semiconductor layer using a gallium nitride compound semiconductor and Mg as a dopant has been used. As a result, the brightness has improved and the spotlight has been hit.

Here, the gallium nitride compound semiconductor is a compound of Ga of a group III element and N of a group V element or
A semiconductor comprising a group III element in which a part of Ga is substituted with another group III element such as Al or In and / or a compound in which a part of N of a group V element is substituted with another group V element such as P or As. Say.

A conventional LED using a gallium nitride compound semiconductor is manufactured as follows. FIG. 4 shows a perspective view of a completed gallium nitride compound semiconductor LED chip.

First, an organic metal compound and a carrier gas H ₂ are deposited on a substrate 21 made of sapphire (Al ₂ O ₃ single crystal) at a low temperature of 400 to 700 ° C. by a metal organic compound vapor phase epitaxy (hereinafter referred to as MOCVD). By supplying trimethylgallium (hereinafter, referred to as TMG) as a gas, ammonia (NH ₃ ), SiH ₄ as a dopant, and the like, a low-temperature buffer layer 22 composed of an n-type GaN layer is formed to a thickness of about 0.01 to 0.2 μm. Then 700-12
The same gas is supplied at a high temperature of 00 ° C. and the n-type Ga
A high-temperature buffer layer 23 made of N is formed in a thickness of about 2 to 5 μm.

Then, a source gas of trimethylaluminum (hereinafter referred to as TMA) is further added to the above-described gas into the reaction tube, and n-type Al _z G containing n-type dopant Si is added.
a _{1- z} N (0 <z ≦ 1) layer is formed, and the n-type cladding layer 2 is formed.
4 is formed in a thickness of about 0.1 to 0.3 μm.

Next, a material whose band gap energy becomes smaller than that of the cladding layer, for example, trimethylindium (hereinafter referred to as T
MI) and In _y Ga _1-y N (0 ≦ y ≦
The active layer 25 of 1) is formed in a thickness of about 0.05 to 0.1 μm.

Further, Mg or Zn as a p-type impurity is replaced by biscyclopentadienyl magnesium (hereinafter referred to as Cp ₂₎ instead of SiH ₄ with the same source gas as the gas used to form the n-type cladding layer 24. Mg)
Alternatively, it is added as dimethylzinc (hereinafter referred to as DMZn) and introduced into a reaction tube, and p-type A
An l _z Ga ₁ -zN layer is grown in vapor phase. Here, the reaction gas is supplied such that the Al composition ratio z becomes the same value as z of the n-type cladding layer 24 from the viewpoint of ease of manufacture. These n
A double hetero junction is formed by the mold cladding layer 24, the active layer 25, and the p-cladding layer 26.

Next, in order to form the cap layer 27, Cp ₂ Mg or DMZn is supplied as an impurity source gas with the same source gas as the buffer layer 23 described above, and a p-type GaN layer is grown to about 0.3 to 2 μm.

After that, a protective film is provided and heat treatment for annealing the p-type layer or electron beam irradiation is performed to activate the p-type cladding layer 26 and the cap layer 27.

Then, after removing the protective film, a resist is applied and patterned to form an n-side electrode, and a part of each grown semiconductor layer is removed by etching to form an n-type cladding layer. 24 or the buffer layer 23 is exposed.

Next, a metal film of Au, Al, or the like is formed by, for example, vapor deposition, sputtering, or the like to form both the p-side and n-side electrodes 29, 30, respectively.
LED chips are formed by dicing.

[0014]

In a conventional gallium nitride compound semiconductor, a double heterojunction semiconductor light emitting device has high luminous efficiency but high operating voltage. When a material having a small band gap energy is used for the n-type cladding layer and the p-type cladding layer in order to lower the operating voltage, that is, a material having a small Al composition ratio z of Al _z Ga ₁ -zN, the operating voltage is low. However, there is a problem that the outflow of electrons from the active layer to the p-type cladding layer increases, and the luminous efficiency decreases.

An object of the present invention is to provide a semiconductor light emitting device having a double hetero structure, which does not decrease the luminous efficiency and has a low operating voltage.

[0016]

