JP4852322B2 - Nitride semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a nitride semiconductor light emitting device with improved light extraction efficiency and a method for manufacturing the same.

  In general, a compound semiconductor constituting an LED has a high refractive index, and the numerical value of the refractive index is usually 2 or more. For this reason, when the light generated in the LED chip is emitted into the atmosphere, a phenomenon occurs in which total reflection occurs at the interface between the compound semiconductor constituting the LED and the atmosphere, and the LED chip itself is trapped. To do. The critical angle at which total reflection occurs is smaller as the refractive index difference between the compound semiconductor and the atmosphere is larger. Therefore, more light is trapped in the LED chip itself due to total reflection, and the light extraction efficiency is further reduced. For this reason, various methods for increasing the efficiency of extracting light have been proposed.

  A nitride semiconductor light emitting device is often used as an LED. The p-side contact layer of the nitride semiconductor light emitting device is composed of a p-type GaN-based semiconductor layer containing GaN. Since the specific resistance of the p-type GaN-based semiconductor layer is usually as high as several Ωcm, a sufficient current spread in the layer direction (lateral direction) cannot be obtained with the p-type layer. In order to increase the current spread, it is sufficient to increase the film thickness. However, if the specific resistance is on the order of several Ωcm, the standard size of the chip is about several hundreds μm in the lateral direction. The film thickness needs to be on the order of several mm, which is not realistic at all. Therefore, normally, a p-electrode that substantially covers the entire p-type GaN-based contact layer is formed so that current flows in the entire lateral direction. However, since the p electrode absorbs light in this state, a very thin metal electrode (semi-transparent electrode) of about several tens of millimeters is used.

  However, even a very thin translucent electrode is made of metal, so absorption is unavoidable, and usually 30 to 40% of absorption occurs. In order to solve this, it has been proposed to use a transparent electrode such as ZnO or ITO. Since these transparent electrodes are made of a material having a transmittance of almost 100%, the light extraction efficiency can be increased.

As a structure of a conventional nitride semiconductor light emitting device using a transparent electrode, for example, there is a structure as shown in FIG. 14 (see, for example, Patent Document 1). An n-type nitride semiconductor layer 52, an active layer 53, a p-type nitride semiconductor layer 54, and a ZnO film 55 are formed in this order on a conductive substrate 51. The n electrode is formed on the entire surface, and the p electrode is provided on a part of the ZnO film 55. In this nitride semiconductor light emitting device, light is extracted from above the ZnO film 55.
Japanese Patent No. 3720341

  The conventional nitride semiconductor light emitting device described above improves the light extraction efficiency by effectively utilizing not only the emitted light from the upper surface of the ZnO film 55 but also the emitted light from the side surface of the chip. As shown in FIG. 14, among the light generated in the active layer 53, the light traveling to the side surface of the chip is emitted as it is into the atmosphere as indicated by the solid line T.

  However, as described above, the compound semiconductor constituting the light emitting element has a high refractive index, and total reflection occurs at the interface between the compound semiconductor and the atmosphere not only on the top surface of the chip but also on the side surface of the chip. Total reflection occurs at the boundary surface when light travels from a medium with a high refractive index to a medium with a low refractive index, and occurs when the incident angle of light incident on the boundary surface exceeds a critical angle.

  The light extraction cone 40 shows a range of light incident on the boundary surface within a critical angle where total reflection does not occur. Light entering the range of the light extraction cone 40 is in the atmosphere as indicated by the solid line T arrow. However, the light that does not enter the range of the light extraction cone 40 causes total reflection at the interface between the semiconductor layer and the atmosphere, as indicated by the solid line R, and cannot be extracted.

  Here, when trying to increase the amount of light extraction by making maximum use of the light entering the light extraction cone 40, the p-side surface becomes a problem. That is, since the thickness of the ZnO film 55 formed on the p side is insufficient, the ZnO film 55 is further grown, for example, like the ZnO film 56 shown by the broken line in FIG. If it is thick enough to completely contain the light, effective light extraction can be performed. If the lateral size A of the light emitting element is 100 to 1000 μm, the radius of the light extraction cone 40 needs to be 45 to 450 μm.

