JP4767303B2 - Method for manufacturing nitride-based semiconductor light-emitting device - Google Patents

Description

The present invention has the general formula _{In x Al y Ga 1-xy} N (x + y + z = 1,0 ≦ x ≦ 1,0 ≦ y ≦ 1 and 0 ≦ z ≦ 1) nitride using a nitride-based semiconductor represented by The present invention relates to a semiconductor light emitting device and a method for manufacturing the same.

  Most conventional nitride-based semiconductor light-emitting devices are manufactured by laminating a nitride-based semiconductor layer on a sapphire substrate. However, in recent years, silicon (Si) substrates that are cheaper and have a larger area than sapphire substrates are increasingly used from the viewpoint of reducing the manufacturing cost of light-emitting elements.

  FIG. 12 shows a schematic perspective view of a conventional nitride-based semiconductor light-emitting element using a Si substrate. In this nitride semiconductor light emitting device, an AlN buffer layer 101, an n-type GaN layer 102, an InGaN light emitting layer 103, a p-type AlGaN carrier block layer 104, and a p-type GaN contact layer 105 are sequentially stacked on a Si substrate 100. A translucent electrode 106 is formed on the p-type GaN contact layer 105, and an n-type electrode 107 is formed on the n-type GaN layer 102. Further, a p-type pad electrode 108 is formed on the translucent electrode 106, and an n-type pad electrode 109 is formed on the n-type electrode 107.

  However, since the light emitted from the InGaN light emitting layer 103 of this nitride semiconductor light emitting element toward the Si substrate 100 is absorbed by the Si substrate 100, the light emitted from the InGaN light emitting layer 103 is external to the light. There was a problem that the extraction efficiency was lowered.

  Further, there is a method of preventing light from entering the Si substrate 100 by forming a reflective film such as a metal on the Si substrate 100 and extracting light from the side surface of the semiconductor light emitting element as in the case of using a sapphire substrate. Conceivable. However, the nitride semiconductor layer cannot be formed thick due to a crack in the nitride semiconductor layer caused by the difference in thermal expansion coefficient between the nitride semiconductor layers, and the portion from which light emitted from the light emitting layer is transmitted and extracted As a result, there is a problem that the light extraction efficiency cannot be improved by extracting light from the side surface of the nitride-based semiconductor layer.

  In order to solve these problems, Japanese Patent Application Laid-Open No. 2000-196152 discloses a light-emitting element having irregularities formed on a p-type GaN semiconductor layer and light having irregularities on the surface via a transparent electrode formed on the p-type GaN semiconductor layer. A light emitting device in which an extraction layer is provided is disclosed. However, when the thickness of the p-type GaN semiconductor layer is increased to provide unevenness, there is a problem that many cracks are generated in the p-type GaN semiconductor layer and the drive voltage of the element increases. This is because when a p-type GaN semiconductor layer is grown at a high temperature and the temperature is returned to room temperature after the growth, a tensile stress is applied to the p-type GaN semiconductor layer to cause a crack, and the film thickness of the p-type GaN semiconductor layer further increases. It is presumed that cracks were more likely to occur due to the thicker thickness. In addition, the p-type GaN semiconductor layer is inherently unlikely to have a low resistance, and has a problem that the driving voltage of the element is further increased because the p-type GaN semiconductor layer is not thick because of its thick film thickness. Further, even when a transparent electrode is formed on the p-type GaN semiconductor layer, the ohmic characteristics between the p-type GaN semiconductor layer and the transparent electrode are poor and the contact resistance is high, so that the drive voltage of the element increases. There was a problem.

  In view of the above circumstances, the present invention provides a nitride-based semiconductor light-emitting device capable of improving the external extraction efficiency of light emitted from the light-emitting layer and reducing the drive voltage of the device, and a method for manufacturing the same. The purpose is to do.

In order to achieve the above object, the present invention includes a reflective layer formed on a support substrate and a p-type nitride semiconductor layer, a light emitting layer, and an n-type nitride semiconductor layer sequentially stacked above the reflective layer. A method of manufacturing a nitride-based semiconductor light-emitting device having irregularities formed on a light extraction surface located above an n-type nitride-based semiconductor layer , comprising: preparing a Si substrate; A step of forming a groove having a facet surface, a step of forming a SiO ₂ mask on the opposite surface of the (111) facet surface, and a state in which an SiO ₂ mask is formed on the opposite surface , n on the (111) facet surface Sequentially laminating a nitride semiconductor layer, a light emitting layer, and a p-type nitride semiconductor layer, forming a reflective layer on the p-type nitride semiconductor layer, and forming a support substrate on the reflective layer And removing the Si substrate , And forming a high refractive index film on the irregularities of the n-type nitride semiconductor layer formed by the step of removing the Si substrate, a high refractive index film has a refractive than the n-type nitride-based semiconductor layer It is a film having a low refractive index, and the upper surface of the high refractive index film is the light extraction surface.

Here, in the method for manufacturing a nitride-based semiconductor light-emitting device of the present invention, the high refractive index film is silicon nitride (Si ₃ N ₄ ), indium oxide (In ₂ O ₃ ), neodymium oxide (Nd ₂ O ₂ ). , zirconium oxide (ZrO _2), titanium oxide (TiO _2), cerium oxide (CeO ₂₎ and any one Tona Rukoto made from the group of bismuth oxide (BiO ₃₎ is preferable.

