JP2017117844A - Semiconductor light emitting element and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element and a manufacturing method of the same which enable proper doping of an impurity from an initial stage of growth of an electron block layer.SOLUTION: A semiconductor light emitting element including a multiquantum well active layer where barrier layers and well layers are alternately laminated one by one; and an electron block layer formed on the multiquantum well active layer, in which a last barrier layer as an uppermost layer of the barrier layers includes a doped region doped with an impurity the same with an impurity doped in the electron block layer.SELECTED DRAWING: Figure 3

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 including a multiple quantum well structure and an electron block layer and a method for manufacturing the same.

  Conventionally, in order to increase the light emission efficiency of a semiconductor light emitting device such as a light emitting diode, a multiple quantum well (MQW) structure in which barrier layers and well layers are alternately stacked as an active layer has been adopted. Further, an electron block layer is formed of a material having an electron barrier higher than that of the barrier layer on the last barrier layer which is the uppermost barrier layer constituting the MQW active layer, and carriers overflow to the p-type semiconductor layer side. Some have been proposed to prevent the trapping of carriers in the MQW active layer (for example, Patent Documents 1 and 2).

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

  FIG. 12 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 material in the prior art. In a semiconductor light emitting device using a nitride material, after growing a GaN layer as a last barrier layer, an AlGaN layer doped with Mg as 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 time, ammonia as a nitrogen material and TEG (Triethylgallium) as a gallium material are flown to grow a GaN layer. Next, the supply of TEG is stopped while maintaining the flow rate of ammonia, and the temperature is raised from 800 ° C. to 1000 ° C. In this temperature raising step, the growth of the GaN layer is interrupted because the supply of TEG, which is a gallium raw material, is stopped.

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 (Trimethylgallium), TMA (Trimethylaluminum), and Cp ₂ Mg (Bis (Cyclopentadienyl) magnesium) are used. ). As described above, in the prior art, after the last barrier layer is grown, the growth is interrupted in the temperature raising step, and after the temperature rise, the supply of Cp ₂ Mg as the Mg raw material is started simultaneously with the start of the growth of the electron block layer. The layer is doped with Mg, which is a p-type impurity.

JP 2001-015809 A JP 2009-130097 A

  However, in the prior art, since Mg doping is started at the same time as the growth of the electron block layer, the Mg density in the device atmosphere is low at the initial stage of growth, and the impurity concentration in the semiconductor layer is low due to the difficulty of taking in the Mg raw material. turn into. As the growth of the electron blocking layer continues, Mg is gradually taken into the semiconductor layer, but the impurity concentration of the entire electron blocking layer is lowered because there is a low concentration region in the early stage of growth. Also, if the impurity concentration is low on the light-emitting layer side of the electron blocking layer, the hole injection efficiency to 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.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a semiconductor light-emitting element capable of appropriately doping impurities from the initial growth stage of the electron block layer and a method for manufacturing the same. .

  In order to solve the above problems, a semiconductor light emitting device of the present invention comprises a multiple quantum well active layer in which barrier layers and well layers are alternately stacked, and an electron block layer formed on the multiple quantum well active layer. The last barrier layer, which is the uppermost layer among the barrier layers, includes a doped region doped with the same impurity as the impurity doped in the electron blocking layer.

  In such a semiconductor light emitting device of the present invention, since the same impurity as the electron block layer is doped from the growth stage of the last barrier layer, the impurity can be sufficiently taken into the semiconductor layer from the initial growth stage of the electron block layer. It becomes possible to dope impurities appropriately.

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

  The last barrier layer may further include a non-doped region that is not doped with the impurity, and the doped region may be formed on the non-doped region.

  The last barrier layer may have a thickness in the range of 20 nm to 30 nm, and the doped region may have a thickness of 15 nm or less.

  The film thickness of the last barrier layer may be larger than the film thickness of the other barrier layers.

  In order to solve the above-described problems, a method of manufacturing a semiconductor light emitting device according to the present invention includes growing a multiple quantum well active layer in which barrier layers and well layers are alternately stacked, and forming an electron block layer on the multiple quantum well active layer. A method of manufacturing a semiconductor light emitting device by growing a last barrier layer, which is the uppermost layer of the barrier layers, is a non-doped region growth in which crystal growth is performed without doping an impurity to be doped in the electron blocking layer. And a doped region growing step of growing the crystal by doping the impurities.

  In such a method of manufacturing a semiconductor light emitting device according to the present invention, since the process of growing the last barrier layer includes a doped region growth process, impurities are sufficiently taken into the semiconductor layer from the initial growth stage of the electron block layer. And it becomes possible to dope impurities appropriately.

