JP6725242B2 - Semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

The present invention relates to a semiconductor light emitting device and a method for manufacturing the same, and more particularly to a semiconductor light emitting device having a multiple quantum well structure and an electron block layer and a method for manufacturing the same.

2. Description of the Related Art Conventionally, in order to improve the light emission efficiency of a semiconductor light emitting device such as a light emitting diode, a multiple quantum well (MQW) structure in which a barrier layer and a well layer are alternately stacked is used as an active layer. Further, on the last barrier layer which is the uppermost barrier layer forming the MQW active layer, an electron block layer is formed of a material having an electron barrier higher than that of the barrier layer, and carriers overflow to the p-type semiconductor layer side. There is also proposed a method of preventing the carrier from being confined in the MQW active layer (for example, Patent Documents 1 and 2).

In such a semiconductor light emitting device, holes and electrons are respectively injected from the p-type layer and the n-type layer formed above and below the active layer to recombine light emission in the active layer. It is necessary to dope with an appropriate impurity concentration. Further, by doping the electron blocking layer with p-type impurities, the barrier against carriers in the electron blocking layer is increased, and the effect of preventing carriers from overflowing from the light emitting layer is enhanced.

FIG. 12 is a timing chart showing the growth temperatures of the last barrier layer and the electron block layer of the semiconductor light emitting device and the supply of the impurity raw material in the conventional technique. In a semiconductor light emitting device using a nitride-based material, after growing a GaN layer which is a last barrier layer, an AlGaN layer doped with Mg which is a p-type impurity is grown as an electron block layer.

As shown in FIG. 12, in the growth process of the last barrier layer, the growth temperature is maintained at 800° C., and during that period, a nitrogen raw material ammonia and a gallium raw material TEG (Triethylgallium) are flown to grow the GaN layer. Next, the flow rate of ammonia is maintained, the supply of TEG is stopped, and the temperature is raised from 800°C to 1000°C. In this temperature raising step, since the supply of TEG which is a gallium raw material is stopped, the growth of the GaN layer is interrupted.

Next, in the growth process of the AlGaN electron block layer containing Mg as a p-type impurity, the growth temperature is maintained at 1000° C., and during that time, ammonia, TMG (Trimethylgallumium), TMA (Trimethylethylaluminium), and Cp ₂ Mg(Bis(cyclopentadieneyl)magnesium) are used. ) Supply. As described above, in the conventional technique, after the last barrier layer is grown, the growth is interrupted in the temperature raising step, and after the temperature is raised, the growth of the electron block layer is started, and at the same time, the supply of Cp ₂ Mg, which is a Mg source, is started, and the electron block The layer is doped with Mg which is a p-type impurity.

JP, 2001-015809, A JP, 2009-130097, A

However, in the conventional technique, since Mg doping is started at the same time as the growth of the electron block layer is started, the Mg density in the device atmosphere is low in the initial stage of growth, it is difficult to take in the Mg raw material, and the impurity concentration in the semiconductor layer is low. turn into. As the growth of the electron block layer continues, Mg is gradually taken into the semiconductor layer, but the impurity concentration of the entire electron block layer decreases due to the low concentration region at the initial stage of growth. Further, if the impurity concentration on the light emitting layer side of the electron blocking layer is low, the efficiency of injecting holes into the light emitting layer also decreases, and the effect of preventing carrier overflow from the light emitting layer also decreases, so the light emitting efficiency of the semiconductor light emitting element decreases. Resulting in.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a semiconductor light emitting device capable of appropriately doping impurities from an early stage of growth of an electron block layer, and a manufacturing method thereof. ..

In order to solve the above problems, a light emitting diode of the present invention comprises a multiple quantum well active layer in which barrier layers and well layers are alternately laminated, and an electron block layer formed on the multiple quantum well active layer. In the light emitting diode, the last barrier layer, which is the uppermost layer of the barrier layers, comprises a doped region doped with the same impurity as the impurity doped in the electron block layer, and a non-doped region not doped with the impurity, The doped region is formed on the non-doped region, the thickness of the last barrier layer is thicker than the thickness of the other barrier layer and is in the range of 20 nm to 30 nm, and the doped region is The impurity concentration is 1×10 ¹⁸ cm ⁻³ or more and the thickness is in the range of 5 nm to 15 nm.