The semiconductor light emitting device of the present invention has a sandwich structure in which an n-type cladding layer made of n-type AlGaN and a p-type cladding layer made of p-type AlGaN sandwich an active layer made of InGaN. And the Al of the n-type cladding layer
The ratio is reduced to less than half the Al ratio of the p-type cladding layer determined by the band gap energy of the active layer, and the band gap energy of the n-type cladding layer is different from the band gap energy of the active layer. The difference between the band gap energy of the p-type cladding layer and the band gap energy of the active layer is about 1/2. 2. The semiconductor light emitting device according to claim 1, wherein the n-type cladding layer is connected to an n-side electrode, and a buffer layer made of GaN is provided between the n-type cladding layer and the n-side electrode. Is interposed. Third of the present invention
The double heterojunction type semiconductor light-emitting device according to claim 1, wherein the semiconductor light-emitting device according to claim 1, wherein the n-type clad layer made of n-type AlGaN and the p-type clad layer made of p-type AlGaN are made of InG.
It has a sandwich structure sandwiching an active layer consisting of aN,
The Al ratio of the n-type cladding layer is reduced to be equal to or less than half of the Al ratio of the p-type cladding layer determined by the band gap energy of the active layer, and the band gap energy of the n-type cladding layer is reduced. The difference between the band gap energy of the p-type cladding layer and the band gap energy of the active layer is set to be about half the difference between the band gap energy and the band gap energy of the active layer, so that the injection of electrons into the active layer is reduced. In addition to being able to be performed with a voltage, by utilizing the fact that the effective mass of holes is larger than the effective mass of electrons, it is possible to prevent holes from leaking from the active layer to the n-type cladding layer, thereby reducing the reactive current. It is characterized in that it is not increased. The fourth semiconductor light emitting device of the present invention is the semiconductor light emitting device according to claim 3, wherein the n-type cladding layer is connected to an n-side electrode,
A buffer layer made of GaN is interposed between the side electrodes. A fifth double heterojunction light emitting diode of the present invention includes a substrate, a buffer layer made of n-type GaN provided on the substrate, and an n-type clad layer made of n-type AlGaN provided on the buffer layer. ,
An active layer made of InGaN provided on the n-type clad layer, and a p-type clad layer made of p-type AlGaN provided on the active layer, by reducing the Al ratio of the n-type clad layer, The ratio of the bandgap energy of the n-type cladding layer to the bandgap energy of the active layer is not more than half the Al ratio of the p-type cladding layer determined by the bandgap energy of the active layer.
The difference between the bandgap energy of the mold cladding layer and the bandgap energy of the active layer is reduced to about ２ so that injection of electrons into the active layer can be performed at a low voltage. By utilizing the fact that the effective mass of holes is larger than the effective mass of electrons, it is possible to prevent holes from leaking from the active layer to the n-type cladding layer, thereby preventing the reactive current from increasing. And A sixth semiconductor laser according to the present invention includes a substrate, a buffer layer made of an n-type GaN layer provided on the substrate, an n-type clad layer made of n-type AlGaN provided on the GaN layer, and
An active layer made of InGaN provided on the mold cladding layer,
A p-type clad layer provided on the active layer and made of p-type AlGaN; and a p-type GaN provided on the p-type clad layer.
And a cap layer comprising:
The ratio is reduced to an Al ratio determined by the band gap energy of the active layer, and the band gap energy of the n-type cladding layer is set to the band gap energy of the p-type cladding layer. And the band gap energy of the active layer is set to about 1/2 of the difference between them so that electrons can be injected into the active layer at a low voltage and the effective mass of holes is By utilizing the fact that the effective mass is larger than the effective mass of the active layer, leakage of holes from the active layer to the n-type cladding layer can be prevented, and the reactive current is not increased. According to a seventh aspect of the present invention, in the semiconductor laser according to the sixth aspect, the substrate is a sapphire substrate. An eighth semiconductor light emitting device according to the present invention has a sandwich structure in which an active layer made of InGaN is sandwiched between an n-type clad layer made of n-type AlGaN and a p-type clad layer made of p-type AlGaN. The band gap energy of the n-type cladding layer is reduced to such an extent that holes can be prevented from leaking to the n-type cladding layer so that electrons can be injected into the active layer at a low voltage. The Al ratio of the n-type cladding layer is reduced by a value determined by the band gap energy of the active layer so that the reactive current is not increased. The ninth semiconductor light emitting device of the present invention is the semiconductor light emitting device according to claim 8, wherein the n-type cladding layer is connected to an n-side electrode, and a buffer layer made of GaN is provided between the n-type cladding layer and the n-side electrode. Is interposed. A tenth semiconductor light emitting device according to the present invention is the semiconductor light emitting device according to claim 1, wherein the n-type A
An n-type cladding layer made of lGaN and a p-type cladding layer made of p-type AlGaN have a sandwich structure sandwiching an active layer made of InGaN, and reducing the Al ratio of the n-type cladding layer to form the active layer The bandgap energy of the n-type cladding layer is reduced so that the value is determined by the bandgap energy of the n-type cladding layer, so that electrons can be injected into the active layer at a low voltage and the effective mass of holes is reduced. By utilizing the fact that it is larger than the effective mass of electrons, it is possible to prevent holes from leaking from the active layer to the n-type cladding layer, so that the reactive current is not increased. An eleventh semiconductor light emitting device according to the present invention is the semiconductor light emitting device according to claim 10, wherein the n-type cladding layer is connected to an n-side electrode, and a buffer layer made of GaN is provided between the n-type cladding layer and the n-side electrode. Is interposed. A twelfth semiconductor laser according to the present invention includes:
-Type AlGaN n-type cladding layer and p-type AlGaN p-type
Having a sandwich structure sandwiching an active layer made of InGaN with the n-type cladding layer, reducing the Al ratio of the n-type cladding layer to an Al ratio determined by the bandgap energy of the active layer, By lowering the band gap energy of the cladding layer so that electrons can be injected into the active layer at a low voltage, and utilizing the fact that the effective mass of holes is larger than the effective mass of electrons, , The hole leakage to the n-type cladding layer can be prevented, the reactive current is not increased, and the thickness of the active layer is such that laser oscillation is possible. A thirteenth semiconductor laser according to the present invention, in the semiconductor laser according to claim 12, wherein the sandwich structure is provided on a substrate, and a buffer layer made of at least GaN is provided between the sandwich structure and the substrate. Become. A fourteenth semiconductor laser according to the present invention, in the semiconductor laser according to claim 12 or 13, wherein the sandwich structure is provided on a substrate, and a cap made of at least GaN is provided on a surface side of the sandwich structure opposite to the substrate. It is characterized in that a layer is provided. According to a fifteenth semiconductor laser of the present invention, in the semiconductor laser of claim 14, a part of the cap layer and the sandwich structure is etched to have a mesa shape. A sixteenth semiconductor light emitting device of the present invention has a sandwich structure in which an InGaN layer is sandwiched between an n-type AlGaN layer and a p-type AlGaN layer. The Al gap ratio of the p-type AlGaN layer determined by the band gap energy of the layer is equal to or less than half, and the band gap energy of the n-type AlGaN layer is different from the band gap energy of the InGaN layer. And said