  The present invention can provide a semiconductor light emitting device capable of appropriately doping impurities from the initial growth stage of the electron blocking layer and a method for manufacturing the same.

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 the structure of the light emitting layer 14 shown in FIG. 1 in detail. 6 is a timing chart showing the growth temperature of the last barrier layer 14c and the electron block layer 15 and the supply of impurity materials in the first embodiment. It is a SIMS profile in a comparative example in which a doped region is not formed in the last barrier layer 14c. It is a SIMS profile in Example 1 which formed 5 nm of dope area | regions in the last barrier layer 14c. It is an impurity concentration profile of only Mg concentration shown in FIG. It is a SIMS profile in Example 2 which formed 10 nm of dope area | regions in the last barrier layer 14c. It is a SIMS profile in Example 3 in which a doped region of 15 nm was formed in the last barrier layer 14c. It is a table | surface which shows the relative light emission intensity of a comparative example and Examples 1-3. It is a timing chart which shows supply temperature of the growth temperature of the last barrier layer 14c and the electron block layer 15, and impurity raw material in 2nd Embodiment. It is a timing chart which shows supply temperature of the growth temperature and impurity raw material of the last barrier layer 14c and the electronic block layer 15 in 3rd Embodiment. It is a timing chart which shows supply temperature of the growth temperature and impurity raw material of the last barrier layer and electron block layer of the semiconductor light-emitting device in a prior art.

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

  FIG. 1 is a schematic view showing a layer structure of a semiconductor light emitting device 1 in the present 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. It has.

  The sapphire substrate 10 is a substrate cut out with the c-plane of the sapphire single crystal as the 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-plane other than the c-plane, m-plane, r-plane, and other A high-order plane orientation may be used as the principal plane.

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 underlayer 12 is a layer made of a single crystal of GaN that is intentionally grown as non-doped without impurities. The film thickness of the GaN foundation layer 12 is, for example, about 3000 nm, but may be adjusted as necessary. The n-type AlGaN foundation layer 13 is a layer made of a single crystal of GaN doped with Si as an n-type impurity. The 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 may be adjusted as 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 blocking layer 15 is a semiconductor layer that is formed on the light emitting layer 14 to prevent carrier overflow, and is made of a material that has a larger barrier to electrons than the barrier layer. The p-type GaN contact layer 16 is a layer made of a single crystal of GaN 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 preferred film thickness range of the p-type GaN contact layer 16 is 50 to 150 nm, more preferably 80 to 100 nm.

  Although no electrode is shown in the semiconductor light emitting device 1 in FIG. 1, a known electrode structure may be adopted as the semiconductor light emitting device. For example, a partial region of the semiconductor layer is etched until the n-type AlGaN underlayer 13 is exposed. An n-side electrode is formed, and a p-side electrode is formed on the p-type GaN contact layer 16. Details of the structure of the light emitting layer 14, the electron blocking layer 15, and the p-type GaN contact layer 16 will be described later.

  Here, the GaN buffer layer 11, the GaN foundation layer 12, the n-type AlGaN foundation layer 13, and the p-type GaN contact layer 16 are given as examples of materials constituting the buffer layer, the GaN foundation layer, and the p-type contact layer. Any other material such as GaN, AlGaN, InGaN, or InAlGaN may be used. For example, both the non-doped base layer and the n-type doped base layer may be GaN layers, or both may be AlGaN layers. Further, conventionally known structures used for semiconductor light emitting devices such as a clad layer, a current confinement layer, and a current diffusion layer may be applied as necessary.

  FIG. 2 is a schematic diagram for explaining in detail the structure of the light emitting layer 14 shown in FIG. 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 repeated for five periods, and a last barrier layer 14c is formed on the last well layer 14b. . Examples of the barrier layer 14a include a GaN layer having a thickness of 12 nm, and examples of the well layer 14b include an InGaN layer having a thickness of 3 nm.

  The preferable film thickness range of the barrier layer 14a is 5 to 15 nm, and more preferably 8 to 12 nm. The preferable thickness range of the well layer 14b is 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 has a film thickness that is thicker than that of the barrier layer 14a. A preferable film 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 blocking layer 15 is formed on the last barrier layer 14c and is made of a material having a larger barrier to electrons than the last barrier layer 14c. The electron blocking layer 15 extends from the light emitting layer 14 having the multiple quantum well structure to the p-type GaN contact layer 16. To prevent carrier overflow. The electron blocking layer 15 is, for example, a p-type AlGaN layer doped with about 1 × 10 ¹⁸ cm ^{−3 to} 5 × 10 ²⁰ cm ⁻³ of Mg as a p-type impurity, and a preferable thickness range is 10 to 40 nm. Yes, more preferably 20 to 30 nm.