In such a semiconductor light emitting device of the present invention, since the same impurities as in the electron block layer are doped from the growth stage of the last barrier layer, it is necessary to sufficiently incorporate the impurities into the semiconductor layer from the initial growth stage of the electron block layer. Therefore, it becomes possible to dope the impurities appropriately.

Further, the impurity concentration of the doped region may be lower than the impurity concentration of the electron block layer.

The impurity concentration of the doped region may be 3×10 ¹⁸ cm ⁻³ or more .

Further, the last barrier layer may be made of GaN .

Further, the electron blocking layer may be that formed of AlGaN.

In order to solve the above problems, a method for manufacturing a light emitting diode according to the present invention comprises growing a multiple quantum well active layer in which barrier layers and well layers are alternately laminated, and forming an electron block layer on the multiple quantum well active layer. In the method for manufacturing a light emitting diode to be grown, the step of growing the last barrier layer, which is the uppermost layer of the barrier layers, comprises a non-doped region growth step of crystal growth without doping impurities for doping the electron block layer. A doping region growing step of doping the impurities to perform crystal growth, wherein the thickness of the last barrier layer is thicker than the thickness of the other barrier layer and is in the range of 20 nm to 30 nm. The region is characterized in that the concentration of the impurities is 1×10 ¹⁸ cm ⁻³ or more and the thickness is in the range of 5 nm or more and 15 nm or less.

In such a method for manufacturing a semiconductor light emitting device of the present invention, since the step of growing the last barrier layer includes the step of growing the doped region, impurities can be sufficiently incorporated into the semiconductor layer from the initial stage of growth of the electron block layer. Therefore, the impurities can be appropriately doped.

The present invention can provide a semiconductor light emitting device that can be appropriately doped with impurities from an initial stage of growth of an electron block layer, and a manufacturing method thereof.

It is a schematic diagram which shows the layer structure of the semiconductor light-emitting device 1 in 1st Embodiment. It is a schematic diagram explaining in detail the structure of the light emitting layer 14 shown in FIG. 6 is a timing chart showing the growth temperatures of the last barrier layer 14c and the electron block layer 15 and the supply of the impurity raw material in the first embodiment. It is a SIMS profile in a comparative example which does not form a doped region in the last barrier layer 14c. 5 is a SIMS profile in Example 1 in which a doped region having a thickness of 5 nm was formed in the last barrier layer 14c. 6 is an impurity concentration profile of only Mg concentration shown in FIG. 5. It is a SIMS profile in Example 2 which formed the doped region 10 nm in the last barrier layer 14c. 9 is a SIMS profile in Example 3 in which a doped region of 15 nm is formed in the last barrier layer 14c. It is a table which shows the relative light emission intensity of a comparative example and Examples 1-3. 9 is a timing chart showing the growth temperatures of the last barrier layer 14c and the electron block layer 15 and the supply of the impurity raw material in the second embodiment. 11 is a timing chart showing the growth temperatures of the last barrier layer 14c and the electron block layer 15 and the supply of impurity raw materials in the third embodiment. 7 is a timing chart showing the growth temperature of the last barrier layer and the electron block layer of the semiconductor light emitting device and the supply of the impurity raw material in the conventional technique.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and duplicated description will be omitted as appropriate.

FIG. 1 is a schematic view showing the layer structure of the semiconductor light emitting device 1 according to this embodiment. The semiconductor light emitting device 1 includes a GaN buffer layer 11, a GaN foundation layer 12, an n-type AlGaN foundation layer 13, a light emitting layer 14, an electron block layer 15, and a p-type GaN contact layer 16 on a sapphire substrate 10. Equipped with.

The sapphire substrate 10 is a substrate obtained by cutting out a c-plane of sapphire single crystal as a main surface. Although the sapphire substrate 10 having the c-plane as the main surface is shown here, it may be an off-substrate tilted from the c-plane in a predetermined crystal axis direction, and a-planes other than the c-plane, m-planes, r-planes and other A high-order surface orientation may be used as the main surface.

