WO2016143574A1 - Iii族窒化物半導体発光素子および該素子構成を含むウエハ - Google Patents
Iii族窒化物半導体発光素子および該素子構成を含むウエハ Download PDFInfo
- Publication number
- WO2016143574A1 WO2016143574A1 PCT/JP2016/055992 JP2016055992W WO2016143574A1 WO 2016143574 A1 WO2016143574 A1 WO 2016143574A1 JP 2016055992 W JP2016055992 W JP 2016055992W WO 2016143574 A1 WO2016143574 A1 WO 2016143574A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- electrode
- mesa
- light emitting
- layer
- type layer
- Prior art date
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/26—Materials of the light emitting region
- H01L33/30—Materials of the light emitting region containing only elements of group III and group V of the periodic system
- H01L33/32—Materials of the light emitting region containing only elements of group III and group V of the periodic system containing nitrogen
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/04—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
- H01L33/06—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/36—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
- H01L33/38—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
- H01L33/58—Optical field-shaping elements
Definitions
- the present invention relates to a group III nitride semiconductor light emitting device having an emission peak wavelength of ultraviolet rays.
- the present invention relates to a technique for preventing deterioration of an element due to current concentration at an end portion of a mesa structure of a light emitting element.
- the present invention also relates to a wafer including the light emitting device configuration.
- FIG. 7A and 7B show a typical schematic structure of the group III nitride semiconductor light emitting device 20.
- FIG. 7A is a top view of the element
- FIG. 7B is a cross-sectional view taken along line AA of FIG. 7A.
- the group III nitride semiconductor light emitting device 20 includes a stacked body (hereinafter sometimes referred to as “laminated semiconductor layer”) including an n-type layer 12, an active layer 13, and a p-type layer 14 on one surface side of the substrate 11.
- laminated semiconductor layer stacked body
- the mesa structure 15 is formed by forming a laminated semiconductor layer including the n-type layer 12, the active layer 13, and the p-type layer 14 on one surface side of the substrate 11, and then removing a part of the laminated structure by etching or the like. A part of 12 is exposed. A mesa structure 15 is formed by leaving a plateau-like portion (also referred to as a mesa) including the active layer 13 and the p-type layer 14 (see Patent Document 1). An n electrode 16 is formed on the exposed n-type layer 12 surface, and a p-electrode 17 is formed on the p-type layer 14 surface.
- the current flows between the p electrode and the n electrode. Since the current tends to flow through a low resistance path (usually the shortest path), the current is in the vicinity of the end of the mesa structure 15 (hereinafter sometimes referred to as “mesa end”) close to the n electrode and the p electrode. Concentrate on the flow. As a result, the current does not flow uniformly in the active layer 13 and light emission unevenness occurs. Further, since the current is concentrated on the mesa end, heat is locally generated in the vicinity of the mesa end. As a result, deterioration of the light emitting element is likely to proceed, leading to a decrease in light emission efficiency, an increase in operating voltage, a decrease in reliability, and the like.
- Patent Document 2 discloses an ultraviolet semiconductor in which a p-type layer or a high-resistance layer having a higher resistance than a p-electrode is formed on the surface of the p-type layer on the side close to the n-electrode along the shape of the p-type layer side. A light emitting device is disclosed.
- a high resistance layer is formed on a p-type layer near the mesa edge as in Patent Document 2, it is possible to suppress current concentration in a region near the mesa edge.
- the presence of the high-resistance layer increases the resistance between the p-electrode and the semiconductor layer, which causes a problem that the operating voltage increases.
- Patent Document 3 discloses a semiconductor light emitting device in which a trench is formed between a p electrode and an n electrode. By forming the trench, the variation in the length of the current path flowing between the p electrode and the n electrode is reduced, and the current is prevented from concentrating on a specific portion.
- it is necessary to increase the depth of the trench. Increasing the depth of the trench results in a problem that the current path becomes longer as a whole, the resistance increases, and the operating voltage increases.
- the current flowing between the p-electrode and the n-electrode is concentrated in a region near the mesa end without increasing the number of steps in manufacturing the light-emitting element and without excessively increasing the operating voltage. It aims at providing the technique which suppresses deterioration of the light emitting element by this.
- the inventors of the present invention have studied earnestly, thinking that the above problem can be solved by adjusting the structure of the p-electrode. Then, it was found that the above problem can be solved by forming the p-electrode at a certain distance from the end of the mesa structure in a part of the mesa structure, particularly in the protruding part of the mesa structure, and the present invention was completed. It came to do.
- the first invention includes an active layer between an n-type layer and a p-type layer, has an n-electrode on the n-type layer, a p-electrode on the p-type layer, and includes a p-type layer
- a group III nitride semiconductor light emitting device having a mesa structure, wherein a distance between a part of a mesa end and an outer periphery of the p electrode is 1 / d of a diffusion length L s in a top view of the group III nitride semiconductor light emitting device.
- a group III nitride semiconductor light emitting device in which a distance between a part of a mesa end and an outer periphery of the p electrode is 12 ⁇ m or more in a top view of the group III nitride semiconductor light emitting device.
- the object of the present invention can be sufficiently achieved if the distance between a part of the mesa end and the outer periphery of the p electrode is 12 ⁇ m or more.
- the second invention is the first invention, the distance between the outer periphery of the projecting portion and the p electrode of the mesa edge is group III nitride semiconductor light-emitting device is 1/3 or more of the diffusion length L s. Since current tends to concentrate on the p-electrode part at the protrusion at the mesa end, the distance between the protrusion at the mesa end and the outer periphery of the p-electrode is preferably within the above range.
- the third invention is the group III nitride semiconductor light emitting device according to the first invention, wherein the distance between the protrusion at the mesa end and the outer periphery of the p electrode is 12 ⁇ m or more.
- the fourth invention is a group III nitride semiconductor light-emitting device having a light emission peak wavelength of 200 to 350 nm in the first to third inventions.
- a Group III nitride semiconductor light emitting device having an emission peak wavelength of 200 to 350 nm is difficult to manufacture itself, and improvement in yield is strongly desired, and the present invention is suitable.
- the fifth invention provides a group III nitride semiconductor light emitting device including an active layer between an n-type layer and a p-type layer, and having an n-electrode on the n-type layer and a p-electrode on the p-type layer.
- the group III nitride semiconductor light-emitting device has the structure of the first to fourth aspects of the invention.
- the distance between a part of the mesa end and the outer periphery of the p electrode is set to a predetermined value or more, and the p electrode is limited to the vicinity of the end of the mesa structure.
- the p electrode restriction region the formation rate of the p electrode is restricted to be lower than that of the mesa portion other than this region.
- an ultraviolet light-emitting device having an emission peak wavelength in the range of 200 to 350 nm is more difficult to manufacture due to the influence of the composition of each layer and a yield is lower than a light-emitting device having an emission peak wavelength exceeding 350 nm, for example, a light-emitting device in the visible light region.
- the present invention is suitable for an ultraviolet light emitting element having an emission peak wavelength in the range of 200 to 350 nm because it can suppress a decrease in yield due to local deterioration in the mesa structure.
- An example of a group III nitride semiconductor light emitting device viewed from above is shown.
- An example of a group III nitride semiconductor light emitting device viewed from above is shown.
- An example of a group III nitride semiconductor light emitting device viewed from above is shown.
- An example of a group III nitride semiconductor light emitting device viewed from above is shown.
- An example of a group III nitride semiconductor light emitting device viewed from above is shown.
- An example of a group III nitride semiconductor light emitting device viewed from above is shown.
- An example of a group III nitride semiconductor light emitting device viewed from above is shown.
- a method for determining a “mesa edge protrusion” using a definition circle is shown.
- Various mesa end shapes are shown.
- a method for determining the p-electrode restriction region will be described.
- a method for determining the p-electrode restriction region will be described.
- the positional relationship between the mesa end of the element and the p electrode in the example is shown.
- An example of the positional relationship between the mesa end and the p-electrode is shown.
- An example of the positional relationship between the mesa end and the p-electrode is shown.
- An example of a typical group III nitride semiconductor light emitting device viewed from above is shown. 1 shows a cross-sectional view of a typical group III nitride semiconductor light emitting device.