  Here, GaN is given as a material constituting the barrier layer 14a and the last barrier layer 14c, InGaN is given as a material constituting the well layer 14b, and AlGaN is given as a material constituting the electron block layer 15, but other materials are used. There may be. 2 shows a multi-quantum well structure having five periods as the light emitting layer 14, the number of periods may be adjusted as appropriate.

  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 (MOCVD) method. FIG. 3 shows a timing chart showing the growth temperature of the last barrier layer 14c and the electron block layer 15 and the supply of impurity materials 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 reactor 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. Thereby, the GaN buffer layer 11 which is a low-temperature buffer layer is formed on the main surface of the sapphire substrate 10 with 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. As a result, the GaN foundation layer 12 is formed on the GaN buffer layer 11 to a thickness of 3000 nm.

  Next, hydrogen is supplied as a carrier gas while maintaining the substrate temperature at 1000 ° C., and TMG and ammonia as source gases and silane (SiH 4) as a dopant gas are supplied. As a result, an n-type AlGaN underlayer 13 doped with Si as an n-type impurity is formed on the GaN underlayer 12 with a film 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 thickness of 12 nm is formed on the n-type AlGaN underlayer 13 as a barrier layer (barrier layer) 14a.

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

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

  Next, while raising the substrate temperature from 800 ° C. to 1000 ° C., nitrogen is supplied as a carrier gas to supply TEG and ammonia as raw material gases. Thereby, the growth of the last barrier layer 14c grown in the constant temperature growth process is continued, and the last barrier layer 14c is thickened. This step continues the growth of the last barrier layer 14c while raising the temperature 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 growth step of the present invention.

Even after the temperature rising growth process, the substrate temperature is maintained at 1000 ° C. and the supply of the carrier gas and the source gas is continued, and the growth of the last barrier layer 14c is performed at the same temperature as the growth of the electron block layer 15 which is the subsequent process. To increase the thickness of 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 process of the last barrier layer 14c, as a doped region growth process, Cp ₂ Mg as an Mg raw material is supplied 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. In the growth process of the last barrier layer 14c, the period in which the Mg raw material 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 five periods of the barrier layer 14a and the well layer 14b and the last barrier layer 14c. Here, the last barrier layer 14c is formed to be thicker than the other barrier layers 14a because the growth is continued in the temperature rising growth step after the same thickness as the other barrier layers 14a is formed in the constant temperature growth step. The Further, since the crystal growth continues while the temperature is raised, it is possible to prevent the surface state of the last barrier layer 14c from being deteriorated and the crystal quality from being lowered.

Next, hydrogen is supplied as a carrier gas while maintaining the substrate temperature at 1000 ° C., and TMG, ammonia, and TMA as source gases and Cp ₂ Mg as 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 blocking layer 15 on the last barrier layer 14c to a thickness of 30 nm.

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

  When the growth of each layer of the semiconductor light emitting device 1 is completed, the substrate on which the crystal has been grown is taken out from the MOCVD apparatus, a mask is patterned on the p-type GaN contact layer 16, and the n-type AlGaN underlayer 13 is formed by etching. Expose part. Thereafter, an n-side contact electrode and a pad electrode are formed on the exposed surface of the n-type AlGaN base layer 13, and a transparent electrode and a pad electrode are formed on the p-type GaN contact layer 16. Further, the back surface of the sapphire substrate 10 is polished and then diced to divide the element into chips, thereby obtaining the semiconductor light emitting device 1.

  Here, the growth process of the barrier layer 14a, the growth process of the well layer 14b, and the constant temperature growth process of the last barrier layer 14c are described with an example where the growth temperature is 800 ° C., but the preferred growth temperature range is 700 to 900. It is 750 degreeC, More preferably, it is 750-850 degreeC. Moreover, although the example whose growth temperature is 1000 degreeC was given as a growth process of the electron block layer 15 and a growth process of the p-type GaN contact layer 16, it is not limited, A preferable growth temperature range is 900-1100 degreeC, More preferably Is 950-1050 ° C.

In the present embodiment, a doped region growth step of supplying Cp ₂ Mg as an Mg raw material is provided in the growth step of the last barrier layer 14c, and a doped region having a predetermined thickness is formed on the non-doped region of the last barrier layer 14c. Yes. Thereby, the Mg raw material is sufficiently supplied into the MOCVD apparatus from the initial growth stage 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 blocking 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 emission efficiency of the semiconductor light emitting device 1 can be improved. it can.

