JP3671938B2 - Semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device having a structure in which electrodes for applying a voltage to a light emitting semiconductor layer are formed on the same side of a support substrate.
[0002]
[Prior art]
FIG. 3 shows a conventional semiconductor light emitting device proposed in JP-A-10-93138. In this structure, an n-type contact layer 103 is laminated on a support substrate 101 made of sapphire via a buffer layer 102, and further a light emitting semiconductor layer 104 having a light emitting junction layer (active layer) 104c made of a nitride semiconductor, and a p-type. A contact layer 105 and a second electrode (positive electrode) 106 are sequentially stacked. Among these, the light-emitting semiconductor layer 104 has a structure in which n-type cladding layers 104a and 104b and p-type cladding layers 104d and 104e made of a nitride semiconductor are arranged below and above the light-emitting junction layer 104c, respectively. In addition, the second electrode (positive electrode) 106 is a strip having a substantially rectangular shape in plan view. Further, in the exposed region of the n-type contact layer 103, a first electrode (negative electrode) 107 having a substantially long square shape in plan view is spaced apart from the light emitting semiconductor layer 104 and is planar with the second electrode (positive electrode) 106. It is formed substantially parallel in view.
[0003]
According to this semiconductor light emitting device, a current in the forward direction (direction in which current flows from the second electrode (positive electrode) 106 to the first electrode (negative electrode) 107) flows between the electrodes 106 and 107. As a result, holes that are majority carriers in the p-type cladding layers 104d and 104e and electrons that are majority carriers in the n-type cladding layers 104a and 104b move to the light-emitting junction layer 104c, where holes and electrons recombine. It emits light.
[0004]
[Problems to be solved by the invention]
By the way, in such a semiconductor light emitting device, the current flowing in the light emitting semiconductor layer 104 tends to flow mainly in a region where the resistance value is relatively small in the light emitting semiconductor layer 104. That is, the current concentrates in a region where the current path from the second electrode (positive electrode) 106 to the first electrode (negative electrode) 107 becomes short. This region is a region closer to the first electrode (negative electrode) with respect to the formation position of the second electrode (positive electrode) 106 when the light emitting semiconductor layer 104 is viewed in cross section (the light emitting semiconductor layer 104 in FIG. 3). This is substantially equivalent to the right half), and a large amount of recombination of holes and electrons occurs in the light-emitting bonding layer 104c in this region, and light is emitted strongly. Therefore, the entire light emitting bonding layer 104c cannot be used as a light emitting region, and as a result, it becomes difficult to emit light uniformly.
[0005]
In order to solve this problem, the second electrode (positive electrode) 106 can be formed by forming the second electrode (positive electrode) 106 far from the first electrode (negative electrode) 107 (left side in FIG. 3). As a result, the region where the current path from the first electrode (negative electrode) 107 to the first electrode (negative electrode) 107 is shortened increases, and as a result, the region of the light emitting bonding layer 104c that can be used as the light emitting region is enlarged. ) Becomes longer, the resistance value becomes larger, the power loss increases, and the light emission efficiency is reduced.
[0006]
The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor light-emitting element that can improve the uniformity of light emission and increase the light emission efficiency.
[0007]
[Means for Solving the Problems]
To achieve the above object, a semiconductor light emitting device according to a first aspect of the present invention includes a support substrate, a first contact layer provided on the support substrate, and a first cladding layer and a second cladding via the light emitting bonding layer. A light emitting semiconductor layer provided in the first contact layer, a second contact layer provided in the light emitting semiconductor layer, and provided in the first contact layer and opposed to the light emitting semiconductor layer. A semiconductor light emitting device comprising: a first electrode; and a second electrode provided on the second contact layer having a substantially constant distance inward from the peripheral edge of the second contact layer and having an end face located on the second contact layer. In addition, the light emitting semiconductor layer and the first electrode are provided in a concavo-convex shape in which peripheral edges of each of the light emitting semiconductor layer and the first electrode are engaged with each other with a certain interval, and the convex portion in the concavo-convex shape of the first electrode is provided in the light emitting semiconductor. Width towards layer Current density which flows in the convex part in the concave-convex shape of the light-emitting semiconductor layer by providing the convex part in the concave-convex shape of the light-emitting semiconductor layer to a substantially trapezoidal shape whose width decreases toward the first electrode. It is characterized by a constant value .
[0008]
According to a second aspect of the present invention, there is provided the semiconductor light emitting device according to the first aspect, wherein the convex portion of the light emitting semiconductor layer has a tip width greater than a tip width of the first electrode convex portion. .
[0009]
According to a third aspect of the present invention, in the semiconductor light emitting device according to the first or second aspect, the convex portions of the light emitting semiconductor layer and the first electrode are chamfered at the corners.