The GaN buffer layer 11 is a buffer layer made of GaN formed on the main surface of the sapphire substrate 10, and is grown at a relatively low temperature of about 500° C., for example. The GaN base layer 12 is a layer made of a single crystal of GaN grown intentionally as non-doped and containing no impurities. The film thickness of the GaN base layer 12 is, for example, about 3000 nm, but it may be appropriately adjusted if necessary. The n-type AlGaN base layer 13 is a layer made of GaN single crystal doped with Si as an n-type impurity. The film thickness of the n-type AlGaN underlayer 13 is, for example, about 3000 nm, and the impurity concentration is, for example, about 1×10 ¹⁹ cm ⁻³ , but it may be appropriately adjusted if necessary.

The light emitting layer 14 is a multiple quantum well active layer in which well layers and barrier layers (barrier layers) are alternately stacked. The electron block layer 15 is a semiconductor layer formed on the light emitting layer 14 to prevent overflow of carriers, and is made of a material having a larger electron barrier than the barrier layer. The p-type GaN contact layer 16 is a layer made of a GaN single crystal doped with Mg as a p-type impurity.

The impurity concentration of the p-type GaN contact layer 16 is, for example, about 1×10 ¹⁹ cm ⁻³ , but may be in the range of about 1×10 ¹⁸ cm ^{−3 to} 5×10 ²⁰ cm ⁻³ . The preferable thickness range of the p-type GaN contact layer 16 is 50 to 150 nm, and more preferably 80 to 100 nm.

Although an electrode is not shown in the semiconductor light emitting element 1 in FIG. 1, a known electrode structure for a semiconductor light emitting element may be adopted. For example, a partial region of the semiconductor layer is etched until the n-type AlGaN underlayer 13 is exposed. Forming an n-side electrode, and forming a p-side electrode on the p-type GaN contact layer 16. Details of the structures of the light emitting layer 14, the electron blocking layer 15, and the p-type GaN contact layer 16 will be described later.

Here, as the material forming the buffer layer, the GaN base layer, and the p-type contact layer, the GaN buffer layer 11, the GaN base layer 12, the n-type AlGaN base layer 13, and the p-type GaN contact layer 16 are given as examples. Alternatively, other materials such as GaN, AlGaN, InGaN, InAlGaN may be used. For example, both the non-doped underlayer and the n-type doped underlayer may be GaN layers, or both may be AlGaN layers. Further, if necessary, a conventionally known structure such as a clad layer, a current confinement layer, and a current diffusion layer used in a semiconductor light emitting device may be applied.

FIG. 2 is a schematic diagram for explaining the structure of the light emitting layer 14 shown in FIG. 1 in detail. As shown in FIG. 2, the light emitting layer 14 of the present embodiment has a structure in which barrier layers 14a and well layers 14b are alternately formed by repeating five cycles, and a last barrier layer 14c is formed on the last well layer 14b. .. The barrier layer 14a is, for example, a GaN layer having a thickness of 12 nm, and the well layer 14b is, for example, an InGaN layer having a thickness of 3 nm.

The thickness of the barrier layer 14a is preferably 5 to 15 nm, more preferably 8 to 12 nm. The thickness of the well layer 14b is preferably 2 to 4 nm, and more preferably 2.5 to 3.5 nm. The last barrier layer 14c is made of GaN, which is the same material as the barrier layer 14a, and is formed thicker than the barrier layer 14a. A preferable thickness range is about 1.5 to 3 times that of the barrier layer 14a. The film thickness is 15 to 30 nm, and more preferably 20 to 30 nm.

The electron block layer 15 is formed on the last barrier layer 14c, is made of a material having a larger barrier against electrons than the last barrier layer 14c, and is formed from the light emitting layer 14 of the multiple quantum well structure to the p-type GaN contact layer 16. To prevent carrier overflow into the. The electron block layer 15 is, for example, a p-type AlGaN layer doped with Mg as a p-type impurity in the range of 1×10 ¹⁸ cm ^{−3 to} 5×10 ²⁰ cm ⁻³ , and the preferable thickness range is 10 to 40 nm. Yes, and more preferably 20 to 30 nm.

Here, GaN is used as the material of the barrier layer 14a and the last barrier layer 14c, InGaN is used as the material of the well layer 14b, and AlGaN is used as the material of the electron block layer 15, but other materials are used. It may be. Although the light emitting layer 14 has a multi-quantum well structure of 5 periods in FIG. 2, the number of periods may be appropriately adjusted.

