JPH1041549A - Light emitting element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device using a known gallium nitride compound semiconductor, which can avoid reduction of throughput and deterioration of a grown layer caused by formation of an undoped single crystalline GaN layer, for the purpose of improving the crystallization of a high- concentration N type layer under an active layer. SOLUTION: A light emitting element includes gallium nitride compound semiconductor layers 12 to 14 of an N type formed on a substrate 11, and a gallium nitride compound semiconductor layer 16 of a P type formed above the N type layers. The N type gallium nitride compound semiconductor layers include a region 13 in which an impurity concentration increases gradually from the substrate side according to the film thickness. In the method for fabricating the light emitting element, the gallium primary nitride compound semiconductor layer 12 is formed on the substrate in a reaction chamber, a silane gas as the doping gas is introduced onto the gallium primary nitride compound semiconductor layer to form the gallium secondary nitride compound semiconductor layer 13 doped with N type impurity, by changing the amount of silane gas introduced into the reaction chamber to increase its impurity concentration gradually from its substrate side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device and a method of manufacturing the same, and more particularly, to a structure of a light emitting device such as a light emitting diode and a semiconductor laser and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, practical materials for light emitting devices include gallium nitride (GaN), indium gallium nitride (InGaN), and gallium aluminum nitride (GaAl).
Gallium nitride-based compound semiconductors such as N) are known.

As an example of a light-emitting device manufactured using these materials, a structure of a conventional light-emitting diode, a method of manufacturing the same, and problems will be described with reference to FIGS.

FIG. 7A is a cross-sectional view of a light emitting diode having a heterogeneous heterojunction in which a plurality of growth layers are formed by epitaxial growth. FIG. 7 (b) is the same as FIG.
7 shows the profile of the N-type impurity in the light emitting diode shown in FIG. 7, the horizontal axis shows the impurity concentration of the N-type impurity, and the vertical axis shows the distance from the lower surface of the substrate, corresponding to FIG. ing.

As shown in FIG. 7A, a conventional light emitting diode has a buffer layer 112 (first GaN layer) made of amorphous GaN and a single crystal GaN layer on a substrate 111 made of sapphire, SiC or the like. Spacer layer 113 made of
(Second GaN layer), high-concentration N-type layer 114 (third GaN layer) heavily doped with N-type impurities, active layer 115 (InGaN layer) made of InGaN, AlGaN layer doped with P-type impurities 116, a contact layer made of GaN heavily doped with P-type impurities (fourth GaN
Each of the growth layers (layer) 117 is configured as a stacked layer.

[0006] The impurity concentration of the N-type impurity in the third GaN layer is about 1 to 5 × 10 ¹⁸ atoms · cm ^-3 ,
In the other layers, the impurity concentration of the N-type impurity is about 1 × 10 ¹⁵ atoms · cm ⁻³ which is the background level. Each of these growth layers can be formed by MO-CVD (MatalOrg) by changing the type and temperature of the gas to be introduced.
It is formed by a vapor phase growth method such as an anic-Chemical Vapor Deposition method. In the above configuration, the third GaN
After forming the second GaN layer 113 by introducing hydrogen as a carrier gas and ammonia (NH ₃ ) and TMGa (trimethylgallium) as a source gas in a reaction chamber at a temperature of about 1000 to 1100 degrees Celsius,
Subsequently, SiH ₄ (silane gas) is further supplied while the above-mentioned gas is introduced, so that an N-type impurity is doped at a high concentration. The thickness of the second GaN layer is 0.01 μm or more, and the thickness of the third GaN layer is 0.1 μm.
It is desirable to form with.

Incidentally, the second GaN layer 113 is not originally a layer that is functionally necessary. That is, if a third GaN layer heavily doped with an N-type impurity is formed on the first GaN layer formed as a buffer layer, a desired operation as a light emitting element is achieved. However, when a high-concentration single-crystal GaN layer is to be formed on the surface of a non-crystalline GaN layer, for example, FIG.
As shown in (b), on the surface of the first GaN layer 112,
A pinhole 211 occurs, or G
Abnormal growth 212 of the aN layer may occur. Therefore, in the conventional light emitting diode, a single crystal second GaN layer 113 is formed on the surface of the first GaN layer 112 as a spacer layer, and then a fourth GaN layer 114 heavily doped with N-type impurities is formed. Has formed.