The difference between the InGaN layer and the band gap energy of the InGaN layer is about 1/2. A seventeenth semiconductor light emitting device according to the present invention is the semiconductor light emitting device according to claim 16, wherein the n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is provided between the n-type AlGaN layer and the n-side electrode. Is interposed. An eighteenth semiconductor light emitting device of the present invention has a sandwich structure in which an AlGaN layer and a p-type AlGaN layer sandwich an InGaN layer, and reduce the Al ratio of the n-type AlGaN layer to reduce the Al ratio of the InGaN layer. The p-type AlGaN determined by band gap energy
The bandgap energy of the n-type AlGaN layer is less than half the Al ratio of the layer, and the difference between the bandgap energy of the InGaN layer and the bandgap energy of the p-type AlGaN layer is less than the bandgap energy of the InGaN layer. To be about 1/2 of that, so that the injection of electrons into the InGaN layer can be performed at a low voltage, and that the effective mass of holes is larger than the effective mass of electrons. It is characterized in that the leakage of holes from the InGaN layer to the n-type AlGaN layer can be prevented so that the reactive current is not increased. A nineteenth semiconductor light emitting device according to the present invention is the semiconductor light emitting device according to claim 18, wherein the n
The type AlGaN layer is connected to the n-side electrode, and a buffer layer made of GaN is interposed between the n-type electrode and the n-side electrode. A twentieth semiconductor diode according to the present invention includes: a substrate; an n-type buffer layer provided on the substrate, the n-type buffer layer including an n-type GaN layer; an n-type AlGaN layer provided on the n-type buffer layer; InGa provided on AlGaN layer
An N layer, and a p-type AlGaN layer provided on the InGaN layer, wherein the Al ratio of the n-type AlGaN layer is reduced,
The p-type determined by the band gap energy of the aN layer
The ratio of the bandgap energy of the n-type AlGaN layer to the bandgap energy of the p-type AlGaN layer and the bandgap energy of the InGaN layer is less than half the Al ratio of the AlGaN layer. The InGa is reduced so as to be about half the difference.
Injection of electrons into the N layer can be performed at a low voltage, and leakage of holes from the InGaN layer to the n-type AlGaN layer can be prevented by utilizing that the effective mass of holes is larger than the effective mass of electrons. It is characterized in that the reactive current is prevented from being increased by preventing the reactive current. A twenty-first semiconductor laser according to the present invention includes a substrate, a buffer layer made of n-type GaN provided on the substrate, and an n-type AlGaN provided on the buffer layer.
A layer, an InGaN layer provided on the n-type AlGaN layer,
a p-type AlGaN layer provided on the nGaN layer, and a cap layer made of p-type GaN provided on the p-type AlGaN layer,
By reducing the Al ratio of the n-type AlGaN layer to an Al ratio determined by the bandgap energy of the InGaN layer, the bandgap energy of the n-type AlGaN layer,
The difference from the band gap energy of the InGaN layer is p-type Al
The difference between the bandgap energy of the GaN layer and the bandgap energy of the InGaN layer is reduced to about １ ／ so that electrons can be injected into the InGaN layer at a low voltage. Using the fact that the effective mass of holes is larger than the effective mass of electrons, the n-type A
A semiconductor laser characterized in that leakage of holes to an lGaN layer can be prevented and reactive current is not increased. According to a twenty-second aspect of the present invention, in the semiconductor laser according to the twenty-first aspect, the substrate is a sapphire substrate. The twenty-third semiconductor light emitting device of the present invention has an n-type AlGaN layer and a sandwich structure with an In GaN layer interposed between a p-type AlGaN layer and holes from the InGaN layer to the n-type AlGaN layer. To the extent that leakage can be prevented, the bandgap energy of the n-type AlGaN layer is reduced, and the Al ratio of the n-type AlGaN layer is set so that electrons can be injected into the InGaN layer at a low voltage. The reactive current is reduced by a value determined by the band gap energy of the InGaN layer so as not to increase the reactive current. A twenty-fourth semiconductor light emitting device according to the present invention is directed to claim 23.
In the semiconductor light emitting device according to the above, the n-type AlGaN layer,
connected to the n-side electrode, and Ga
It is characterized in that a buffer layer made of N is interposed. A twenty-fifth semiconductor light emitting device of the present invention is an n-type AlG
aN layer, a sandwich structure sandwiching the In GaN layer between the p-type AlGaN layer, to reduce the Al ratio of the n-type AlGaN layer, so as to have a value determined by the band gap energy of the InGaN layer By lowering the bandgap energy of the n-type AlGaN layer so that electrons can be injected into the InGaN layer at a low voltage and utilizing the fact that the effective mass of holes is larger than the effective mass of electrons. Thus, leakage of holes from the InGaN layer to the n-type AlGaN layer can be prevented, and the reactive current is not increased. According to a twenty-sixth semiconductor light emitting device of the present invention,
The semiconductor light emitting device according to claim 5, wherein the n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type AlGaN layer and the n-side electrode. The twenty-seventh semiconductor light emitting device of the present invention is the semiconductor light emitting device according to claim 1, wherein the n-type AlGaN layer comprises:
It has a sandwich structure sandwiching an InGaN layer with a p-type AlGaN layer, reducing the Al ratio of the n-type AlGaN layer,
The Al ratio is determined by the band gap energy of the nGaN layer, and the band gap energy of the n-type AlGaN layer is lowered so that electrons can be injected into the InGaN layer at a low voltage, and the effective mass of holes is increased. Is larger than the effective mass of electrons by utilizing the n-type A from the InGaN layer.
It is characterized in that holes can be prevented from leaking to the lGaN layer, reactive current is not increased, and the thickness of the InGaN layer is such that laser oscillation is possible. A twenty-eighth semiconductor laser according to the present invention, in the semiconductor laser according to claim 27, wherein the sandwich structure is provided on a substrate, and a buffer layer made of at least GaN is provided between the sandwich structure and the substrate. Become. According to a twenty-ninth aspect of the present invention, there is provided a semiconductor laser comprising:
29. The semiconductor laser according to 28, wherein the sandwich structure is provided on a substrate, and at least GaN is provided on a surface side of the sandwich structure opposite to the substrate.
Characterized by being provided with a cap layer made of According to a thirtieth semiconductor light emitting device of the present invention, in the semiconductor light emitting device according to claim 29, a part of the cap layer and the sandwich structure is etched to have a mesa shape.

