JP2007088269A - Semiconductor light emitting element, lighting device using the same and manufacturing method of semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve emission efficiency in a semiconductor light emitting element where an n-type nitride semiconductor layer, a light emitting layer (active layer) and a p-type nitride semiconductor layer are sequentially laminated on a substrate. <P>SOLUTION: Well layers 14a, 14b and 14c of the light emitting layer 14 are formed of an Al<SB>0.02</SB>In<SB>0.18</SB>Ga<SB>0.80</SB>N layer and a band gap at a room temperature is 2.7 eV. Barrier layers 14d, 14e, 14f and 14g are formed of an Al<SB>0.3</SB>In<SB>0.12</SB>Ga<SB>0.58</SB>N layer, and the band gap at the room temperature is 3.5 eV higher than 3.4 eV of GaN layers 13 and 16. An electron blocking layer 15 is formed of an Al<SB>0.4</SB>In<SB>0.1</SB>Ga<SB>0.5</SB>N layer, and the band gap at the room temperature is 3.8 eV. Thus, a deep well can be obtained and it can be formed at a temperature which is remarkably lower than a case when the electron blocking layer 15 is created by AlGaN. A deposition temperature is brought close to the light emitting layer 14, sufficient film quality can be obtained and emission efficiency can be improved much more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting element that emits light by combining electrons and holes in a semiconductor, an illumination device using the same, and a method for manufacturing the semiconductor light emitting element.

  In recent years, a III-N compound (hereinafter referred to as a nitride) is used to form a multiple quantum well as a light emitting layer (active layer) therein, and an electric current is passed from the outside. The development of semiconductor solid-state light emitting devices that emit light by combining holes is remarkable.

A typical example of such a semiconductor light emitting device is Non-Patent Document 1. According to the prior art, in the semiconductor light emitting device emitting light from near ultraviolet to blue, the structure of the light emitting layer is such that the well layer is In _x Ga _(1-x) N (0 <x <1) and the barrier layer is GaN. It is common to do. Furthermore, since the electron mobility is very large and easily leaks into the p-layer through the light-emitting layer, in order to prevent electrons from overflowing from the quantum well and flowing into the p-layer, in the above-mentioned document, non-patent document 2 As also shown, an AlGaN layer having a band gap larger than that of the barrier layer is provided between the light emitting layer and the p layer. This is generally called an electron blocking layer, which prevents leakage of electrons into the p layer and improves injection efficiency into the light emitting layer.

  A typical conventional example of such a semiconductor light emitting device is shown in FIG. Using MOCVD, the buffer layer 2 is formed on the sapphire substrate 1, and then the Si-doped n-type GaN layer 3 is formed at 1020 ° C., and the light emitting layer 4 and the electron blocking layer 5 are formed thereon. A p-type GaN layer 6 is formed thereon to complete the epitaxial layer. Thereafter, the p-type electrode 7 and the n-type electrode 8 are formed using a known technique to complete the semiconductor light emitting device.

  The light emitting layer 4 is formed by alternately depositing three well layers 4a, 4b, 4c and barrier layers 4d, 4e, 4f, 4g sandwiching them, and the well layers 4a, 4b, 4c are made of InGaN. The barrier layers 4d, 4e, 4f and 4g are made of GaN, and the well layers 4a, 4b and 4c and the barrier layers 4d, 4e, 4f and 4g are also formed at 1020 ° C. Further, the electron blocking layer 5 that prevents leakage of electrons from the light emitting layer 4 to the p-type GaN layer 6 is made of AlGaN, and is also formed at 1020 ° C.

FIG. 4 shows an energy band diagram of the semiconductor light emitting device configured as described above. For simplicity, the band offset is omitted. Here, the band gap of the n-type GaN layer 3 and the p-type GaN layer 6 is 3.4 eV at room temperature, the barrier layers 4d, 4e, 4f, and 4g in the light emitting layer 4 are also made of GaN, and the band gap is 3 .4 eV. On the other hand, the well layers 4a, 4b, and 4c are formed of In _0.17 Ga _0.83 N, have a band gap of 2.7 eV, and an emission wavelength of 460 nm in blue.
M. Koide.S, S. Yamasaki, S. Nagai, N. Koide, and S. Asam, H. Amano, and I. Akasak, Appl. Phys. Lett. 68, 1403 (1996) `` Introduction to Solid-State Lighting (John Wiley & Sons, Inc 2002) '' pp53-54

  However, in the above-described prior art, first, since the light emitting layer 4 is made of GaN / InGaN, the width and depth of the well layers 4a, 4b, and 4c cannot be made so large. Carriers cannot enter the layers 4a, 4b, and 4c, overflow from the well layers 4a, 4b, and 4c, and do not contribute to light emission. As a result, there is a problem that the luminous efficiency decreases monotonously as the current density is increased.