[0008]

As described above, in a conventional semiconductor device using a gallium nitride-based compound semiconductor, when forming a high-concentration N-type layer under an active layer functioning as a light emitting layer, the crystal is In order to improve the performance, an undoped single-crystal GaN layer is previously formed as a spacer layer on the lower surface thereof. MO-C is used for forming each of these growth layers.
Although a vapor phase growth method such as a VD method is used, the growth rate is slow, and a layer that is originally not functionally necessary is formed, so that the throughput is reduced. Further, by forming a layer that is not functionally necessary, the overall thickness of the light emitting element also increases. When the film thickness is large, the amount of strain of each growth layer increases due to lattice non-bonding, and the functionally necessary growth layer is deteriorated.

Accordingly, the present invention has been made in view of the above problems, and provides a novel manufacturing method and a manufacturing method for improving the throughput and quality when manufacturing a light emitting device using a gallium nitride-based compound semiconductor. The purpose is to do.

[0010]

According to the light emitting device of the present invention, an N-type gallium nitride compound semiconductor layer formed on a substrate and the N-type gallium nitride compound semiconductor layer formed on the N-type gallium nitride compound semiconductor layer are formed. And a P-type gallium nitride-based compound semiconductor layer, wherein the N-type gallium nitride-based compound semiconductor layer has a region where the impurity concentration increases from the substrate side in accordance with the film thickness.

Further, according to the light emitting device of the present invention,
A substrate, a first N-type gallium nitride-based compound semiconductor layer formed on the substrate by increasing an impurity concentration of the first N-type impurity to an impurity concentration of the second N-type impurity, and A second N-type gallium nitride-based compound semiconductor layer formed on the first N-type gallium nitride-based compound semiconductor layer and having an impurity concentration of the N-type gallium nitride-based compound semiconductor layer; P-type gallium nitride-based semiconductor layer.

[0012] The change in the impurity concentration of the N-type impurity in the first N-type gallium nitride-based compound semiconductor layer changes in any of an exponential, linear, saturation curve, and stepwise manner according to the film thickness. Is preferred.

The impurity concentration of the first and second N-type impurities is 1 × 10 ¹³ atoms · cm ^{−3 to} 1 × 10 ²³ atoms · cm.
^-3 , and the thickness of the first N-type gallium nitride-based compound semiconductor layer is preferably in the range of 0.01 to 2.00 μm.

Further, the light emitting device according to the present invention comprises a substrate, a first N-type gallium nitride-based compound semiconductor layer formed on the substrate surface and having a first impurity concentration, and the first N-type gallium nitride-based compound semiconductor layer. Formed on the surface of the compound semiconductor layer,
A second N-type gallium nitride-based compound semiconductor layer that increases from the first impurity concentration to a second impurity concentration according to a film thickness, and is formed on the surface of the second N-type gallium nitride-based compound semiconductor layer; A third N-type gallium nitride-based compound semiconductor layer having a second impurity concentration; and a P-type gallium nitride-based compound semiconductor layer formed on the third N-type gallium nitride-based compound semiconductor layer. I do.

Further, a light emitting device according to the present invention is formed by a substrate and an epitaxial growth on the substrate,
It has a first growth layer formed by increasing the impurity concentration from the substrate side, and a second growth layer formed by epitaxial growth on the first growth layer and having a heterogeneous heterojunction.

The light emitting device according to the present invention has at least one P-type gallium nitride compound semiconductor layer formed on a substrate, and the P-type gallium nitride compound semiconductor layer has an impurity concentration of a film thickness. Characterized by having a region that increases from the substrate according to.