Next, a method for manufacturing the semiconductor light emitting device 1 of this embodiment will be described. The semiconductor light emitting device 1 is manufactured by growing each layer by a conventionally used metal organic chemical vapor deposition method (MOCVD: Metal Organic Chemical Vapor Deposition). FIG. 3 shows a timing chart showing the growth temperatures of the last barrier layer 14c and the electron block layer 15 and the supply of the impurity raw material as part of the method for manufacturing the semiconductor light emitting device 1 of the present embodiment.

First, the sapphire substrate 10 is installed in the reaction furnace of the MOCVD apparatus, the substrate temperature is raised to 500° C., and TMG and ammonia are supplied as source gases while flowing hydrogen as a carrier gas. As a result, the GaN buffer layer 11, which is a low temperature buffer layer, is formed on the main surface of the sapphire substrate 10 to have a film thickness of several hundred nm.

Next, the substrate temperature is raised to 1000° C., and TMG and ammonia are supplied as source gases while flowing hydrogen as a carrier gas. Thus, the GaN base layer 12 is formed on the GaN buffer layer 11 to have a film thickness of 3000 nm.

Next, the substrate temperature is maintained at 1000° C., hydrogen is flown as a carrier gas, and TMG and ammonia that are raw material gases and silane (SiH 4) that is a dopant gas are supplied. As a result, the n-type AlGaN underlayer 13 doped with Si, which is an n-type impurity, is formed on the GaN underlayer 12 with a thickness of 3000 nm.

Next, the substrate temperature is lowered to 800° C., and TEG and ammonia, which are raw material gases, are supplied while flowing nitrogen as a carrier gas. As a result, a GaN layer having a film thickness of 12 nm is formed as a barrier layer (barrier layer) 14a on the n-type AlGaN base layer 13.

Next, the substrate temperature is maintained at 800° C., nitrogen is flown as a carrier gas, and TEG (a source gas), ammonia, and TMI (Trimethylethylene) are supplied. As a result, an InGaN layer having a thickness of 3 nm is formed on the barrier layer 14a as the well layer 14b.

After the barrier layer 14a and the well layer 14b are alternately grown for 5 cycles, the substrate temperature is maintained at 800° C., nitrogen is flown as a carrier gas, and TEG and ammonia, which are source gases, are supplied. As a result, a GaN layer having a film thickness of 12 nm is formed as a part of the last barrier layer 14c. This step corresponds to the constant temperature growth step of the present invention, in which the last barrier layer 14c is grown while maintaining the same temperature conditions as the other barrier layers 14a.

Next, while raising the substrate temperature from 800° C. to 1000° C., nitrogen is made to flow as a carrier gas, and TEG and ammonia which are raw material gases are supplied. As a result, the last barrier layer 14c grown in the constant temperature growth step continues to grow, and the last barrier layer 14c is thickened. In this step, the growth of the last barrier layer 14c is continued while the temperature is raised from the growth temperature of the other barrier layer 14a to the growth temperature of the electron block layer 15, and corresponds to the temperature rising growth step of the present invention.

Even after the temperature-rising growth step, the substrate temperature is maintained at 1000° C. and the supply of the carrier gas and the source gas is continued, and the last barrier layer 14c is grown at the same constant temperature as the growth of the electron block layer 15 which is the subsequent step. Is continued to thicken the last barrier layer 14c to 20 to 30 nm. At this time, as shown in FIG. 3, in the last predetermined period in the growth step of the last barrier layer 14c, Cp ₂ Mg which is a Mg raw material is supplied to dope impurities as a doping region growth step. As a result, a doped region doped with Mg as an impurity is formed on the electron blocking layer 15 side of the last barrier layer 14c. In the growth process of the last barrier layer 14c, a period in which the Mg source is not supplied is a non-doped region growth process, and a non-doped region in which Mg as an impurity is not intentionally doped is formed.

As described above, the light emitting layer 14 having the multiple quantum well structure is formed by growing the barrier layer 14a and the well layer 14b for five periods and the last barrier layer 14c. Here, since the last barrier layer 14c is formed to have the same film thickness as the other barrier layers 14a in the constant temperature growth step and then continues to grow in the temperature rising growth step, the last barrier layer 14c is formed to be thicker than the other barrier layers 14a. It Further, since the crystal growth continues while the temperature rises, it is possible to prevent the surface quality of the last barrier layer 14c from deteriorating and the crystal quality from deteriorating.