[0017]

Further, by providing a buffer layer made of GaN between one of the cladding layers and the substrate,
This is preferable because strain in the cladding layer can be reduced, crystal defects and dislocations in the cladding layer can be prevented, and the resistance of the semiconductor layer can be reduced.

According to the semiconductor light emitting device of the present invention, since a material having a smaller band gap energy than that of the p-type cladding layer is used for the n-type cladding layer, the injection of electrons from the n-type cladding layer to the active layer requires a low voltage. Is easily done with On the other hand, since the p-type cladding layer is made of a material having a large band gap energy as in the conventional case, the escape of electrons from the active layer to the p-type cladding layer is small, and the recombination of electrons and holes in the active layer is prevented. Contribute. Since holes have a larger effective mass than electrons, even if the band gap energy of the n-type cladding layer is small, holes injected into the active layer do not escape to the n-type cladding layer side. This contributes to recombination in the active layer without wasting holes, and the operating voltage can be reduced by the reduction of the band gap energy of the n-type cladding layer. I do.

The rate at which the band gap energy of the n-type cladding layer can be reduced is about 1/2 of the band gap energy difference between the p-type cladding layer and the active layer because the effective mass of holes is about three times that of electrons. And A
_{If the} lzGa1 _-zN material is used for the cladding layer, the ratio z of Al can be reduced to half or less of the ratio of Al in the p-type cladding layer, and the operating voltage can be reduced by 5 to 10%.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a semiconductor light emitting device according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an explanatory cross-sectional view of a semiconductor laser chip having a mesa shape, which is an embodiment of a semiconductor light emitting device of the present invention.
FIG. 2 is a manufacturing process diagram, and FIG. 3 is a schematic view of an energy band mainly showing a forbidden band of the n-type cladding layer, the active layer and the p-type cladding layer of the semiconductor light emitting device of the present invention.

In FIG. 1, reference numeral 1 denotes sapphire (Al ₂ O).
₃ in the substrate, such as single crystal), an n-type GaN, 0.0
A low-temperature buffer layer 2 of about 1 to 0.2 μm, an n-type GaN, a high-temperature buffer layer 3 of about 2 to 3 μm, an n-type material having a band gap energy (forbidden band width) smaller than that of a p-type cladding layer, for example, Al _x Ga _1-x N (0 ≦ x ≦
0.5, for example, x = 0.07), from 0.1 to
An n-type cladding layer 4 of about 0.3 μm, a non-doped or n-type or p-type material having a smaller band gap energy and a higher refractive index than both cladding layers, for example, In _y Ga _1-y N (0 ≦ y ≦ 1) consisting of 0.05
Active layer 5 of about 0.1 μm, p-type Al _z Ga ₁ -z N
(0 <z ≦ 1, 2x ≦ z, for example, z = 0.15), a p-type cladding layer of about 0.1 to 0.3 μm, p-type G
aN, a cap layer 7 having a thickness of about 0.3 to 2 μm is sequentially stacked, a p-side electrode 8 made of Au or the like is formed on the cap layer 7, and a part of the stacked semiconductor layer is removed by etching to expose a high-temperature buffer. An n-side electrode 9 made of Al or the like is formed on the layer 3, and a part of the cap layer 7 and the p-type cladding layer is etched to form a mesa shape to form a current stripe. Is formed.

In the semiconductor light emitting device of the present invention, the band gap energy of the n-type cladding layer 4 is smaller than the band gap energy of the p-type cladding layer 6 as shown in the above-described embodiment of the semiconductor laser. The cladding layers 4 and 6 and the active layer 5 are made of a material having a gap energy larger than the band gap energy of the active layer 5.
Is formed.