- the light emitting region of light emitted from the group III nitride semiconductor light emitting device of the present invention is not particularly limited. According to the present invention, it is possible to suppress a decrease in output caused by deterioration due to local current concentration in the mesa structure regardless of the light emitting region, and to improve the yield.
- the present invention is applied to a group III nitride semiconductor light emitting device having an emission peak wavelength in the visible light region or the ultraviolet region. More preferably, the present invention is applied to a group III nitride semiconductor light emitting device that emits ultraviolet light having an emission peak wavelength of 200 to 350 nm.
- a group III nitride semiconductor light emitting device having an emission peak wavelength of 200 to 350 nm will be mainly described.
- a typical group III nitride semiconductor light emitting device 20 has a mesa structure 15 (laminated semiconductor layer) including a substrate 11, an n-type layer 12, an active layer 13, and a p-type layer 14. ) And an n-electrode 16 and a p-electrode 17.
- mesa structure 15 laminated semiconductor layer
- substrate 11 an n-type layer 12, an active layer 13, and a p-type layer 14.
- the refractive index, transmittance, and reflectance were based on light having a wavelength of 265 nm. This is because light of wavelength 265 nm is most suitable for sterilization because DNA has maximum absorption in the vicinity of wavelength 265 nm, and is considered to have high industrial utility value.
- the refractive index, the transmittance, and the reflectance are simply used, the values are for light with a wavelength of 265 nm.
- the substrate 11 is not particularly limited as long as it can epitaxially grow a group III nitride semiconductor crystal on the surface and transmits ultraviolet rays.
- Examples of the material used for the substrate 11 include sapphire, SiC (silicon carbide), AlN (aluminum nitride), Si (silicon), and the like. Among them, an AlN single crystal substrate having a c-plane as a main surface is preferable.
- the transmittance of the substrate 11 with respect to light having a wavelength of 265 nm is preferably as high as possible, preferably 50% or more, and more preferably 60% or more.
- the upper limit of the transmittance of the substrate 11 is preferably 100%, but the upper limit is 80% in consideration of industrial production.
- the transmittance of the light-transmitting substrate can be adjusted by the material, the thickness of the substrate, the crystallinity, and the impurity content.
- the thickness of the substrate 11 is not particularly limited, but is preferably 30 to 150 ⁇ m, more preferably 50 to 100 ⁇ m. By setting the thickness of the substrate 11 in the above range, the transmittance is improved and the productivity is improved.
- the thickness of the substrate 11 only needs to satisfy the above range after the manufacture of the group III nitride semiconductor light-emitting device, and after laminating a laminated semiconductor layer or electrode to be described later on the substrate, the lower surface of the substrate is ground or polished. The thickness may be in the above range.
- the laminated semiconductor layer (the main part of the element including the mesa structure 15 in FIG. 7) is formed on the substrate 11 as shown in FIG. 7B, and the n-type layer 12, the active layer 13, and the p-type layer 14 (p-type cladding layer). And a p-type contact layer) are laminated in this order. Non-limiting examples are described below for each layer.
- Group III nitride semiconductor preferably containing impurities.
- the impurity concentration is 1.0 ⁇ 10 17 cm ⁇ 3 or more and 5.0 ⁇ 10 20 cm ⁇ 3 or less, preferably 1.0 ⁇ 10 18 cm ⁇ 3 or more and 5.0 ⁇ 10 19 cm ⁇ 3 or less.
- the refractive index of the n-type layer is not particularly limited, but is 1.5 to 3.0.
- the refractive index may be adjusted by the composition of the n-type layer.
- the thickness of the n-type layer is 100 nm or more and 10,000 nm or less, preferably 500 nm or more and 3000 nm or less.
- the group III nitride semiconductor light-emitting element 20 is formed of AlN or III having the same or similar composition as that of the n-type layer between the substrate 11 and the n-type layer 12.
- a buffer layer including a group nitride semiconductor may be included.
- a well layer having a bandgap energy larger than that of the well layer (x, y, z are 0 ⁇ x ⁇ 1.0, 0 ⁇ y ⁇ 0.1, 0 ⁇ z ⁇ 1.0).
- the active layer may be a multiple quantum well structure or a single quantum well structure.
- the thickness of the well layer is 1 nm or more, preferably 2 nm or more, and the upper limit is 100 nm.
- the thickness of the barrier layer is 1 nm or more, preferably 2 nm or more, and the upper limit is 1 ⁇ m.
- Such an active layer can be manufactured by the MOCVD method.
- the p-type layer 14 includes a p-type cladding layer and a p-type contact layer.
- Group III nitride semiconductor preferably containing impurities.
- the impurity of the p-type cladding layer is preferably Mg.
- the impurity concentration in the p-type cladding layer is 1.0 ⁇ 10 17 cm ⁇ 3 or more and 5.0 ⁇ 10 20 cm ⁇ 3 or less, preferably 1.0 ⁇ 10 18 cm ⁇ 3 or more and 5.0 ⁇ 10 20 cm ⁇ . 3 or less.
- the thickness of the p-type cladding layer is 5 nm to 100 nm, preferably 10 nm to 50 nm.
- the p-type contact layer is made of GaN. If the p-type contact layer is made of GaN, that is, a p-GaN layer, the contact characteristics of the p-type contact layer can be improved.
- the p-type contact layer preferably contains an impurity.
- the impurity of the p-type contact layer is preferably Mg, like the p-type cladding layer.
- the impurity concentration in the p-type contact layer is 1.0 ⁇ 10 17 cm ⁇ 3 or more and 5.0 ⁇ 10 20 cm ⁇ 3 or less, preferably 1.0 ⁇ 10 18 cm ⁇ 3 or more and 2.0 ⁇ 10 20 cm ⁇ . 3 or less.
- the p-type contact layer has a thickness of 1 nm to 100 nm, preferably 5 nm to 50 nm. By setting the thickness of the p-type contact layer within the above range, the ultraviolet transmittance and contact characteristics of the p-type layer are improved.
- the transmittance of the p-type layer 14, that is, the transmittance with respect to light having a wavelength of 265 nm is preferably 50% or more, and more preferably 60% or more.
- the upper limit of the transmittance is not particularly limited, but is 85% in consideration of production stability.
- the transmittance of the p-type layer 14 greatly depends on the composition and layer thickness of the p-type contact layer.
- the p-type contact layer is composed of GaN (p-GaN layer)
- GaN has an absorption edge at a wavelength of 365 nm
- light with a wavelength of 265 nm hardly transmits when the layer thickness is too large.
- the absorption coefficient ⁇ of GaN at a wavelength of 265 nm is 1.8 ⁇ 10 5 (cm ⁇ 1 ).
- the thinner the thickness of the p-GaN layer the higher the transmittance can be obtained.
- the thickness of the p-GaN layer is too small, the current does not spread sufficiently and the electrical characteristics of the light emitting element may be inferior.
- the thickness of the p-GaN layer is preferably 1 nm to 40 nm, and more preferably 10 nm to 30 nm.
- the current is sufficiently spread in the p-type contact layer to improve the electrical characteristics of the light-emitting element, and the ultraviolet transmittance of the p-type layer is improved.
- Such a p-type layer can be manufactured by the MOCVD method.
- the n electrode 16 is formed on the exposed surface of the n-type layer 12.
- the exposed surface of the n-type layer is formed by means such as etching.
- the stacked semiconductor layer remains in a plateau shape, and the mesa structure 15 is formed.
- the n-electrode on the n-type layer is formed along the lower end of the mesa structure in the low-level portion of the mesa structure, but is slightly spaced from the bottom of the mesa structure and is n-type between the mesa structure 15 and the n-electrode 16.
- the structure in which the layer 12 is exposed may be used.
- the n electrode 16 may be formed so as to surround the entire p electrode 17 along the mesa edge, and the n electrode may surround a part of the p electrode. It may be formed. Alternatively, the p electrode may be formed so as to surround the n electrode.
- Etching techniques include dry etching such as reactive ion etching and inductively coupled plasma etching.
- the exposed surface is preferably surface-treated with an acid or alkali solution in order to remove etching damage.
- an n-type electrode 16 having ohmic properties is formed on the exposed surface of the n-type layer.