Next, maintaining the substrate temperature at 1000° C., hydrogen is flown as a carrier gas, and TMG, ammonia and TMA which are raw material gases and Cp ₂ Mg which is a dopant gas are supplied. As a result, an AlGaN layer doped with Mg, which is a p-type impurity, is formed as the electron block layer 15 to a thickness of 30 nm on the last barrier layer 14c.

Next, while maintaining the substrate temperature at 1000° C., hydrogen is flown as a carrier gas to supply TMG and ammonia as a source gas and Cp ₂ Mg as a dopant gas. Thus, the p-type GaN contact layer 16 is formed to 100 nm on the electron block layer 15. After growing the uppermost layer of the semiconductor light emitting device 1, the substrate temperature is cooled to room temperature in a state of flowing nitrogen as a carrier gas into the reaction furnace.

After the growth of each layer of the semiconductor light emitting device 1 is completed, the crystal-grown substrate is taken out from the MOCVD apparatus, a mask is formed on the p-type GaN contact layer 16 by patterning, and the n-type AlGaN underlayer 13 is formed by etching. Part exposed. After that, an n-side contact electrode and a pad electrode are formed on the exposed surface of the n-type AlGaN underlayer 13, and a transparent electrode and a pad electrode are formed on the p-type GaN contact layer 16. Further, after polishing the back surface of the sapphire substrate 10, dicing is performed to divide the device into chips, and the semiconductor light emitting device 1 is obtained.

Here, as the growth step of the barrier layer 14a, the growth step of the well layer 14b, and the constant temperature growth step of the last barrier layer 14c, the example in which the growth temperature is 800° C. is given, but the growth temperature is not limited, and the preferable growth temperature range is 700 to 900. C., and more preferably 750 to 850.degree. Further, the growth temperature of the electron blocking layer 15 and the growth process of the p-type GaN contact layer 16 are not limited, but the preferable growth temperature range is 900 to 1100°C. Is 950 to 1050°C.

In the present embodiment, a doped region growth process of supplying Cp ₂ Mg that is a Mg raw material is provided in the growth process of the last barrier layer 14c to form a doped region of a predetermined thickness on the non-doped region of the last barrier layer 14c. There is. As a result, the Mg raw material is sufficiently supplied into the MOCVD apparatus from the initial stage of growth of the electron block layer 15, and Mg is appropriately taken in. Therefore, the impurity concentration on the side of the last barrier layer 14c of the electron block layer 15 can be increased, the hole injection efficiency into the light emitting layer 14 and the carrier overflow prevention effect can be improved, and the light emitting efficiency of the semiconductor light emitting device 1 can be improved. it can.

The impurity concentration for doping the doped region of the last barrier layer 14c may be such that a sufficient source of the impurity material is supplied into the device in the initial stage of growth of the electron block layer 15, and the diffusion of the impurity into the well layer 14b is suppressed. Therefore, it is preferable to make the impurity concentration lower than that of the electron block layer 15.

(Example)
In order to investigate the relationship between the thickness of the doped region and the impurity concentration, a plurality of semiconductor light emitting devices 1 having different thicknesses of the doped region were prepared and the distribution of the impurity concentration was measured. A semiconductor light emitting device 1 having a thickness of the entire last barrier layer 14c of 25 nm and having no doped region as a comparative example and having the thickness of the doped region set to 5 nm, 10 nm and 15 nm as Examples 1 to 3 respectively. It was created. Comparative Examples and Examples 1 to 3 of the obtained semiconductor light emitting device 1 were measured by secondary ion mass spectrometry (SIMS).

FIG. 4 is a SIMS profile in a comparative example in which the doped region is not formed in the last barrier layer 14c. In the figure, the horizontal axis is the depth from the upper surface of the semiconductor light emitting device 1, the left vertical axis is the Mg concentration, and the right vertical axis is the secondary ion intensity of Al and In. The solid line in the graph indicates the secondary ion intensity of In, the broken line indicates the secondary ion intensity of Al, and the alternate long and short dash line indicates the Mg concentration. The p-type GaN contact layer 16, the electron blocking layer 15, the light emitting layer 14, and the n-type AlGaN layer are shown from the left side of the drawing. Although Mg is detected in the p-type GaN contact layer 16 but Al and In are not detected, Mg and Al are detected in the electron block layer 15 but In is not detected, and In is detected in the light emitting layer 14. Mg and Al are not detected, Al is detected in the n-type AlGaN layer, but Mg and In are not detected. As shown in FIG. 4, in the electron block layer 15 of the comparative example, the Mg concentration is in the range of 2×10 ¹⁸ to 4×10 ¹⁸ pieces/cm ³ , and the average Mg concentration is 2×10 ¹⁸ pieces/cm ³ . there were.