  Therefore, even when the lateral size A of the light emitting element is small, the thickness of the ZnO film needs to be on the order of several tens of μm. If this thickness can be realized, the thickness direction (chip side surface) The light extraction from the light increases, and the light extraction efficiency is improved. However, since the ZnO film is formed by using a thin film forming method, it takes a long time to form a film thickness on the order of several tens of μm.

  Further, as shown in Patent Document 1, the ZnO film formed on the p side in particular is doped with impurities in order to lower the specific resistance, and in the state where this doping is controlled, it is several tens of μm as described above. It takes too much time to grow the film thickness of the order, which has been a problem because the yield of chip production has deteriorated.

  The present invention was devised to solve the above-described problems, and not only the amount of light extracted from the stacking direction of the chips but also the amount of light extracted from the side surfaces of the chip is increased, and the chip fabrication does not take time. An object of the present invention is to provide a nitride semiconductor light emitting device and a method for manufacturing the same.

In order to achieve the above object, the invention according to claim 1 is a nitride semiconductor light emitting device comprising at least an n-type GaN-based semiconductor layer, an active layer, and a p-type GaN-based semiconductor layer in this order. An n-type ZnO film made of ZnO or a ZnO compound is formed on the growth surface side of the layer, a ZnO substrate is disposed on the growth surface side of the n-type ZnO film, and the surface of the ZnO substrate is (000− 1) A nitride semiconductor light emitting device comprising a surface and having irregularities formed thereon .

The invention according to claim 2 is characterized in that the n-type ZnO film is doped with impurities so as to have a carrier concentration of 1 × 10 ²⁰ cm ⁻³ or more. It is.

  The invention according to claim 3 is the nitride semiconductor light emitting element according to claim 1, wherein the thickness of the ZnO substrate is 45 μm or more.

The invention according to claim 4 is the nitride semiconductor light emitting device according to any one of claims 1 to 3 , wherein the unevenness of the surface of the ZnO substrate is a cone shape. There is .

According to a fifth aspect of the present invention, in the method for manufacturing a nitride semiconductor light emitting device in which an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer are formed with an active layer interposed therebetween, the p-type GaN-based semiconductor layer includes: After forming an n-type ZnO film made of ZnO or a ZnO compound on the growth surface side, a ZnO substrate having a (0001) plane on the side in contact with the n-type ZnO film is attached to the surface of the n-type ZnO film, and thereafter An unevenness is formed on the surface of the ZnO substrate by roughening the surface of the nitride semiconductor light emitting device.

According to a sixth aspect of the present invention, in the method for manufacturing a nitride semiconductor light emitting device in which an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer are formed so as to sandwich an active layer, the surface of the p-type GaN-based semiconductor layer A ZnO substrate having a (0001) plane on the side in contact with the surface and having an n-type ZnO film made of ZnO or a ZnO compound formed thereon is attached to the surface of the p-type GaN-based semiconductor layer, and then roughened by roughening the ZnO substrate. A method of manufacturing a nitride semiconductor light emitting device, wherein irregularities are formed on the surface of the nitride semiconductor light emitting device.

The invention according to claim 7 is a method of manufacturing a nitride semiconductor light emitting device in which an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer are formed so as to sandwich an active layer.
After forming a first n-type ZnO film made of ZnO or a ZnO compound on the growth surface side of the p-type GaN-based semiconductor layer, the p-type GaN-based semiconductor layer has a (0001) plane on the side in contact with the first n-type ZnO film. A ZnO substrate on which a second n-type ZnO film made of ZnO or a ZnO compound is formed is attached to the surface of the first n-type ZnO film, and then unevenness is formed on the surface of the ZnO substrate by roughening. It is a manufacturing method of the nitride semiconductor light emitting device characterized.

The invention according to claim 8 is characterized in that the bonding of the ZnO substrate or the ZnO substrate on which the n-type ZnO film is formed is performed by heating in an atmosphere not containing oxygen. It is a manufacturing method of the nitride semiconductor light emitting element of any one of Claim 7.

The invention according to claim 9 is characterized in that the rough surface processing is performed by wet etching with an acid, and manufacturing a nitride semiconductor light emitting element according to any one of claims 5 to 7 Is the method.