- the patterning of the n electrode can be performed using a lift-off method.
- a photoresist is applied to the surface on which the electrode is to be formed, irradiated with ultraviolet rays using a UV exposure machine equipped with a photomask, and immersed in a developer to dissolve the exposed photoresist to form a desired pattern.
- an electrode metal is deposited on the patterned photoresist, and the photoresist is dissolved with a stripping solution to form an electrode metal pattern.
- an electrode metal film is formed on the electrode formation surface, a photoresist is applied, the photoresist is patterned through an exposure and development process, and dry etching or wet etching is performed using the photoresist as a mask.
- a method of patterning the electrode metal and dissolving the photoresist with a stripping solution is preferable because the process is relatively simple.
- Examples of the method for depositing the n-electrode metal include vacuum deposition, sputtering, and chemical vapor deposition. In particular, vacuum deposition is preferable because impurities in the electrode metal can be eliminated.
- the material used for the n-electrode can be selected from known materials. For example, Ti, Al, Rh, Cr, In, Ni, Pt, Au, etc. are mentioned. Among these, Ti, Al, Rh, Cr, Ni, and Au are preferable. In particular, a combination of Ti, Al, and Au is preferable because it can improve ohmic properties and reflectivity.
- the n-electrode may be a single layer containing an alloy or oxide of these metals, or a multilayer structure.
- the layer thickness of the n electrode is not particularly limited, but it is preferably 2 nm or more in consideration of production stability, and the upper limit is 2 ⁇ m.
- the n-electrode pattern is not particularly limited, and may be formed so as to surround the entire mesa structure 15 along the mesa edge (FIGS. 1A to 1F). It may be formed so as to surround a part of the structure 15 (FIG. 1G).
- the n electrode may be formed so as to surround the p electrode (FIGS. 1A to E and G), and conversely, the p electrode may be formed so as to surround the n electrode (FIG. 1F).
- the width of the n electrode is not particularly limited, but is usually about 5 to 100 ⁇ m, preferably 10 to 50 ⁇ m.
- the width of the n electrode may not be uniform.
- a narrow part and a wide part may be mixed.
- the average width of the n electrodes may be in the above range.
- heat treatment is performed at a temperature of 300 ° C. to 1100 ° C. for 30 seconds to 3 minutes.
- optimal conditions can be selected suitably according to the metal seed
- the p-electrode 17 is formed on the p-type layer 14 of the mesa structure 15.
- the formation pattern of the p-electrode 17, that is, the shape and size of the p-electrode 17 are almost similar to the mesa structure 15.
- the formation position of the p-electrode 17 is set based on a predetermined pointer related to the shape of the mesa structure 15. As a result, a current that tends to concentrate near the mesa end is diffused, and current concentration at the mesa end is suppressed.
- a guideline for setting a p-electrode formation pattern will be described later. First, a typical non-limiting example of a general p-electrode property and formation method will be described.
- the p-electrode 17 may have ultraviolet transparency.
- the transmittance of the p-electrode with respect to 265 nm light is preferably 60% or more, more preferably 70% or more.
- the upper limit of the transmittance is not particularly limited, and is preferably 100%, but is industrially 90% or more. If the wavelength transmittance for light having a wavelength of 265 nm is 60% or more, the film has sufficient transparency in the wavelength range of 200 to 350 nm.
- the patterning of the p-electrode is preferably performed using the lift-off method, similarly to the patterning of the n-electrode.
- the metal material used for the p-electrode can be selected from known materials. For example, Ni, Cr, Au, Mg, Zn, Pd, Pt, etc. are mentioned. Among these, a combination of Ni and Au is preferable.
- the p-electrode may be a single layer or multilayer structure containing an alloy or oxide of these metals.
- the shape of the p electrode is not particularly limited, but is formed in a similar shape slightly smaller than the mesa structure 15 as described above. Therefore, the shape of the p electrode is a rectangular shape that is substantially similar to the mesa structure 15 shown in FIG. 1A, a cross shape as shown in FIGS. 1B and C, and a comb shape as shown in FIGS. 1D to 1G. There may be.
- the width of the p-electrode is not particularly limited, but in the shape similar to the mesa structure 15 shown in FIGS. 1B to 1G, it is usually about 5 to 100 ⁇ m, preferably 10 to 50 ⁇ m.
- the width of the p electrode may not be uniform. For example, a narrow part and a wide part may be mixed. In this case, the average width of the p electrode may be in the above range.
- the method for depositing the p-electrode metal includes, for example, vacuum deposition, sputtering, chemical vapor deposition, etc., as in the n-electrode formation method.
- vacuum deposition is preferable because impurities in the electrode metal can be eliminated.
- a heat treatment is performed at a temperature of 200 ° C. to 800 ° C. for 30 seconds to 3 minutes. About the temperature and time of heat processing, optimal conditions can be selected suitably according to the metal seed
- the p-electrode 17 is formed on the p-type layer 14 located on the plateau-like mesa structure 15 in a substantially similar shape to the mesa structure 15.
- the n-electrode 16 is formed in a lower low area as viewed from the mesa structure 15.
- a path with low resistance is given priority, so that the current is likely to be concentrated in a region near the end of the mesa structure 15 at the shortest distance between the n-electrode and the p-electrode.
- the present invention in order to avoid current concentration at the mesa end, a certain distance or more is provided between the mesa end and the p-electrode. That is, according to the first aspect of the present invention, when the group III nitride semiconductor light emitting device is viewed from the top, the distance between a part of the mesa end and the outer periphery of the p electrode is set to 1/3 or more of the diffusion length L s. . In other words, there is a p-electrode limiting region in which electrode formation is limited between a part of the mesa end and the p-electrode. In other words, the present invention is, in a part near the end of the mesa structure is characterized by a width with 1/3 or more of the p-electrode restricted area of the diffusion length L s.
- the “mesa end” is the outline of the mesa structure 15, the end of the mesa structure in the top view, and is shown as the outer periphery (that is, the outline) of the p-type layer 14.
- the mesa structure is formed by etching the stacked semiconductor layer substantially vertically, but does not have to be completely vertical, and may be formed in a tapered shape from the top to the bottom of the mesa structure.
- the taper part is observed in a top view.
- the taper part is formed in an overhang shape, so that it is difficult to observe in a top view.
- the mesa end is the end of the mesa structure as viewed from above, and is defined as the outer periphery (that is, the contour) of the p-type layer 17 located at the uppermost layer of the mesa structure, and does not include the tapered portion.
- the distance between the mesa end and the outer periphery of the p electrode is the length of the shortest path from the arbitrarily selected mesa end to the outline of the p electrode in the top view.
- a "portion" of the mesa end, all of the mesa end not intended to essential and that apart more than 1/3 of the diffusion length L s from the p-electrode, in part, the mesa end and p electrode and contour means that may be close in less than one third of the distance of the diffusion length L s. That is, in a portion where current concentration is likely to occur, if the mesa end and the p-electrode are separated by a predetermined distance or more, the current concentration that causes the element failure is eliminated. On the other hand, the hard portion occur current concentration near the contour of the mesa end and p electrode, in a top view, the p electrode and the n electrode is also in close proximity at a distance of less than 1/3 of the diffusion length L s Good.
- the mesa end where current concentration tends to occur is in the state surrounded by the n electrode.
- the mesa end in such a state varies depending on the contour shape of the mesa structure, but usually exists at a ratio of 5 to 30% with respect to the entire circumference of the mesa structure. Therefore, in the present invention, the mesa end surrounded by the n electrode among the mesa ends has a distance of a predetermined value or more between the mesa end and the p electrode, and the p electrode limiting region is provided.
- the distance between the mesa end and the p-electrode may be set to a predetermined value or more particularly in a portion where current tends to concentrate.
- the diffusion length L s is a distance in which most electrons can diffuse in the n-type layer from the end of the n-electrode closer to the mesa end toward the mesa end in consideration of electrons moving to the p-type layer. Point to. In the prior art, the distance between the outer peripheral part of the mesa end and the p-electrode, is not performed can be adjusted based on the diffusion length L s. The present inventors have found that an excellent effect can be exhibited by setting the distance to 1/3 or more of the diffusion length L s , and have completed the present invention.