Further, the deposition temperature of In _x Ga _(1-x) N (0 <x <1) is about 700 to 800 ° C., whereas the deposition temperature of GaN is about 1000 to 1100 ° C. In order to continuously grow GaN, the growth temperature of GaN must be lowered in accordance with InGaN or rapidly increased from 800 ° C. to 1000 ° C. For this reason, the crystallinity of GaN that becomes the barrier layers 4d, 4e, 4f, and 4g is deteriorated, and a carrier trap level and a non-radiative recombination center are formed at the interface and inside the GaN layer, thereby causing the carriers to be trapped. It becomes. In addition, since the formation temperature of AlGaN in the electron blocking layer 5 is higher than that of GaN, for example, AlGaN must be deposited at a temperature lower than the optimum temperature, and defects or impurity levels are also formed at the interface between GaN and AlGaN. To form trapping levels of the carriers and non-radiative recombination centers.

  An object of the present invention is to form a light emitting layer deeper than an InGaN / GaN light emitting layer to increase carrier injection efficiency, and to have a semiconductor light emitting element having an electron stopper layer with good film quality, an illumination device using the same, and a semiconductor light emitting element It is to provide a manufacturing method.

  The semiconductor light-emitting device of the present invention is a semiconductor light-emitting device in which at least an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer are sequentially stacked on a substrate, wherein the light-emitting layer, the p-type nitride semiconductor layer, An electron blocking layer, and the well layer and barrier layer of the light emitting layer having a multiple quantum well structure and the electron blocking layer are made of AlInGaN, and the band gap of the barrier layer is larger than the band gap of GaN. The band gap of the electron blocking layer is larger than the band gap of the barrier layer.

  According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor light-emitting device, wherein the semiconductor light-emitting device is formed by sequentially stacking at least an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer on a substrate. A step of forming an n-type nitride semiconductor layer on the substrate at ℃, and the temperature is lowered, and at 800 ± z2 ℃, the barrier layer of the light emitting layer having a multiple quantum well structure is formed of AlInGaN, and 800 ± z3 A step of forming the well layer with AlInGaN at a temperature of ° C., a step of repeating the combination of the barrier layer and the well layer several times, a step of forming an electron blocking layer with AlInGaN at the temperature of 800 ± z 2 ° C., and And raising the temperature to form the p-type nitride semiconductor layer at 1000 ± z1 ° C.

According to the above configuration, in the semiconductor light emitting device in which at least the n-type nitride semiconductor layer, the light emitting layer (active layer), and the p type nitride semiconductor layer are sequentially stacked on the substrate, the light emitting layer and the p type nitride are provided. An electron blocking layer is provided between the semiconductor layer and an electron blocking layer for preventing light from flowing into the p-type nitride semiconductor layer to increase light emission efficiency, and the well layer of the light emitting layer having a multiple quantum well structure (MQW) _Is formed with a quaternary element of Al _y1 In _x1 Ga _(1-x1) N (0 <x1 <1, 0 <y1 <1), and the barrier layer of the light emitting layer is also Al _y2 In _x2 Ga _{(1-x2-y2). )} N (0 <x2 <1, 0 <y2 <1), and the electron blocking layer is also Al _y3 In _x3 Ga _(1-x3-y3) N (0 <x3 <1, Formed with quaternary elements of 0 <y3 <1) . The band gap of the barrier layer is larger than the band gap of GaN, and the band gap of the electron blocking layer is larger than the band gap of the barrier layer.

  And in realizing such a band gap, the band gap can be adjusted by the amount of Al in AlInGaN (the band gap can be increased by increasing the amount of Al), and InGaN adds Al at a lower temperature than GaN. be able to.

  Therefore, the electron blocking layer has a band gap as high as AlGaN, and can prevent the leakage of electrons from the light emitting layer to the p layer, thereby increasing the injection efficiency. In addition, a well layer having a band gap equivalent to that of InGaN can be formed, a barrier layer having a band gap higher than that of GaN can be formed, and a light emitting layer having a higher injection efficiency than that of the conventional example can be formed. Furthermore, the electron blocking layer can be formed at a temperature much lower than that of AlGaN. The well layer and barrier layer made of the same AlInGaN are brought close to the film formation temperature, and the film quality with few defects or impurity levels at the interface or inside the layer. A good electron blocking layer can be formed, and further improvement in luminous efficiency can be realized.