[0010]
According to a fourth aspect of the present invention, there is provided the semiconductor light emitting device according to any one of the first to third aspects, wherein a predetermined portion of the light emitting semiconductor layer is covered with a reflective film.
[0011]
According to a fifth aspect of the present invention, in the semiconductor light emitting device according to the first aspect, the reflective film has a reflectance equal to or higher than that of the material constituting the first electrode and the second electrode. It is supposed to be made of material.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
[First Embodiment]
1A and 1B show a semiconductor light emitting device according to the present embodiment, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along line AA.
[0014]
The semiconductor light emitting device of this embodiment includes a support substrate 1 having a buffer layer 2, a first contact layer 3, a light emitting semiconductor layer 4, a second contact layer 5, a first electrode 6, a second electrode 7, Is a component.
[0015]
The support substrate 1 is a base of the semiconductor light emitting device, and is formed of an insulating substrate made of sapphire, for example. On the support substrate 1, for example, a buffer layer 2 made of GaN is stacked. The buffer layer 2 is interposed between the support substrate 1 and a first contact layer 3 described later, and has a function of relieving stress generated due to the difference in linear expansion coefficient between the two.
[0016]
The first contact layer 3 and the second contact layer 5 are for realizing ohmic contact by reducing a contact barrier (Schottky barrier) generated at the interface when an electrode is formed on the light emitting semiconductor layer 4 described later. is there. This is made of, for example, GaN. Impurities are added so that the first contact layer 3 is n-type conductivity and the second contact layer 5 is p-type conductivity. The first contact layer 3 has a size substantially the same as that of the support substrate 1 in plan view and is stacked on the upper portion of the buffer layer 2 (above FIG. 1B), and the first cladding layer of the light emitting semiconductor layer 4 The contact barrier between the layer 4a and the first electrode 6 described later is reduced. In addition, the second contact layer 5 has a size substantially equal to that of the light emitting semiconductor layer 4 in a plan view and is stacked on the upper part of the second cladding layer 4c of the light emitting semiconductor layer 4 (above FIG. 1B). The contact barrier with the 2nd electrode 7 mentioned later is reduced.
[0017]
The light emitting semiconductor layer 4 has a multilayer structure, and realizes light emission by recombining majority carriers existing in an upper layer and a lower layer in a predetermined intermediate layer. This is composed of three layers of a light emitting bonding layer 4b, a first cladding layer 4a, and a second cladding layer 4c, and the first cladding layer 4a, the second cladding layer 4c, and the like via the light emitting bonding layer 4b. Are formed by laminating. Further, the shape protrudes along the first contact layer 3 from a region having a substantially rectangular shape in plan view, and has substantially trapezoidal convex portions 41, 41, 41 having a width that decreases toward the first electrode 6. .. And a plurality of substantially inverted trapezoidal concave portions 43, 43,. In addition, the convex portions 41, 41,... Are formed so that the width of the tips (the left-right direction in FIG. 1A) is wider than the width of the tips of the convex portions 61, 61,. Thus, the shape of the convex portions 41, 41,... In plan view is larger than the convex portions 61, 61,. Further, the convex portions 41, 41,... Are chamfered with a predetermined curvature at the corner portions 42, 42,.
[0018]
Among these, the light emitting bonding layer 4b is made of a nitride semiconductor containing In (indium), and is made of, for example, InGaN. In addition, the mixed crystal ratio of In and Ga in the light emitting bonding layer 4b is adjusted, or impurities such as Si (silicon), Ge (germanium), Te (tellurium), and S (sulfur) are appropriately doped to form an n-type. By making it conductive type, or by doping impurities such as Mg (magnesium), Zn (zinc), Cd (cadmium), Be (beryllium), Ca (calcium), etc., the band gap can be made The emission wavelength can be changed by changing.
[0019]
The first cladding layer 4a is made of a nitride semiconductor having a band gap larger than that of the light emitting bonding layer 4b, and is made of, for example, AlGaN. In addition, this is formed into an n-type conductivity type by adding impurities.
[0020]
Further, the second cladding layer 4c is made of a nitride semiconductor having a band gap larger than that of the light emitting bonding layer 4b in substantially the same manner as the first cladding layer 4a, and is made of, for example, AlGaN. Moreover, this thing is formed in the p-type conductivity type by adding an impurity.