Further, the light-emitting device according to the present invention may further comprise a substrate and a light-emitting element on the substrate which increases from the first P-type impurity concentration to the second P-type impurity concentration and increases to the second P-type impurity concentration. A first P-type gallium nitride-based compound semiconductor layer formed on the first P-type gallium nitride-based compound semiconductor layer having an impurity concentration of the second P-type impurity; A light-emitting element comprising a gallium nitride-based compound semiconductor layer.

It is preferable that the impurity concentration of the P-type impurity in the first P-type gallium nitride based compound semiconductor layer changes linearly, exponentially, in a saturation curve, or in a step-like manner in accordance with the film thickness. The first and second P-type impurity concentrations are 1
The thickness is in the range of × 10 ¹³ to 1 × 10 ²³ , and the thickness of the first P-type gallium nitride-based compound semiconductor layer is preferably in the range of 0.01 to 2.00 μm.

According to the method of manufacturing a light emitting device of the present invention, a step of forming a first gallium nitride-based compound semiconductor layer on a substrate in a reaction chamber; A silane gas is introduced as the doping gas, and the second N
Forming a gallium nitride-based compound semiconductor layer, and changing the flow rate of silane gas used as soil in the reaction chamber to reduce the impurity concentration of the second N-type gallium nitride-based compound semiconductor layer. It is characterized by being formed increasing from the substrate side.

With the above structure, the throughput required for manufacturing the light emitting device can be improved, an increase in the amount of strain due to lattice non-bonding in the light emitting device can be prevented, and the deterioration of the growth layer can be prevented.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure of a light emitting device according to the present invention will be described with reference to FIG. FIG. 1A is a cross-sectional view of a light emitting diode having a heterojunction in which a plurality of growth layers are formed by epitaxial growth. FIG.
(B) shows N in the light emitting diode shown in FIG.
The horizontal axis indicates the impurity concentration of the N-type impurity, and the horizontal axis indicates the distance from the lower surface of the substrate, corresponding to FIG.

In the light emitting diode of the present invention, a film thickness of 0.01 μm to 2.00 is formed on the surface of the substrate 11 made of sapphire.
a buffer layer 12 (first GaN layer) made of amorphous GaN having a thickness of about μm, a thickness of about 0.01 μm to 0.05 μm,
The N-type modulation doped layer 13 (for convenience, this increases the impurity concentration of the N-type impurity from the background level to a desired impurity concentration, for example, from about 1 × 10 ¹³ atoms · cm ⁻³ to 1 × 10 ²³ atoms · cm ^−3). Is referred to as a second GaN layer.),
A high-concentration N-type layer 14 (third GaN layer) having a thickness of 0.01 μm or more and an N-type impurity having a desired impurity concentration, for example, about 1 × 10 ²³ atoms · cm ⁻³ ;
The active layer 15 (InG) made of 0.03 μm InGaN
aN layer), an AlGaN layer 16 doped with a P-type impurity having a thickness of 0.1 μm to 0.3 μm, and a contact layer (fourth layer) made of GaN doped with a high concentration of P-type impurity having a thickness of 0.05 μm or more. A stack of GaN layers 17 is formed.

The film thickness and impurity concentration of each film described above are not limited to only the above values, and particularly, the third G
The impurity concentration of the aN layer may be in the range of about 1 × 10 ¹³ atoms · cm ⁻³ or more to 1 × 10 ²³ atoms · cm ⁻³ or less.
At the same time, the impurity concentration of the third GaN layer may be changed from the impurity concentration of the first GaN layer to the impurity concentration of the third GaN layer.

Here, the structure different from the conventional light emitting device is that an N-type modulation doped layer 13 is formed instead of the conventionally formed spacer layer (second GaN layer), and a high concentration N The point is that the mold layer 14 is formed. That is, according to the present invention, the impurity concentration of the N-type impurity is gradually increased from the surface of the buffer layer to the N-type layer necessary for the operation from the surface of the buffer layer without forming a layer that is not functionally necessary. Formed.