  The impurity concentration doped in the doped region of the last barrier layer 14c may be such that a sufficient amount of impurity material is supplied into the device in the initial growth stage of the electron block layer 15 and suppresses impurity diffusion into the well layer 14b. For this purpose, it is preferable to lower the impurity concentration than the electron blocking 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 doped region thicknesses were prepared, and the impurity concentration distribution was measured. A semiconductor light emitting device 1 in which the film thickness of the entire last barrier layer 14c is 25 nm, no doped region is provided as a comparative example, and the thickness of the doped region is set to 5 nm, 10 nm, and 15 nm. It was created. The comparative example and Examples 1-3 of the obtained semiconductor light-emitting device 1 were measured by secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectroscopy).

FIG. 4 is a SIMS profile in a comparative example in which a doped region is not formed in the last barrier layer 14c. In the figure, the horizontal axis represents the depth from the upper surface of the semiconductor light emitting device 1, the left vertical axis represents the Mg concentration, and the right vertical axis represents the secondary ion intensity of Al and In. Further, 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. From the left side of the figure, a p-type GaN contact layer 16, an electron block layer 15, a light emitting layer 14, and an n-type AlGaN layer are shown. 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, but In is detected in the light emitting layer 14. Mg and Al are not detected, and Al is detected in the n-type AlGaN layer, but Mg and In are not detected. As shown in FIG. 4, in the electronic 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 of 5 nm is 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 is doped with Mg, and the Mg concentration on the last barrier layer 14c side of the electron blocking layer 15 is higher than that of the comparative example. I understand that. 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 is formed in the last barrier layer 14c. Also in Example 2, it can be seen that Mg is doped in the doped region of the last barrier layer 14c, and the Mg concentration on the side of the last barrier layer 14c of the electron block layer 15 is higher than that of the 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 shows a SIMS profile in Example 3 in which a doped region of 15 nm is formed in the last barrier layer 14c. Also in Example 3, the doped region of the last barrier layer 14c is doped with Mg, and it is understood that the Mg concentration on the side of the last barrier layer 14c of the electron block layer 15 is higher than that of the comparative example, Example 1 and Example 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. In addition, Mg seems to be detected even at a position deeper than the last barrier layer 14c, but the measurement result is displayed with a spread, and actually Mg is detected from the well layer 14b of the light emitting layer 14. Not.

  Next, the light emission intensity was measured for Comparative Example 1 and Examples 1 to 3 under the same conditions except for the thickness of the doped region and the applied voltage. FIG. 9 is a table showing the relative light emission intensity of the comparative example and Examples 1-3. As shown in FIG. 9, the relative light emission intensities of Examples 1 to 3 were 1.13, 1.10, and 1.05, respectively, where the light emission intensity of the comparative example was 1. The highest emission intensity was 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. 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 Example 1. Therefore, the thickness of the doped region is preferably 15 nm or less.

  In the present embodiment, the last barrier layer 14c is grown in the constant temperature growth process having the same thickness as the other barrier layers 14a. However, the film thickness of the other barrier layer 14a is grown in the constant temperature growth process. Further, the growth of the last barrier layer 14c may be continued in the temperature rising growth step to increase the thickness.

  In the present embodiment, since the growth of the last barrier layer 14c is continued even during the temperature rise in the temperature rise 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. Efficiency can be improved. The film thickness of the last barrier layer 14c is thicker than that of the other barrier layers 14a, and is about 1.5 to 3 times that 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 blocking layer 15 is thermally diffused in a subsequent process, the influence of impurity diffusion on the multiple quantum well structure of the light emitting layer 14 is affected. It can suppress and can improve luminous efficiency.

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

  As shown in FIG. 10, in this embodiment, the barrier layer 14a and the well layer 14b are alternately grown repeatedly for five periods, and then the substrate temperature is maintained at 800 ° C. and nitrogen is allowed to flow as a carrier gas. Supply TEG and ammonia. As a result, a GaN layer is formed to a thickness of 12 nm as a part of the last barrier layer 14c.

Next, while raising the substrate temperature from 800 ° C. to 1000 ° C., nitrogen is supplied as a carrier gas to supply TEG and ammonia as raw material gases. Thereby, the growth of the last barrier layer 14c grown in the constant temperature growth process is continued, and the thickness of the last barrier layer 14c is increased to 20 to 30 nm. At this time, Cp ₂ Mg which is an Mg raw material is supplied from the middle of the temperature rising growth process as a doped region growth process 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.

