JP2000196143A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance emission intensity and make excellent in monochromaticity by a method wherein an active layer is sandwiched between both specific buffer layers in contact with them, and the thickness of buffer layers are each prescribed. SOLUTION: An Si-doped n-type AlGaN low-temperature buffer layer 102 is grown on the (0001) surface of an n-type SiC substrate 101 as thick as 50 nm, and an Si-doped GaN clad layer 103 is grown thereon. Then, an Si-doped n-type In0.2Ga0.8N n-side buffer layer 104, an In0.35Ga0.65N single quantum well active layer 105, and an Mg-doped p-type buffer layer 106 are grown. It is preferable that the p-side buffer layer 106 is formed as thick as 3 to 25 nm so as to improve a semiconductor light emitting element in emission intensity. The InGaN n-side buffer layer 104 and the p-side buffer layer 106 are provided on both upper and down sides of the active layer 105, where the light emitting efficiency and monochromaticity can be improved by making the thickness of n-side buffer layer 104 3 to 25 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light-emitting device, and more particularly, to a semiconductor light-emitting device having a gallium nitride-based material that efficiently emits visible wavelength light and a low threshold current.
The present invention relates to a semiconductor laser device realizing high reliability.

[0002]

2. Description of the Related Art A gallium nitride based semiconductor light emitting device can emit light in a wide range from ultraviolet to yellow and is important as a light source for optical information processing and display devices.

(Conventional example 1) Conventional nitride-based (GaN-based)
FIG. 10 is a cross-sectional structural view of a light emitting diode (LED) disclosed in Japanese Patent Application Laid-Open No. 8-330630 as a semiconductor light emitting device.
Shown in The structure of this conventional example is composed of sapphire substrates 1001, 5
0 nm thick GaN buffer layer 1002, 4 μm thick Si
Doped n-type GaN second cladding layer 1003, 50 nm
N-type thick Si-doped In _0.01 Ga _0.99 N first cladding 1004,2.5nm thick undoped n-type an In _0.30 Ga
_0.70 N single quantum well active layer 1005, 5 nm thick Mg-doped p-type In _0.01 Ga _0.99 N first cladding layer 1006,
0.1 μm thick Mg-doped p-type Al _0.3 Ga _0.7 N second cladding layer 1007, 0.5 μm thick Mg-doped p-type Ga
N-type Ga which is constituted by a laminate comprising an N-contact layer 1008 and is exposed on the surface in a region of 100 μm square.
An n-type electrode 1010 is formed on the N-cladding layer 1003, and a p-type electrode 1011 and a pad electrode 1012 are formed on the p-type GaN contact layer 1008. The light-emitting device thus prepared is used for a 250 μm square (100 μm square n
(Excluding the forming part of the mold electrode 1010), the light output at 20 mA was 1.5 m
W. The peak wavelength of the emission spectrum was 465 nm, and the full width at half maximum was 23 nm.

(Conventional Example 2) FIG. 11 shows a structure of a conventional GaN-based semiconductor laser. 1100 is a sapphire substrate, 1
101 is an n-type GaN contact layer, 1102 is an n-type Al
GaN clad layer, 1103 is n-type GaN guide layer, 1
105 is a multiple quantum well active layer and 1107 is a p-type AlGa
N protective layer, 1108 is a p-type GaN guide layer, 1109 is a p-type AlGaN cladding layer, 1110 is a p-type GaN contact layer, 1111 is a mesa stripe, 1112 is Si
An O ₂ insulating film, 1120 is a p-type electrode, and 1211 is an n-type electrode.

The threshold current of the device of the prior art was 78 mA, and the differential efficiency was 0.85 W / A. 35m at room temperature
The drive current value at the time of W light output is as large as 120 mA, and is 35 m
The drive voltage at the time of W output was also as high as 5.3V. When a reliability test was performed on this comparative example device under the conditions of 60 ° C. and 35 mW, the laser device life was as short as 35 hours or less. Further, when a current of 10 mA was passed, the optical output power from the front end face was 0.3 mW, and the full width at half maximum of the gain spectrum was 19 nm.

[0006]

As described above, in the GaN-based semiconductor light-emitting device according to the prior art, in the case of an LED, the light output is as small as 1.5 mW, the full width at half maximum of the emission spectrum is as wide as 23 nm, and a monochromatic light is emitted. There was a problem of poor sex.

In the case of a semiconductor laser, the threshold current value is as high as 78 mA, and the driving currents are 120 mA and 100 mA.
, The driving voltage also increases to 5.3 V,
As a result, the element life is 35 hours, which is a practical time (5000 hours).
For more than an hour).

[0008]

The device according to claim 1 application of the means for solving the problem] includes an n-type GaN-based cladding layer, an In _a
In _a gallium nitride based semiconductor light emitting device including _a Ga _1-a N quantum well layer (0.15 ≦ a ≦ 1) and a p-type GaN-based contact layer, the active layer is In _x Ga _1-x N−.
n-side buffer layer (0.03 ≦ x ≦ a-0.1) and In _y Ga
It is formed so as to be in contact with both of the _1-y Np side buffer layers (0.03 ≦ y ≦ a−0.15), and In _x G
The layer thicknesses of the a _1-x N-n side buffer layer and the In _y Ga _1-y N-p side buffer layer are each 3 nm or more and 25 nm or less.

According to a second aspect of the present invention, in the semiconductor light emitting device, the active layer is an In _a Ga _{1 -a} N first quantum well layer, an In _b1 Ga _{1 -b} 1 N from _a side close to the n-type GaN-based cladding layer. First
Barrier layer, In _a Ga _1-a N second quantum well layer, In _b2 Ga
_1-b2 N second barrier layer ··· In _bn Ga _1-bn N n-th barrier layer, In _a Ga _1-a N (n + 1) th quantum well layer (where, n is an integer of 1 or more) formed in this order It is a multiple quantum well active layer, and the composition of the In _x Ga _1-x Nn side buffer layer is 0.03 ≦
x ≦ a−0.1, b1−0.02 ≦ x ≦ b1 + 0.02
The composition of the In _y Ga _1-y Np side buffer layer is 0.03
≦ y ≦ a−0.15, bn−0.02 ≦ y ≦ bn + 0.
02.

A semiconductor light emitting device according to a third aspect of the present invention is characterized in that the number of the quantum well layers is four or less and the number of the barrier layers is three or less.