- ⁇ c contact resistance between p electrode / p type layer and n electrode / n type layer
- ⁇ p specific resistance of p type layer
- ⁇ n specific resistance of n type layer
- t p p type layer Thickness
- t n the thickness of the n-type layer.
- the contact resistance is measured by a TLM (Transfer Length Method) method.
- a p-electrode pattern having a donut-shaped electrode non-formation region is formed on the p-GaN surface by the same method as that for manufacturing a light-emitting element (interelectrode distance: 5, 10, 20, 40, 60, 80, 100 ⁇ m).
- the resistance value at each inter-electrode distance is measured, and the contact resistance between the p-electrode / p-type layer and the n-electrode / n-type layer is calculated from the relationship between the inter-electrode distance and the resistance value.
- circular p-electrodes and n-electrodes having a diameter of 1.5 mm are formed at four corners of the surface of 7 mm square p-GaN, p-AlGaN and n-AlGaN using the same method as that for manufacturing a light emitting device. Form four each.
- the specific resistance of the p-type layer (p-GaN, p-AlGaN) and the n-type layer (n-AlGaN) is calculated by measuring the Hall effect for the obtained sample.
- the distance between the outer peripheral part of the mesa end and the p-electrode, by 1/3 or more of the diffusion length L s the yield can be improved in the ultraviolet light-emitting device.
- the distance between the outer peripheral part of the mesa end and the p-electrode preferably 1/3 or more of the diffusion length L s, the diffusion length 1.2 times the L s or less, more preferably 1/3 or more of the diffusion length L s, and more than 1.0 times the diffusion length L s.
- the diffusion length L s does not depend on the width of the electrode, it becomes a guideline for device design for suppressing current concentration even when the element is downsized and the electrode is thinned.
- the distance between the outer peripheral part of the mesa end and p electrode defined 1/3 or more and the diffusion length L s, at the present time in the art of the present invention, the mesa edge one It is sufficient that the distance between the portion and the outer periphery of the p-electrode is 12 ⁇ m or more (second invention).
- the distance between a part of the mesa end and the outer periphery of the p electrode is preferably 12 to 80 ⁇ m, more preferably 15 to 80 ⁇ m, The thickness is preferably 20 to 80 ⁇ m, more preferably 20 to 40 ⁇ m. This distance is sufficient for the current (2015) device design.
- the distance between a part of the mesa end and the outer periphery of the p electrode may not be 12 ⁇ m or more.
- the distance between a part of the mesa end and the outer periphery of the p electrode may be set using the diffusion length L s as a guide.
- the present invention there is a p-electrode restriction region in which formation of an electrode is restricted between a part of the mesa end and the p-electrode.
- the present invention is characterized in that a p-electrode limiting region having a width of 12 ⁇ m or more exists in a part near the end of the mesa structure.
- the distance between a part of the mesa end and the outer periphery of the p electrode is a predetermined value or more when the light emitting element is viewed from the top.
- the meaning of “part” of the mesa end is mainly because it is sufficient that the distance between the mesa end and the outer periphery of the p-electrode is a predetermined value or more in a portion where current concentration is likely to occur.
- the portion where current tends to concentrate refers to a portion where the p-electrode projects into the n-electrode formation region in top view.
- the p electrode is surrounded by the n electrode, electrons from the n electrode are easily concentrated. As a result, the portion emits light more strongly, but the load is large and the deterioration tends to occur.
- the p-electrode 17 is formed on the mesa structure 15 in a shape substantially similar to the mesa structure.
- the distance between the mesa end and the p electrode is greater than or equal to a predetermined value in the portion where the mesa structure 15 protrudes into the n-electrode formation region, current concentration at the end of the mesa structure that is likely to deteriorate may be suppressed. is there.
- the distance between the outer circumference of the projection and the p electrode of the mesa edge diffusion length L s of 1/3 or more, 1/3 or more preferably the diffusion length L s, the diffusion length L s 1.2 times or less, more preferably 1/3 or more of the diffusion length L s, and more than 1.0 times the diffusion length L s.
- the distance between the protrusion at the mesa end and the outer periphery of the p electrode is 12 ⁇ m or more, preferably 12 to 80 ⁇ m, more preferably 15 to 80 ⁇ m, still more preferably 20 to 80 ⁇ m, and still more preferably 20 to 20 ⁇ m. 40 ⁇ m. That is, the third and fourth inventions are characterized in that a p-electrode limiting region is provided in the vicinity of the protrusion at the mesa end.
- the “projection at the end of the mesa” refers to a portion where the outline of the mesa structure 15 projects into the n-electrode formation region in a top view.
- the p electrode is formed in this portion, electrons from the n electrode surrounding the periphery are concentrated on the p electrode in the portion, so that the semiconductor layer directly under the p electrode is likely to deteriorate. Therefore, by setting the distance from the protrusion at the mesa end to the p-electrode to a predetermined value or more, current concentration can be suppressed and deterioration of the element can be reduced.
- FIG. 1 shows a non-limiting example of the outline of the mesa structure 15 in the top view of the element and the formation pattern of the n electrode, and the “mesa end protrusion” where current tends to concentrate is indicated by a dashed circle. did.
- the n electrode 12 and the mesa structure 15 are in contact with each other in the top view of FIG. 1, but as shown in FIG. 7B, the taper portion of the mesa structure is between the end of the mesa structure 15 and the n electrode in the cross section. Or an exposed n-type layer may be present.
- the p-electrode is formed at a predetermined distance from the “mesa end protrusion”, and the p-electrode is formed in a region less than the predetermined distance. A limited p-electrode limiting region is formed.
- FIG. 1A shows an element structure in which a rectangular mesa structure 15 is formed in a top view.
- each vertex of the rectangle protrudes into the n-electrode formation region, and when a p-electrode is formed in this area, current tends to concentrate on the mesa portion immediately below the p-electrode.
- FIG. 1B shows a cross-shaped mesa structure 15. Even in this structure, each vertex of the cross protrudes into the n-electrode formation region.
- FIG. 1C shows a mesa structure 15 with a rounded shape at the cross-shaped end. Even in this structure, the end of the cross projects into the n-electrode formation region.
- FIG. 1D shows a comb-like mesa structure 15. Even in this structure, each tip of the comb and the vertex of the rectangle protrude into the n-electrode formation region.
- FIG. 1E is a modification of FIG. 1D and shows a structure in which the electrodes extend in a comb-teeth shape from the back of the comb.
- FIG. 1F shows a structure in which the n-electrode has a linear portion and the electrode extends from the back of the comb forming the n-electrode.
- FIG. 1G shows a state in which a comb-shaped n-electrode surrounding the comb-shaped mesa structure is formed.
- the group III nitride semiconductor light emitting devices according to the third and fourth inventions in the formation pattern of the mesa structure having the illustrated configuration and the similar configuration, from the center of the circle indicating the “projection of the mesa end” There is no p-electrode in the region less than the predetermined distance.
- the “projection at the mesa end” can also be defined as a mesa portion in which an n-electrode is excessively present around the group III nitride semiconductor light-emitting device as viewed from above. Therefore, in order to determine whether or not a “certain point” at the mesa end corresponds to a “projection at the mesa end”, the area of the n-electrode existing around the “certain point” may be considered. Specifically, a circle with a predetermined radius (hereinafter sometimes referred to as a “definition circle”) is drawn around the “certain point” to be determined, and the larger the area of the n electrode existing inside the circle, It is determined that the “certain point” is highly surrounded by the n electrode.
- a circle with a predetermined radius hereinafter sometimes referred to as a “definition circle”
- a circle having a predetermined radius is drawn around the “certain point” to be determined, and the smaller the area of the mesa portion (including the p-electrode) existing inside the circle, the “certain point” is n It can be said that the degree of being surrounded by the electrodes is high.
- the radius of the definition circle may be as long as the circle does not touch the other mesa edges. However, if the circle is too small, the area of the tapered portion between the mesa end and the n electrode or the exposed n-type layer area is overestimated, so it is necessary that the circle be larger than a certain size. That is, if the definition circle at the mesa end is too small, the area of the taper portion of the mesa portion and the area of the exposed n-type layer are overestimated in the definition circle, and the mesa portion (including the p electrode) and the n electrode The total area is relatively reduced, and appropriate evaluation cannot be performed.