FIG. 5 is a SIMS profile in Example 1 in which a doped region having a thickness of 5 nm was formed in the last barrier layer 14c. FIG. 6 is an impurity concentration profile of only the Mg concentration shown in FIG. As shown in FIGS. 5 and 6, in Example 1, the doped region of the last barrier layer 14c was doped with Mg, and the Mg concentration on the side of the last barrier layer 14c of the electron block layer 15 was higher than that of the comparative example. I understand. In the electron blocking layer 15 of Example 1, the Mg concentration was in the range of 3×10 ¹⁸ to 1×10 ¹⁹ pieces/cm ³ , and the average Mg concentration was 5×10 ¹⁸ pieces/cm ³ .

FIG. 7 is a SIMS profile in Example 2 in which a doped region of 10 nm was formed in the last barrier layer 14c. In Example 2 as well, Mg is doped in the doped region of the last barrier layer 14c, and it can be seen that the Mg concentration on the side of the last barrier layer 14c of the electron block layer 15 is higher than in Comparative Example and Example 1. In the electron blocking layer 15 of Example 2, the Mg concentration was in the range of 5×10 ¹⁸ to 1×10 ¹⁹ pieces/cm ³ , and the average Mg concentration was 8×10 ¹⁸ pieces/cm ³ .

FIG. 8 is a SIMS profile in Example 3 in which a doped region of 15 nm was formed in the last barrier layer 14c. In Example 3 as well, Mg is doped in the doped region of the last barrier layer 14c, and it can be seen that the Mg concentration on the side of the last barrier layer 14c of the electron block layer 15 is higher than in Comparative Examples, Examples 1 and 2. .. In the electron blocking layer 15 of Example 3, the Mg concentration was in the range of 1×10 ¹⁹ to 2×10 ¹⁹ pieces/cm ³ , and the average Mg concentration was 1.5×10 ¹⁹ pieces/cm ³ .

4 to 8, Mg of 1×10 ¹⁶ pieces/cm ³ or less cannot be detected because it is a measurement limit. Further, although it seems that Mg is detected even at a position deeper than the last barrier layer 14c, this is because the measurement result is displayed in a spread manner, and in fact, Mg is detected from the well layer 14b of the light emitting layer 14. Not not.

Next, the emission intensity of Comparative Example 1 and Examples 1 to 3 was measured under the same conditions except for the thickness of the doped region, the applied voltage, and the like. FIG. 9 is a table showing the relative light emission intensities of Comparative Example and Examples 1 to 3. As shown in FIG. 9, the relative emission intensities of Examples 1 to 3 when the emission intensity of the comparative example was 1, were 1.13, 1.10 and 1.05, respectively. The highest emission intensity was obtained in Example 1 in which a doped region of 5 nm was formed on the electron blocking layer 15 side of the last barrier layer 14c, and in Example 3 in which the thickness of the doped region was increased to 15 nm, the emission intensity was high. It was lower than in Example 1. Therefore, the thickness of the doped region is preferably 15 nm or less.

In the present embodiment, an example was shown in which the last barrier layer 14c was grown in the constant temperature growth step with the same thickness as the other barrier layers 14a. Further, the growth of the last barrier layer 14c may be continued to increase the film thickness in the temperature rising growth step.

Further, in the present embodiment, since the growth of the last barrier layer 14c is continued during the temperature rise in the temperature rising growth step, the interface between the last barrier layer 14c and the electron block layer 15 is not deteriorated, and the crystal quality is maintained and light emission is performed. The efficiency can be improved. The thickness of the last barrier layer 14c is thicker than the other barrier layers 14a and is formed to be about 1.5 to 3 times the thickness of the barrier layer 14a. As a result, even if Mg, which is a p-type impurity doped in the doped region of the last barrier layer 14c or the electron block layer 15, is thermally diffused in a later step, the influence of the impurity diffusion to the multiple quantum well structure of the light emitting layer 14 is affected. It is possible to suppress and improve the luminous efficiency.