  As described above, according to the present invention, a nitride-based semiconductor light-emitting element is epitaxially grown on a highly workable Si substrate, and an electrode having a high reflectivity is provided on the p-type nitride-based semiconductor layer side. The wafer is turned upside down by using the substrate, and unevenness is provided on the highly conductive n-type nitride semiconductor layer side, thereby producing a high-brightness nitride-based semiconductor light-emitting device with low driving voltage and high light extraction efficiency. It became possible.

Embodiments of the present invention will be described below.
(Light extraction surface)
The nitride-based semiconductor light-emitting device according to the present invention is characterized in that a light extraction surface having an uneven surface is provided above the n-type nitride-based semiconductor layer. That is, when the light extraction surface is a flat surface, light emitted from the light emitting layer and incident at a normal angle larger than the critical refraction angle with respect to the light extraction surface is totally reflected on the light extraction surface. However, since the light can be extracted to the outside by providing irregularities on the light extraction surface, the external extraction efficiency of the light can be improved.

  In addition, when unevenness is provided on the upper surface of the p-type nitride semiconductor layer as in the prior art, the thickness of the p-type nitride semiconductor layer having high resistance is increased, so that the series resistance is increased and the drive voltage is increased. Results were obtained. However, when the light extraction surface is installed on the upper surface of the n-type nitride semiconductor layer having a low resistance as in the present invention, the n-type nitride is formed even if the n-type nitride semiconductor layer is formed thick. The driving voltage of the element can be lowered because of the conductivity of the semiconductor layer. Further, even when the transparent electrode layer is provided on the n-type nitride semiconductor layer, the electric resistance does not increase so much, so that the driving voltage of the element is almost the same as when the transparent electrode layer is not provided.

The light extraction surface can also be the upper surface of the n-type nitride-based semiconductor layer, but silicon nitride (Si ₃ N ₄ ), indium oxide (In ₂ O ₃ ), neodymium oxide (Nd ₂ O ₂ ), zirconium oxide ( ZrO ₂ ), titanium oxide (TiO ₂ ), cerium oxide (CeO ₂ ), and bismuth oxide (BiO ₃ ) are formed on the n-type nitride semiconductor layer. The upper surface of the high refractive index film can be used as a light extraction surface. Since the refractive index of the high refractive index film is smaller than that of the n-type nitride semiconductor layer, more light can be extracted to the outside, so that the light extraction efficiency can be improved. In addition, since it is not necessary to directly process the n-type nitride semiconductor layer, it is possible to reduce the driving voltage of the device equivalent to or higher than that when the light extraction surface is the upper surface of the n-type nitride semiconductor layer. It can be done.

Further, _a nitride semiconductor layer represented by In _a Ga _1-a N (0 <a ≦ 1) is formed on the n-type nitride semiconductor layer, and the upper surface of the nitride semiconductor layer is formed as a light extraction surface. It can also be. Since the In _a Ga _1-a N layer has _a refractive index smaller than that of the GaN layer, the external extraction efficiency of light can be further improved. In addition, since the In _a Ga _1-a N layer has lower crystallinity than the GaN layer, it is possible to make unevenness easier.

Here, it is preferable that the maximum thickness of the nitride-based semiconductor layer represented by the above In _a Ga _1-a N (0 <a ≦ 1) is in the range of 200 to 800 nm. In order to improve the light extraction efficiency, it is necessary to have a film thickness equivalent to the wavelength of light emitted from the light emitting layer, and the light emission wavelength divided by the refractive index inside the nitride semiconductor layer. This is because the maximum thickness of the layer is preferably in the range of 200 to 800 nm in consideration of the necessity of unevenness of a size or larger. Note that if the maximum thickness of the layer is less than 200 nm, light tends to be totally reflected, and thus the light extraction efficiency tends to be reduced. If the thickness is greater than 800 nm, cracks occur due to distortion due to regrowth of the layer. Occurrence occurs, a leak current occurs between n and p, and the light emission efficiency tends to decrease.

In addition, a nitride-based semiconductor layer represented by In _a Ga _1-a N (0 <a ≦ 1) doped with Si is formed on the n-type nitride-based semiconductor layer. The upper surface of the layer is a light extraction surface, and the Si concentration contained in the nitride-based semiconductor layer is preferably in the range of 5 × 10 ^{20 to} 5 × 10 ²¹ cm ⁻³ . In this case as well, the light extraction efficiency can be further improved. In addition, when the Si concentration is in the range of 5 × 10 ^{20 to} 5 × 10 ²¹ cm ⁻³ , it is easier to form the light extraction surface in a pyramid shape. Further, when the Si concentration is less than 5 × 10 ²⁰ cm ^−3, it is difficult to form pyramidal irregularities, and when the Si concentration is higher than 5 × 10 ²¹ cm ⁻³ , crystal growth hardly occurs and a film is formed. May not be possible.

  In addition, a translucent electrode made of any one metal selected from the group consisting of Al, Ti, Zr, Hf, V, Nb, and ITO can be provided on the light extraction surface on which the unevenness is formed. In this case, the current injected into the element can be further expanded in the element.