- the center point an arbitrary point (the point to be determined) on the mesa edge, draw a circle of radius r n gradually increases.
- the radius of the circle is small, the relative ratio of the taper area and the n-electrode area is large, but as the circle increases, the relative ratio decreases, and the mesa part (including the p-electrode) and the n-electrode The area can be properly evaluated. Therefore, it is preferable that the radius of the circle in which the total area of the mesa portion (including the p electrode) and the n electrode in the circle is 80% of the total area of the circle is the radius of the “definition circle”. Note that the radius of the definition circle may be increased as long as the definition circle does not contact other mesa ends.
- a method for determining a “mesa end protrusion” using a definition circle will be described.
- a definition circle is drawn around a certain point on the mesa edge, a mesa portion (p electrode), an n-type layer, and an n electrode region exist in the definition circle, and the taper portion of the mesa structure in a top view May be observed.
- the above evaluation parameters are calculated from the area of the mesa portion, the area of the electrode, and the total area of the circle.
- the p-electrode is omitted.
- the p-electrode is formed on the mesa structure 15 in the same shape as the mesa portion or smaller than this.
- FIG. 3 schematically shows a top view of mesa edges and n-electrodes of various contours.
- the n-type layer exposed between the electrodes and the tapered portion have a small area, and thus the illustration is omitted.
- the p electrode has a similar shape slightly smaller than the mesa portion, and the area of the p electrode is included in the area of the mesa portion, and thus illustration is omitted.
- the area of the mesa portion in the definition circle is smaller than the area of the n electrode. That is, although the evaluation parameter is smaller than that in the state A, the area of the n electrode is excessive, and current concentration is likely to occur in this portion of the p electrode.
- the area of the mesa portion in the definition circle is smaller than the area of the n electrode. That is, the area of the n electrode is excessive, and current concentration tends to occur in this portion of the p electrode.
- the area of the mesa portion in the definition circle is smaller than the area of the n electrode. That is, the area of the n electrode is excessive, and current concentration tends to occur in this portion of the p electrode.
- the area of the mesa portion in the definition circle is larger than the area of the n electrode. That is, the evaluation parameter is less than 100%. Current concentration is less likely to occur in this portion of the p-electrode than in state E.
- the area of the mesa structure in the definition circle is larger than the area of the n electrode. That is, the evaluation parameter is less than 100%. Current concentration is unlikely to occur in this portion of the p-electrode.
- the p electrode when the area of the n electrode is excessive with respect to the area of the mesa portion as in the states A to D, the p electrode is not provided in the vicinity of the mesa end.
- a p-electrode limiting region is used. That is, the vicinity of the mesa end having a large evaluation parameter is set as a p-electrode limiting region.
- preferred embodiments of the present invention are as follows. Draw a definition circle with an arbitrary point on the mesa edge as the center point. When the evaluation parameter calculated by the area of each part in the definition circle exceeds 100%, it is determined that the center of the definition circle is located at the “projection at the mesa end”. If it is determined to be located on the protrusion of the mesa edge, and center of the circle, the distance between the p-electrode is provided with a p-electrode on the range of the (12 [mu] m or more in absolute distance) 1/3 or more of the diffusion length L s . In other words, the range of less than 1/3 of the diffusion length L s from the center of the circle (less than 12 ⁇ m in absolute distance), a p-electrode restricted area.
- the n-type layer and the tapered portion exposed between the electrodes are not shown because they have a small area.
- the evaluation parameter is approximately 300%. Therefore, the p-electrode is not formed in the range of less than 1/3 of the diffusion length L s (absolute distance is less than 12 ⁇ m) from the X point which is the vertex of the rectangle.
- the evaluation parameter is almost 100%.
- the radius from the Y point circle of the length of 1/3 of the diffusion length L s (12 [mu] m in absolute distance), the limit point of the p-electrode formation is obtained.
- regulated by 4th this invention is obtained by making distance from X point and Y point into 12 micrometers or more and making it a p electrode restriction
- a p-electrode is formed in all of the p-electrode limiting regions defined above.
- the object of the present invention is achieved. As long as it does not inhibit, it is acceptable in the present invention.
- the p electrode may not be formed in an area of 90% or more, more preferably 98% or more, and particularly preferably 99% or more of the p electrode limiting region defined above.
- the lower limit of the evaluation parameter is set to 100%, but these lower limit values can be appropriately set according to the material of the laminated semiconductor layer (mesa structure portion) and the operating environment of the element.
- the lower limit value of the allowable evaluation parameter is lowered from the viewpoint of surely suppressing the current concentration on the mesa portion, and the p electrode limiting region is set. Make it wider.
- the evaluation parameter may be 80% or more, or 60% or more.
- the evaluation parameter may be 120% or more, or 140% or more.
- 12 ⁇ m can be used as a guideline for the radius of the definition circle for the current product. Further, as the electrodes become thinner in the future, appropriate evaluation is possible by reducing the radius of the definition circle. In this case as well, the circle is prevented from coming into contact with other mesa ends.
- the predetermined range from the “projection at the end of the mesa” is defined as the p-electrode limiting region.
- the p electrode is formed in a mesa portion other than the p electrode limiting region (hereinafter sometimes referred to as “p electrode allowable region”), it is not necessary that the p electrode is formed in all the p electrode allowable regions.
- the p electrode only needs to be formed so as to be conductive to at least a part of the p electrode allowable region.
- the outer peripheral shape of the p electrode formed in the vicinity of the protrusion at the mesa end is preferably formed so as to have a circular arc shape, an elliptical arc shape, a parabolic shape, or the like as shown in FIG.
- FIG. 5 shows an example in which a blank portion having a width of 5 ⁇ m is formed.
- the p electrode is not provided within a predetermined range from the “projection at the mesa end” where the evaluation parameter is equal to or greater than a specified value.
- the evaluation parameter indicating the degree of protrusion of the portion continuously changes depending on the shape of the mesa end. Therefore, the distance from the mesa end to the p-electrode can be set according to the degree of protrusion of the mesa portion.
- the evaluation parameter value at point X is high (the mesa portion protrudes highly), it is prohibited to form a p-electrode around this point (for example, within 12 ⁇ m).
- the evaluation parameter at the Y point is low and current concentration is unlikely to occur, the distance between the Y point and the p electrode may be less than 1/3 of the diffusion length L s or less than 12 ⁇ m.
- the mesa end with a high degree of protrusion to the n-electrode formation region should have a sufficient distance from the p electrode, and the mesa end with a low degree of protrusion should have a shorter distance between the p electrode and the mesa end.
- the evaluation parameter may be determined at an arbitrary point on the mesa end, the “degree of protrusion” may be evaluated based on the result, and the p-electrode limiting region from the mesa end may be set.
- the p-electrode limiting region can be made wider at the mesa end with a high evaluation parameter, and the p-electrode limiting region can be made narrower than the above definition at the mesa end with a low evaluation parameter. For this reason, it is considered effective to define the p-electrode restriction region using the absolute value or square value of the evaluation parameter.
- the distance from the apex of the rectangle to the p-electrode is long in the longitudinal direction, and the distance from the midpoint in the short side of the rectangle to the p-electrode is A p-electrode is provided so as to be short.
- the distance from the p-electrode is long from the apex and short from the midpoint in the longitudinal direction, the distance changes continuously, and the distance changes more gradually as the midpoint is approached.
- the mesa end may eventually coincide with the p electrode end.
- the distance from the apex of the arc (elliptical arc) to the p-electrode is long in the short direction.
- the p-electrode is provided so that the distance from the mesa end to the p-electrode decreases as the arc at the mesa end (elliptical arc) changes in a straight line along the longitudinal direction.
- the distance to the p electrode is longer from the apex of the arc at the mesa end, shorter from both ends of the arc, the distance changes continuously, and the distance changes more gradually as it approaches both ends.
- the mesa end may eventually coincide with the p electrode end.
- the light emission intensity in the light emission intensity distribution of light emitted from the surface opposite to the laminated surface of the substrate 11 (hereinafter sometimes referred to as the light emitting surface).