(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is different from the first embodiment in that the growth of the electron block layer 15 is started after the temperature rising growth process, including the doped region growth process in the temperature rising growth process, and duplicated description will be omitted. .. FIG. 10 is a timing chart showing the growth temperatures of the last barrier layer 14c and the electron block layer 15 and the supply of the impurity raw material in the present embodiment.

As shown in FIG. 10, in the present embodiment, after the barrier layers 14a and the well layers 14b are alternately grown for five cycles, the substrate temperature is maintained at 800° C. and nitrogen is supplied as a carrier gas, which is a source gas. Supply TEG and ammonia. As a result, a GaN layer having a film thickness of 12 nm is formed as a part of the last barrier layer 14c.

Next, while raising the substrate temperature from 800° C. to 1000° C., nitrogen is made to flow as a carrier gas, and TEG and ammonia which are raw material gases are supplied. As a result, the growth of the last barrier layer 14c grown in the constant temperature growth step continues, and the last barrier layer 14c is thickened to 20 to 30 nm. At this time, Cp ₂ Mg, which is a Mg raw material, is supplied as a doping region growth step from the middle of the temperature-rising growth step to dope impurities. As a result, a doped region doped with Mg as an impurity is formed on the electron blocking layer 15 side of the last barrier layer 14c.

After that, as in the first embodiment, the electron block layer 15 and the p-type GaN contact layer 16 are grown, and each step of etching up to the n-type AlGaN underlayer 13, n-side electrode formation, p-side electrode formation, and dicing is performed. After that, the semiconductor light emitting device 1 is obtained.

Also in the present embodiment, a doped region growth process of supplying Cp ₂ Mg that is a Mg raw material is provided in the growth process of the last barrier layer 14c to form a doped region of a predetermined thickness on the non-doped region of the last barrier layer 14c. There is. As a result, the Mg raw material is sufficiently supplied into the MOCVD apparatus from the initial stage of growth of the electron block layer 15, and Mg is appropriately taken in. Therefore, the impurity concentration on the side of the last barrier layer 14c of the electron block layer 15 can be increased, the hole injection efficiency into the light emitting layer 14 and the carrier overflow prevention effect can be improved, and the light emitting efficiency of the semiconductor light emitting device 1 can be improved. it can.

(Third Embodiment)
Next, a third embodiment of the invention will be described with reference to FIG. The present embodiment is different from the first embodiment in that the growth of the last barrier layer 14c is interrupted during the temperature rise without providing the temperature rising growth step, and the duplicated description will be omitted. FIG. 11 is a timing chart showing the growth temperatures of the last barrier layer 14c and the electron block layer 15 and the supply of the impurity raw material in the present embodiment.

As shown in FIG. 11, in the present embodiment, after the barrier layers 14a and the well layers 14b are alternately grown for 5 cycles, the substrate temperature is maintained at 800° C. and nitrogen is flown as a carrier gas, which is a source gas. Supply TEG and ammonia. As a result, a GaN layer having a film thickness of 12 nm is formed as a part of the last barrier layer 14c.

Next, nitrogen is flown as a carrier gas, ammonia as a source gas is supplied, the supply of TEG is stopped, the growth of the last barrier layer 14c is interrupted, and the substrate temperature is raised from 800°C to 1000°C.

After the temperature rise is completed, the substrate temperature is maintained at 1000° C., nitrogen is flowed as a carrier gas, and TEG and ammonia, which are source gases, are supplied. Thereby, the growth of the last barrier layer 14c is restarted, and the last barrier layer 14c is thickened to 20 to 30 nm. At this time, Cp ₂ Mg, which is a Mg raw material, is supplied to dope impurities as a step of growing the doped region from the middle. As a result, a doped region doped with Mg as an impurity is formed on the electron blocking layer 15 side of the last barrier layer 14c.

After that, as in the first embodiment, the electron block layer 15 and the p-type GaN contact layer 16 are grown, and each step of etching up to the n-type AlGaN underlayer 13, n-side electrode formation, p-side electrode formation, and dicing is performed. After that, the semiconductor light emitting device 1 is obtained.