The semiconductor light-emitting device according to claim 4 of the present application provides the semiconductor light-emitting device, wherein all of the barrier layers, the n-side buffer layer,
The side buffer layers have the same In mixed crystal ratio (x = b1 = b2 =...).
. = Bn = y).

A semiconductor light emitting device according to a fifth aspect of the present invention is characterized in that the thickness of the p-side buffer layer is 6.5 nm or more and 25 nm or less.

According to the semiconductor light emitting device of the present invention, the n-side buffer layer contains an n-type impurity at a concentration of 5 × 10 ¹⁶ c.
m- ³ or more and 1 × 10 ²⁰ cm ⁻³ or less The p-side buffer layer is doped with a p-type impurity at a concentration of 1 × 1
It is characterized by being doped within a range from 0 ¹⁷ cm ^{−3 to} 5 × 10 ²¹ cm ⁻³ .

According to a seventh aspect of the present invention, in the semiconductor light emitting device, an n-type light guide layer composed of a graded composition layer is provided on a side of the n-side buffer layer opposite to the active layer; An n-type AlGaN-based cladding layer containing Al is provided on the opposite side of the active layer, and the n-type light guide layer comprises a gradient composition layer in which the Al composition increases or the In composition decreases as the distance from the active layer increases. It is characterized by the following.

The semiconductor light emitting device according to claim 8 of the present application has a p-type light guide layer made of a graded composition layer on a side of the p-type buffer layer opposite to the active layer, and the p-type light guide layer A p-type AlGaN-based cladding layer containing Al on the opposite side of the active layer, and the p-type light guide layer has a gradient composition in which the Al composition increases or the In composition decreases as the distance from the active layer increases It is characterized by comprising a layer.

The semiconductor light emitting device according to claim 9, wherein one of the n-type and p-type light guide layers has a first guide layer whose In composition decreases with increasing distance from the active layer; And a second guide layer whose Al composition increases as the distance from the first guide layer increases, wherein the first guide layer is formed closer to the active layer than the second guide layer.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A device embodying the present invention will be described.

(Embodiment 1) FIG. 1 shows an embodiment of the present invention.
1 shows a cross-sectional structural view of a GaAlN-based semiconductor light emitting device (LED). 101 is an n-type SiC substrate, 102 is a 50 nm-thick Si-doped n-type AlGaN low-temperature buffer layer, 103 is a 3 μm-thick Si-doped n-type GaN cladding layer, 104
Is a 25 nm thick Si-doped n-type In _0.2 Ga _0.8 N-n
Side buffer layer, 105 is an active layer, 2 nm in this embodiment.
The thickness is a thick undoped In _0.35 Ga _0.65 N single quantum well active layer. 106 is a 7 nm thick Mg-doped p-type I
n _{0. 2} Ga _0.8 N-p-side buffer layer, 107 of 30nm thickness M
g-doped p-type GaAlN protective layer, 108 μm
Thick Mg-doped p-type GaN contact layer, 109 is p-type
A semi-transparent electrode, 110 is a p-type pad electrode, and 111 is an n-type electrode.

Next, a method of manufacturing the device of this embodiment will be described. First, a 50 nm thick Si-doped n-type AlG is formed on a (0001) plane n-type SiC substrate 101 at a substrate temperature of 550 ° C. by a normal metal organic chemical vapor deposition (MOCVD) method.
After growing the aN low-temperature buffer layer 102, the substrate temperature is raised to 1100 ° C. to grow the Si-doped n-type GaN cladding layer 103. Next, after lowering the substrate temperature to 760 ° C., the Si-doped n-type In _0.2 Ga _0.8 N-n
A side buffer layer 104, an active layer 105 of In _0.35 Ga _0.65 N single quantum well, and a p-type p-side buffer layer 106 doped with Mg are grown. Subsequently, the substrate temperature was increased to 1050 ° C., and the Mg-doped p-type GaAlN protective layer 107 and p-type G
An aN contact layer 108 was formed. Finally, n-type Si
After grinding the back surface of the C substrate 101 to reduce the substrate thickness to 120 μm, a p-type translucent electrode 109 made of Ni is formed on the growth surface side of the wafer by a normal vapor deposition method, and a 100 μm diameter P-type pad electrode 110 made of Au, and n-type electrode 1 on the back surface of n-type SiC substrate 101
11 was formed, and a chip was cut out by scribing to a size of 250 μm square to produce an LED.

When a forward current of 20 mA was applied to the LED according to the present embodiment, light emission at a wavelength of 465 nm was observed, and the light output from one chip was 6.1 mW, which is about four times the luminous efficiency of the conventional LED. Was confirmed. Also,
The full width at half maximum of the emission spectrum of the device of the embodiment is 16n.
m, which is dramatically narrower than 25 nm for the LED according to the prior art. Thus, the monochromaticity was improved by reducing the full width at half maximum of the emission spectrum.

In FIG. 2, in the LED manufactured by the same structure and method as the above-mentioned LED, the thickness and composition of the n-side buffer layer 104 and the composition of the p-side buffer layer 106 are fixed.
The measurement results of the full width at half maximum of the emission spectrum and the emission intensity when only the thickness of the p-side buffer layer 106 is changed from 0 nm to 25 nm are shown. Assuming that the light emission intensity of the conventional example LED is 1, the light emission intensity of the LED in which the p-side buffer layer 106 is not inserted (that is, only the n-side buffer layer 104) is almost 1, and there is no improvement from the conventional example element. . On the other hand, by using the p-side buffer layer 106 having a thickness of 3 nm, the n-side buffer layer 104 and the p-side buffer layer 106 made of InGaN are formed in contact with the upper and lower sides of the active layer. It was found that emission intensity could be obtained. Further, the thickness of the p-side buffer layer 106 is most preferably in the range of 6.5 nm to 13 nm, and the effect of increasing the light emission intensity in the LED is maximized.
Approximately four times that of the conventional device was obtained. Further, the p-side buffer layer 10
In the device in which the thickness of No. 6 was increased to 25 nm, the emission intensity was confirmed to be about twice as large as that of the conventional device. Further, when only the thickness of the p-side buffer layer was increased to 30 nm, I
An increase in crystal defects and a decrease in light transmittance due to the thermal decomposition of the nGaN-p-side buffer layer 106 itself were observed, and the emission intensity was reduced to be equal to or less than that of the conventional device. When the thickness was more than 30 nm, the decrease was further remarkable, and the emission intensity was further reduced.