  According to the present invention, since the ZnO substrate is disposed on the n-type ZnO film, the length of the side surface of the p-side chip can be particularly increased, and the light generated in the active layer is applied to the side surface of the chip. Thus, the length of the side surface of the chip can be ensured up to the maximum range of the light extraction cone that can be emitted into the atmosphere via the air, and the light extraction efficiency is improved.

  Further, in the manufacturing method, not only one n-type ZnO film is formed thick, but the n-type ZnO film is formed to have a normal thickness for use as a p-side transparent electrode, and this n-type ZnO film is formed. Since the ZnO substrate is attached on the top, when obtaining a desired length of the p-side chip side, it is much shorter than forming a thick n-type ZnO film whose impurity doping must be controlled. Can be formed in time.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross section of a first nitride semiconductor light emitting device according to the present invention.

  A GaN substrate 2, an n-type GaN-based semiconductor layer 3, an active layer 4 as a light emitting layer, a p-type GaN-based semiconductor layer 5, a ZnO electrode film 6, and a ZnO substrate 7 are stacked on the n-side metal electrode 1. The n-type GaN-based semiconductor layer 3 is an n-type semiconductor layer containing a GaN component, and the p-type GaN-based semiconductor layer 5 is a p-type semiconductor layer containing a GaN component.

  In addition, a p-side metal electrode used for wire bonding or the like is formed in a partial region on the ZnO substrate 7, and the exposed surface of the ZnO substrate 7 is roughened by roughing as shown in the figure. . The unevenness formed by the rough surface processing is formed in a cone shape such as a hexagonal pyramid.

The ZnO electrode film 6 is composed of an n-type n-type ZnO film, and ZnO or a ZnO compound is used as a material. When this n-type ZnO film is composed of a ZnO compound, as described in Patent Document 1 developed by the inventor and patented, for example, Mg _Z Zn _1-Z O (doped with Ga) is used. The MgZnO electrode film is formed of 0 ≦ Z <1). Also, Ga instead doped _{Mg Z Zn 1-Z O (} 0 ≦ Z <1) is, B may be doped _{Mg Z Zn 1-Z O (} 0 ≦ Z <1). Here, Mg is added to the ZnO film because the transmittance can be kept high even at a short wavelength of about 400 nm. If the transmittance at a short wavelength does not need to be kept high, Mg is added. Alternatively, a ZnO film doped with impurities such as Ga and B into ZnO can be used without adding Zn.

As described above, when the MgZnO electrode film is used as the ZnO electrode film 6, the sputtering method and the ion plating method are performed using a target obtained by firing a mixture of Ga ₂ O ₃ , MgO and ZnO powder. And so on. Further, metal Ga, metal Mg, and metal Zn are heated by a heater and supplied as a molecular beam, and oxygen can also be formed by a vapor deposition method similar to a molecular beam epitaxy method that supplies an RF radical cell.

  Normally, ZnO as the material of the transparent electrode film is non-doped with no impurities doped, and it is difficult to form an ohmic contact at the junction with the p-type GaN-based semiconductor. In addition, since the conductivity of the non-doped ZnO film is not high, there is a problem that the driving voltage is high, and the current is not diffused in the lateral direction, so that the light emission efficiency is lowered. By raising the above, the above problem is solved.

Therefore, as shown in Patent Document _{1, Mg Z Zn 1-Z} O in the doping with Ga or B is a Group IIIB elements, makes use of the fact that significant resistance decreases. The relationship between the carrier concentration of Ga with respect to _{Mg Z} Zn _1-Z O shown in Patent Document 1 is shown again in FIG. The horizontal axis represents carrier concentration, and the vertical axis represents resistivity. It can be seen that when the carrier concentration is increased, the resistivity decreases, and when the carrier concentration exceeds 1 × 10 ²¹ , the resistivity increases rapidly. As an electrode for diffusing current, resistivity when Ga uses doped _{Mg Z Zn 1-Z O (} 0 ≦ Z <1) electrode film made of is the 1 × ^{10 -2} Ωcm or less It is desirable.