The impurity concentration of the N-type impurity in the third GaN layer is about 1 × 10 ¹⁸ atoms · cm ⁻³ ,
In the N layer, the background level on the substrate side, the third GaN
On the layer side, the impurity concentration is increased so as to be about 1 × 10 ¹⁸ atoms · cm ⁻³ . Various modes can be considered for the change in the impurity concentration of the N-type impurity. These aspects will be described with reference to FIG. In FIG. 2, the horizontal axis mainly represents the distance from the second GaN layer substrate side (the range indicated by 14 in the figure), and the vertical axis represents the impurity concentration.

The change in the impurity concentration is preferably formed by an exponential change such as a gentle change on the substrate side and a large change on the third GaN layer side as shown by the curve (A).
This is because the N-type modulation doped layer grown on the surface of the first GaN layer needs a finite thickness that does not generate pinholes, and the N-type modulation doped layer is formed to a thickness that does not generate pinholes.
This is because the type modulation doped layer grows stably even if the impurity concentration is gradually increased thereafter. Embodiment 2 A second embodiment of the present invention will be described with reference to the line (B) in FIG. As shown by the line (B), the N-type modulation doped layer increases linearly from the substrate side to the impurity concentration of the third N-type GaN layer. By performing such a modulation doping method, it is possible to reduce fluctuations in the growth rate and the doping efficiency.

For example, a change in the gas supply system / gas type that occurs when the doping gas is supplied causes minute fluctuations such as immediately before reaching the substrate or cooling of the atmospheric gas on the substrate. Here, when the doping gas is changed linearly, the temperature control catches up, and the growth temperature is kept constant. Therefore, fluctuations in the growth rate and the doping efficiency due to the temperature are reduced. Embodiment 3 A third embodiment of the present invention will be described with reference to the line (C) in FIG. As shown by the line (C), the N-type modulation doped layer is stepwise increased from the substrate side to increase the third N-type Ga.
It is formed up to the impurity concentration of the N layer. When such modulation doping is performed, the growth is performed while restoring the growth surface. Therefore, a heavily doped N layer is formed on the modulation dope layer having a relatively short growth time or a relatively thin layer. It becomes possible.

Since the crystal is grown while recovering the crystal, the growth surface has good flatness. In an extreme case, an undoped layer may be interposed periodically in order to realize this effect.

Further, although this step depends on the degree, the effect can be obtained even with one step. Embodiment 4 A fourth embodiment of the present invention will be described with reference to a curve (D) in FIG. As shown by the line (D), an N-type modulation doped layer is formed so as to increase in a saturation curve from the substrate side. By forming such a modulation doping layer, the low concentration region in the modulation doping layer can be set to a minimum. Therefore, the growth time can be shortened by reducing the overall growth thickness. Therefore, a high-throughput process can be formed in mass production. Embodiment 5 A fifth embodiment of the present invention will be described with reference to FIG. FIG. 3A is a cross-sectional view of a device formed from a gallium nitride-based compound semiconductor formed using this embodiment. FIG. 3B is a diagram (top view) of the element of FIG. 3A viewed from above. Portions denoted by 51 and 52 in the figure are an n-side electrode and a p-side electrode, respectively. Wafers grown using the techniques of Examples 1 to 4 described above were used. This is patterned and RIE (reactive
ion etching), RIBE (reactive ion beam etchin)
g), dry etching such as CDE (chemical dry etching) was performed. The surface 53 after the etching is obtained in the high concentration N-type GaN layer 14.

Here, the thickness of the high-concentration N-type GaN layer 14 requires a certain standard (determined by the carrier concentration and the mobility) to allow a current to flow in the lateral direction.

An N-type electrode is formed on the surface 53 of the high-concentration N-type GaN layer 14. Next, the p-type electrode 52 is formed on the surface 54 of the contact layer 17. In addition, these p surface,
The n surface, including the p / n interface, is held by an insulating film, a dielectric thin film, or the like. Thereafter, separation into element shapes is performed by dicing and scribing.