A double heterojunction structure in which an active layer 5 made of a material having a small bandgap energy is sandwiched by a cladding layer made of a material having a large bandgap energy in order to efficiently perform recombination of electrons and holes and increase luminous efficiency. Are used in semiconductor lasers and high-brightness LEDs. When a material with a large band gap energy is used for the cladding layer, the effect of confining electrons and holes increases, which contributes to light emission without waste. However, the operating voltage increases, and in fact, the leakage of electrons and holes from the active layer is ignored. A material having a bandgap energy that is as large as possible is selected. However, the operating voltage is higher than that of the pn junction. In the present invention, the operating voltage can be reduced while maintaining the leakage of the electrons and holes to a negligible level. That is, the effective mass of holes is as large as about three times the effective mass of electrons, and leakage is smaller than that of electrons even if the band gap energy is small. Therefore, by using a material having a bandgap energy smaller than the bandgap energy of the p-type cladding layer for the n-type cladding layer, electrons can be injected into the active layer at a low voltage, thereby preventing holes from leaking from the active layer. It is made possible.

The operation of the present invention will be described in detail with reference to FIG. 3, which is a schematic diagram showing the energy band diagram of the semiconductor laser shown in FIG. In FIG. 3, V indicates a valence band, F indicates a forbidden band, C indicates an energy band of a conduction band, and A indicates n.
High-temperature buffer layer 3 made of n-type GaN, B is n-type Al _0.07
An n-type cladding layer 4 made of Ga _0.93 N, where D is In _y Ga
_The active layer 5 made of _1-yN , G shows a p-type cladding layer made of Al _0.15 Ga _0.85 N, and J shows an energy band of a cap layer 7 made of p-type GaN.

In the semiconductor laser of this embodiment, as shown in FIG. 3, the band gap energy of the n-type cladding layer indicated by B is smaller than the band gap energy of the p-type cladding layer indicated by G. . Broken line B1
Indicates the case of the same band gap energy as that of the p-type cladding layer in the conventional structure.

In this configuration, when a voltage is applied between the p-side electrode 8 and the n-side electrode 9, the electrons E flow from the n-type GaN (high-temperature buffer layer A) side to the p-side, and the conduction band of the active layer K ₁
Flows into. Since the band gap energy of the time n-type clad layer is low, electrons E is easy to flow into the conduction band K ₁ of the active layer, the electron in the active layer is supplied at a low voltage.
The electrons E that flows in the conduction band K ₁ of the active layer is pulled to the p-side electrode, since the band gap energy of the p-type cladding layer is large, confined in the active layer. On the other hand, the holes H flow from the p-type GaN (contact layer J) side to the n-side and flow into the valence band K ₂ of the active layer. The holes H flowing into the valence band K ₂ of the active layer are pulled by the n-side electrode, but the effective mass of the holes H is as large as about three times the effective mass of the electrons, and the band gap of the n-type cladding layer B is large. Even if the energy is low, it cannot be overcome and is effectively confined within the valence band of the active layer. As a result, electrons and holes are efficiently recombined in the active layer, and high luminous efficiency is obtained.

As described above, according to the present invention, each semiconductor layer is selected so that the band gap energy of the n-type cladding layer is smaller than that of the p-type cladding layer. The electron injection can be performed, and the luminous efficiency can be improved without increasing the reactive current. The extent to which the bandgap energy of the n-type cladding layer is smaller than that of the p-type cladding layer is determined by the bandgap energy of the active layer, and the difference in bandgap energy from the active layer is 1/3 to 1 of that in the case of the p-type layer. It may be set to be about / 2 lower.

The general formula Al _p Ga _q In _1-pq N (0 ≦ p
<1, 0 <q ≦ 1, 0 <p + q ≦ 1) In order to reduce the band gap energy using a gallium nitride-based compound semiconductor, p is reduced, that is, the composition ratio of Al is reduced, or p + q is reduced. It can be obtained by making it small, that is, by increasing the composition ratio of In. Therefore, by adjusting the composition ratio of Al and In so that the band gap energy of the cladding layer is larger than that of the active layer and the band gap energy of the n-type cladding layer is smaller than that of the p-type cladding layer, A semiconductor layer having a band gap energy of

Further, since the embodiment shown in FIG. 1 is a semiconductor laser, it is necessary to confine light in the active layer and oscillate, and the refractive index of the cladding layer is made smaller than that of the active layer. In the case of an LED, it is not always necessary. However, when the Al composition ratio is increased in the above composition ratio, the refractive index decreases.

Next, a method of manufacturing the semiconductor laser shown in FIG. 1 will be described with reference to FIG.

First, as shown in FIG. 2A, a low-temperature buffer layer 2 made of, for example, a gallium nitride-based compound semiconductor such as n-type GaN is deposited on a substrate 1 made of sapphire or the like by the MOCVD method in a range of 0.01 to 0.01. A high-temperature buffer layer 3 made of n-type GaN having the same composition at a high temperature of about 700 to 1200 ° C.
Degree formed.