According to this condition, the carrier concentration is preferably 1 × 10 ¹⁹ cm ⁻³ or more and 5 × 10 ²¹ cm ⁻³ or less from FIG. The same applies when doping B instead of Ga. Since the specific resistance of the MgZnO electrode film formed under such conditions is smaller than the specific resistance of the p-type GaN-based semiconductor layer, in the GaN-based semiconductor light emitting device, the current injected from the p-side metal electrode 8 is ZnO. The electrode film 6 can easily diffuse in the lateral direction. The current diffused in the lateral direction is widely supplied from the p-type GaN-based semiconductor layer 5 to the active layer 4. Since the current spread is sufficient, holes are widely supplied to the active layer 4 to enable efficient light emission.

  On the other hand, the ZnO substrate 7 may be a non-doped substrate that is not doped with impurities, or the specific resistance may be controlled to 1 Ωcm or less by doping. Since the main components of the ZnO substrate 7 and the ZnO electrode film 6 are the same, ohmic contact is obtained.

  In the first nitride semiconductor light emitting device configured as described above, electrons injected from the n-side metal electrode 1 pass through the n-type GaN-based semiconductor layer 3 from the GaN substrate 2 and are regenerated as holes in the active layer 4. Join. Of the light emitted by recombination, the light directed toward the p-type GaN-based semiconductor layer 5 (upward) is transmitted through the ZnO electrode film 6 and also transmitted through the ZnO substrate 7 and emitted to the outside.

  Here, a critical angle exists due to a refractive index difference between the ZnO substrate 7 and the atmosphere, and emitted light having an incident angle larger than the critical angle cannot be totally reflected and extracted to the outside, but the surface of the ZnO substrate 7 Since the irregularities are formed by roughing the surface, the rate at which the incident angle becomes smaller than the critical angle can be increased, and the light extraction efficiency is improved.

  On the other hand, the light generated from the active layer 4 and traveling to the side surface of the chip is extracted from the side surface to the outside. Since the GaN substrate 2 is provided under the n-type GaN-based semiconductor layer 3 on the n side of the first nitride semiconductor light emitting device, the distance in the stacking direction (vertical direction) from the active layer 4 to the GaN substrate 2 is sufficient. In addition, since the ZnO substrate 7 is disposed on the ZnO electrode film 6 on the p side, the distance in the stacking direction from the active layer 4 to the ZnO substrate 7 is also sufficiently secured.

  Since it is configured as described above, it is possible to cover the entire region (shaded portion) of the light extraction cone 40 shown in FIG. 14, and the amount of light extraction from the side surface of the chip is also increased. Here, the spread angle from the center of the light extraction cone 40 usually reaches about 60 degrees, and generally when the chip is manufactured, the lateral size A of the chip is about 100 μm to 1000 μm. The radius of the light extraction cone 40 on the corresponding chip side surface is about 45 μm to 450 μm. Therefore, in order to cover the radius of the light extraction cone 40, the thickness of the ZnO substrate 7 is desirably 45 μm or more.

  Next, a method for manufacturing the first nitride semiconductor light emitting device of FIG. 1 will be described with reference to FIGS. First, as shown in FIG. 3, an n-type GaN-based semiconductor layer 3, an active layer 4, and a p-type GaN-based semiconductor layer 5 are grown on a GaN substrate 2 in order.

Here, n-type GaN-based semiconductor layer 3 is, for example, the Si doping concentration is 1 × ¹⁰ 18 ^{cm -3} with a thickness of 5μm of n-type GaN layer, thickness 10Å of Si doping concentration of 1 × ¹⁰ 18 ^{cm -3} The InGaN / GaN superlattice layer in which In _0.05 GaN and Si doping concentration of 1 × 10 ¹⁸ cm ⁻³ and GaN with a thickness of 20 mm are alternately stacked for 10 periods is stacked.

As the active layer 4, for example, an InGaN / InGaN active layer having a quantum well structure including an In _0.16 GaN well layer having a thickness of 30 mm and an In _0.01 GaN barrier layer having a thickness of 200 mm is used. In the case of a well structure, the well layer and the barrier layer are alternately stacked for several cycles.

The p-type GaN-based semiconductor layer 5 is, for example, a film having an Mg doping concentration of 1 × 10 ²⁰ cm ⁻³ on a p-type Al _0.07 GaN cladding layer having an Mg doping concentration of 5 × 10 ¹⁹ cm ⁻³ and a thickness of 200 mm. A stacked body in which a p-type GaN contact layer having a thickness of 700 mm is grown can be used. The p-type GaN contact layer may be a p-type InGaN contact layer.