(Unevenness)
The shape and number of irregularities formed on the light extraction surface are not particularly limited, but as the shape of the irregularities, for example, an innumerable hole such as a crater is formed on the light extraction surface, the light extraction surface is a semi-cylindrical shape Protruding form, projecting in a pyramid shape with a triangular prism formed at intervals on the light extraction surface, or prism shape with a triangular prism continuously formed without spacing on the light extraction surface There are protruding forms.

As a method for producing the unevenness, for example, after growing an n-type nitride semiconductor layer, the growth temperature, the amount of gas introduced, and the growth rate are adjusted as appropriate, and the n-type nitride semiconductor layer is regrown. A method of selectively regrowing an n-type nitride semiconductor layer by forming a mask such as SiO ₂ or Si ₃ N _{4 on the} nitride semiconductor layer, an n-type nitride system using diamond grains or alumina grains There is a method of polishing a semiconductor layer.

  As another manufacturing method, for example, a method of applying particles such as diamond grains or alumina grains and partially etching the n-type nitride semiconductor layer by RIE, or on the n-type nitride semiconductor layer There is a method in which after the mask pattern is formed, heat treatment is performed, and this mask is vertically etched using the RIE method. In addition, when the portion where the mask is not formed has a stripe width of about 1 μm, it is possible to produce a concavo-convex structure having a taper by controlling the etching conditions. Further, by performing both of the heat treatment and the control of the etching conditions, it is possible to produce a concave-convex structure including a kamaboko-shaped light extraction surface and a taper. The taper is a V-shaped groove.

(Support substrate)
The material of the support substrate used in the present invention is not particularly limited. For example, it supports a metal substrate typified by Ni, an alloy made of Au, Au and Sn, and a semiconductor substrate such as Si, GaAs, GaP, and InP having conductivity. It is also possible to fuse the substrate with an adhesive metal made of Pd and In. Especially, it is preferable that the support substrate is formed by Ni plating. In this case, the support substrate can be manufactured at low cost.

(Reflective layer)
The reflective layer used in the present invention preferably uses Ag, which is a material having the highest reflectivity, for the reflective layer from the viewpoint of efficiently extracting light from the light extraction surface.

  Further, from the viewpoint of reducing the drive voltage of the element, the reflective layer is preferably a p-type electrode that makes ohmic contact with the p-type nitride semiconductor layer. Here, for example, Pd, Ni, Ag, or the like can be used as the material of the reflective layer to be the p-type electrode, and among these, it is preferable to use Pd. These materials do not have a large difference with respect to the drive voltage at a drive current of 20 mA that is normally used. However, when Pd is used, the drive voltage of the element can be further reduced.

  Therefore, the reflective layer is more preferably a p-type electrode in which Au is vapor-deposited on Pd or a p-type electrode in which Au is vapor-deposited on Ag, and also has a reflection of light composed of Pd / Ag / Au. Most preferred is a p-type electrode.

(P-type nitride semiconductor layer)
As the material of the p-type nitride semiconductor layer used in the present invention, the general formula _{In x Al y Ga 1-xy} N (x + y + z = 1,0 ≦ x ≦ 1,0 ≦ y ≦ 1 and 0 ≦ z ≦ 1 In this case, a p-type dopant is implanted into a nitride-based semiconductor represented by (). Here, as the p-type dopant, a conventionally known material can be used, and for example, one or more kinds of Mg, Zn, Cd, Be, or the like can be used.

(Light emitting layer)
The material of the light-emitting layer used in the present invention, represented for example by the general formula _{In x Al y Ga 1-xy} N (x + y + z = 1,0 ≦ x ≦ 1,0 ≦ y ≦ 1 and 0 ≦ z ≦ 1) Nitride based semiconductors can be used. The light emitting layer used in the present invention may be either an MQW (multiple quantum well) light emitting layer or an SQW (single quantum well) light emitting layer. Note that the effect of the present invention can also be obtained when the light emitting layer is a III-V group nitride semiconductor mainly containing N as a group V element such as InGaAlN, GaAsN, GaInAsN, GaPN, and GaInPN.

(N-type nitride semiconductor layer)
As the material of the n-type nitride semiconductor layer used in the present invention, the general formula _{In x Al y Ga 1-xy} N (x + y + z = 1,0 ≦ x ≦ 1,0 ≦ y ≦ 1 and 0 ≦ z ≦ 1 In which a nitride semiconductor is implanted with an n-type dopant. Here, conventionally known materials can be used for the n-type dopant, and for example, one or more of Si, O, Cl, S, C, Ge, or the like can be used.

(Production method)
The method for producing a nitride-based semiconductor light-emitting device of the present invention includes a step of preparing a Si substrate and sequentially stacking an n-type nitride-based semiconductor layer, a light-emitting layer, and a p-type nitride-based semiconductor layer on the Si substrate forming a reflective layer on the p-type nitride semiconductor layer, forming a support substrate on the reflective layer, inverting the wafer using the support substrate, removing the Si substrate, Forming a light extraction surface having irregularities on the surface above the n-type nitride semiconductor layer.

  In the prior art, unevenness is provided above the p-type nitride semiconductor layer. However, in the present invention, an n-type nitride semiconductor layer, a light emitting layer, and a p-type nitride semiconductor layer are stacked in this order on a Si substrate, and then a support substrate is placed on the p-type nitride semiconductor layer. This is characterized in that the wafer is inverted and the Si substrate is removed thereafter to form a light extraction surface having irregularities above the n-type nitride semiconductor layer.