Furthermore, in the semiconductor light emitting device of the present invention, the well layer is made of Al _y1 In _x1 Ga _(1-x1) N (0 <x1 <1, 0 <y1 <1), and the barrier layer is Al _y2 In _x2. Ga _(1-x2-y2) N (0 <x2 <1,0 <y2 <1), and the electron blocking layer is Al _y3 In _x3 Ga _(1-x3-y3) N (0 <x3 <1 , 0 <y3 <1), and x1 = 0.18, y1 = 0.02, x2 = 0.12, y2 = 0.3, x3 = 0.1, y3 = 0.4 And

  According to the above configuration, the quantum well can be deepened to obtain a large injection current, and the band gap of the electron blocking layer can be increased to suppress the leakage current, and the film forming temperature is set to about 800 ° C. Can be set relatively close to each other, and good film quality can be obtained.

  The semiconductor light emitting device of the present invention is characterized in that a central emission wavelength by the light emitting layer is 380 nm or more and 470 nm or less.

  According to said structure, said wavelength range is a wavelength range with high luminous efficiency of the light emitting layer (active layer) of AlInGaN / AlInGaN, and it is set as the composition which can obtain a desired band gap within the wavelength range. It is desirable.

  Furthermore, the lighting device of the present invention is characterized by using the semiconductor light emitting element.

  According to the above configuration, the lighting device can obtain a desired color rendering property by adjusting the phosphor, and efficient excitation light is required. Therefore, the semiconductor light emitting device having high luminous efficiency as described above. It is particularly suitable for the lighting device.

As described above, the semiconductor light-emitting device and the method for manufacturing the same according to the present invention are obtained by sequentially laminating at least an n-type nitride semiconductor layer, a light-emitting layer (active layer), and a p-type nitride semiconductor layer on a substrate. An electron blocking layer is provided between the light emitting layer and the p-type nitride semiconductor layer to increase the light emission efficiency by preventing electrons from flowing into the p-type nitride semiconductor layer. The well layer of the light emitting layer made of (MQW) is formed of a quaternary element of Al _y1 In _x1 Ga _(1-x1) N (0 <x1 <1, 0 <y1 <1), and the barrier layer of the light emitting layer is also Al _{y2 in x2 Ga (1-x2} -y2) N (0 <x2 <1,0 <y2 <1) of the form with quaternary elements, further wherein the electron blocking layer also _{Al y3 in x3 Ga (1-} x3- _y3) N (0 <x3 The band gap of the barrier layer is larger than the band gap of GaN, and the band gap of the electron blocking layer is larger than the band gap of the barrier layer. To do.

  Therefore, the electron blocking layer has a band gap with a height close to that of AlGaN, and can prevent the leakage of electrons from the light emitting layer to the p layer and increase the injection efficiency. In addition, a well layer having a band gap equivalent to that of InGaN can be formed, a barrier layer having a band gap higher than that of GaN can be formed, and a light emitting layer having a higher injection efficiency than that of the conventional example can be formed. Furthermore, the electron blocking layer can be formed at a temperature much lower than that of AlGaN. The well layer and barrier layer made of the same AlInGaN are brought close to the film formation temperature, and the film quality with few defects or impurity levels at the interface or inside the layer. A good electron blocking layer can be formed, and a further improvement in luminous efficiency can be realized.

  Furthermore, the illumination device of the present invention uses the semiconductor light emitting element as described above.

  Therefore, it is particularly preferable to use the above-described semiconductor light-emitting element in an illumination device that requires efficient excitation light.

  FIG. 1 is a cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention. The basic structure of the semiconductor light emitting device of the present invention is the same as that of the semiconductor light emitting device shown in FIG. 3, and the structure will be described below. On the sapphire substrate 11, the buffer layer 12, the n-type GaN layer 13, the light emitting layer 14, the electron blocking layer 15 and the p-type GaN layer 16 are sequentially laminated to complete the epi. Thereafter, the p-type electrode 17 and the n-type electrode 18 are formed. The light emitting layer 14 includes three well layers 14a, 14b, and 14c and barrier layers 14d, 14e, 14f, and 14g sandwiching the well layers.

