JP2006032665A - Light emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high luminance light emitting diode which is manufactured inexpensively with high yield while exhibiting excellent productivity as compared with a conventional light emitting diode provided with a current block layer. <P>SOLUTION: In a light emitting diode having such a structure as a light emitting part sandwiching at least an active layer 5 between an n-type clad layer 4 and a p-type clad layer 6 is formed on a substrate 1, an ohmic contact layer 7 containing conductivity determining impurities in high concentration is formed thereon, a transparent conductive film 8 is formed thereon, and a surface electrode 9 and a back electrode 10 are formed, respectively, on the surface side and the back side thereof, a metallic current block layer 11 is provided between the light emitting part and the transparent conductive film 8 in a surface region substantially not matching the surface electrode 9 of light emitting diode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light-emitting diode (LED) made of a compound semiconductor, and in particular, includes a current blocking layer in the light-emitting diode to suppress the occurrence of leakage current and reduce reverse voltage failure, thereby increasing the brightness. The present invention relates to a light-emitting diode that is low in manufacturing cost.

  The AlGaInP-based material is a direct transition type semiconductor having the largest band gap among III-V group compound semiconductors excluding nitride, and a light-emitting diode manufactured using the AlGaInP-based material has a very high emission band of 560 nm to 660 nm. Since high brightness can be obtained, research and development are still actively carried out, and research on further enhancement of brightness is particularly active. Recently, AlGaInP light emitting diodes are in the midst of price competition, and manufacturers of each company are working to reduce the cost of light emitting diodes and improve throughput.

  Here, the cost for manufacturing the AlGaInP-based light emitting diode is mainly the cost for forming the current diffusion layer. One factor for this is that it is necessary to increase the thickness of the current diffusion layer in order to obtain high luminance. In order to solve this problem, it is effective to use a material having a resistivity as low as possible as the material for the current diffusion layer. The material for the current diffusion layer is mainly made of GaP or AlGaAs. However, even if these low-resistivity materials are used, in order to improve the current dispersion effect and increase the luminance and the operating voltage of the light-emitting diode, the thickness of the current diffusion layer is about 8 μm or more. It was necessary to. Then, the raw material cost required for the growth of the current spreading layer is increased, and further, the time required for the growth deteriorates the throughput, and the manufacturing cost of the AlGaInP light emitting diode is increased overall.

  As a solution to this problem, a metal oxide ITO (Indium Tin Oxide), which has a very high carrier concentration and can obtain a sufficient current dispersion effect with a thin film thickness, is used instead of a window layer made of a semiconductor. A method of using a transparent conductive film made of) as a window layer has been developed.

  Normally, when a metal oxide is used for the window layer, a metal electrode is formed on the window layer, but a contact resistance is generated between the semiconductor layer and the transparent conductive film, which is a metal oxide film, and a forward operating voltage. There is a problem that becomes high.

  However, on the other hand, a method of driving the LED by a tunnel current by increasing the carrier concentration of the uppermost semiconductor layer is also disclosed (see ELECTRONICS LETTERS, 7Th December 1995, pages 2210 to 2212).

Further, as a method for achieving sufficient characteristics as an LED, a p-type GaAs contact layer is used between the uppermost semiconductor layer, that is, the cladding layer and the ITO transparent electrode, thereby reducing the contact resistance with the ITO transparent electrode. Technology has been developed. That is, a GaAs contact layer with C as an additive is used as the uppermost semiconductor layer, and carbon tetrabromide (CBr ₄ ) is used as a raw material for the C additive, so that semiconductor light emission with high luminance, low operating voltage, and high reliability is achieved. A method of manufacturing an element is also disclosed (Patent Document 1).