  After the growth to the p-type GaN-based semiconductor layer 5, the natural oxide film on the surface of the p-type contact layer of the p-type GaN-based semiconductor layer 5 is removed with hydrochloric acid. Next, the ZnO electrode film 6 and the ZnO substrate 7 are formed. There are three methods for forming this, as shown in FIGS.

  First, according to the method of FIG. 4, the n-type ZnO electrode film 6 doped with impurities is formed on the surface of the p-type contact layer of the p-type GaN-based semiconductor layer 5 by the method described above. Thereafter, a previously prepared ZnO substrate 7 is attached (bonded). At the time of bonding, the bonding surface of the ZnO substrate 7 is the (0001) plane (also referred to as C surface), that is, the exposed surface opposite to the bonding surface of the ZnO substrate 7 is the (000-1) plane (-C (Also called the surface).

For example, the bonding method is such that the ZnO electrode film 6 and the ZnO substrate 7 are brought into contact with each other and sandwiched by a carbon jig in a state heated at 500 to 900 ° C. in nitrogen or in a vacuum of 1 × 10 ⁻³ Torr or less. Then, the ZnO substrate 7 and the ZnO electrode film 6 are bonded. The atmosphere at the time of pasting should not contain oxygen. This is because, if oxygen is contained in the atmosphere, the ZnO substrate and the ZnO electrode film are oxidized and the conductivity is lowered.

  On the other hand, according to the method of FIG. 5, the n-type ZnO electrode film 6a (first n-type ZnO film) in which impurities are doped on the surface of the p-type contact layer of the p-type GaN-based semiconductor layer 5 is the method described above. Form. In advance, an n-type ZnO electrode film 6b (second n-type ZnO film) doped with impurities is prepared on the ZnO substrate 7 by the method described above, and the ZnO electrode film 6a and A ZnO electrode film 6b is attached. This pasting method is performed in the same manner as in FIG. As in FIG. 4, the exposed surface opposite to the bonding surface of the ZnO substrate 7 is a (000-1) plane.

  On the other hand, according to the method of FIG. 6, an n-type ZnO electrode film 6 doped with impurities is previously prepared on the ZnO substrate 7 by the method described above. The p-type contact layer of the p-type GaN-based semiconductor layer 5 is attached. This pasting method is performed in the same manner as in FIG. As in FIG. 4, the exposed surface opposite to the bonding surface of the ZnO substrate 7 is a (000-1) plane.

  After forming up to the ZnO substrate 7 by any of the above methods, for example, an Al metal electrode is laminated on the back side of the GaN substrate 2 and is sintered at 500 to 700 [deg.] C. to obtain ohmic, and on the Al metal electrode An n-side metal electrode 1 made of a multilayer metal film is formed by laminating Ti / Au films for wire bonding.

Here, since the exposed surface of the ZnO substrate 7 is the (000-1) plane, it is etched very fast particularly against acid. Taking advantage of this, when the formation region of the p-side metal electrode 8 is covered with a mask such as SiO ₂ and a flat surface is secured, and wet etching with hydrochloric acid is performed, cone-shaped irregularities are naturally formed. Formed and roughened. When the roughening is finished, the mask is lifted off, and the p-side metal electrode 8 made of, for example, Ti / Au is formed on the portion protected by the mask. Thereafter, when the chip is formed, the first nitride semiconductor light emitting device of FIG. 1 is completed.

  As described above, the thickness of the ZnO electrode film 6 that requires n-type doping control is not greatly increased, but the thickness of the p-side chip side surface is secured by attaching the ZnO substrate 7. Therefore, the manufacturing time for chip fabrication can be shortened.

  Next, the second nitride semiconductor light emitting device of the present invention is shown in FIG. A conductive bonding layer 18 is formed on the support substrate 19, and the ZnO substrate 17 and the support substrate 19 are bonded and electrically connected by the conductive bonding layer 18. On the ZnO substrate 17, a ZnO electrode film 16, a p-type GaN-based semiconductor layer 15, an active layer 14, an n-type GaN-based semiconductor layer 13, and a GaN layer 12 are sequentially stacked. Here, the n-type GaN-based semiconductor layer 13 is an n-type semiconductor layer containing a GaN component, and the p-type GaN-based semiconductor layer 15 is a p-type semiconductor layer containing a GaN component.