On the other hand, the full width at half maximum of the emission spectrum at an emission wavelength of 465 nm is obtained when only the n-side buffer layer 104 is used (when the thickness of the p-side buffer layer 106 in FIG. 2 is 0 nm).
When the p-side buffer layer 106 having a thickness of 3 nm was inserted, the width was 23 nm, which was almost the same as that of the conventional device using no buffer layer both above and below the active layer. On the other hand, the p-side buffer layer 1
When 06 is in the range of 6.5 nm to 25 nm thick, the full width at half maximum is 16 nm to 18 nm, and the p-side buffer layer 106
Was reduced from 50% to 60% as compared with the LED not using. At this time, the full width at half maximum of the emission spectrum at the wavelength of 465 nm is 6.5 nm to p-side buffer layer 106.
As in the case of the 25 nm-thickness, it was as narrow as 16 to 18 nm, but the thickness of the conventional element and the p-side buffer layer 106 was 25 nm.
In the following cases, another light emission having a full width at half maximum of 100 nm or more was observed near the wavelength of 500 nm, which could not be observed. This is presumed to be due to the deterioration of the active layer 105 due to the decrease in crystallinity of the p-side buffer layer 106.

As described above, the thickness of the p-side buffer layer 106 should be 3 nm in order to improve the emission intensity.
It is desirable that the thickness be at least 25 nm or less. Further, by setting the thickness of the p-side buffer layer 106 at 6.5 nm or more and 25 nm or less, an effect of improving monochromaticity can also be exhibited.

Next, the p-side buffer layer 106 and the n-side buffer layer 10
4 was fixed as in the above example, and the n-side buffer layer 10 was fixed.
The result of examining the light emission characteristics of the LED manufactured by changing only the thickness of No. 4 will be described. FIG. 3 shows the result. In addition,
The emission intensity was expressed as 1 for the conventional device. n
The thickness of the side buffer layer 104 is set to 0 nm (that is, the p-side buffer layer 1).
06 only), the emission intensity is 1
% Or less, and the crystal defects of the p-side buffer layer 106 increased and the light transmittance decreased significantly. For this reason,
It was not possible to measure the full width at half maximum of the emission spectrum. However, when the n-side buffer layer 104 was introduced with a thickness of 3 nm, the intensity was improved to 1.3 times that of the device of the conventional example, and the light emission intensity of each of the LEDs whose thickness was increased to 5 nm, 13 nm, and 25 nm was the same. It was found that the improvement was about twice that of the example device. Further, the n-side buffer layer 10
When the thickness of Sample No. 4 was set to 30 nm or more, only a light emission intensity equal to or less than that of the conventional device could be obtained. The reason is presumed to be the same as in the case where the thickness of the p-side buffer layer 106 is set to 30 nm or more.

Further, by setting the thickness of the n-side buffer layer 104 to 3 nm or more, the full width at half maximum of the emission spectrum at 465 nm emission can be drastically reduced from 16 nm to 18 nm as compared with the conventional device. . Therefore, with the element having a thickness in this range, light emission with good monochromaticity could be obtained. Even if the thickness of the n-side buffer layer 104 was further increased, the full width at half maximum of the emission spectrum was kept narrow, but the emission intensity was lower than that of the conventional device as described above,
Along with this, unnecessary light emission having a full width at half maximum near 550 nm of 100 nm or more was generated. For this reason, it was found that even when the thickness of the n-side buffer layer 104 was set to 30 nm or more, the monochromaticity was lower than that of the conventional device. As described above, the n-side buffer layer 1 of InGaN is in contact with and above and below the active layer 105.
04, in the device into which the p-side buffer layer 106 is introduced, by setting the thickness of the n-side buffer layer 104 to 3 nm or more and 25 nm or less, it is possible to improve the luminous efficiency and the monochromaticity as compared with the conventional device. Do you get it.

Next, the n-side buffer layer 104 and the p-side buffer layer 10
The result of confirming the effect by changing the composition of No. 6 will be described with reference to FIG. The thickness of each of the n-side buffer layer 104 and the p-side buffer layer 106 was fixed to 10 nm, and the n-type In _x
With the composition x of the Ga _1-x N-n-side buffer layer 104 fixed at 0.2, the composition _{y of} the p-type In _y Ga _1-y N-p-side buffer layer 106 was changed to 0.01, 0.03 , 0.1, 0.2, 0.2
It was changed to 5, 0.3. Also in FIG. 4, the emission intensity is expressed as 1 in the case of the conventional device. When y = 0.01, no change was observed in the emission intensity and the full width at half maximum from the conventional device. In the LED with y = 0.03, the emission intensity was improved to 3.5 times that of the conventional device, and the full width at half maximum of the emission spectrum was 17 nm, which was narrower than that of the conventional device, and monochromaticity was improved. In the device of 0.1 ≦ y ≦ 0.2, the emission intensity is improved to four times that of the device of the prior art, and the full width at half maximum of the emission spectrum can be as narrow as 18 nm or less. Improvement was also observed in the properties.
Further, when y = 0.25 and y = 0.3, light emission having a peak at a wavelength of 415 nm other than the light emission in the active layer 105 is mixed, and the desired light emission intensity at 465 nm is smaller than that of the conventional device. Decreased to the same level or less. Needless to say, the monochromaticity of the device emitting two wavelengths having different emission wavelengths as much as 40 nm is lower than that of the conventional device.
This is because, when y ≧ 0.25, electrons to be efficiently injected into the active layer 105 having the quantum well structure leak to the p-type p-side buffer layer 106. (Emission at a peak wavelength of 415 nm) was observed. That is, since the p-side buffer layer 106 is p-type, the p-side buffer layer 106 has the n-type n-side buffer layer 104.
A function to effectively confine electrons injected from the active layer 105 into the active layer 105 is required. Therefore, the mixed crystal ratio y of the p-side buffer layer 106 is smaller than the forbidden band width of the active layer 105.
Is desirably sufficiently wide on the conduction band side, and it can be seen from the results of FIG. 4 that in the case of an InGaN-based material, a difference of 0.3 eV or more is sufficient as the difference in the forbidden band width. That is, the mixed crystal ratio y of the p-side buffer layer 106 is
05 with respect to the In mixed crystal ratio (assumed to be a), y ≦ a−0.
This means that the upper limit value of the mixed crystal ratio y of the p-side buffer layer 106 needs to be determined based on this criterion when changing the mixed crystal ratio of the active layer 105 itself. Therefore, in the above embodiment, since a = 0.35, the mixed crystal ratio of the p-side buffer layer 106 is set to 0.03 ≦ y ≦ 0.2.
By doing so, it can be seen that it is possible to realize an LED with higher luminous efficiency and improved monochromaticity as compared with the element of the conventional example.