  Therefore, when a nitride-based semiconductor light-emitting device is manufactured using the manufacturing method of the present invention, the device can be formed even if the n-type nitride-based semiconductor layer is formed thick to form an uneven surface as described above. The driving voltage of the light emitting device can be greatly reduced as compared with the prior art, and the support substrate also serves as an electrode, so that the upper and lower electrode structures of the light emitting device can be easily manufactured. It can be easily achieved.

  The nitride semiconductor layer can be laminated by a conventionally known method. For example, the LPE method (liquid phase epitaxy method), the VPE method (vapor phase epitaxy method), the MOCVD method (organometallic vapor phase growth method). ), MBE method (molecular beam epitaxy method), gas source MBE method, or a combination of these methods. Moreover, as a formation method of a reflection layer, a support substrate, or an electrode, the vacuum evaporation method, sputtering method, the electroplating method, the electroless-plating method, or the method which combined these methods etc. can be used, for example.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to this.

Example 1
FIG. 1 is a schematic perspective view of a nitride-based semiconductor light-emitting element according to Example 1 of the present invention. In the nitride semiconductor light emitting device of this example, a p-type electrode 12 is formed on a support substrate 11 made of Ni plating which also serves as an electrode, and a p-type GaN cladding layer 13 and a p-type are formed on the p-type electrode 12. AlGaInN carrier block layer 14, light-emitting layer 15 made of In _x Ga _1-x N, Si-doped n-type In _0.03 Ga _0.97 N cladding layer 16, Si-doped n-type In _0.1 Ga _0.9 N layer 17 and Si-doped n-type GaN layer A clad layer 18 is sequentially laminated. Further, an n-type GaN light extraction layer 19 having irregularities produced by regrowth is formed on the upper surface of the n-type GaN cladding layer 18, and an n-type GaN light extraction layer 19 is partially formed on the n-type GaN light extraction layer 19. An electrode 110 and an n-type bonding electrode 111 are formed.

A method for manufacturing the nitride-based semiconductor light-emitting device of this example will be described below with reference to FIGS. First, the Si (111) substrate 10 slightly turned off by about 1 ° is washed with an organic cleaning and further with a 5% HF aqueous solution for 1 minute, and then introduced into the MOCVD apparatus. In a hydrogen (H ₂ ) atmosphere, Cleaning is performed at a high temperature of 900 ° C.

Next, while flowing H ₂ as a carrier gas at a rate of 10 L / min, NH ₃ is introduced at a rate of 5 L / min at 1200 ° C. and trimethylaluminum (TMA) is introduced into the device at a rate of 20 μmol / min. Then, an AlN buffer layer 112 having a thickness of 200 nm is grown on the Si substrate 10 as shown in FIG.

Next, while flowing H ₂ into the apparatus at a rate of 10 L / min as a carrier gas, NH ₃ at a rate of 5 L / min at 1150 ° C., TMA at a rate of 20 μmol / min, and trimethylgallium (TMG) at 20 μmol. An Al _0.5 Ga _0.5 N layer 113 having a thickness of 150 nm and Si doping is introduced into the device at a rate of / min.

Then, while flowing of H ₂ as a carrier gas into the apparatus at a rate of 10L / min, the NH ₃ at 1150 ° C. at a flow rate of 5L / min, and introduced into the apparatus and TMG at a rate of 20 [mu] mol / min, further SiH ₄ gas is introduced to grow the n-type GaN layer 18 doped with Si having a thickness of 1 μm.

Next, the growth temperature was lowered to 910 ° C., TMG was introduced at a rate of 20 μmol / min, and trimethylindium (TMI) was introduced into the device at a rate of 20 μmol / min, and Si-doped In _0.1 Ga _0.9 having a thickness of 300 nm was introduced. N layer 17 is grown.

Next, by reducing the amount of TMI introduced into the device to about 5 μmol / min, a Si-doped In _0.03 Ga _0.97 N cladding layer 16 having a thickness of 20 nm is grown.

Next, the substrate temperature is lowered to 760 ° C., TMI is introduced into the apparatus at a rate of 6.5 μmol / min and TMG at a rate of 2.8 μmol / min, and a 3 nm-thick well layer made of In _0.18 Ga _0.82 N is grown. Let Thereafter, the temperature is raised again to 850 ° C., TMG is introduced into the 14 μmol / min apparatus, and a barrier layer made of GaN is grown. Similarly, the well layer and the barrier layer are repeatedly grown to grow the light emitting layer 15 made of four pairs of multiple quantum well (MQW) InGaN. Here, the In _x Ga _1-x N light _- emitting layer can emit light between bands from ultraviolet to red by changing the composition x of In _x Ga _1-x N. It was supposed to emit light.