Next, TMI is further supplied to, for example, n-type Al _x Ga ₁ -xN (0 ≦ x ≦ 0.5, for example, x
= 0.07).
It is formed about 3 μm. Then, instead of TMA, TMI
To supply undoped or n-type or p-type In _y G
An active layer 5 made of a _1-y N (0 ≦ y ≦ 1, for example, y = 0.06) is grown to a thickness of about 0.05 to 0.1 μm. Then, using the same source gas as that used for forming the n-type cladding layer 4, TMA was applied to the n-type cladding layer 4.
A p-type cladding layer 6 is supplied to the reaction tube at a flow rate of 20~100sccm about fold in the case of p-type Al _z Ga
_1-z N (0 <z ≦ 1, 2x ≦ z, for example, z = 0.1
5) Form a layer of about 0.1 to 0.3 μm. Further, the same source gas as that for forming the buffer layer 3 is supplied to supply p-type GaN.
Is formed to a thickness of 0.3 to 2 μm.

In order to form the buffer layer 3 and the cladding layer 4 to be n-type, Si, Ge, and Te are converted to SiH ₄ , G
In order to form the clad layer 6 and the cap layer 7 into p-type by mixing them into the reaction gas as impurity source gases such as eH ₄ and TeH ₄ , Mg or Zn is converted into an organic metal gas such as Cp ₂ Mg or DMZn. Mix in gas. However, in the case of n-type, even if impurities are not mixed, N is easily evaporated at the time of film formation and naturally becomes n-type.

Thereafter, a protective film 10 such as SiO ₂ or Si ₃ N ₄ is provided on the entire surface of the growth layer of the semiconductor layer (FIG. 2B).
Annealing is performed at 400 to 800 ° C. for about 20 to 60 minutes to activate the p-type clad layer 6 and the cap layer 7 which are p-type layers.

When the annealing is completed, as shown in FIG. 2 (c), a mask such as a resist film 11 is provided, and the layers are stacked until the n-type cladding layer 4 or the n-type high temperature buffer layer 3 is exposed. Etch the semiconductor layer. This etching is performed by, for example, reactive ion etching under an atmosphere of a mixed gas of Cl ₂ and BCl ₃ .

Next, a metal film of Au, Al, or the like is formed by sputtering or the like, and the p-side electrode 8 electrically connected to the p-type layer on the surface of the laminated compound semiconductor layer and the exposed surface of the high-temperature buffer layer 3 An n-side electrode 9 electrically connected to the n-type layer is formed, and a portion of the cap layer 7 and a part of the p-type cladding layer 6 are mesa-etched (see FIG. 1).

Next, dicing is performed on each chip to form a semiconductor laser chip.

In the above embodiment, a semiconductor laser having a mesa-shaped current stripe structure has been described. However, a semiconductor laser having various structures such as a current limiting layer embedded type or a gallium nitride compound semiconductor such as an LED having a double hetero junction structure. The present invention can also be applied to a semiconductor light emitting device using a.
Further semiconductor material is not limited to the material of Example composition, the _{Al p Ga q In 1-pq} N of some or all substituted with such as As and / or P materials and gallium arsenide-based compound semiconductor N The present invention can be similarly applied to a semiconductor light-emitting device using the same.

[0041]

According to the semiconductor light emitting device of the present invention, the semiconductor material is selected so that the band gap energy of the n-type cladding layer is smaller than the band gap energy of the p-type cladding layer. Less,
In addition, high-luminance light can be emitted at a low operating voltage, and a semiconductor light-emitting element with high luminous efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of one embodiment of a semiconductor light emitting device of the present invention.

FIG. 2 is an explanatory sectional view showing the manufacturing process of FIG. 1;

FIG. 3 is an energy band diagram mainly showing a forbidden band of a cladding layer and an active layer in one embodiment of the semiconductor light emitting device of the present invention.

FIG. 4 is a perspective view showing an example of a conventional semiconductor light emitting device.

[Explanation of symbols]

 Reference Signs List 1 substrate 4 n-type cladding layer 5 active layer 6 p-type cladding layer

Claims (30)