Similarly, the n-side buffer layer 10 in the first embodiment
4 and the thickness of the p-side buffer layer 106 were fixed at 10 nm, respectively, and the mixed crystal ratio of the p-side buffer layer 106 was set to y = 0.
2 is also fixed, and the mixed crystal ratio of only the n-side buffer layer 104: x is set to 0.01, 0.03, 0.1, 0.2, 0.25,.
Changed to 3. Also in FIG. 5, the emission intensity is expressed as 1 in the case of the conventional example. When x = 0.01, no change was observed in the emission intensity and the full width at half maximum from the conventional device. In the LED with x = 0.03, the emission intensity was 3.3 times as large as that of the conventional device, and the full width at half maximum of the emission spectrum was 19 nm, which was narrower than that of the conventional device, and monochromaticity was improved. In the device of 0.1 ≦ x ≦ 0.2, the emission intensity is improved to about four times that of the device of the prior art, and the full width at half maximum of the emission spectrum can be realized as narrow as 18 nm or less. The monochromaticity was also improved. Further, even when x = 0.25, the emission intensity was improved to 3.1 times that of the conventional device, and the full width at half maximum of the emission spectrum was also 16 nm, indicating an improvement in monochromaticity. However, when x = 0.3, light emission having a peak at a wavelength of 415 nm other than light emission from the active layer 105 is mixed, and
The desired emission intensity at 465 nm was reduced to a level equal to or lower than that of the conventional device. Needless to say, 40
The monochromaticity of an element that emits light at two wavelengths different from each other in nm is lower than that of a conventional element. This is because, when x ≧ 0.3, holes to be efficiently injected into the active layer 105 having the quantum well structure leak to the n-type n-side buffer layer 104.
Light emission (peak wavelength 415 nm) from the n-side buffer layer 104 itself
Can be understood as having been observed. That is, n
Since the side buffer layer 104 is n-type, the p-type buffer layer 1
It is necessary to have a function of effectively confining holes injected from the active layer 105 into the active layer 105. Therefore, the mixed crystal ratio x of the n-side buffer layer 104 is smaller than the forbidden band width of the active layer 105 by the n-side buffer layer 1.
It is desirable that the forbidden band of No. 04 is sufficiently wide on the valence band side, and from the results of FIG. 5, it can be seen that the difference of the forbidden band of 0.19 eV or more is sufficient for the InGaN-based material. That is, the mixed crystal ratio x of the n-side buffer layer 104 is smaller than the In mixed crystal ratio (a) of the active layer 105 by x ≦ a
-0.1 is important, and even when changing the mixed crystal ratio of the active layer 105 itself, the n-side buffer layer 104
It is necessary to determine the upper limit of the mixed crystal ratio x. Therefore, in the above embodiment, since a = 0.35, the mixed crystal ratio of the n-side buffer layer 104 is set to 0.03 ≦ y ≦ 0.
By setting to 25, it can be seen that an LED with higher luminous efficiency and improved monochromaticity can be realized as compared with the element of the conventional example.

In the above embodiment, the n-side buffer layer 104,
Although the p-side buffer layer 106 was doped with p-type impurities and n-type impurities, the effect of narrowing the full width at half maximum of the emission spectrum of the LED was recognized regardless of the amount of impurities added to these layers. Although it is possible to achieve improvement, the Si concentration of the n-side buffer layer 104 must be 5 × 10 ¹⁶ cm ⁻³ in order to make the emission intensity twice or more as compared with the conventional device.
More than 1 × 10 ²⁰ cm ^-3 range, Mg concentration in the p-side buffer layer 106 was required to be in the range of 1 × 10 ¹⁷ cm ^-3 or more 5 × 10 ²¹ cm ^-3 or less. When the impurity is doped more than these impurity concentration ranges, the light emission intensity of the LED is reduced due to the deterioration of the crystallinity of the n-side buffer layer 104 and the p-side buffer layer 106 or the thermal diffusion of the impurity to the active layer 105. Smaller than. Further, in a device having a doping concentration lower than the above impurity concentration range, the efficient injection of electrons and holes into the active layer 105 was inhibited, and the emission intensity was lower than that of the conventional device. In this embodiment, Si is selected as the n-type impurity to be doped and Mg is selected as the p-type impurity.
Elements such as e, Sn, Te, and Ge can be used, and elements such as Zn, Cd, and C can be used as the p-type impurities.

In the above embodiment, the active layer 105 is made of In
_{Although the} single quantum well layer is _0.35 Ga _0.65 N, the mixed crystal ratio is desirably in the range of 0.15 ≦ a ≦ 1, and the emission intensity and the monochromaticity are improved by inserting the n-side and p-side buffer layers. Can be achieved. Further, the thickness of the active layer 105 having the quantum well structure is desirably in the range of 1 nm to 5 nm,
It was confirmed that the emission intensity and the monochromaticity were improved by inserting the n-side and p-side buffer layers. Further, in order to make the emission intensity twice or more that of the conventional device, the thickness of the active layer must be 1 n.
It was most desirable that the thickness be not less than m and not more than 3 nm.

As described above, in the LED having the active layer 105 having a single quantum well structure, the n-side buffer layer 104 and the p-side buffer layer 106 of InGaN are directly above and below the active layer 105.
By contacting with, an LED having high emission intensity, a narrow full width at half maximum of the emission spectrum, and good monochromaticity could be realized. As described above, this n-side buffer layer 1
04, the p-side buffer layer 106 has no effect when only one of them is inserted. However, when the p-side buffer layer 106 is inserted on both the upper and lower sides of the active layer 105, a remarkable improvement in LED characteristics is recognized.
It is presumed that the crystallinity of the active layer 105 and / or the flatness of the interface between the active layer 105 and the n-side buffer layer 104 and the p-side buffer layer 106 have been improved.

In this embodiment, n-type SiC is used as the substrate.
Although a substrate was used, p-type SiC,
It goes without saying that a material that can generally grow a GaN-based crystal, such as c-plane or a-plane sapphire, n-type or p-type GaN, is applicable.