After the growth of the light emitting layer 15 is completed, at the same temperature as the last barrier layer, TMG is 11 μmol / min, TMA is 1.1 μmol / min, TMI is 40 μmol / min, and p-type doping source gas biscyclopenta. Dienylmagnesium (Cp ₂ Mg) is introduced into the apparatus at a rate of 10 nmol / min, and a p-type carrier block layer 14 made of an Al _0.20 Ga _0.75 In _0.05 N layer doped with 50 nm thick Mg is grown. When the growth of the p-type carrier block layer 14 is completed, the temperature is raised to 1000 ° C., the introduction of TMA into the device is stopped, and the growth of the p-type cladding layer 13 made of a GaN layer doped with 100 nm thick Mg. To do.

When the growth of the nitride-based semiconductor layer is completed as described above, the supply of TMG and Cp ₂ Mg is stopped, and then the wafer is cooled to room temperature and taken out from the MOCVD apparatus.

  Next, using an electron beam (EB) deposition apparatus, Pd is deposited as a p-type electrode 12 on the p-type cladding layer 13 to a thickness of 5 nm, and then Au metal is deposited to 500 nm. Thereafter, Ni plating is formed to 100 μm on the p-type electrode 12 by an electrolytic plating method to form the support substrate 11.

Next, as shown in FIG. 3, the wafer is inverted using the support substrate 11, and the Si substrate 10 is removed by etching with an etchant made of HF and HNO ₃ , and the AlN buffer layer 112 and the Al _0.5 Ga _{0.5 are} removed. The N layer 113 is removed by RIE (reactive ion etching).

Then, after setting the wafer from which the Si substrate or the like has been removed to the MOCVD apparatus, the surface of the wafer is cleaned by removing the surface damage layer and the oxide layer once at a high temperature of about 1000 ° C. in an H ₂ atmosphere.

Then, while flowing H ₂ as a carrier gas at a rate of 10 L / min, NH ₃ at a rate of 5 L / min at 900 ° C., TMG at a rate of 50 μmol / min, and further as a dopant gas for Si for n-type SiH ₄ is introduced into the apparatus, and a light extraction layer 19 having a concavo-convex structure made of n-type GaN having a maximum thickness of 400 nm is grown. At 900 ° C., the light extraction layer 19 having a concavo-convex structure having innumerable holes can be produced by increasing the growth rate of the light extraction layer 19 or decreasing the amount of NH ₃ gas introduced.

  In this embodiment, an n-electrode 110 and a bonding electrode 111 are formed on a part of the nitride-based semiconductor light-emitting element having irregularities formed by the above-described method, and finally the substrate is divided into 300 μm squares by a dicing apparatus. This completes the nitride-based semiconductor light-emitting device.

  As described above, a nitride-based semiconductor light-emitting device is epitaxially grown on a highly workable Si substrate, an electrode having a high reflectance is provided on the p-type GaN side, and then inverted using the support substrate 11 to form an n-type GaN. By providing irregularities made of the same nitride crystal on the layer side, it is possible to produce a high-brightness nitride-based semiconductor light-emitting device that has high light extraction efficiency and does not interfere with electrical conductivity.

(Example 2)
FIG. 4 shows a schematic perspective view of a nitride-based semiconductor light-emitting element according to Example 2 of the present invention. The nitride-based semiconductor light-emitting device of this example is characterized in that a translucent electrode layer 213 made of Al is formed on the upper surface of an uneven n-type GaN light extraction layer 29 by vapor deposition.

In the nitride-based semiconductor light-emitting device of this example, a p-type electrode 22 is formed on a support substrate 21 made of Ni plating that also serves as an electrode, and a p-type GaN cladding layer 23 and a p-type are formed on the p-type electrode 22. AlGaInN carrier block layer 24, light emitting layer 25 made of In _x Ga _1-x N, Si-doped n-type In _0.03 Ga _0.97 N cladding layer 26, Si-doped n-type In _0.1 Ga _0.9 N layer 27 and Si-doped n-type GaN layer The clad layer 28 is sequentially laminated. On the upper surface of the n-type GaN clad layer 28, an n-type GaN light extraction layer 29 having irregularities produced by regrowth is formed.

  Furthermore, in the nitride-based semiconductor light-emitting device of Example 2, a translucent electrode layer 213 made of Al is formed on the upper surface of the n-type GaN light extraction layer 29 having irregularities by a vapor deposition method. An n-type electrode 210 and an n-type bonding electrode 211 are formed on part of the upper surface of the layer 213. Also in the present embodiment described above, a high-brightness nitride-based semiconductor light-emitting element with high light extraction efficiency and low driving voltage can be manufactured. Others are the same as in the first embodiment.

(Example 3)
FIG. 5 shows a schematic perspective view of a nitride-based semiconductor light-emitting element according to Example 3 of the present invention. In the nitride-based semiconductor light-emitting device of this embodiment, a mask 314 made of SiO ₂ is formed on the upper surface of the Si-doped n-type GaN layer cladding layer 38, and the selectively grown n-type GaN light extraction layer 39 is formed. Is formed with a pyramidal light extraction surface 39a.