Also in the present embodiment, a doped region growth process of supplying Cp ₂ Mg that is a Mg raw material is provided in the growth process of the last barrier layer 14c to form a doped region of a predetermined thickness on the non-doped region of the last barrier layer 14c. There is. As a result, the Mg raw material is sufficiently supplied into the MOCVD apparatus from the initial stage of growth of the electron block layer 15, and Mg is appropriately taken in. Therefore, the impurity concentration on the side of the last barrier layer 14c of the electron block layer 15 can be increased, the hole injection efficiency into the light emitting layer 14 and the carrier overflow prevention effect can be improved, and the light emitting efficiency of the semiconductor light emitting device 1 can be improved. it can.

(Fourth Embodiment)
In the first to third embodiments, the last barrier layer 14c is made of GaN and the electron block layer 15 is made of AlGaN. However, both are made of AlGaN having different Al compositions, and the band gap of the electron block layer 15 is larger than that of the last barrier layer 14c. It may be configured. Further, as another material system, a multi-component material including Al, In, B, Ga may be used.

Furthermore, the present invention is not limited to the nitride-based semiconductor material, and can be applied to other semiconductor material-based materials, for example, an oxide-based semiconductor material such as ZnO. In the case of an oxide-based semiconductor material, ZnO can be used as the well layer and MgZnO can be used as the barrier layer and the electron block layer.

In any material system, by including a doped region growth process for supplying p-type impurities in the growth process of the last barrier layer 14c, the impurity raw material is sufficiently contained in the device from the initial growth stage of the electron block layer 15. It is supplied and impurities are properly incorporated. Therefore, the impurity concentration on the side of the last barrier layer 14c of the electron block layer 15 can be increased, the hole injection efficiency into the light emitting layer 14 and the carrier overflow prevention effect can be improved, and the light emitting efficiency of the semiconductor light emitting device 1 can be improved. it can.

The present invention is not limited to the above-described embodiments, but various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in the different embodiments Is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Semiconductor light emitting element 10... Sapphire substrate 11... GaN buffer layer 12... GaN foundation layer 13... n-type AlGaN foundation layer 14... Light emitting layer 14a... Barrier layer 14b... Well layer 14c... Last barrier layer 15... Electron block layer 16... p-type GaN contact layer

Claims (6)

A light emitting diode comprising a multiple quantum well active layer in which barrier layers and well layers are alternately laminated, and an electron block layer formed on the multiple quantum well active layer,
The last barrier layer, which is the uppermost layer of the barrier layers, includes a doped region doped with the same impurity as the impurity doped in the electron block layer and a non-doped region not doped with the impurity, and the doped region is the non-doped region. Is formed on the
The film thickness of the last barrier layer is thicker than the film thickness of the other barrier layers and is in the range of 20 nm to 30 nm.
The light emitting diode , wherein the doped region has a concentration of the impurities of 1×10 ¹⁸ cm ⁻³ or more and a thickness of 5 nm or more and 15 nm or less . The light emitting diode according to claim 1, wherein
The light emitting diode according to claim 1, wherein the impurity concentration of the doped region is lower than the impurity concentration of the electron block layer. The light emitting diode according to claim 1 or 2, wherein
The doped region has a concentration of the impurities of 3×10 ¹⁸ cm ⁻³ or more . It is a light emitting diode as described in any one of Claim 1 to 3, Comprising:
The light emitting diode according to claim 1, wherein the last barrier layer is made of GaN. The light emitting diode according to claim 1 or 2, wherein
The light emitting diode according to claim 1, wherein the electron blocking layer is made of AlGaN. A method of manufacturing a light emitting diode , comprising: growing a multiple quantum well active layer in which barrier layers and well layers are alternately laminated, and growing an electron block layer on the multiple quantum well active layer,
The step of growing the last barrier layer, which is the uppermost layer of the barrier layers, is a non-doped region growing step of growing crystals without doping impurities for doping the electron blocking layer, and a doping step of doping crystals with the impurities. Area growth process ,
The film thickness of the last barrier layer is thicker than the film thickness of the other barrier layers and is in the range of 20 nm to 30 nm.
The method for manufacturing a light-emitting diode , wherein the doped region has a concentration of the impurities of 1×10 ¹⁸ cm ⁻³ or more and a thickness of 5 nm or more and 15 nm or less .

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