  Further, an n-electrode 20 used for wire bonding or the like is formed in a partial region on the GaN layer 12. The exposed surface of the GaN layer 12 is roughened by roughing as shown in the figure, and the unevenness is formed in a pyramid shape such as a hexagonal pyramid as in FIG.

  On the p side of the second nitride semiconductor light emitting device, the surface opposite to the active layer of the p-type GaN-based semiconductor layer, that is, the growth surface of the p-type GaN-based semiconductor layer 15 is the same as the first nitride semiconductor light-emitting device. A p-type ZnO electrode film 16 is formed on the side, and a ZnO substrate 17 is formed in contact with the ZnO electrode film 16.

As in the case of the first nitride semiconductor light emitting device, the ZnO electrode film 16 is composed of an n-type n-type ZnO film, and this n-type ZnO film is Mg _Z Zn doped with Ga or B. _An MgZnO electrode film made of _{1-Z 2} O (0 ≦ Z <1) is used. Since these characteristics, manufacturing methods, and the like are the same as those of the first nitride semiconductor light emitting device, description thereof will be omitted. In addition, the ZnO substrate 17 may be a non-doped substrate that is not doped with impurities, or the specific resistance may be controlled to 1 Ωcm or less by doping.

  In the second nitride semiconductor light emitting device, the light emitted from the active layer 14 and directed toward the n-type GaN-based semiconductor layer 13 (upward) passes through the GaN layer 12 and is emitted to the outside. Here, a critical angle exists due to a difference in refractive index between the GaN layer 12 and the atmosphere, and emitted light having an incident angle larger than the critical angle cannot be totally reflected and extracted to the outside. Since the irregularities are formed by roughing the surface, the rate at which the incident angle becomes smaller than the critical angle can be increased, and the light extraction efficiency is improved.

  On the other hand, the light generated from the active layer 14 and traveling to the side surface of the chip is extracted from the side surface to the outside. Since the GaN substrate 12 is provided on the n-type GaN-based semiconductor layer 13 on the n side of the second nitride semiconductor light emitting device, the distance in the stacking direction (vertical direction) from the active layer 14 to the GaN substrate 12 is sufficient. Further, since the ZnO substrate 17 is disposed under the ZnO electrode film 16 on the p side, the distance in the stacking direction from the active layer 14 to the ZnO substrate 17 is also sufficiently secured.

  Since it is configured as described above, it is possible to cover the entire region (shaded portion) of the light extraction cone 40 shown in FIG. 14, and the amount of light extraction from the side surface of the chip is also increased. Further, the thickness of the ZnO substrate 17 is desirably 45 μm or more for the same reason described in the first nitride semiconductor light emitting device.

  Next, a method for manufacturing the second nitride semiconductor light emitting device will be described with reference to FIGS. As shown in FIG. 8, first, a GaN buffer layer 11 and an undoped GaN layer 12 that are grown at a low temperature are grown on a sapphire substrate 10, and then an n-type GaN-based semiconductor layer 13, an active layer 14, and p-type GaN. The system semiconductor layer 15 is grown in this order.

Here, n-type GaN-based semiconductor layer 13 is, for example, the Si doping concentration is 1 × ¹⁰ 18 ^{cm -3} with a thickness of 5μm of n-type GaN layer, thickness 10Å of Si doping concentration of 1 × ¹⁰ 18 ^{cm -3} The InGaN / GaN superlattice layer in which In _0.05 GaN and Si doping concentration of 1 × 10 ¹⁸ cm ⁻³ and GaN with a thickness of 20 mm are alternately stacked for 10 periods is stacked.

The active layer 14 uses, for example, an InGaN / InGaN active layer composed of a quantum well structure composed of an In _0.16 GaN well layer with a thickness of 30 mm and an In _0.01 GaN barrier layer with a thickness of 200 mm. In the case of a structure, the well layer and the barrier layer are alternately stacked for several cycles.