In the nitride semiconductor light emitting device of this example, a p-type electrode 32 is formed on a support substrate 31 made of Ni plating which also serves as an electrode, and a p-type GaN cladding layer 33 and a p-type are formed on the p-type electrode 32. AlGaInN carrier block layer 34, light emitting layer 35 made of In _x Ga _1-x N, Si-doped n-type In _0.03 Ga _0.97 N cladding layer 36, Si-doped n-type In _0.1 Ga _0.9 N layer 37 and Si-doped n-type GaN layer A clad layer 38 is sequentially laminated. Further, an n-type GaN light extraction layer 39 having irregularities produced by regrowth is formed on the upper surface of the n-type GaN cladding layer 38. An n-type electrode 310 and an n-type bonding electrode 311 are formed on part of the n-type GaN light extraction layer 39. Further, a mask 314 made of SiO ₂ is formed on the upper surface of the n-type GaN layer cladding layer 38, and a pyramidal light extraction surface 39a is formed on the selectively grown n-type GaN light extraction layer 39. Yes. Also in the present embodiment described above, a high-brightness nitride-based semiconductor light-emitting element with high light extraction efficiency and low driving voltage can be manufactured. Others are the same as in the first embodiment.

Example 4
FIG. 6 shows a schematic perspective view of a nitride-based semiconductor light-emitting element according to Example 4 of the present invention. In the nitride-based semiconductor light-emitting device of Example 4, a kamaboko-shaped light extraction surface 49a is formed in the n-type GaN light extraction layer 49, and a taper structure is formed between the light extraction surfaces 49a. To do.

In the nitride-based semiconductor light-emitting device of this example, a p-type electrode 42 is formed on a support substrate 41 made of Ni plating which also serves as an electrode, and a p-type GaN cladding layer 43 and a p-type are formed on the p-type electrode 42. AlGaInN carrier block layer 44, light emitting layer 45 made of In _x Ga _1-x N, Si-doped n-type In _0.03 Ga _0.97 N cladding layer 46, Si-doped n-type In _0.1 Ga _0.9 N layer 47 and Si-doped n-type GaN layer A clad layer 48 is sequentially laminated. An n-type GaN light extraction layer 49 is formed on the upper surface of the n-type GaN cladding layer 48. An n-type electrode 410 and an n-type bonding electrode 411 are formed on a part of the n-type GaN light extraction layer 49. Further, the n-type GaN light extraction layer 49 is formed with a semi-cylindrical light extraction surface 49a, and a taper structure is formed between the light extraction surfaces 49a.

  This kamaboko-shaped light extraction surface 49a is produced as follows. First, after forming a mask pattern composed of stripes having a width of about 1 μm on the n-type GaN cladding layer 48, heat treatment is performed at 180 ° C. for 30 minutes to deform the mask pattern into a kamaboko shape. Then, the kamaboko shape is transferred to the n-type GaN light extraction layer 49 by etching vertically using RIE. Also in the present embodiment described above, a high-brightness nitride-based semiconductor light-emitting element with high light extraction efficiency and low driving voltage can be manufactured. Others are the same as in the first embodiment.

(Example 5)
FIG. 7 shows a schematic perspective view of a nitride-based semiconductor light-emitting element according to Example 5 of the present invention. The nitride-based semiconductor light-emitting device of this example is characterized in that the n-type GaN light extraction layer 59 is formed in a prism shape.

In the nitride semiconductor light emitting device of this embodiment, a p-type electrode 52 is formed on a support substrate 51 made of Ni plating which also serves as an electrode, and a p-type GaN cladding layer 53 and a p-type are formed on the p-type electrode 52. The Al _0.20 Ga _0.75 In _0.05 N carrier block layer 54, the light emitting layer 55, and the Si-doped n-type GaN layer clad layer 58 are sequentially stacked, and the upper surface of the n-type GaN clad layer 58 is formed by regrowth. An n-type GaN light extraction layer 59 having irregularities is formed in a prism shape. An n-type electrode 510 and an n-type bonding electrode 511 are formed on a part of the n-type GaN light extraction layer 59.

  Below, the manufacturing method of the nitride type semiconductor light-emitting device of a present Example is demonstrated. First, FIG. 8A is a diagram showing the relationship between the (001) main surface 60 and the (111) facet surface 61 of the Si substrate 20, and FIG. 8B and FIG. FIG. 7 is a cross-sectional view and a conceptual diagram showing the relationship of a nitride semiconductor film having a (001) plane, a (111) facet plane 61, and a (1-101) facet plane 70 off by 7.3 °.

As shown in FIGS. 8A to 8C, the Si substrate 20 rotated by 7.3 ° around the [01-1] axis from the (001) main surface 60 or 3 in an arbitrary direction from this surface. relative inclined plane within a range of °, partially masked by SiO ₂ 514, by performing the etching with respect to free the opening portion of the mask of the SiO ₂ 514, the (001) principal surface 60 A groove having a (111) facet surface 61 with an angle of 62 ° is formed, and a nitride-based semiconductor film is epitaxially grown on the groove to thereby form a GaN-based material having the (1-101) facet surface 70 as a growth surface. A semiconductor film can be obtained.

  The Si substrate 20 used here is inclined 7.3 ° [0-1-1] from the (001) main surface 60, that is, 7. (xi) around the (01-1) axis from the (001) main surface 60. With the main surface 60 rotated by 3 °, the (1-101) facet surface 70 can have substantially the same plane orientation as the main surface 60 of the Si substrate 20. In addition, even when it is inclined within a range of 3 ° in any direction from this surface, a very flat surface having the (1-101) surface can be obtained.