[0021]
The first electrode 6 realizes electrical connection between the low potential side of the light emitting semiconductor layer 4 and the outside. This is made of, for example, Al (aluminum), and the shape has a width from the region having a substantially rectangular shape in plan view to the distance between the convex portions 41, 41,... Of the light emitting semiconductor layer 4. Has a plurality of substantially trapezoidal convex portions 61, 61,... Through substantially inverted trapezoidal concave portions 63, 63,. In addition, the convex portions 61, 61,... Are formed to engage with the concave portions 43, 43,... And the concave portions 63, 63,. The first electrode 6 is stacked on the first contact layer 3 and is provided with a substantially constant interval between the light emitting semiconductor layer 4 and the planar direction thereof (the left-right direction in FIG. 1B). Yes. Further, the shape of the convex portions 61, 61, ... in plan view is smaller than the convex portions 41, 41, ..., and the corner portions 62, 62, ... are chamfered with a predetermined curvature. is there.
[0022]
The second electrode 7 realizes electrical connection between the high potential side of the light emitting semiconductor layer 4 and the outside. This is formed of Al like the first electrode 6, and the shape thereof is substantially the same as that of the light-emitting semiconductor layer 4 in plan view, but at the peripheral edge facing the first electrode 6. The light emitting semiconductor layer 4 is formed inwardly by a predetermined distance.
[0023]
The operation is as follows. When a forward bias is applied to the light emitting semiconductor element, that is, when a positive voltage is applied to the second electrode 7 and a negative voltage is applied to the first electrode 6, the holes that are the majority carriers of the second cladding layer 4 c and the first Electrons that are majority carriers of the cladding layer 4a are injected into the light emitting junction layer 4b. Therefore, energy is released when holes and electrons recombine and disappear, and this energy is emitted as light. At this time, a current path is formed between the second electrode 7 and the first electrode 6, but the first electrode 6 and the second electrode 7 are substantially bases that become smaller in width toward each other. Since it has a shape and the interval is kept substantially constant, the current density flowing through the light emitting semiconductor layer 4 is substantially constant in the entire region.
[0024]
According to the semiconductor light emitting device of the embodiment described above, the light emitting semiconductor layer 4 has a substantially trapezoidal convex portion that protrudes while narrowing (decreasing) the width along the first contact layer 3 from a substantially rectangular region. .. And alternating inverted trapezoidal concave portions 43, 43,... Are alternately provided, so that the current amount is reduced at the substantially trapezoidal tip due to current loss in the second electrode 7 and the like. However, since the cross-sectional area of the convex portions 41, 41,... Decreases accordingly, the current density can be kept substantially constant as a result, and the uniformity of light emission can be improved. Further, the first electrode 6 has convex portions 61, 61,... That protrude between the concave portions 43, 43,. The current path from the second electrode 7 to the first electrode 6 is formed substantially uniformly without being biased to a specific location, the distance between the electrodes can be shortened, and the light emission efficiency can be increased. Moreover, since the width | variety of the front-end | tip of convex part 41,41, ... is made larger than that of convex part 61,61, ..., the area in planar view of convex part 41,41, ... is convex part 61,61, ... ..., And the light emission efficiency can be further improved. Moreover, since each corner part 42, ..., 62, ... of the 1st convex part 41,41, ... and the 2nd convex part 61,61, ... is chamfered, the current concentration in the position is eased. It is possible to suppress the local heat generation and further improve the light emission efficiency.
[0025]
The material of the buffer layer 2 is not limited to GaN, and may be any material that can relieve stress generated between the support substrate 1 and the first contact layer 3, such as AlGaN or AlN.
[0026]
The material of the first electrode 6 and the second electrode 7 is not limited to Al, and may be, for example, Ni (nickel), Ti (titanium), or Au (gold).
[0027]
The material of the first clad layer 4a and the second clad layer 4c is a nitrogen-group III element compound semiconductor (In _x Al _y Ga _1-xy N, 0 ≦ x, 0 ≦ y, x + y ≦ 1). As long as it is configured, it is not limited to AlGaN.
[0028]
[Second Embodiment]
2A and 2B show a semiconductor light emitting device according to this embodiment, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along the line AA.
[0029]
The semiconductor light emitting device of this embodiment is different from that of the first embodiment in that a reflective film 8 is added, and the other components are substantially the same as those of the first embodiment. The same reference numerals are given to the members and the description thereof is omitted.
[0030]
The reflective film 8 reduces the scattering of light generated in the light emitting bonding layer 4b from the upper surface (above FIG. 2B) and side surfaces of the light emitting bonding layer 4b. This is made of, for example, Au, and covers a predetermined portion such as a side surface of the light emitting semiconductor layer 4 facing the first electrode 6 or a portion where the second electrode 7 of the second contact layer 5 is not formed. Is provided via an insulating film 9. The insulating film 9 is formed of an oxide film, for example, and electrically insulates the light emitting semiconductor layer 4 and the reflective film 8 from each other.
[0031]
According to the semiconductor light emitting device of the embodiment described above, in addition to the effects described in the first embodiment, the exposed surface of the light emitting semiconductor layer 4 is equal to or more than the material constituting the first electrode 6 and the second electrode 7. Since it is covered with Au having a high reflectance, the light generated in the light emitting bonding layer 4b can be output almost in the direction of the support substrate 1, and the light emission efficiency can be improved.