The p-type GaN-based semiconductor layer 15 is, for example, a film having a Mg doping concentration of 1 × 10 ²⁰ cm ⁻³ on a p-type Al _0.07 GaN cladding layer having an Mg doping concentration of 5 × 10 ¹⁹ cm ⁻³ and a thickness of 200 mm. A stacked body in which a p-type GaN contact layer having a thickness of 700 mm is grown can be used. The p-type GaN contact layer may be a p-type InGaN contact layer.

  After the growth up to the p-type GaN-based semiconductor layer 15, the natural oxide film on the surface of the p-type contact layer of the p-type GaN-based semiconductor layer 15 is removed with hydrochloric acid, and then the ZnO electrode film 16 and the ZnO substrate 17 are formed. However, in this formation method, there are three methods shown in FIGS. 9 to 11 as in the methods of FIGS.

  First, according to the method of FIG. 9, the n-type ZnO electrode film 16 doped with impurities is formed on the surface of the p-type contact layer of the p-type GaN-based semiconductor layer 15 by the method described above. Thereafter, a previously prepared ZnO substrate 17 is attached. At the time of bonding, the bonding surface of the ZnO substrate 17 is set to the (0001) plane, that is, the exposed surface opposite to the bonding surface of the ZnO substrate 17 is set to the (000-1) plane. This pasting method is performed in the same manner as the method described in FIG.

  On the other hand, according to the method of FIG. 10, an n-type ZnO electrode film 16 doped with impurities is previously prepared on the ZnO substrate 17 by the method described above. The p-type contact layer of the p-type GaN-based semiconductor layer 5 is attached. This pasting method is performed in the same manner as the method described in FIG. The exposed surface opposite to the bonding surface of the ZnO substrate 17 is set to the (000-1) plane.

  On the other hand, according to the method of FIG. 11, the n-type ZnO electrode film 16a (first n-type ZnO film) doped with impurities on the p-type contact layer surface of the p-type GaN-based semiconductor layer 15 is the method described above. Form. In advance, an n-type ZnO electrode film 16b (second n-type ZnO film) doped with impurities is formed on the ZnO substrate 17 by the method described above, and the ZnO electrode film 16a and A ZnO electrode film 16b is attached. This pasting method is performed in the same manner as the method described in FIG. The exposed surface opposite to the bonding surface of the ZnO substrate 17 is set to the (000-1) plane.

  After forming up to the ZnO substrate 17 by any of the above methods, Ti / Au or the like is formed on the ZnO substrate 17 as a part of the conductive bonding layer 18 as shown in FIG. Further, AuSn solder or the like is used as the conductive bonding layer 18, and the ZnO substrate 17 is bonded to a support substrate 19 made of a highly thermally conductive substrate such as CuW or AlN by Au—Au pressure bonding.

  Thereafter, a laser beam having a wavelength of 365 nm or less such as KrF is irradiated from the sapphire substrate 10 side. Then, the GaN buffer layer 11 absorbs the laser light and decomposes into Ga and N, and the sapphire substrate 10 is peeled from the wafer. FIG. 13 shows a state where the wafer is turned upside down after the sapphire substrate 10 is peeled off in FIG.

  In the rough surface processing, the region where the n-electrode 20 is laminated is covered with a mask such as SOG or SiN, and etching is performed using UV light including KOH and a wavelength of 365 nm to form irregularities on the exposed surface of the GaN layer 12. Next, the mask is peeled off, for example, an Al metal electrode is laminated, and the ohmic is removed by sintering at 500 to 700 ° C., and a Ti / Au film for wire bonding is laminated on the Al metal electrode to form a multilayer metal. An n-electrode 20 made of a film is formed. Thereafter, when a chip is formed, the second nitride semiconductor light emitting device shown in FIG. 7 is obtained.

  In addition, after the sapphire substrate 10 is peeled off, the chip is not formed into a chip, but in the bonding method of FIG. 9, the ZnO electrode film 16 is formed on the p-type GaN-based semiconductor layer 15 and then the bonding method of FIG. After laminating up to the p-type GaN-based semiconductor layer 15, after the ZnO electrode film 16 a is formed on the p-type GaN-based semiconductor layer 15, a chlorine-based gas is introduced using an ICP etcher to generate plasma. By generating, etching may be performed until the sapphire substrate 10 reaches the sapphire substrate 10 beyond the GaN buffer layer 11 and may be separated into chips.