  Therefore, in the order of FIG. 9A, FIG. 9B, FIG. 9C, and FIG. 9D, the crystal growth of the nitride-based semiconductor film gradually progresses only on the groove, A nitride-based semiconductor light emitting device is formed on the substrate, and a p-type electrode 52 and a Ni plating 51 are formed thereon as a support substrate. Then, the Si substrate 20 is removed, whereby the (111) facet surface of the Si substrate 20 is removed. The nitride-based semiconductor light-emitting device of this example using the light extraction surface having prism-like irregularities formed by 61 can be completed.

More specifically, the Si substrate 20 described above is first cleaned, and then a SiO ₂ mask 514 is deposited to a thickness of 100 nm as shown in FIG. . Thereafter, the SiO ₂ mask 514 is partially removed in a stripe shape by performing a photolithographic technique. Further, a groove having a (111) facet surface 61 is formed on the wafer by acid etching such as buffered hydrofluoric acid as shown in FIG. This groove is a stripe-shaped groove extending in the [01-1] direction of the Si substrate 20. Here, the angle formed between the main surface 60 of the Si substrate 20 and the (111) facet surface 61 is about 62 °. Next, as shown in FIG. 10C, a SiO ₂ mask 514a is formed on the opposite surface of the (111) facet surface 61.

  Next, a nitride semiconductor film is grown on the facet surface 61 of the Si substrate 20 using MOCVD (metal organic chemical vapor deposition) under the following growth conditions. This will be specifically described below.

First, the silicon substrate 20 having grooves formed by the process described above is introduced into an MOCVD apparatus, and cleaning is performed at a high temperature of about 1100 ° C. in an H ₂ atmosphere.

Next, while flowing H ₂ as a carrier gas at a rate of 10 L / min, NH ₃ was introduced at a rate of 5 L / min and TMA at a rate of 10 μmol / min at 800 ° C. into the apparatus, respectively. As shown in (a), an AlN buffer layer 120 having a thickness of about 50 nm is grown, and then at the same temperature, the supply of TMA is stopped, TMG is added at a rate of about 20 μmol / min, and SiH ₄ gas is added at 0.05 μmol / min. Each is introduced into the apparatus at a rate of min, and a Si-doped n-type GaN cladding layer 58 having a thickness of about 3 μm is grown.

Next, supply of TMA, TMI, and TMG is stopped, the substrate temperature is lowered to 760 ° C., and TMI is introduced into the apparatus at a rate of 6.5 μmol / min and TMG at a rate of 2.8 μmol / min. A 3 nm thick well layer made of In _0.18 Ga _0.82 N is grown. Thereafter, the temperature is raised again to 850 ° C., TMG is introduced into the apparatus at a rate of 14 μmol / min, and a barrier layer made of GaN is grown. Similarly, the growth of the well layer and the barrier layer is repeated, and as shown in FIG. 11B, the light emitting layer 55 made up of four pairs of multiple quantum wells (MQW) is grown.

After the growth of the light emitting layer is completed, at the same temperature as the last barrier layer, TMG is 11 μmol / min, TMA is 1.1 μmol / min, TMI is 40 μmol / min, Cp ₂ Mg is allowed to flow into the apparatus at a rate of 10 nmol / min, and a p-type Al _0.20 Ga _0.75 In _0.05 N carrier block layer 54 having a thickness of 50 nm is grown. Next, when the growth of the p-type Al _0.20 Ga _0.75 In _0.05 N carrier blocking layer 54 is completed, the supply of TMA is stopped at the same growth temperature, and the p-type In _0.1 Ga _0.9 N cladding layer 53 having a thickness of 80 nm is grown. At the stage shown in FIG. 11C, the growth of the light emitting device structure is completed. Thereafter, the supply of TMG, TMI and Cp ₂ Mg is stopped, and then cooled to room temperature and taken out from the MOCVD apparatus.

  On the nitride semiconductor light emitting device fabricated on the Si substrate 20 using the above growth conditions, the p-type electrode 52 is deposited to a thickness of 100 nm using an electron beam (EB) deposition apparatus. Ni plating was applied to the p-type electrode 52 by 100 μm to form a support substrate 51 of the semiconductor light emitting device as shown in FIG.

  Subsequently, the SiN 20 on the n-type GaN cladding layer 58 side is removed by etching using a hydrofluoric acid-based etchant, and further, the AlN buffer layer is intended to increase the conductivity on the n-type-GaN side. The prismatic light extraction layer 59 is formed by removing a layer having low crystallinity in the vicinity of 120 and the Si substrate interface using an RIE apparatus. Finally, an n-electrode 510 and a bonding electrode 511 are partially formed on the light extraction layer 59, and the resulting wafer is divided into 300 μm squares by a dicing apparatus. Also in the present embodiment described above, a high-brightness nitride-based semiconductor light-emitting element with high light extraction efficiency and low driving voltage can be manufactured.

(Comparative Example 1)
In the configuration of the nitride-based semiconductor light-emitting device of Example 1, the configuration in which the n-type electrode 110 is directly provided on the n-type GaN layer cladding layer 18 without forming the light extraction surface 19 is the same as that of Comparative Example 1. A nitride semiconductor light emitting device was obtained.

(Comparative Example 2)
In the configuration of the nitride-based semiconductor light-emitting device of Example 1, a configuration in which n-type and p-type are interchanged was used as the nitride-based semiconductor light-emitting device of Comparative Example 2.