  Thereafter, the electron blocking layer 15 and the p-type GaN contact layer 16 are grown in the same manner as in the first embodiment, and the etching, n-side electrode formation, p-side electrode formation, and dicing steps up to the n-type AlGaN underlayer 13 are performed. Then, the semiconductor light emitting device 1 is obtained.

Also in the present embodiment, a doped region growth step of supplying Cp ₂ Mg as an Mg raw material is provided in the growth step of the last barrier layer 14c, and a doped region having a predetermined thickness is formed on the non-doped region of the last barrier layer 14c. Yes. Thereby, the Mg raw material is sufficiently supplied into the MOCVD apparatus from the initial growth stage 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 blocking 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 emission efficiency of the semiconductor light emitting device 1 can be improved. it can.

(Third embodiment)
Next, a third 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 last barrier layer 14c is interrupted during the temperature rise without providing the temperature rise growth step, and a duplicate description is omitted. FIG. 11 is a timing chart showing the growth temperature of the last barrier layer 14c and the electron block layer 15 and the supply of impurity materials in the present embodiment.

  As shown in FIG. 11, in this embodiment, the barrier layer 14a and the well layer 14b are alternately grown repeatedly for five periods, and then the substrate temperature is maintained at 800 ° C. and nitrogen is allowed to flow as a carrier gas. Supply TEG and ammonia. As a result, a GaN layer is formed to a thickness of 12 nm as a part of the last barrier layer 14c.

  Next, nitrogen is supplied as a carrier gas, ammonia as a raw material gas is supplied, supply of TEG is stopped, 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 supplied as a carrier gas, and TEG and ammonia as source gases are supplied. As a result, the growth of the last barrier layer 14c is resumed, and the thickness of the last barrier layer 14c is increased to 20 to 30 nm. At this time, as a doped region growth step, Cp ₂ Mg as an Mg raw material is supplied from the middle 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.

  Thereafter, the electron blocking layer 15 and the p-type GaN contact layer 16 are grown in the same manner as in the first embodiment, and the etching, n-side electrode formation, p-side electrode formation, and dicing steps up to the n-type AlGaN underlayer 13 are performed. Then, the semiconductor light emitting device 1 is obtained.

Also in the present embodiment, a doped region growth step of supplying Cp ₂ Mg as an Mg raw material is provided in the growth step of the last barrier layer 14c, and a doped region having a predetermined thickness is formed on the non-doped region of the last barrier layer 14c. Yes. Thereby, the Mg raw material is sufficiently supplied into the MOCVD apparatus from the initial growth stage 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 blocking 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 emission 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 is good also as a structure. Also, other material systems may be multi-component materials including Al, In, B, and Ga.

  Furthermore, the present invention is not limited to the nitride-based semiconductor material, and can be applied to other semiconductor material systems, 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.

  Regardless of the material system, by including a doped region growth step for supplying a p-type impurity in the growth step of the last barrier layer 14c, the impurity material is sufficiently contained in the device from the initial growth stage of the electron block layer 15. Supplied and properly incorporated with impurities. Therefore, the impurity concentration on the side of the last barrier layer 14c of the electron blocking 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 emission efficiency of the semiconductor light emitting device 1 can be improved. it can.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in 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 base layer 13 ... n-type AlGaN base 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 semiconductor light emitting device comprising a multi-quantum well active layer in which barrier layers and well layers are alternately stacked, and an electron block layer formed on the multi-quantum well active layer,
The last barrier layer, which is the uppermost layer among the barrier layers, includes a doped region doped with the same impurity as the impurity doped in the electron blocking layer. The semiconductor light emitting device according to claim 1,
The semiconductor light emitting device, wherein an impurity concentration of the doped region is lower than an impurity concentration of the electron block layer. The semiconductor light-emitting device according to claim 1 or 2,
The last barrier layer further includes a non-doped region that is not doped with the impurity, and the doped region is formed on the non-doped region. The semiconductor light-emitting device according to claim 1,
A film thickness of the last barrier layer is in a range of 20 nm to 30 nm, and a thickness of the doped region is 15 nm or less. The semiconductor light-emitting device according to claim 1,
The semiconductor light emitting device according to claim 1, wherein a film thickness of the last barrier layer is larger than a film thickness of the other barrier layers. A method for manufacturing a semiconductor light emitting device, comprising: growing a multiple quantum well active layer in which barrier layers and well layers are alternately stacked; 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, includes a non-doped region growing step of growing crystals without doping impurities doped in the electron blocking layer, and a doping of growing crystals by doping the impurities. A method for manufacturing a semiconductor light emitting device, comprising: a region growing step.

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