These separated elements are mounted and assembled as shown in FIG. The electrode pads of the chip may be ball-bonded as shown in FIG.
The wedge bonding shown in (b) is performed. FIG.
The use of wedge bonding as shown in FIG. 5B is more preferable than the ball bonding of FIG. There is also a method of performing flip chip mounting as shown in FIG. FIG.
FIG. 5D shows a top view when the wedge bonding of FIG. 5B is applied. As can be seen from the figure, the pad 76 is smaller than the pad 75 when performing ball bonding. This is because a pad for performing ball bonding requires a ball diameter + α of 100 μm to 120 μm, whereas a wedge has a wire diameter of 25 μm to 50 μm.
m is enough. FIG. 5E shows a top view when the flip chip mount of FIG. 5C is applied. As can be seen from FIG. 5E, the pads 77 and 78 are further reduced as compared with the ball pad 75. This is because a pad of several to several tens μm is sufficient for forming a solder bump for performing flip chip mounting. Usually, two electrodes (one or both sides of 77 or 78) are sufficient, but it is better to provide all four points for fixing as shown in FIG. 5 (e). After connecting these electrodes, they are fixed by molding with resin or the like to complete. Embodiment 6 A sixth embodiment of the present invention will be described using the gallium nitride-based compound semiconductor described above as an example.
This will be described with reference to FIGS. FIG. 4 is a cross-sectional view of an MO-CVD apparatus schematically illustrating this embodiment. The growth chamber 51 has a pipe 5 for supplying carrier gas.
7, a pipe for supplying a group V atom such as ammonia, a pipe 58 for supplying a group III atom such as TMG (trimethylgallium), n
A pipe 56 for supplying a mold dopant 59 and a pipe 55 for supplying a background compensation gas 60 (hereinafter abbreviated as compensation gas) are connected, and a gas contributing to the growth is supplied from here. After the reaction, the residual gas that has not contributed to the growth is discharged to the exhaust gas treatment device through the exhaust gas 54. Inside the growth chamber, a substrate 53 is disposed on a heater 52, and the above-described growth gas is supplied to grow a gallium nitride-based compound semiconductor layer.

Incidentally, the gist of the present invention is to have a growth layer formed by increasing the impurity concentration from the substrate side. Accordingly, FIG. 2A obtained by lowering the background impurity concentration on the substrate side and increasing it in the growth direction.
To (D) are naturally included.

Hereinafter, this forming method will be described with reference to the apparatus shown in FIG. In addition to the carrier gas and the growth gas, for example, 1 ppm or less (for example, about 1 ppb)
A compensation gas 60 such as ₂ is supplied. The supply amount of the compensation gas is reduced from the lower limit to the background level.
Alternatively, a doping gas such as SiH ₄ is supplied, for example, sequentially increased while the background level is lowered by the compensation gas. With these methods, the desired impurity concentration profiles shown in FIGS. 2A to 2D can be easily provided. Embodiment 7 A seventh embodiment of the present invention will be described with reference to FIG. FIG. 6A is a cross-sectional view of a light emitting device having a heterogeneous heterojunction in which a plurality of growth layers are formed by epitaxial growth. FIG. 6B shows a profile of a p-type impurity of the light emitting element corresponding to FIG. 6A. 6, the horizontal axis represents the impurity concentration of the p-type impurity, and the vertical axis represents the impurity concentration in FIG.
The distance from the substrate is shown corresponding to (a).

As the heterogeneous heterojunction, GaAs / S
i · Inp / GaAs · GaN / Al ₂ O ₃ · GaN /
Includes various heterojunctions such as Si-GaN / SiC.