(Embodiment 2) Next, an example in which the present invention is applied to a semiconductor laser will be described with reference to the sectional structural view of FIG. 20
1 is an n-type GaN substrate, 202 is an n-type AlGaN cladding layer, 203 is an GaN n-type guide layer, and 204 is n-type In.
An n-side buffer layer made of GaN, 205 is an active layer having a multiple quantum well structure, 206 is a p-side buffer layer made of p-type InGaN, 207 is a p-type AlGaN protective layer, 208 is a p-type guide layer made of GaN, and 209 is P-type cladding layer made of AlGaN, 210 is a p-type GaN contact layer, 211
Is a mesa stripe, 212 is an n-type AlGaN current confinement layer, 213 is a p-type GaN second contact layer, and 220 is p-type GaN.
The mold electrode 221 is an n-type electrode.

Next, a method of manufacturing the device of this embodiment will be described. First, a Si-doped n-type Al _0.1 Ga _0.9 N cladding layer 202 having a thickness of 0.5 μm is formed on a (0001) plane n-type GaN substrate 201 at a substrate temperature of 950 ° C. by a normal molecular beam epitaxy (MBE) method. N of Si-doped GaN
The mold guide layer 203 is grown to a thickness of 0.1 μm. Next, the substrate temperature is lowered to 710 ° C., and the Si-doped n-type In
_0.05 Ga _0.95 N-n side buffer layer 204 is 20 nm thick,
Active layer of multiple quantum well structure composed of 2.5 nm In0.2Ga0.8N quantum well layer 2 layer having a thickness and In _0.05 Ga _0.95 N barrier layers one layer of 5nm thickness sandwiched them 20
5. Mg-doped p-type In _0.05 Ga _0.95 Np side buffer layer 2
06 is grown. Subsequently, while increasing the substrate temperature to 950 ° C., the Mg-doped p-type Al _0.1 Ga _0.9 N protective layer 2 is formed.
07 with a thickness of 40 nm, a substrate temperature of 950 ° C., a Mg-doped GaN p-type guide layer 208 having a thickness of 0.1 μm, and a Mg-doped p-type Al _0.1 Ga _0.9 N cladding layer 209 having a thickness of _0.1 μm.
A 4 μm, 0.3 μm Mg-doped p-type GaN contact layer 210 is grown.

Next, the GaN-based crystal is made to be <1-10 by a usual photolithography technique and a dry etching technique.
A mesa stripe 211 having a width of 2 μm and a height of 0.7 μm was formed in parallel with the 0> direction. On both sides of the mesa stripe 211, etching is performed until the p-type guide layer 208 is reached. Subsequently, the mesa stripe 211 outside of the area of the portion, by selective growth by conventional MOCVD method, a thickness of 0.4μm Si-doped n-type Al _0.1 Ga _0.9 N current blocking layer 212 at a substrate temperature of 900 ° C., Mg-doped p-type Ga
The N second contact layer 213 was grown to a thickness of 0.3 μm. After the n-type GaN substrate 201 was polished to a thickness of 50 μm, a p-type electrode 220 was formed on the entire surface of the growth layer, and an n-type electrode 221 was formed on the entire back surface of the substrate. Next, Ga is applied to the (1-100) plane perpendicular to the mesa stripe 211 described above.
A laser resonator having a length of 650 μm was formed by cleaving the N-based crystal. A dielectric multilayer film of titanium oxide and magnesium fluoride having a reflectance of 70% (not shown) is formed on the back end surface, and a silicon nitride film having a reflectance of 12% is formed on the front end surface. , Individual chips were cut out to obtain laser elements.

When the characteristics of the laser device thus manufactured were measured, a threshold current of 24 mA and a differential luminous efficiency of 0.97 W / A were obtained, and a low threshold and high efficiency laser oscillation were obtained. The operating current value at room temperature when the optical output was 35 mW was 60 mA, and the operating voltage was 4.3 V. Further, the laser device in this embodiment was set in a 60 ° C.
When a reliability test was performed under the conditions of mW light output, MT
1350 as TF value (hereinafter referred to as laser element life)
It was found that 0 hours were obtained.

On the other hand, a current of 10 mA was passed through the device of this example, and the light output from the front end face was measured. As a result, a light emission power of 0.8 mW was obtained. The emission gain spectrum at this time (corresponding to the emission spectrum of the LED)
Was measured, the full width at half maximum of the spectrum was very narrow at 12 nm.

As is clear from the comparison between the characteristics of the device of the present embodiment and the characteristics of the laser device of the conventional example 2, by inserting the upper and lower n-side buffer layers 204 and p-side buffer layers 206, the active layer 205 It can be seen that the full width at half maximum of the gain spectrum is as narrow as 74% of the device of the conventional example, and the emission intensity is increased by 2.7 times. Therefore, by the synergistic effect of these two effects, the light output per wavelength can be improved by 3.6 times, and the threshold current of laser oscillation can be effectively reduced to less than half of the conventional device. It is inferred. In the second embodiment, the drive voltage is reduced because the drive current can be reduced by 60 mA by the above-described effect, and the voltage consumed by the series resistance of the laser element can be reduced. Due to the reduction of the drive current and the drive voltage, the input power to the laser device at the time of 35 mW light output is 260 mW in the present embodiment, compared to 640 mW of the conventional device.
W was reduced to less than half. As a result, heat generation inside the laser element can be suppressed, and long-term reliability in high-temperature operation can be ensured.

As described above, by forming the n-side buffer layer 204 and the p-side buffer layer 206 in contact with the quantum well layer of the active layer 205 having a multiple quantum well structure, the luminous efficiency is improved and the emission spectrum ( The full width at half maximum of the gain spectrum of the laser device can be reduced, and a nitride semiconductor laser device having a low threshold current, a low drive current, a low drive voltage, and a long life can be obtained. Note that the n-side buffer layer 204 and the p-side buffer layer 20
The desirable thickness of No. 6 and the desirable concentrations of the n-type impurity and the p-type impurity were the same as in Example 1, respectively.

In this embodiment, the active layer 2 which is a light emitting layer is used.
05 is a multiple quantum well (in the above embodiment, the well layer is 2
Layer). Therefore, the n-side buffer layer 204 and p
The quantum well layer in contact with the side buffer layer 206 is in contact with the barrier layer on the side opposite to the buffer layer. Here, based on the structure of Example 2, the mixed crystal ratios x and y of the n-side buffer layer 204 and the p-side buffer layer 206 were fixed to 0.05, and the mixed crystal ratio: b of the barrier layer was set to 0.1. Semiconductor lasers having different values of 01, 0.03, 0.07, and 0.1 were fabricated, and the light output from the front end face when a current of 10 mA was passed and the full width at half maximum of the gain spectrum were examined. When b = 0.01 and 0.1, the full width at half maximum of the gain spectrum of the light output is 24 nm and 26 nm.
Thus, the above-described embodiment was significantly wider, and the oscillation threshold currents of these laser devices were also as high as 60 mA or more. On the other hand, when b = 0.03 and 0.07, the full width at half maximum of the gain spectrum is wider than 14 nm in the case of Example 2 where b = 0.05, but is 15 to 16 nm, which is more than the conventional example. It was confirmed that it became narrow.
The oscillation threshold current of these laser devices is as small as about 30 mA, and a remarkable improvement has been seen as compared with the prior art.