(Measurement result)
The drive voltage and light extraction efficiency of the nitride-based semiconductor light emitting devices of Examples 1 to 5 and Comparative Examples 1 to 2 were measured. Table 1 below shows the measurement results of the nitride semiconductor light emitting devices of Examples 1 to 5 and Comparative Examples 1 and 2.

  As can be seen from Table 1, the nitride-based semiconductor light-emitting devices of Examples 1 to 5 are equivalent to the nitride-based semiconductor light-emitting device of Comparative Example 1 at a driving voltage of 3.5 V. The light extraction efficiency of the nitride-based semiconductor light-emitting device is 2.0 mW, and the light extraction efficiency of the nitride-based semiconductor light-emitting device of Comparative Example 1 is 1.5 mW. Therefore, the nitride-based semiconductor of Examples 1 to 5 The light emitting device was superior in light extraction efficiency than the nitride-based semiconductor light emitting device of Comparative Example 1.

  Further, the driving voltage of the nitride-based semiconductor light-emitting elements of Examples 1 to 5 is 3.5V, and the driving voltage of the nitride-based semiconductor light-emitting element of Comparative Example 2 is 4.5V. The nitride-based semiconductor light-emitting device of No. 5 was able to lower the drive voltage than the nitride-based semiconductor light-emitting device of Comparative Example 2.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic perspective view of a nitride-based semiconductor light-emitting element of Example 1. FIG. It is a typical perspective view of the nitride-type semiconductor light-emitting device of Example 1 after forming a p-type cladding layer. It is a typical perspective view of the nitride-type semiconductor light-emitting device of Example 1 after Si substrate removal. 6 is a schematic perspective view of a nitride-based semiconductor light-emitting element according to Example 2. FIG. 6 is a schematic perspective view of a nitride-based semiconductor light-emitting element according to Example 3. FIG. 6 is a schematic perspective view of a nitride-based semiconductor light-emitting element of Example 4. FIG. 6 is a schematic perspective view of a nitride-based semiconductor light-emitting element according to Example 5. FIG. It is the typical conceptual diagram which showed the relationship between Si substrate and a facet surface. It is the typical conceptual diagram which showed progress of the crystal growth of the nitride-type semiconductor film. It is the typical conceptual diagram which showed an example of the process in which a part of Si substrate is removed and a facet surface is formed. FIG. 6 is a schematic conceptual diagram showing an example of a manufacturing process of the nitride-based semiconductor light-emitting element of Example 5. It is a typical perspective view of the conventional nitride semiconductor light-emitting device.

Explanation of symbols

11, 21, 31, 41, 51 Support substrate, 12, 22, 32, 42, 52 p-type electrode, 13, 23, 33, 43, 53 p-type cladding layer, 14, 24, 34, 44, 54 p Type carrier block layer, 15, 25, 35, 45, 55 light emitting layer, 16, 26, 36, 46 n-type In _0.03 Ga _0.97 N cladding layer, 17, 27, 37, 47 n-type In _0.1 Ga _0.9 N layer, 18, 28, 38, 48, 58 n-type GaN layer cladding layer, 19, 29, 39, 49, 59 light extraction layer, 39a, 49a light extraction surface, 110, 210, 310, 410, 510 n-type electrode, 111,211,311,411,511 n-type bonding electrode, 112,101,120 buffer layer, 113 Al _0.5 Ga _0.5 n layer, 213 transparent electrode layer, 314,514,514A trout 10, 20, 100 Si substrate, 60 main surface, 61, 70 facet surface, 102 n-type GaN layer, 103 InGaN light emitting layer, 104 p-type AlGaN carrier block layer, 105 p-type GaN contact layer, 106 translucent electrode 107 n-type electrode, 108 p-type pad electrode, 109 n-type pad electrode.

Claims (2)

And formed on the support substrate reflective layer, the reflective layer above sequentially laminated p-type nitride semiconductor layer, seen including a light emitting layer and the n-type nitride semiconductor layer, the n-type nitride semiconductor layer A method of manufacturing a nitride-based semiconductor light-emitting device having irregularities formed on a light extraction surface located above ,
Preparing a Si substrate;
Forming a groove having a (111) facet surface in the Si substrate;
Forming a SiO ₂ mask on the opposite surface of the (111) facet surface ;
A step of sequentially laminating the n-type nitride semiconductor layer, the light emitting layer, and the p-type nitride semiconductor layer on the (111) facet surface with the SiO ₂ mask formed on the opposing surface. When,
Forming the reflective layer on the p-type nitride-based semiconductor layer;
Forming the support substrate on the reflective layer;
Removing the Si substrate;
Forming a high refractive index film on the irregularities of the n-type nitride semiconductor layer formed by the step of removing the Si substrate,
Before Symbol high refractive index film is the film refractive index is smaller than the n-type nitride semiconductor layer, and a nitride-based semiconductor light-emitting, characterized in that the upper surface of the high refractive index film is the light extraction surface Device manufacturing method . 2. The nitride according to claim 1, wherein the high refractive index film is made of any one of a group consisting of silicon nitride, indium oxide, neodymium oxide, zirconium oxide, titanium oxide, cerium oxide, and bismuth oxide. For manufacturing a semiconductor light emitting device.

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