In the light emitting device of this embodiment, a buffer layer 82 made of amorphous GaN having a thickness of about 0.01 to 2.00 μm is formed on a surface of a substrate 81 made of sapphire.
The p-type impurity concentration of Be, Mg, Ca, etc. is about 1 to 0.5 μm and the desired impurity concentration from the background level, for example, about 1 × 10 ¹³ cm ⁻³ to 1 × 10 ²³ cm ^−3.
A p-type modulation doping layer 84 increasing to about
When the impurity concentration of the p-type impurity is 1 μm or more, the impurity concentration is a desired impurity concentration, for example, about 1 × 10 ¹⁸ cm ⁻³ to 1 × 10 ²³ cm ^−3.
High concentration p-type layer 85 and a thickness of 0.01 to 0.03 μm
m, an active layer 86 of InGaN, and a film thickness of 0.
An AlGaN layer 87 having an n-type impurity concentration of about 01 to 2.0 μm is formed.

The above film thickness and impurity concentration were determined in Example 1.
It is not limited to the above numerical values for the same reason as described above.

The structure of each layer is not limited to the above type, and it is possible to form each layer using various gallium nitride-based compound semiconductors. For example, the substrate 11
Other sapphire, SiC, GaAs, Si, also the first GaN layer _{In x Al y Ga 1- (x} + y) N, also the second, third GaN is _{Al x Ga (1-x)} N Also, InGaN layer is I
n _x Ga _(1-x) N, and the AlGaN layer is Al _x Ga
_(1-x) N, also the fourth GaN layer is _In x _Al y Ga
_{1- (x + y)} N (x and y are each 0 or 1)
Can be formed respectively.

Next, a method of manufacturing the light emitting diode of the present invention shown in FIG. 1 will be described.

First, the sapphire substrate 11 is placed in a reaction chamber and heated to about 500 to 600 degrees Celsius. Next, non-crystalline first GaN layer 12 is formed by introducing hydrogen (nitrogen) or a mixed gas thereof as a carrier gas and ammonia (NH ₃ ) and TMGa (trimethylgallium) as a source gas into the reaction chamber. Next, the temperature in the reaction chamber is raised to about 1000 ° C. to 1100 ° C., a gas similar to the above is introduced, and together with this, SiH ₄ (silane gas) is introduced for doping N-type impurities.

Here, the film to be grown is formed so that the impurity concentration of the N-type impurity gradually increases. This control can be easily controlled by controlling the flow rate of the silane gas. That is, if the flow rate of the silane gas is increased exponentially with the growth of the GaN layer,
The impurity concentration of the N-type modulation doped layer formed correspondingly can also be increased exponentially. When the impurity concentration is increased linearly, the flow rate of the silane gas is also increased linearly. When the impurity concentration is increased in a saturation curve, the flow rate of the silane gas is increased in a saturation curve. In the case where the impurity concentration is increased stepwise, the flow rate of the silane gas may be increased stepwise.

As an example of the present invention, the GaN gas is formed by changing the concentration of silane gas to about 1 ppm and the flow rate to about 0 to 200 sccm to change the impurity concentration of the second GaN layer to a desired value. can do.

Next, an InGaN layer is formed by introducing TMI (trimethylindium) while maintaining or slightly lowering the temperature in the reaction chamber. Further TMAl
(Trimethylaluminum) and Cp ₂ Mg (biscyclopentadienyl magnesium) to introduce P
An AlGaN layer into which a type impurity has been introduced is formed. Further, TMGa (trimethylgallium), NH ₃ , Cp ₂ Mg
To form a GaN contact layer. With the above steps, one example of the manufacturing process of the light emitting diode of the present invention is completed.

In the above embodiment, the structure of the light emitting diode and the method of manufacturing the same are mainly shown, but the present invention is also applicable to light emitting devices such as semiconductor lasers without departing from the gist of the present invention. Can be applied.

According to the present invention, an N-type modulation doped layer and a high-concentration N-type layer are formed on the buffer layer surface without forming an undoped single-crystal GaN layer as a spacer layer formed in a conventional light emitting device. By continuously changing the flow rate of silane gas, crystallinity can be stably formed without abnormal growth. That is, the N-type layer that directly contributes to the operation can be formed on the surface of the buffer layer without forming a functionally unnecessary spacer layer. Can be prevented. Further, since the spacer layer is not formed, the thickness of the entire light emitting element is slightly reduced, so that an increase in strain due to lattice mismatch can be prevented, and deterioration of the growth layer can be prevented.