As described above, in order to obtain a GaN-based semiconductor laser that can be driven at a low current, the mixed crystal ratio of the n-side buffer layer 204 and the p-side buffer layer 206 must be equal to the mixed crystal ratio of the barrier layer in the multiple quantum well. It is desirable that they are almost the same, and the range is b
-0.02 ≦ x ≦ b + 0.02 or b−0.02 ≦
It can be seen that y ≦ b + 0.02. This is because the materials of the barrier layer and the buffer layer on both sides sandwiching the quantum well are almost the same, so that the degree of crystal distortion in the plurality of quantum wells is the same, and the internal self-electric field due to the piezo effect, which is a phenomenon peculiar to the InGaN system. Is the same in each quantum well layer, and as a result, the degree of the quantum confinement Stark effect due to the self-electric field of the piezo effect in each quantum well layer is made uniform,
This is considered to be due to the effect of making the peak wavelength of light emission the same. That is, as demonstrated in the LED of Example 1, even if the mixed crystal ratios of the buffer layers on both sides of the single quantum well are different, the monochromaticity is improved (the effect of narrowing the full width at half maximum of the gain spectrum in the laser device). However, when these have a multiple quantum well structure, the emission from each of the quantum well layers is observed in an overlapping manner, so that the full width at half maximum of the emission from each of the quantum well layers is 15n.
Even when it is as narrow as about m, the full width at half maximum is widened as a whole by shifting the emission peak wavelength by several nm.
Therefore, when the improvement of monochromaticity of the present invention is applied to a laser device or an LED having a multiple quantum well structure in an active layer,
The above conditions of the mixed crystal ratio are such that the mixed crystal ratio of the barrier layer of the multiple quantum well layer is set to b1, b2,. Assuming that the mixed crystal ratio of the barrier layer in contact with the lower side of the quantum well layer is bn, b1−0.02 ≦ x ≦ b1 + 0.02, bn−0.
It is important that 02 ≦ y ≦ bn + 0.02. Further, the most desirable form when the multiple quantum well active layer is used is x = b1 = b2 =... = Bn = y, and the full width at half maximum of the 14 nm gain spectrum becomes the narrowest as in the second embodiment. The threshold current decreases.
This can be seen in the above description. However, as described in the first embodiment, x ≧ 0.03 and y ≧ 0.03 are required to exhibit the effect of improving monochromaticity as a buffer layer. The same was true for.

When the active layer has a multiple quantum well structure having two or more quantum well layers, unlike the first embodiment, the n-side buffer layer 204 and the n-side buffer layer 206 When the doping with the p-type impurity and the p-type impurity was not performed, a phenomenon in which the threshold current increased to a value equal to or higher than that of the conventional example 2 was observed. This is because it is necessary for electrons and holes to reach a plurality of quantum well layers beyond at least one barrier layer.
This is probably because it is necessary to control the p-type. The desirable range of the impurity doping concentration in each of the n-side buffer layer 204 and the p-side buffer layer 206 is, as in the case of the single quantum well of the first embodiment, the case where the Si concentration of the n-side buffer layer 104 is 5 × 10 5
^{The range of 16} cm ^{−3 to} 1 × 10 ²⁰ cm ^{−3 and} the Mg concentration of the p-side buffer layer 106 is 1 × 10 ¹⁷ cm ^{−3 to} 5 × 10 ²¹ c.
It is important that the range is not more than m ^-3 , and the threshold current of the semiconductor laser manufactured in this range can be made as small as 40 mA or less, which is practically acceptable. In addition, the device life of the laser device in this range was 5,000 hours or more at 60 ° C., which was a sufficiently long time.

Embodiment 3 In this embodiment, an example in which an active layer having a multiple quantum well structure is applied to an LED will be described. This structure is n
The side buffer layer 104 is a 10 nm thick In _0.05 Ga _0.95 N layer doped with Si at a concentration of 1 × 10 ¹⁸ cm ⁻³ , and the active layer 105 is a 2.0 nm thick In _0.55 Ga
_0.45 N quantum well layers and I inserted between the quantum well layers
The active layer was a multiple quantum well active layer composed of two layers of n _0.05 Ga _0.95 N barrier layers.
5 nm thick I doped at a concentration of 10 ¹⁹ cm ^-3
The structure is the same as that of the first embodiment except that an n _0.05 Ga _0.95 N layer is used. The light output and full width at half maximum of the emission spectrum of the LED of this embodiment are LE values without using the n-side buffer layer and the p-side buffer layer.
D and 3 times and 80%, respectively.
Improvement was confirmed in both monochromaticity.

By inserting the buffer layer as in the second and third embodiments, it is possible to increase the light emission intensity of the nitride semiconductor light emitting device having the multiple quantum well active layer and to improve the monochromaticity. When applied to a semiconductor laser, a low current and a long life can be achieved. In this case, the effect is most remarkable when the number of multiple quantum well layers is two or more and four or less. . Even in a light emitting device having five or more quantum well layers, improvement in monochromaticity may be observed,
It is thought that the emission wavelengths from the quantum well active layers differ from each other due to the misalignment of the mixed crystal ratio and the thickness difference between the quantum well layers and the difference in the degree of crystal distortion. It is presumed that the effect of improving the monochromaticity by the insertion of the buffer layer is not remarkable because the spread easily occurs.