[Claims] 1. An n-type cladding layer made of n-type AlGaN and a p-type A
a p-type cladding layer made of lGaN, having a sandwich structure sandwiching an active layer made of InGaN, reducing the Al ratio of the n-type cladding layer, and forming the p-type cladding determined by the band gap energy of the active layer. The bandgap energy of the n-type cladding layer is less than half the Al ratio of the layer, and the difference between the bandgap energy of the active layer is the difference between the bandgap energy of the p-type cladding layer and the bandgap energy of the active layer. 1 /
A double-heterojunction semiconductor light-emitting device characterized in that it is configured to be about two. 2. The n-type cladding layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type cladding layer and the n-side electrode.
The semiconductor light-emitting device according to claim 1. 3. An n-type cladding layer made of n-type AlGaN and a p-type Al
A p-type cladding layer made of GaN, having a sandwich structure sandwiching an active layer made of InGaN, reducing the Al ratio of the n-type cladding layer, and forming the p-type cladding determined by the band gap energy of the active layer. The bandgap energy of the n-type cladding layer is less than half the Al ratio of the layer, and the difference between the bandgap energy of the active layer is the difference between the bandgap energy of the p-type cladding layer and the bandgap energy of the active layer. 1 /
It is lowered to about 2 so that electrons can be injected into the active layer at a low voltage, and from the active layer utilizing the fact that the effective mass of holes is larger than the effective mass of electrons. A double heterojunction semiconductor light emitting device, characterized in that holes can be prevented from leaking to the n-type cladding layer and reactive current is not increased. 4. The n-type cladding layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type cladding layer and the n-side electrode.
The semiconductor light-emitting device according to claim 1. 5. A substrate, a buffer layer made of n-type GaN provided on the substrate, and n provided on the buffer layer.
An n-type cladding layer made of n-type AlGaN, an active layer made of InGaN provided on the n-type cladding layer, and a p-type cladding layer made of p-type AlGaN provided on the active layer, wherein the n-type The p ratio determined by the band gap energy of the active layer by reducing the Al ratio of the cladding layer.
The band gap energy of the n-type cladding layer, the band gap energy of the active layer is the difference between the band gap energy of the p-type cladding layer and the band gap energy of the active layer. So that it is about 1/2 of the difference between
Injection of electrons into the active layer can be performed at a low voltage, and leakage of holes from the active layer to the n-type cladding layer by utilizing that the effective mass of holes is larger than the effective mass of electrons. A double hetero-junction type light emitting diode in which a reactive current is prevented from increasing and a reactive current is not increased. 6. A substrate, a buffer layer comprising an n-type GaN layer provided on the substrate, and an n-type Al layer provided on the GaN layer.
An n-type cladding layer made of GaN, an active layer made of InGaN provided on the n-type cladding layer, a p-type cladding layer made of p-type AlGaN provided on the active layer, and the p-type cladding layer A cap layer made of p-type GaN provided thereon, and reducing the Al ratio of the n-type cladding layer to an Al ratio determined by the band gap energy of the active layer; The difference between the band gap energy of the active layer and the gap energy of the active layer is １ ／ of the difference between the band gap energy of the p-type cladding layer and the band gap energy of the active layer.
So that the electron injection into the active layer can be performed at a low voltage, and by utilizing the fact that the effective mass of holes is larger than the effective mass of electrons, A semiconductor laser characterized in that leakage of holes to an n-type cladding layer can be prevented and reactive current is not increased. 7. The semiconductor laser according to claim 6, wherein said substrate is a sapphire substrate. 8. An n-type cladding layer made of n-type AlGaN, and a p-type A
It has a sandwich structure in which an active layer made of InGaN is sandwiched by a p-type clad layer made of lGaN, and the n-type is formed to such an extent that holes can be prevented from leaking from the active layer to the n-type clad layer. The Al ratio of the n-type cladding layer is reduced by a value determined by the band gap energy of the active layer so that the band gap energy of the cladding layer is reduced so that electrons can be injected into the active layer at a low voltage. Wherein the reactive current is not increased. 9. The n-type cladding layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type cladding layer and the n-side electrode.
The semiconductor light-emitting device according to claim 1. 10. An n-type cladding layer made of n-type AlGaN,
A sandwich structure in which an active layer made of InGaN is sandwiched between a p-type clad layer made of n-type AlGaN and an Al ratio of the n-type clad layer so as to have a value determined by the band gap energy of the active layer. In addition, the band gap energy of the n-type cladding layer is reduced so that electrons can be injected into the active layer at a low voltage, and the effective mass of holes is larger than the effective mass of electrons. A semiconductor light-emitting device characterized by preventing holes from leaking from the active layer to the n-type cladding layer so as not to increase reactive current. 11. The n-type clad layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type clad layer and the n-side electrode. Semiconductor light emitting device. 12. An n-type cladding layer made of n-type AlGaN,
Having a sandwich structure sandwiching an active layer made of InGaN with a p-type cladding layer made of AlGaN, reducing the Al ratio of the n-type cladding layer, and determining the Al ratio determined by the band gap energy of the active layer. And lowering the band gap energy of the n-type cladding layer,
Injection of electrons into the active layer can be performed at a low voltage, and leakage of holes from the active layer to the n-type cladding layer by utilizing that the effective mass of holes is larger than the effective mass of electrons. A semiconductor laser characterized in that the reactive current is prevented from increasing, the reactive current is not increased, and the thickness of the active layer is such that laser oscillation is possible. 13. The semiconductor laser according to claim 12, wherein said sandwich structure is provided on a substrate, and a buffer layer made of at least GaN is provided between said sandwich structure and said substrate. 14. The semiconductor laser according to claim 12, wherein said sandwich structure is provided on a substrate, and a cap layer made of at least GaN is provided on a surface side of said sandwich structure opposite to said substrate. 15. The semiconductor laser according to claim 14, wherein a part of said cap layer and said sandwich structure is etched to form a mesa. 16. An n-type AlGaN layer and a p-type AlGaN layer comprising InGaN