[0046]

According to the light emitting device of the present invention, an N-type gallium nitride compound semiconductor layer formed on a substrate and a P-type nitride semiconductor formed on an N-type gallium nitride compound semiconductor layer are formed. A gallium-based compound semiconductor layer, and the N-type gallium nitride-based compound semiconductor layer has a region in which the impurity concentration increases from the substrate side according to the film thickness, so that crystallinity is stabilized without abnormal growth. Therefore, the throughput required for manufacturing a light-emitting element can be improved.

Further, according to the method of manufacturing a light emitting device according to the present invention, an N-type modulation is formed on the buffer layer surface without forming an undoped single crystal GaN layer as a spacer layer formed in a conventional light emitting device. Only by continuously changing the flow rate of the silane gas between the doped layer and the high-concentration N-type layer, the crystallinity can be stably formed without abnormal growth, thereby improving the throughput required for manufacturing a light emitting device. Can be. Furthermore, since the thickness of the entire light emitting element can be reduced somewhat, an increase in strain due to lattice mismatch can be prevented, and deterioration of the grown layer can be prevented.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a light-emitting diode illustrating a first embodiment of the present invention, and FIG. 1B is a graph showing an impurity profile of an N-type impurity.

FIG. 2 is an impurity profile of an N-type modulation doped layer of the present invention.

3A is a cross-sectional view of a gallium nitride-based compound semiconductor, and FIG. 3B is a top view thereof.

FIG. 4 is a configuration diagram showing an MO-CVD apparatus.

FIGS. 5A and 5B are views for explaining the assembling of the light emitting diode of the present invention, wherein FIGS. 5A and 5B are views showing how a wire is bonded to an electrode, and FIG. 5C is a conventional problem of wedge bonding. (D) is a top view showing a state in which the wedge bonding of (b) is performed, and (e) is a top view showing a state in which the bonding of (c) is performed.

6A is a cross-sectional view of a light emitting device including a heterogeneous heterojunction, and FIG. 6B is a graph showing a profile of a P-type impurity.

FIG. 7A is a sectional view showing a conventional light emitting diode,
(B) is a graph showing the profile of the N-type impurity.

FIG. 8 is a schematic diagram showing a problem inherent to the conventional technique.

[Explanation of symbols]

 11,111 substrate 12,112 buffer layer (first GaN layer) 13 N-type modulation doped layer (second GaN layer) 14,114 high concentration N-type layer (third GaN layer) 15,115 active layer (InGaN layer) 16, 116 AlGaN layer 17, 117 Contact layer (fourth GaN layer) 113 Spacer layer 113 (second GaN layer) 211 Pinhole 212 Abnormal growth of GaN layer

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hideto Sugawara 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Kawasaki Office (72) Inventor Kenji Isomoto Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa 72 Toshiba Kawasaki Office

Claims (19)