(Embodiment 4) This embodiment has the same layer structure as the embodiment 2, but the composition, thickness and impurity doping concentration of each layer are as follows. After forming up to the n-type AlGaN cladding layer 202 by the same process as in Example 2,
The n-type guide layer 203 is formed on a graded composition layer doped with 0.15 μm thick Si of 9 × 10 ¹⁷ cm ^−3, in which the Al mixed crystal ratio gradually decreases from Al _0.2 Ga _0.8 N to GaN in the growth direction. The buffer layer 204 is made of 15 nm thick n-type In _0.06 Ga _0.94 N doped with 5 × 10 ¹⁷ cm ⁻³ of Si,
The active layer 205 is a 2.0 nm thick In _0.18 Ga _0.82 N single quantum well layer doped with Si at a concentration of 1 × 10 ¹⁷ cm ⁻³ , and the p-side buffer layer 206 is a Mg concentration of 3 × 10 ¹⁸ cm 3. ^-3
On the doped In _0.03 Ga _0.97 N layer having a thickness of 5 nm, a p-type guide layer 208 is formed from GaN to Al _0.2 Ga _0.8 N.
Mg whose Al composition gradually increases up to 5 × 10 ¹⁹ cm ⁻³
The doped graded composition layer was 0.15 μm thick. Thereafter, the semiconductor laser device has a configuration in which the p-type cladding layer 209 and the p-type GaN contact layer 210 are formed in the same manner as in the second embodiment.

In the device of this embodiment, the threshold current is 18 mA,
A life of 18,000 hours was confirmed under the conditions of an operating current of 50 mA at room temperature at the time of output of 5 mW, the same driving voltage of 4.5 V, and a temperature of 35 mW at 60 ° C. These characteristics are the same as those of the n-side buffer layer 2 of the present configuration.
04, threshold current = 59 mA, 35 mW operating current = 1 in the case of a semiconductor laser device not using the p-side buffer layer 206
02 mA, operating voltage = 5.2 V, and element life = 300 hours were significantly improved.

Further, a lower current and a longer life are achieved as compared with the second embodiment. This is because the gradient composition layer is applied to the n-type guide layer 203 and the p-type guide layer 208. , N-side buffer layer 204 and p-side buffer layer 2
06 and the effect of reducing the crystal lattice distortion in the active layer 205 having the quantum well structure. Further, the n-type guide layer 203 and the p-type guide layer 208 having the gradient composition have the effect of reducing crystal cracking of the n-type clad layer 202 and the p-type clad layer 209 made of the hardest AlGaN, and the n-side buffer layer 204 and p-type There is also an effect of reducing the crystal strain of the side buffer layer 206, and the device fabrication yield of the device of this example was improved from 45% to 78% as compared with the device of Example 2. The n-type guide layer 20 having a gradient composition in this embodiment
3. The p-type guide layer 208 has a form in which the Al composition of AlGaN increases as the distance from the active layer 205 increases.
It may be formed of a composition gradient layer that reduces the n composition. Further, the n-type guide layer 203 or the p-type guide layer 208
A quaternary semiconductor layer of l _s Ga _1-sp In _p N may be used, and p may gradually decrease while s gradually increases as the distance from the side closer to the active layer 205 increases.

(Embodiment 5) The structure of still another embodiment is shown in FIG.
Shown in In the present embodiment, the n-type guide layer 203 of the second embodiment is formed of a graded composition layer in which the Al composition gradually increases from GaN to Al _0.1 Ga _0.9 N from the side farther from the active layer 205 as the distance from the active layer increases. .1 μm thick n
-Type second optical guide layer 5032, and the In composition increases from In _0.08 Ga _0.92 N to GaN as the distance from the active layer increases.
Consisting of an InGaN graded composition layer that gradually decreases to
The structure was changed to a two-layer structure including the n-type first optical guide layer 5031 having a thickness of 1 μm. In this case, the device characteristics were not changed from those in Example 4, but the production yield of the device was further improved to about 85%. Was observed.

(Embodiment 6) FIG. 8 shows a semiconductor laser structure according to a different embodiment of the present invention. In this embodiment, the p-type guide layer 208 of the second embodiment is replaced with the active layer 2.
05, a 0.05 μm thick p-type first optical guide layer 6081 comprising an InGaN graded composition layer in which the In composition gradually decreases from In _0.03 Ga _0.97 N to GaN as the distance from the active layer increases, The p-type second optical guide layer 6082 having a thickness of 0.1 μm and having a graded composition layer in which the Al composition gradually increases from GaN to Al _0.1 Ga _0.9 N as the distance from the active layer increases is changed to a two-layer structure. In this case as well, the device characteristics were not changed from those in Example 4, but the production yield of the device was improved to about 82%.

(Embodiment 7) FIG. 9 shows the configuration of an embodiment device (semiconductor laser device) separately. In this embodiment, the second embodiment
The n-type guide layer 203 in Example 2 is the two gradient composition layers 5032 and 5031 in Example 5, and the p-type guide layer 208 in Example 2 is the two gradient composition layer 60 in Example 6.
81 and 6082. That is, both the n-type light guide layer and the p-type light guide layer were composed of two graded composition layers. In this case, the device characteristics were as good as those of Example 4, such as low current and high reliability. Fabrication yield was improved over Examples 5 and 6, rising to 91%.

As described above, the embodiments of the present invention have been described with reference to the various embodiments. However, the present invention is not limited to the above-described embodiments, and similar effects can be obtained in the following cases. Obtainable. (1) Unlike the above embodiment, each layer such as a quantum well active layer, a barrier layer, a cladding layer, a guide layer, and a contact layer is formed of a quaternary mixed crystal of AlGaInN or GaInAsN, or a quinary nitride semiconductor material of AlGaInNAs. When configured with (2) A case where a different layer is inserted in a portion other than between the quantum well and the buffer layer in the above embodiment. (3) The case where the conductivity types are all inverted with respect to the above embodiment.

[0051]

As described above, by applying the present invention, it is possible to realize a semiconductor light emitting device (LED) having a high luminous intensity and excellent monochromaticity. In addition, by applying the present invention to a gallium nitride based semiconductor laser, a laser device having low threshold current and operating current and having high reliability under high temperature and high output conditions can be obtained. Further, by applying the graded composition layer to the guide layer of the semiconductor laser, it is possible to further reduce the current and extend the life, and at the same time, to improve the production yield.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a GaN-based LED according to a first embodiment.

FIG. 2 is a graph showing the dependence of the emission intensity and the full width at half maximum of the emission spectrum on the p-side buffer layer thickness in Example 1.

FIG. 3 is a graph showing the n-side buffer layer thickness dependence of the emission intensity and the full width at half maximum of the emission spectrum in Example 1.

FIG. 4 is a graph showing the dependence of the emission intensity and the full width at half maximum of the emission spectrum on the p-side buffer layer mixed crystal ratio: y in Example 1.

FIG. 5 is a graph showing the dependence of the emission intensity and the full width at half maximum of the emission spectrum on the n-side buffer layer mixed crystal ratio: x in Example 1.