- the ratio of the maximum value to the minimum value (hereinafter sometimes referred to as the emission intensity ratio) is preferably 2.1 or less. According to the present invention, since it is possible to prevent local current concentration in the mesa structure, variation in light emission intensity in the light emitting region of the light emitting surface can be suppressed.
- the ratio between the maximum value and the minimum value of the emission intensity is more preferably 2.05 or less.
- the light emission intensity distribution can be obtained according to the measurement of the light emission intensity distribution of the light emitting element described later, and the maximum value and the minimum value of the light emission intensity are the maximum value and the minimum value of the light emission intensity in the light emitting region of the light emitting surface.
- the light emitting region of the light emitting surface is a region emitting light among the surface opposite to the laminated surface of the substrate 11.
- the transmittance of the light-transmitting substrate can be reduced by grinding or polishing the lower surface of the light-transmitting substrate 11 to improve the transmittance. it can. Thereafter, a light-emitting element is manufactured by appropriately using a known light-emitting element separation method such as scribing, dicing, or laser cutting.
- the light-emitting element of the present invention includes the conventional technology. For example, it is possible to combine techniques of forming a high resistance layer and forming a trench.
- the light emission intensity distribution evaluation apparatus includes an electric control circuit that applies a voltage to the light emitting element, an optical system that controls a measurement range by a lens and a camera, a light detection unit, and a data analysis apparatus.
- the distribution of the emission intensity is measured by measuring and mapping the emission intensity in the emission region of the light emitting surface with 10 ⁇ m ⁇ 10 ⁇ m as one range. Since the emission intensity is observed strongly where current concentration occurs, the effect of suppressing current concentration by adjusting the distance between the mesa edge and the p electrode can be confirmed by this measurement.
- a laminated semiconductor layer having the cross-sectional structure shown in FIG. 7B was formed.
- an Al 0.7 Ga 0.3 N layer doped with 1.0 ⁇ 10 19 [cm ⁇ 3 ] of Si on a C-plane AlN substrate (side 7 mm square, thickness 500 ⁇ m) using MOCVD ( 1 ⁇ m) was formed as an n-type semiconductor layer.
- An active layer (well layer 2 nm, barrier layer 7 nm) having a quantum well structure was formed on the n-type layer.
- the composition of the well layer and the barrier layer is Al 0.5 Ga 0.5 N and Al 0.7 Ga 0.3 N, respectively, and the barrier layer has 1.0 ⁇ 10 18 [cm ⁇ 3 ] Si.
- the active layer has a laminated structure of three well layers and four barrier layers.
- an AlN layer (15 nm) doped with 5 ⁇ 10 19 [cm ⁇ 3 ] of Mg was formed as an electron blocking layer on the active layer.
- an Al 0.8 Ga 0.2 N layer (50 nm) doped with 5 ⁇ 10 19 [cm ⁇ 3 ] Mg was formed as a p-cladding layer on the electron blocking layer.
- a GaN layer (100 nm) doped with 2 ⁇ 10 19 [cm ⁇ 3 ] of Mg was formed as a p-contact layer on the p-cladding layer.
- the obtained semiconductor wafer was heat-treated in N 2 at 900 ° C. for 20 minutes. Thereafter, a predetermined metal mask pattern is formed on the surface of the p-contact layer by photolithography and vacuum deposition, and then the p-contact layer surface on which no pattern is formed is dry-etched until the n-type layer is exposed. A cross-shaped mesa structure having rounded ends as shown in FIG. At this time, the depth of the n-type layer was 300 nm. Next, after forming a resist pattern on the p-contact layer by photolithography, a Ti (20 nm) / Al (200 nm) / Au (5 nm) layer is formed by vacuum deposition, and then at 1 at 810 ° C. in N 2.
- n-electrode was formed by heat treatment for a minute.
- a Ni (20 nm) / Au (50 nm) layer is formed on the p-type layer so that a predetermined range from the end portion is the p electrode limiting region, and 550 in O 2 .
- a p-electrode was formed by baking at 3 ° C. for 3 minutes. The obtained semiconductor wafer was cut into a 750 ⁇ m square to obtain a nitride semiconductor light emitting device (nitride semiconductor light emitting device having an emission peak wavelength of 265 nm).
- the distance (a) from the mesa end to the p-electrode at the protrusion is 40 ⁇ m (Example 1), 20 ⁇ m (Example 2), 10 ⁇ m (Comparative Example 1), and 5 ⁇ m (Comparative Example 2).
- Four types of devices having a p-electrode restriction region were prepared. The distance between the mesa end and the p electrode in the p electrode allowable region was 5 ⁇ m.
- 50 light emitting elements as described above were manufactured, and the change over time in output characteristics of the obtained light emitting elements was measured.
- the measurement of an instantaneous deterioration rate shows the result at the time of supplying a current of 150 mA.
- the instantaneous deterioration rate after 500 hours was 2. 4% in Example 2, 20% in Comparative Example 1, and 24% in Comparative Example 2, when the distance between the mesa edge and the p electrode in the p electrode allowable region is 20 ⁇ m or more. In addition, a rapid improvement in the instantaneous deterioration rate was observed. Note that when the diffusion length L s of the obtained light emitting element was calculated to be 60 ⁇ m, 20 ⁇ m corresponds to 1/3 of the diffusion length L s .
- Examples 3 and 4 and Comparative Examples 3 and 4 A nitride semiconductor light emitting device was fabricated in the same manner as in Example 1 except that the n-type layer depth by dry etching during n electrode formation was changed to 100 nm.
- the distance (a) from the mesa end to the p-electrode at the protrusion is 20 ⁇ m (Example 3), 12 ⁇ m (Example 4), 8 ⁇ m (Comparative Example 3), 5 ⁇ m (
- Four types of elements provided with a p-electrode restriction region were prepared so as to be Comparative Example 4).
- the distance between the mesa end and the p electrode in the p electrode allowable region was 5 ⁇ m.
- 50 light emitting elements as described above were manufactured, and the change over time in output characteristics of the obtained light emitting elements was measured.
- the instantaneous deterioration rate after the elapse of 500 hours was 2. 4% in Example 4, 16% in Comparative Example 3, and 24% in Comparative Example 4, when the distance between the mesa edge and the p electrode in the p electrode allowable region is 12 ⁇ m or more. In addition, a rapid improvement in the instantaneous deterioration rate was observed. Note that when the diffusion length L s of the obtained light emitting element was calculated to be 36 ⁇ m, 12 ⁇ m corresponds to 1/3 of the diffusion length L s .
- the distance between a part of the mesa edge and the outer periphery of the p-electrode is not less than a predetermined value, thereby excessively increasing the operating voltage. Without suppressing, the current flowing between the p electrode and the n electrode is prevented from being concentrated in the region near the mesa end. As a result, a group III nitride semiconductor light-emitting device in which local deterioration in the mesa structure is less likely to occur and light emission unevenness is less likely to occur due to the current flowing easily through the active layer is obtained.