It should be noted that in the present invention, the composition of the electron blocking layer 15 is different from that of the semiconductor light emitting device shown in FIG. Specifically, the well layers 14a, 14b, 14c, the barrier layers 14d, 14e, 14f, 14g, and the electron blocking layer 15 are all made of AlInGaN. For example, the well layers 14a, 14b and 14c are made of Al _0.02 In _0.18 Ga _0.8 N, and the barrier layers 14d, 14e, 14f and 14g are Al _0.3 In _0.12 Ga _0.58 N. The electron blocking layer 15 is made of Al _0.4 In _0.1 Ga _0.5 N. In order to achieve a desired bandgap, if all layers are made of AlInGaN, the bandgap can be adjusted by the amount of Al (the bandgap can be increased by increasing Al), and more than InGaN. This is because Al can be added at a lower temperature.

Below, the crystal growth method of the semiconductor light-emitting device comprised as mentioned above is demonstrated. The gases used for the growth are hydrogen gas (H ₂ ), nitrogen gas (N ₂ ) as carrier gases, and ammonia (NH ₃ ), trimethyl gallium (Ga (CH ₃ ) ₃ ), and trimethyl aluminum (G) as growth gases. Al (CH ₃ ) ₃ ), trimethylindium, (In (CH ₃ ) ₃ ), silane (SiH ₄ ), and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ).

  First, the sapphire substrate 11 is cleaned with an organic and acid solution. Then, using a MOCVD apparatus, a GaN buffer layer 12 having a thickness of 30 nm is formed at 550 ° C. in a reduced pressure atmosphere of 76 Torr, and then heated to 1000 ± z 1 ° C., for example, 1020 ° C. of z1 = + 20, and doped with Si. Then, 3 μm of the n-type GaN layer 13 is deposited. These techniques are already well known and will not be described in detail.

Thereafter, the temperature is lowered to 800 ± z2 ° C., for example, 840 ° C. where z2 = + 40, and ammonia, trimethylgallium, trimethylindium, and trimethylaluminum are used as material gases, respectively, with an indium composition ratio of 12% and an aluminum composition ratio of The Al _0.3 In _0.12 Ga _0.58 N layer serving as the first barrier layer 14d in the light emitting layer 14 is flowed by selecting a flow ratio so that the composition ratio of gallium is 30% and 58%. A thickness of about 5 nm is formed. Subsequently, the temperature is lowered to 800 ± z3 ° C., for example, 800 ° C. where z3 = 0, and in the same manner as in the formation of the barrier layer, the respective gas flow ratios are selected, the indium composition ratio is 18%, and the aluminum composition The Al _0.02 In _0.18 Ga _0.80 N layer serving as the first well layer 14a in the light emitting layer 14 is about 3 nm thick under the condition that the ratio is 2% and the composition ratio of gallium is 80%. Form. Similarly, the second barrier layer 14e and the well layer 14b, the third barrier layer 14f and the well layer 14c, and the fourth barrier layer 14g are formed.

Thereafter, the gas flow ratio of ammonia, trimethylgallium, trimethylindium and trimethylaluminum is changed while maintaining the temperature of the barrier layer 14g at 840 ° C., which is 800 ± z 2 ° C., and the composition ratio of indium is 10%. The Al _0.4 In _0.1 Ga _0.5 N layer to be the electron blocking layer 15 is formed to a thickness of about 20 nm so that the composition ratio is 40% and the gallium composition ratio is 50%.

  Thereafter, the temperature is raised to 1020 ° C., which is 1000 ± z1 ° C., the p-type GaN layer 16 is formed while doping Mg, and the creation of the epi-wafer is completed to form the p-type electrode 17 and the n-type electrode 18. However, since this is also a conventionally well-known method, details are omitted. Thus, the semiconductor light emitting device of the present invention is completed.

FIG. 2 is an energy band diagram in the semiconductor layer of the semiconductor light emitting device of the present invention prepared as described above. For simplicity, the band offset is omitted. The band gaps of the n-type GaN layer 13 and the p-type GaN layer 16 are 3.4 eV at room temperature. Among the light emitting layers 14, the barrier layers 14d, 14e, 14f, and 14g are composed of the Al _0.3 In _0.12 Ga _0.58 N layer, and the band gap is 3.5 eV at room temperature. Therefore, the quantum well is deeper than the conventional InGaN / GaN and the amount of accumulated carriers can be increased.