[0032]
【The invention's effect】
According to a first aspect of the present invention, a light emitting semiconductor layer and a first electrode are provided in a concave and convex shape in which peripheral edges of each of the light emitting semiconductor layers and the first electrode are engaged with each other with a certain interval, and the convexity of the concave and convex shape of the first electrode is provided. Since the convex portion in the concavo-convex shape of the light emitting semiconductor layer is provided in a substantially trapezoidal shape that becomes narrower toward the first electrode, the portion is provided in a substantially trapezoidal shape that becomes narrower toward the light emitting semiconductor layer . Even if the amount of current is reduced at the tip of the convex portion of the light emitting semiconductor layer due to current loss in the two electrodes, the current density can be kept constant, and the uniformity of light emission can be improved. Further, the current path from the second electrode to the first electrode is formed substantially uniformly without being biased to a specific location, the distance between the electrodes can be shortened, and the luminous efficiency can be increased.
[0033]
In the semiconductor light-emitting device according to the second aspect of the invention, in addition to the effect of the first aspect, the convex portion of the light-emitting semiconductor layer has a tip width larger than a tip width of the first electrode convex portion. Therefore, the area of the convex part of the light emitting semiconductor layer is larger than the area of the convex part of the first electrode, and the light emitting area can be widened, so that the luminous efficiency can be further improved.
[0034]
In the semiconductor light emitting device according to the third aspect of the invention, in addition to the effect of the first or second aspect, the convex portions of the light emitting semiconductor layer and the first electrode have chamfered corners. Current concentration can be relaxed, and local light generation can be suppressed to further improve luminous efficiency.
[0035]
In addition to the effect of any one of claims 1 to 3, the semiconductor light emitting device of the invention according to claim 4 covers a predetermined portion of the light emitting semiconductor layer with a reflective film, so that light generated in the light emitting junction layer is The output can be substantially in the direction of the support substrate.
[0036]
According to a fifth aspect of the present invention, in addition to the effect of any one of the first to fourth aspects, the reflective film has a reflectance equal to or higher than that of the material constituting the first electrode and the second electrode. Since it is formed from the material which has, it can improve the light reflectivity and can further improve luminous efficiency.
[Brief description of the drawings]
1A and 1B show a semiconductor light emitting device according to a first embodiment of the present invention, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along line AA. .
FIGS. 2A and 2B show a semiconductor light emitting device according to a second embodiment of the present invention, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line AA. .
3A and 3B show a conventional semiconductor light emitting device, in which FIG. 3A is a plan view thereof, and FIG. 3B is a cross-sectional view taken along line AA.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Support substrate 3 1st contact layer 4 Light-emitting-semiconductor layer 4a 1st clad layer 4b Light-emitting joining layer 4c 2nd clad layer 41 Convex part 42 Corner part 43 Concave part 5 2nd contact layer 6 1st electrode 61 Convex part 62 Corner angle Part 63 concave part 7 second electrode 8 reflective film

Claims (5)

A support substrate;
A first contact layer provided on the support substrate;
A light emitting semiconductor layer formed by laminating a first clad layer and a second clad layer via a light emitting bonding layer, and provided in the first contact layer;
A second contact layer provided on the light emitting semiconductor layer ;
A first electrode provided on the first contact layer and facing the light emitting semiconductor layer ;
A second electrode provided on the second contact layer with a substantially constant distance inward from the peripheral edge of the second contact layer and having an end face located;
A semiconductor light emitting device comprising:
The light emitting semiconductor layer and the first electrode are provided in a concavo-convex shape in which peripheral edges of the light emitting semiconductor layer and the first electrode are engaged with each other with a certain interval, and a convex portion in the concavo-convex shape of the first electrode is provided in the light emitting semiconductor layer. Protrusions in the concavo-convex shape of the light-emitting semiconductor layer provided in a substantially trapezoidal shape with a narrow width toward the first electrode A semiconductor light emitting device characterized by having a constant current density flowing in the substrate.   2. The semiconductor light emitting element according to claim 1, wherein the convex portion of the light emitting semiconductor layer has a tip width larger than a width of the leading end of the convex portion of the first electrode.   3. The semiconductor light emitting element according to claim 1, wherein the convex portions of the semiconductor layer and the first electrode have chamfered corners.   4. The semiconductor light emitting element according to claim 1, wherein a predetermined portion of the light emitting semiconductor layer is covered with a reflective film.   5. The semiconductor light emitting element according to claim 1, wherein the reflective film is formed of a material having a reflectance equal to or higher than that of the material constituting the first electrode and the second electrode.

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