Abstract
Description
特に、200~350nmに発光ピーク波長を有する紫外発光素子は、350nmを超える発光ピーク波長の発光素子、例えば、可視光領域の発光素子よりも、各層の組成の影響により製造が難しく、歩留まりが低下する傾向にある。本発明は、メサ構造における局所的な劣化を原因とする歩留まりの低下を抑制できるため、200~350nmに発光ピーク波長を有する紫外発光素子に適している。
基板11は、III族窒化物半導体結晶を表面にエピタキシャル成長でき、紫外線を透過する基板であれば特に限定されるものではない。基板11に用いられる材料としては、例えば、サファイア、SiC(炭化ケイ素)、AlN(窒化アルミニウム)、Si(シリコン)などが挙げられる。中でもc面を主面とするAlN単結晶基板が好ましい。
積層半導体層(図7におけるメサ構造15を含む素子の主要部)は、図7Bに示すように基板11上に形成され、n型層12、活性層13ならびにp型層14(p型クラッド層およびp型コンタクト層からなる層)がこの順で積層されてなる。各層について以下に非限定的例を説明する。
n型層12は、AlxInyGazN(x、y、zは、0<x≦1.0、0≦y≦0.1、0≦z<1.0を満たす有理数とし、x+y+z=1.0である)で構成されるIII族窒化物半導体であり、好ましくは不純物を含む。
活性層13は、AlxInyGazN(x、y、zは、0<x≦1.0、0≦y≦0.1、0≦z<1.0を満たす有理数とし、x+y+z=1.0である)で構成される井戸層と、前記井戸層よりもバンドギャップエネルギーの大きいAlxInyGazN(x、y、zは、0<x≦1.0、0≦y≦0.1、0≦z<1.0を満たす有理数とし、x+y+z=1.0である)で構成される障壁層との積層構造からなる。活性層は、多重量子井戸構造であっても単一量子井戸構造であってもよい。
p型層14は、p型クラッド層およびp型コンタクト層で構成される。p型クラッド層は、AlxInyGazN(x、y、zは、0<x≦1.0、0≦y≦0.1、0≦z<1.0を満たす有理数とし、x+y+z=1.0である)で構成されるIII族窒化物半導体であり、好ましくは不純物を含む。
n電極16は、n型層12の露出面に形成される。n型層の露出面はエッチング等の手段により形成される。n型層の露出面形成により、積層半導体層は台地状に残り、メサ構造15が形成される。n型層上のn電極はメサ構造の低地部に、メサ構造の下端に沿って形成されるが、メサ構造の底部からやや距離をあけ、メサ構造15とn電極16との間にn型層12が露出した構造であってもよい。
p電極17は、メサ構造15のp型層14上に形成される。p電極17の形成パターン、すなわちp電極17の形状、大きさはメサ構造15とほぼ相似である。本発明では、p電極17の形成位置を、メサ構造15の形状と関連する所定の指針に基づいて設定する。これにより、メサ端近傍に集中しやすい電流を拡散し、メサ端への電流集中を抑制する。p電極の形成パターンの設定指針については後述し、まず一般的なp電極の性質およびその形成方法について、非限定的な典型例を説明する。
図7に示したように、p電極17は、台地状のメサ構造15の上部に位置するp型層14上に、メサ構造15とほぼ相似形に形成される。n電極16はメサ構造15から見て下方の低地部に形成されている。n電極16とp電極17との導通は、抵抗の低い経路が優先されるため、電流はn電極とp電極との最短距離にあるメサ構造15の端部付近の領域に集中しやすい。
Ls={(ρc+ρptp)tn/ρn}1/2
本発明において、接触抵抗はTLM(Transfer Length Method)法により測定する。まず、発光素子の製造と同様の方法により、p-GaN表面上にドーナツ状の電極不形成領域を有するp電極パターンを形成する(電極間距離:5、10、20、40、60、80、100μm)。得られた電極パターンを用いて、各電極間距離における抵抗値を測定し、電極間距離と抵抗値との関係からp電極/p型層間およびn電極/n型層間の接触抵抗を算出する。
まず、本発明においては、発光素子の製造と同様の方法を用いて、7mm角のp-GaN、p-AlGaNおよびn-AlGaNの表面四隅に直径1.5mmの円形のp電極およびn電極をそれぞれ4つ形成する。得られたサンプルについてホール効果測定を行うことで、p型層(p-GaN、p-AlGaN)およびn型層(n-AlGaN)の比抵抗を算出する。
図1Bは、十字状のメサ構造15を示す。この構造でも十字の各頂点がn電極の形成領域に突出している。
図1Cは、十字状の端部に丸みを帯びた形状のメサ構造15を示す。この構造でも十字の端部はn電極の形成領域に突出している。
図1Dは、櫛状のメサ構造15を示す。この構造でも櫛の各先端や、矩形の頂点はn電極の形成領域に突出している。
図1Eは、図1Dの変形例であり、櫛の背からも櫛歯状に電極が延在する構造を示す。
図1Fは、n電極が線状部分を有し、さらに、n電極を形成する櫛の背からも電極が延在する構造を示す。
図1Gは、櫛状のメサ構造を囲繞する櫛状のn電極が形成された状態を示す。
評価パラメータ=(n電極面積/メサ構造面積)×100(%)
メサ端上の任意の点を中心点として、定義円を描く。定義円内の各部の面積により計算される評価パラメータが100%を超える場合には、当該定義円の中心は「メサ端の突部」に位置すると判定される。メサ端の突部に位置すると判定された場合、当該円の中心と、p電極との距離が拡散長Lsの1/3以上(絶対距離としては12μm以上)となる範囲にp電極を設ける。換言すると、円の中心から拡散長Lsの1/3未満(絶対距離としては12μm未満)の範囲は、p電極制限領域とする。
上記III族窒化物半導体発光素子の構成を含むウエハを製造した後、透光性基板11の下面を研削または研磨することにより、透光性基板の厚みを薄くして透過率を向上させることもできる。その後、スクライビング、ダイシング、レーザ溶断など、公知の発光素子分離方法を適宜用いて、発光素子を製造する。
発光素子のn電極-p電極間へ電流を連続して通電しながら、発光素子の基板11の積層面とは反対側の面から発光する光の発光強度を測定する。発光強度分布の評価装置は、発光素子へ電圧を印加する電気制御回路、レンズとカメラにより測定範囲を制御する光学系、光検出部およびデータ解析装置から成る。10μm×10μmを1範囲として、発光面の発光領域における発光強度を測定しマッピングすることで、発光強度の分布を測定する。電流集中が起こっている場所は発光強度が強く観測されるため、本測定により、メサ端とp電極との距離を調整することによる電流集中抑制の効果が確認できる。
(実施例1、2および比較例1、2)
まず、MOCVD法を用いて、C面AlN基板(一辺7mm角、厚さ500μm)上に、Siを1.0×1019 [cm-3]ドープしたAl0.7Ga0.3N層(1 μm)をn型半導体層として形成した。このn型層上に、量子井戸構造を有する活性層(井戸層2nm、障壁層7nm)を形成した。この時、井戸層および障壁層の組成はそれぞれAl0.5Ga0.5NおよびAl0.7Ga0.3Nとし、障壁層には1.0×1018 [cm-3]のSiをドープした。活性層は、井戸層3層と障壁層4層の積層構造から成る。
n電極形成時のドライエッチングによるn型層の堀量を100nmに変更した以外は、実施例1と同様の方法で窒化物半導体発光素子を作製した。
12…n型層
13…活性層
14…p型層
15…メサ構造
16…n電極
17…p電極
20…III族窒化物半導体発光素子
Claims (5)
- n型層とp型層との間に活性層を含み、前記n型層上にn電極、前記p型層上にp電極を有し、p型層を含むメサ構造を有するIII族窒化物半導体発光素子であって、
前記III族窒化物半導体発光素子の上面視において、メサ端の一部と前記p電極の外周との距離が拡散長Lsの1/3以上である、または、
前記III族窒化物半導体発光素子の上面視において、メサ端の一部と前記p電極の外周との距離が12μm以上である、III族窒化物半導体発光素子。 - 前記III族窒化物半導体発光素子の上面視において、メサ端の突部と前記p電極の外周との距離が拡散長Lsの1/3以上である、請求項1に記載のIII族窒化物半導体発光素子。
- 前記III族窒化物半導体発光素子の上面視において、メサ端の突部と前記p電極の外周との距離が12μm以上である、請求項1に記載のIII族窒化物半導体発光素子。
- 発光ピーク波長が200~350nmである請求項1~3の何れかに記載のIII族窒化物半導体発光素子。
- n型層とp型層との間に活性層を含み、前記n型層上にn電極、前記p型層上にp電極を有するIII族窒化物半導体発光素子の構成を含むウエハであって、
前記III族窒化物半導体発光素子の構成が請求項1~4の何れかに記載の構成であるウエハ。
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2017504984A JP6832842B2 (ja) | 2015-03-06 | 2016-02-29 | Iii族窒化物半導体発光素子および該素子構成を含むウエハ |
US15/555,098 US10312412B2 (en) | 2015-03-06 | 2016-02-29 | Group III nitride semiconductor luminescence element |
EP16761544.2A EP3267498B1 (en) | 2015-03-06 | 2016-02-29 | Group iii nitride semiconductor light emitting element and wafer containing element structure |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2015-044744 | 2015-03-06 | ||
JP2015044744 | 2015-03-06 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2016143574A1 true WO2016143574A1 (ja) | 2016-09-15 |
Family
ID=56879998
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2016/055992 WO2016143574A1 (ja) | 2015-03-06 | 2016-02-29 | Iii族窒化物半導体発光素子および該素子構成を含むウエハ |
Country Status (5)
Country | Link |
---|---|
US (1) | US10312412B2 (ja) |
EP (1) | EP3267498B1 (ja) |
JP (1) | JP6832842B2 (ja) |
TW (1) | TWI679778B (ja) |
WO (1) | WO2016143574A1 (ja) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2019029407A (ja) * | 2017-07-26 | 2019-02-21 | 旭化成株式会社 | 窒化物半導体発光素子、紫外線発光モジュール |
US10312412B2 (en) | 2015-03-06 | 2019-06-04 | Stanley Electric Co., Ltd. | Group III nitride semiconductor luminescence element |
US10818823B2 (en) | 2016-08-26 | 2020-10-27 | Stanley Electric Co., Ltd. | Group III nitride semiconductor light-emitting element and wafer including such element configuration |