[Claims] A light emitting device comprising: an N-type gallium nitride-based compound semiconductor layer formed on a substrate; and a P-type gallium nitride-based compound semiconductor layer formed on the N-type gallium nitride-based compound semiconductor layer. In the element, the N-type gallium nitride-based compound semiconductor layer has a region in which an impurity concentration increases from the substrate side according to a film thickness. A first N-type impurity formed on the substrate by increasing the impurity concentration from the first N-type impurity to the second N-type impurity;
-Type gallium nitride-based compound semiconductor layer; a second N-type gallium nitride-based compound semiconductor layer having an impurity concentration of the second N-type impurity and formed on the first N-type gallium nitride-based compound semiconductor layer; And a P-type gallium nitride-based semiconductor layer formed on the second N-type gallium nitride-based compound semiconductor layer. 3. The light emitting device according to claim 2, wherein said first N-type gallium nitride-based compound semiconductor layer has an N-type impurity whose exponential concentration varies exponentially according to its thickness. . 4. The light emitting device according to claim 2, wherein said first N-type gallium nitride-based compound semiconductor layer has an impurity concentration of an N-type impurity which varies linearly according to a film thickness. 5. The light emitting device according to claim 2, wherein said first N-type gallium nitride-based compound semiconductor layer has an impurity concentration of an N-type impurity changing in a saturation curve according to a film thickness. . 6. The light emitting device according to claim 2, wherein the first N-type gallium nitride-based compound semiconductor layer has an N-type impurity having a stepwise change in impurity concentration according to a film thickness. 7. An impurity concentration of the first and second N-type impurities is 1 × 10 ¹³ atoms · cm ^{−3 to} 1 × 10 ²³ atoms ·
3. The light-emitting device according to claim 2, wherein the light-emitting device is within a range of cm ^-3 . 8. The light emitting device according to claim 2, wherein said first N-type gallium nitride based compound semiconductor layer has a thickness in the range of 0.01 to 2.00 μm. 9. A substrate, a first N-type gallium nitride-based compound semiconductor layer formed on the substrate surface and having a first impurity concentration, and formed on the first N-type gallium nitride-based compound semiconductor layer surface A second N-type gallium nitride-based compound semiconductor layer that increases from the first impurity concentration to a second impurity concentration in accordance with the film thickness, and formed on the surface of the second N-type gallium nitride-based compound semiconductor layer; A third N-type gallium nitride-based compound semiconductor layer having the second impurity concentration; and a P-type gallium nitride-based compound semiconductor layer formed on the third N-type gallium nitride-based compound semiconductor layer. A light emitting element. 10. A substrate, a first growth layer formed on the substrate by epitaxial growth and having an increased impurity concentration from the substrate side, and a heterogeneous heterostructure formed on the first growth layer by epitaxial growth. A light emitting device comprising: a second growth layer having a junction. 11. A light emitting device having at least one P-type gallium nitride-based compound semiconductor layer formed on a substrate, wherein the P-type gallium nitride-based compound semiconductor layer has an impurity concentration depending on the film thickness. A light-emitting element having an increasing region. 12. A substrate, comprising: a first P-type impurity layer formed on the substrate by increasing from a first P-type impurity concentration to a second P-type impurity concentration and increasing to the second P-type impurity concentration; -Type gallium nitride-based compound semiconductor layer, and a second P-type gallium nitride-based compound semiconductor layer having an impurity concentration of the second P-type impurity and formed on the first P-type gallium nitride-based compound semiconductor layer A light-emitting element comprising: 13. The light emitting device according to claim 12, wherein in the first P-type gallium nitride-based compound semiconductor layer, an impurity concentration of a P-type impurity linearly changes according to a film thickness. . 14. The light emission according to claim 12, wherein in the first P-type gallium nitride-based compound semiconductor layer, an impurity concentration of a P-type impurity changes exponentially according to a film thickness. element. 15. The light emission according to claim 12, wherein the impurity concentration of the P-type impurity in the first P-type gallium nitride-based compound semiconductor layer changes in a saturation curve according to the film thickness. element. 16. The light emitting device according to claim 12, wherein the first P-type gallium nitride-based compound semiconductor layer has a step-like change in the impurity concentration of the P-type impurity according to the film thickness. . 17. The method according to claim 17, wherein the first and second P-type impurity concentrations are:
The light emitting device according to claim 12, characterized in that in the 1 × 10 ¹³ ~1 × 10 ²³ in the range of. 18. The light emitting device according to claim 12, wherein the first P-type gallium nitride-based compound semiconductor layer has a thickness in a range of 0.01 to 2.00 μm. 19. A step of forming a first gallium nitride-based compound semiconductor layer on a substrate in a reaction chamber; introducing silane as the doping gas onto the surface of the first gallium nitride-based compound semiconductor layer; Second N doped with impurities
Forming a gallium nitride-based compound semiconductor layer by changing the inflow amount of silane introduced into the reaction chamber to form the second n-type gallium nitride-based compound semiconductor layer. A method for manufacturing a light emitting element, wherein the impurity concentration is increased from the substrate side.