FIG. 6 is a structural diagram of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 7 is a structural diagram of a semiconductor laser device according to a fifth embodiment of the present invention.

FIG. 8 is a structural diagram of a semiconductor laser device according to Embodiment 6 of the present invention.

FIG. 9 is a structural diagram of a semiconductor laser device according to Example 7 of the present invention.

FIG. 10 is a sectional structural view of a conventional semiconductor light emitting device.

FIG. 11 is a sectional structural view of a semiconductor laser device according to a conventional technique.

[Explanation of symbols]

Reference Signs List 101 n-type SiC substrate 102 AlGaN low-temperature buffer layer 103 n-type GaN cladding layer 104 n-side buffer layer 105 active layer 106 p-side buffer layer 107 p-type GaAlN protective layer 108 p-type GaN contact layer 109 p-type translucent electrode 110 p-type Pad electrode 111 n-type electrode 201 n-type GaN substrate 202 n-type AlGaN cladding layer 203 n-type guide layer 204 n-side buffer layer 205 active layer 206 p-side buffer layer 207 p-type AlGaN protective layer 208 p-type guide layer 209 p-type clad Layer 210 p-type GaN contact layer 211 mesa stripe 212 n-type AlGaN current confinement layer 213 p-type GaN second contact layer 220 p-type electrode 221 n-type electrode 5031 n-type first light guide layer 5032 n-type second light guide layer 6081 p-type first light guide layer 6082 p-type second optical guide layer 1001, 1100 sapphire substrate 1002 GaN buffer layer 1003 GaN second cladding layer 1004 In _0.01 Ga _0.99 N first cladding layer 1005 In _0.30 Ga _0.70 N single quantum well active layer 1006 p-type In _0.01 Ga _0.99 N first cladding layer 1007 p-type Al _0.3 Ga _0.7 N second cladding layer 1008 p-type GaN contact layer 1010, 1121 n-type electrode 1011, 1120 p-type electrode 1012 pad electrode 1101 n-type GaN contact layer 1102 n-type AlGaN cladding Layer 1103 n-type GaN guide layer 1105 multiple quantum well active layer 1107 p-type AlGaN protective layer 1108 p-type GaN guide layer 1109 p-type AlGaN cladding layer 1110 p-type GaN contact layer 1111 mesa stripe 1112 SiO ₂ Insulating film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Mori 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside Sharp Corporation (72) Inventor Masafumi Kondo 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka (72) Inventor Eiji Yamada 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka F-term (reference) 5F041 AA03 AA11 CA05 CA33 CA34 CA46 CA60 CA65 CA83 CB11 FF01 FF16 5F073 AA11 AA45 AA55 AA74 AA83 CA07 CB02 CB07 CB08 CB19 DA05 DA32 EA23 EA28

Claims (9)

[Claims] 1. An n-type GaN-based cladding layer and In _a Ga
_{In a} gallium nitride based semiconductor light emitting device including _{a 1-a} N quantum well layer (0.15 ≦ a ≦ 1) and a p-type GaN based contact layer, the active layer is In _x Ga _1-x Nn. Side buffer layer (0.03 ≦ x ≦ a−0.1) and In _y Ga _1-y N
Sandwiched in contact with both -p-side buffer layer (0.03 ≦ y ≦ a-0.15 ) is formed, In _x Ga _1-x N
The semiconductor light emitting device characterized by thickness of -n-side buffer layer and _{In y Ga 1-y N-} p -side buffer layer is 3nm or more 25nm or less, respectively. 2. The method according to claim 1, wherein the active layer is formed of an In _a Ga ₁ -aN first quantum well layer and an In _b1 Ga from the side close to the n-type GaN-based cladding layer.
_1-b1 N first barrier layer, In _a Ga _1-a N second quantum well layer,
_{Inb2Ga1 -b2N} second barrier layer ... _{InbnGa1 -bnN}
A multiple quantum well active layer formed in the order of an n _- th barrier layer, an In _a Ga _1-a N-th n + 1 quantum well layer (where n is an integer of 1 or more), and an In _x Ga _1-x N-n side The composition of the buffer layer is 0.03 ≦ x ≦ a−0.1, b1−0.02 ≦ x ≦ b1
+0.02, and the composition of the In _y Ga _1-y N-p side buffer layer is 0.03 ≦ y ≦ a−0.15, bn−0.02 ≦ y ≦
2. The semiconductor light emitting device according to claim 1, wherein bn + 0.02. 3. The semiconductor light emitting device according to claim 2, wherein the number of the quantum well layers is four or less, and the number of the barrier layers is three or less. 4. The In-crystal ratio of all of the barrier layers, the n-side buffer layer, and the p-side buffer layer is the same (x = b1 =
The semiconductor light emitting device according to claim 2, wherein b2 = ... = bn = y). 5. The method according to claim 1, wherein the thickness of the p-side buffer layer is 6.5 nm or more and 25 nm or less.
3. The semiconductor light emitting device according to item 1. 6. An n-type impurity having a concentration of 5 in the n-side buffer layer.
A range of from × 10 ¹⁶ cm ^{−3 to} 1 × 10 ²⁰ cm ⁻³ is doped into the filament, and a concentration of p-type impurity is 1 × 10 ¹⁷ cm ^{−3 to} 5 × 10 ²¹ cm ^{− in the} p-side buffer layer. ^3. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is doped within a range of ³ or less. 7. An n-type light guide layer comprising a graded composition layer on the opposite side of the n-side buffer layer from the active layer, and an n-type light guide layer containing Al on the opposite side of the active layer from the n-type light guide layer. AlGaN
And the n-type light guide layer has an Al composition that increases as the distance from the active layer increases.
3. The semiconductor light emitting device according to claim 1, comprising a graded composition layer having a reduced n composition. 8. A p-type light guide layer comprising a graded composition layer on a side of the p-type buffer layer opposite to the active layer, and Al on a side of the p-type light guide layer opposite to the active layer. p-type AlG
3. The p-type optical guide layer comprising an aN-based cladding layer, and wherein the p-type light guide layer comprises a graded composition layer in which the Al composition increases or the In composition decreases as the distance from the active layer increases. Or a semiconductor light emitting device according to 7. 9. A first guide layer in which one of the n-type and p-type light guide layers has a reduced In composition as the distance from the active layer increases, and a second guide in which the Al composition increases as the distance from the active layer increases. The semiconductor light-emitting device according to claim 7, wherein the semiconductor light-emitting device is constituted by a layer, and the first guide layer is formed closer to the active layer than the second guide layer.