As described above, the length of the p-side chip side surface is ensured by attaching the ZnO substrate 17 instead of increasing the film thickness of the ZnO electrode film 16 that requires n-type doping control. Therefore, the manufacturing time for chip fabrication can be shortened.

It is a figure which shows the cross-section of the 1st nitride semiconductor light-emitting device of this invention. It is a figure which shows the experimental result of Ga carrier density | concentration and resistivity of an n-type ZnO film. It is a figure which shows one manufacturing process of a 1st nitride semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 1st nitride semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 1st nitride semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 1st nitride semiconductor light-emitting device. It is a figure which shows the cross-section of the 2nd nitride semiconductor light-emitting device of this invention. It is a figure which shows one manufacturing process of a 2nd nitride semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2nd nitride semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2nd nitride semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2nd nitride semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2nd nitride semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2nd nitride semiconductor light-emitting device. It is a figure which shows the light extraction state from the chip | tip side surface of the conventional nitride semiconductor light-emitting device.

Explanation of symbols

1 n-side metal electrode 2 GaN substrate 3 n-type GaN-based semiconductor layer 4 active layer 5 p-type GaN-based semiconductor layer 6 ZnO electrode film 7 ZnO substrate 8 p-side metal electrode

Claims (9)

In a nitride semiconductor light emitting device comprising at least an n-type GaN-based semiconductor layer, an active layer, and a p-type GaN-based semiconductor layer in this order,
An n-type ZnO film made of ZnO or a ZnO compound is formed on the growth surface side of the p-type GaN-based semiconductor layer, and a ZnO substrate is disposed on the growth surface side of the n-type ZnO film ,
A surface of the ZnO substrate is constituted by a (000-1) plane, and unevenness is formed . 2. The nitride semiconductor light emitting device according to claim 1, wherein the n-type ZnO film is doped with an impurity so as to have a carrier concentration of 1 × 10 ²⁰ cm ⁻³ or more.   3. The nitride semiconductor light emitting device according to claim 1, wherein a thickness of the ZnO substrate is 45 μm or more. 4. 4. The nitride semiconductor light emitting device according to claim 1, wherein the unevenness of the surface of the ZnO substrate has a cone shape. 5. In a method for manufacturing a nitride semiconductor light emitting device in which an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer are formed so as to sandwich an active layer,
After forming an n-type ZnO film made of ZnO or a ZnO compound on the growth surface side of the p-type GaN-based semiconductor layer, a ZnO substrate having a (0001) surface on the side in contact with the n-type ZnO film is formed on the n-type ZnO substrate. A method for manufacturing a nitride semiconductor light emitting device, comprising: attaching to the surface of a ZnO film; and then forming irregularities on the surface of the ZnO substrate by roughening. In a method for manufacturing a nitride semiconductor light emitting device in which an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer are formed so as to sandwich an active layer,
A ZnO substrate having a (0001) plane on the side in contact with the p-type GaN-based semiconductor layer surface and an n-type ZnO film made of ZnO or a ZnO compound formed thereon is attached to the p-type GaN-based semiconductor layer surface; A method for manufacturing a nitride semiconductor light emitting device, comprising subsequently forming irregularities on the surface of the ZnO substrate by roughening . In a method for manufacturing a nitride semiconductor light emitting device in which an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer are formed so as to sandwich an active layer,
After forming a first n-type ZnO film made of ZnO or a ZnO compound on the growth surface side of the p-type GaN-based semiconductor layer, the p-type GaN-based semiconductor layer has a (0001) plane on the side in contact with the first n-type ZnO film. A ZnO substrate on which a second n-type ZnO film made of ZnO or a ZnO compound is formed is attached to the surface of the first n-type ZnO film, and then unevenness is formed on the surface of the ZnO substrate by roughening. A manufacturing method of a nitride semiconductor light emitting device characterized in that: 8. The attachment of the ZnO substrate on which the ZnO substrate or the n-type ZnO film is formed is performed by heating in an atmosphere not containing oxygen. 9. Manufacturing method of nitride semiconductor light-emitting device. The method for manufacturing a nitride semiconductor light-emitting element according to claim 5, wherein the rough surface processing is performed by wet etching with an acid.

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