Having a sandwich structure sandwiching the layers, wherein the n-type AlGaN
By reducing the Al ratio of the layer, to less than half the Al ratio of the p-type AlGaN layer determined by the band gap energy of the InGaN layer, the band gap energy of the n-type AlGaN layer, the band gap energy of the InGaN layer and Is 1/2 of the difference between the bandgap energy of the p-type AlGaN layer and the bandgap energy of the InGaN layer.
A double-heterojunction type semiconductor light-emitting device characterized in that it is configured to have the same size. 17. The semiconductor device according to claim 1, wherein the n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type AlGaN layer and the n-side electrode.
7. The semiconductor light emitting device according to item 6. 18. An n-type AlGaN layer and a p-type AlGaN layer comprising InGaN
Having a sandwich structure sandwiching the layers, wherein the n-type AlGaN
By reducing the Al ratio of the layer, to less than half the Al ratio of the p-type AlGaN layer determined by the band gap energy of the InGaN layer, the band gap energy of the n-type AlGaN layer, the band gap energy of the InGaN layer and Is 1/2 of the difference between the bandgap energy of the p-type AlGaN layer and the bandgap energy of the InGaN layer.
In order to make it possible to inject electrons into the InGaN layer at a low voltage, and to make use of the fact that the effective mass of holes is larger than the effective mass of electrons,
A double heterojunction semiconductor light emitting device, characterized in that holes can be prevented from leaking from the layer to the n-type AlGaN layer so that the reactive current is not increased. 19. The n-type AlGaN layer is connected to an n-side electrode, and a buffer layer of GaN is interposed between the n-type AlGaN layer and the n-side electrode.
9. The semiconductor light emitting device according to 8. 20. A substrate, and n-type GaN provided on the substrate.
N-type buffer layer comprising a layer, an n-type AlGaN layer provided on the n-type buffer layer, and provided on the n-type AlGaN layer
An InGaN layer, and a p-type AlGaN layer provided on the InGaN layer, the Al ratio of the n-type AlGaN layer is reduced,
The above p determined by the band gap energy of the nGaN layer
The bandgap energy of the n-type AlGaN layer, the difference between the bandgap energy of the InGaN layer and the bandgap energy of the p-type AlGaN layer and the bandgap energy of the InGaN layer are set to be equal to or less than half the Al ratio of the AlGaN layer. To be about 1/2 of the difference between
The injection of electrons into the GaN layer can be performed at a low voltage, and the leakage of holes from the InGaN layer to the n-type AlGaN layer can be prevented by utilizing that the effective mass of holes is larger than the effective mass of electrons. A double-heterojunction type light-emitting diode that can be prevented from increasing reactive current. 21. A substrate, and an n-type GaN provided on the substrate
A buffer layer consisting of:
an n-type AlGaN layer, an InGaN layer provided on the n-type AlGaN layer, a p-type AlGaN layer provided on the InGaN layer, and the p-type
A cap layer made of p-type GaN provided on the AlGaN layer, and reducing the Al ratio of the n-type AlGaN layer,
The Al ratio determined by the band gap energy of the InGaN layer, the band gap energy of the n-type AlGaN layer, the difference between the band gap energy of the InGaN layer and the band gap energy of the p-type AlGaN layer and the In gap
It is lowered so as to be about half the difference from the band gap energy of the GaN layer so that the injection of electrons into the InGaN layer can be performed at a low voltage and the effective mass of holes is reduced to the effective mass of electrons. A semiconductor laser characterized by preventing leakage of holes from the InGaN layer to the n-type AlGaN layer by utilizing the fact that the mass is larger than the mass, so as not to increase the reactive current. 22. The semiconductor laser according to claim 21, wherein said substrate is a sapphire substrate. 23. An InGaN having an n-type AlGaN layer and a p-type AlGaN layer
The n-type AlGaN layer has a sandwich structure sandwiching the layers, and the band gap energy of the n-type AlGaN layer is reduced to an extent that holes can be prevented from leaking from the InGaN layer to the n-type AlGaN layer. The Al ratio of the n-type AlGaN layer is adjusted to the I ratio so that the implantation into the InGaN layer can be performed at a low voltage.
A semiconductor light emitting device wherein the reactive current is reduced by a value determined by the band gap energy of the nGaN layer so as not to increase. 24. The n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type AlGaN layer and the n-side electrode.
4. The semiconductor light emitting device according to 3. 25. An InGaN having an n-type AlGaN layer and a p-type AlGaN layer
Having a sandwich structure sandwiching the layers, wherein the n-type AlGaN
The n-type so that the Al ratio of the layer is reduced to a value determined by the band gap energy of the InGaN layer.
By lowering the band gap energy of the AlGaN layer,
The electron injection into the nGaN layer can be performed at a low voltage, and the leakage of holes from the InGaN layer to the n-type AlGaN layer can be prevented by utilizing that the effective mass of holes is larger than the effective mass of electrons. A semiconductor light emitting device characterized in that the reactive current can be prevented so as not to increase the reactive current. 26. The n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type AlGaN layer and the n-side electrode.
6. The semiconductor light emitting device according to 5. 27. A sandwich structure in which an InGaN layer is sandwiched between an n-type AlGaN layer and a p-type AlGaN layer, wherein the Al ratio of the n-type AlGaN layer is reduced and determined by the band gap energy of the InGaN layer. Al ratio, the n-type AlGa
By lowering the bandgap energy of the N layer, the InG
The electron injection into the aN layer is performed at a low voltage, and the leakage of holes from the InGaN layer to the n-type AlGaN layer is performed by utilizing that the effective mass of holes is larger than the effective mass of electrons. A semiconductor laser characterized in that the thickness of the InGaN layer is such that laser oscillation can be prevented while preventing reactive current from increasing. 28. The semiconductor laser according to claim 27, wherein said sandwich structure is provided on a substrate, and a buffer layer made of at least GaN is provided between said sandwich structure and said substrate. 29. The semiconductor laser according to claim 27, wherein said sandwich structure is provided on a substrate, and a cap layer made of at least GaN is provided on a surface side of said sandwich structure opposite to said substrate. 30. The semiconductor laser according to claim 29, wherein a part of said cap layer and said sandwich structure is etched to form a mesa.