On the other hand, the well layers 14a, 14b, 14c are composed of the Al _0.02 In _0.18 Ga _0.80 N layer, and the band gap at room temperature is 2.7 eV. The well layers 14a, 14b, 14c emit light again. The wavelength of light emitted by the coupling is 460 nm blue. The electron blocking layer 15 is made of the Al _0.4 In _0.1 Ga _0.5 N layer, and has a band gap at room temperature of 3.8 eV, which is higher than the barrier layers 14d, 14e, 14f, and 14g. The height is high enough to stop leakage to the p-type GaN layer 16.

Here, in order to form the electron blocking layer 5 having the same band gap with the conventional AlGaN of FIG. 3, Al _0.14 Ga ₀₈₆ N having an Al composition of 14% and a Ga composition of 86% is used. It is necessary to deposit at 1100 ° C., and in order to prevent dissociation of the light emitting layer 4, as described above, it must be formed at a temperature considerably lower than the optimum Al _0.14 Ga ₀₈₆ N forming conditions. (750-850 ° C).

  Therefore, it is understood that the electron blocking layer 15 of the present invention can be formed at a remarkably low temperature, and the device can be formed while maintaining both the film quality of the light emitting layer 14 and the film quality of the electron blocking layer 15 at a high quality. Is done. In addition, well layers 14a, 14b, and 14c having a band gap equivalent to InGaN can be formed, and barrier layers 14d, 14e, 14f, and 14g having a band gap higher than that of GaN can be formed, and deeper than the InGaN / GaN light-emitting layer 4. Thus, the light emitting layer 14 capable of accumulating many electrons can be formed. In this way, the light emission efficiency can be improved as compared with the conventional case.

  Further, by adjusting the two parameters x and y of Al and In, the center emission wavelength and the band gap of the light emitting layer 14 can be easily changed, and the center emission wavelength is set to 380 nm or more and 470 nm or less. By doing so, the luminous efficiency of the light emitting layer 14 made of AlInGaN / AlInGaN can be increased.

  Furthermore, in a lighting device using a semiconductor light emitting element, a desired color rendering property can be obtained by adjusting a phosphor, and efficient excitation light is required. The use of the element is particularly suitable for a lighting device.

1 is a cross-sectional view of a semiconductor light emitting element according to an embodiment of the present invention. It is an energy band figure by the semiconductor light-emitting device of this invention. It is sectional drawing of the semiconductor light-emitting device of a prior art. It is an energy band figure by the semiconductor light emitting element of a prior art.

Explanation of symbols

11 Sapphire substrate 12 Buffer layer 13 n-type GaN layer 14 Light-emitting layers 14a, 14b, 14c Well layers 14d, 14e, 14f, 14g Barrier layer 15 Electron blocking layer 16 p-type GaN layer 17 p-type electrode 18 n-type electrode

Claims (5)

In a semiconductor light-emitting device comprising at least an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer sequentially stacked on a substrate,
An electron blocking layer is provided between the light emitting layer and the p-type nitride semiconductor layer,
The well layer and barrier layer of the light emitting layer having a multiple quantum well structure and the electron blocking layer are made of AlInGaN, and the band gap of the barrier layer is larger than the band gap of GaN, and the band gap of the electron blocking layer Is larger than the band gap of the barrier layer. The well layer is made of Al _y1 In _x1 Ga _(1-x1) N (0 <x1 <1, 0 <y1 <1), and the barrier layer is Al _y2 In _x2 Ga _(1-x2-y2) N (0 <X2 <1, 0 <y2 <1), and the electron blocking layer is made of Al _y3 In _x3 Ga _(1-x3-y3) N (0 <x3 <1, 0 <y3 <1), x1 2. The semiconductor light emitting device according to claim 1, wherein: 0.18, y 1 = 0.02, x 2 = 0.12, y 2 = 0.3, x 3 = 0.1, and y 3 = 0.4.   2. The semiconductor light emitting element according to claim 1, wherein a central emission wavelength by the light emitting layer is 380 nm or more and 470 nm or less.   An illumination device using the semiconductor light emitting element according to claim 2. In a method for manufacturing a semiconductor light-emitting element, in which at least an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer are sequentially stacked on a substrate.
Forming an n-type nitride semiconductor layer on the substrate at 1000 ± z1 ° C .;
The barrier layer of the light emitting layer having a multiple quantum well structure is formed of AlInGaN at a temperature of 800 ± z 2 ° C., and the well layer is formed of AlInGaN at a temperature of 800 ± z 3 ° C. A step of repeating the set with the well layer several times;
Forming an electron blocking layer of AlInGaN at a temperature of 800 ± z2 ° C .;
And raising the temperature to form the p-type nitride semiconductor layer at 1000 ± z1 ° C.

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