JP7345615B2 (ja) | 2020-10-16 | 2023-09-15 | 日機装株式会社 | 窒化物半導体発光素子 |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP6832620B2 (ja) | 2015-07-17 | 2021-02-24 | スタンレー電気株式会社 | 窒化物半導体発光素子 |
WO2017023440A1 (en) * | 2015-08-05 | 2017-02-09 | Proteq Technologies Llc | Light-emitting device |
JP6942589B2 (ja) * | 2017-09-27 | 2021-09-29 | 旭化成株式会社 | 半導体発光装置および紫外線発光モジュール |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007214569A (ja) * | 2006-02-09 | 2007-08-23 | Samsung Electro Mech Co Ltd | フリップチップ型の発光素子 |
WO2011033625A1 (ja) * | 2009-09-16 | 2011-03-24 | 株式会社 東芝 | 半導体発光素子 |
JP2013030817A (ja) * | 2012-11-07 | 2013-02-07 | Toshiba Corp | 半導体発光素子及び半導体発光装置 |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3362650B2 (ja) * | 1997-11-19 | 2003-01-07 | 日亜化学工業株式会社 | 窒化物半導体素子の製造方法 |
US7518305B2 (en) | 2004-11-01 | 2009-04-14 | The Regents Of The University Of California | Interdigitated multi-pixel arrays for the fabrication of light-emitting devices with very low series-resistances and improved heat-sinking |
US7566908B2 (en) * | 2004-11-29 | 2009-07-28 | Yongsheng Zhao | Gan-based and ZnO-based LED |
US20060284191A1 (en) | 2005-06-16 | 2006-12-21 | Epistar Corporation | Light emitting diode |
KR100665284B1 (ko) | 2005-11-07 | 2007-01-09 | 삼성전기주식회사 | 반도체 발광 소자 |
JP5628056B2 (ja) * | 2011-01-21 | 2014-11-19 | スタンレー電気株式会社 | 半導体発光素子 |
JP2013008818A (ja) * | 2011-06-24 | 2013-01-10 | Toshiba Corp | 半導体発光素子 |
JP2014096460A (ja) | 2012-11-08 | 2014-05-22 | Panasonic Corp | 紫外半導体発光素子およびその製造方法 |
JP2014096539A (ja) | 2012-11-12 | 2014-05-22 | Tokuyama Corp | 紫外発光素子、および発光構造体 |
US9299883B2 (en) | 2013-01-29 | 2016-03-29 | Hexatech, Inc. | Optoelectronic devices incorporating single crystalline aluminum nitride substrate |
EP3267498B1 (en) | 2015-03-06 | 2021-03-24 | Stanley Electric Co., Ltd. | Group iii nitride semiconductor light emitting element and wafer containing element structure |
-
2016
- 2016-02-29 EP EP16761544.2A patent/EP3267498B1/en active Active
- 2016-02-29 JP JP2017504984A patent/JP6832842B2/ja active Active
- 2016-02-29 US US15/555,098 patent/US10312412B2/en active Active
- 2016-02-29 WO PCT/JP2016/055992 patent/WO2016143574A1/ja active Application Filing
- 2016-03-04 TW TW105106644A patent/TWI679778B/zh active
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007214569A (ja) * | 2006-02-09 | 2007-08-23 | Samsung Electro Mech Co Ltd | フリップチップ型の発光素子 |
WO2011033625A1 (ja) * | 2009-09-16 | 2011-03-24 | 株式会社 東芝 | 半導体発光素子 |
JP2013030817A (ja) * | 2012-11-07 | 2013-02-07 | Toshiba Corp | 半導体発光素子及び半導体発光装置 |
Non-Patent Citations (1)
Title |
---|
See also references of EP3267498A4 * |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10312412B2 (en) | 2015-03-06 | 2019-06-04 | Stanley Electric Co., Ltd. | Group III nitride semiconductor luminescence element |
US10818823B2 (en) | 2016-08-26 | 2020-10-27 | Stanley Electric Co., Ltd. | Group III nitride semiconductor light-emitting element and wafer including such element configuration |
JP2019029407A (ja) * | 2017-07-26 | 2019-02-21 | 旭化成株式会社 | 窒化物半導体発光素子、紫外線発光モジュール |
US10847679B2 (en) | 2017-07-26 | 2020-11-24 | Asahi Kasei Kabushiki Kaisha | Nitride semiconductor light emitting device, ultraviolet light emitting module |
US11309456B2 (en) | 2017-07-26 | 2022-04-19 | Asahi Kasel Kabushiki Kaisha | Nitride semiconductor light emitting device, ultraviolet light emitting module |
JP7345615B2 (ja) | 2020-10-16 | 2023-09-15 | 日機装株式会社 | 窒化物半導体発光素子 |
Also Published As
Publication number | Publication date |
---|---|
US10312412B2 (en) | 2019-06-04 |
EP3267498A4 (en) | 2018-10-17 |
JP6832842B2 (ja) | 2021-02-24 |
TW201707237A (zh) | 2017-02-16 |
EP3267498B1 (en) | 2021-03-24 |
US20180040770A1 (en) | 2018-02-08 |
TWI679778B (zh) | 2019-12-11 |
EP3267498A1 (en) | 2018-01-10 |
JPWO2016143574A1 (ja) | 2017-12-14 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
WO2016143574A1 (ja) | Iii族窒化物半導体発光素子および該素子構成を含むウエハ | |
WO2018038105A1 (ja) | Iii族窒化物半導体発光素子 | |
JP2021182635A (ja) | 半導体レーザーダイオード | |
WO2017014094A1 (ja) | 窒化物半導体発光素子 | |
US9276170B2 (en) | Semiconductor light emitting element and method of manufacturing semiconductor light emitting element | |
CN108417677A (zh) | 一种led芯片及其窗口层的粗化方法 | |
JP2022164879A (ja) | 発光素子の製造方法 | |
TWI721841B (zh) | 紅外線led元件 | |
JP5920186B2 (ja) | 半導体発光素子の製造方法および半導体発光素子 | |
US9553238B2 (en) | Method of manufacturing light emitting element | |
JP6587765B1 (ja) | 赤外led素子 | |
JP2015211135A (ja) | 半導体光装置 | |
WO2022109990A1 (zh) | 半导体发光器件及其制备方法 | |
JP7201574B2 (ja) | 赤外led素子 | |
CN113497406B (en) | Method for manufacturing semiconductor laser diode and semiconductor laser diode | |
JP2022184312A (ja) | 赤外led素子及びその製造方法 | |
US20160247682A1 (en) | Method for manufacturing semiconductor device, and semiconductor device | |
JP2000058909A (ja) | 半導体発光素子 | |
KR20130083884A (ko) | 반도체 발광소자 | |
JP2011155197A (ja) | 発光素子用ウェーハ、発光素子及びその製造方法 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 16761544 Country of ref document: EP Kind code of ref document: A1 |
|
ENP | Entry into the national phase |
Ref document number: 2017504984 Country of ref document: JP Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 15555098 Country of ref document: US |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
REEP | Request for entry into the european phase |
Ref document number: 2016761544 Country of ref document: EP |