Furthermore, as another measure for obtaining high brightness, a current confinement type light emitting diode having a current blocking layer has been proposed (see, for example, Patent Document 2). In the light emitting diode disclosed in Patent Document 2, a semiconductor layer (current blocking layer) having conductivity opposite to that of the current diffusion layer is grown between the light emitting layer and the current diffusion layer, and this is selectively etched. Then, circular patterning of the current blocking layer is performed. Thereafter, a current diffusion layer is regrown on the current blocking layer to obtain a current confinement type light emitting diode.
JP-A-11-307810 JP 2002-64219 A

  However, in the case of the light emitting diode of Patent Document 1 described above, it has been found that there is a problem that peeling of about 5% occurs on the ITO transparent electrode (metal oxide window layer). Furthermore, a problem that the reverse voltage was lowered also occurred (reverse voltage measurement conditions were 10 μA, and the voltage at that time was -5 V or less as a failure). In other words, there was a serious problem that the yield was poor due to peeling of the transparent conductive film, which is the metal oxide window layer, and deterioration of the reverse characteristics (generation of leakage current in the forward direction) (defect rate: about 20%). ). That is, the yield was 80%.

  In Patent Document 1, in order to alleviate the band discontinuity between the GaAs contact layer and the underlying InGaAlP cladding layer, an intermediate band made of GaAlAs or InGaAlP is interposed between the GaAs contact layer and the underlying InGaAlP cladding layer. A structure that includes a gap layer is also disclosed. However, although the forward voltage can be lowered to some extent even in this structure, the contact layer in contact with the transparent conductive film, which is a metal oxide, is a GaAs layer. The peeling of a certain transparent conductive film and the deterioration of reverse characteristics cannot be improved. Further, when an intermediate band gap layer is provided between the GaAs contact layer and the InGaAlP cladding layer, the cost is increased by the amount of the intermediate band gap layer.

  Further, in the method of Patent Document 2 described above, since the growth process by the MOCVD method is required twice, it is difficult to reduce the manufacturing cost of the light emitting diode. In particular, the MOCVD apparatus has a low throughput and a high manufacturing cost because the number of wafers processed in one growth is small. In the reverse mesa direction, since the current blocking layer is reversely tapered, defects often occur during the second growth by the MOCVD method, so that controllability is poor and reproducibility is problematic. That is, it is technically difficult, and the production cost is high due to the poor yield.

  That is, at present, it is difficult to manufacture a high-luminance and low-cost light-emitting diode with a high yield.

  Accordingly, an object of the present invention is to provide a high-intensity light-emitting diode that solves the above-described problems and has a higher productivity than a conventional light-emitting diode having a current blocking layer and can be manufactured with a high yield and a low cost. is there.

  In order to achieve the above object, the present invention is configured as follows.

  The light-emitting diode according to the first aspect of the present invention includes a light-emitting portion on which at least an active layer is sandwiched between n-type and p-type conductivity clad layers on a substrate, and a conductive type determining impurity at a high concentration thereon. In a light emitting diode having a structure in which an ohmic contact layer is formed and a transparent conductive film is formed thereon, and electrodes are formed on the front surface side and the back surface side thereof. A current blocking layer made of metal is provided in a surface region portion that does not substantially coincide with the surface-side electrode. Here, the term “surface region portion that does not substantially coincide with the surface side electrode of the light emitting diode” includes any or all forms of the surface region that does not substantially coincide with the surface side electrode of the light emitting diode.

  According to a second aspect of the present invention, in the light-emitting diode according to the first aspect, a current blocking layer made of a metal is provided almost directly below the surface-side electrode.

  According to a third aspect of the present invention, in the light-emitting diode according to the first aspect, a current blocking layer made of a metal is provided around the light-emitting diode. It is characterized by that.

According to a fourth aspect of the present invention, in the light emitting diode according to any one of the first to third aspects, the ohmic contact layer containing a conductivity-determining impurity at a high concentration contains Mg of 1 × 10 ¹⁹ / cm ³ or more. It is characterized by comprising Ga _x In _1-x P (0 ≦ X ≦ 0.7).

According to a fifth aspect of the present invention, in the light emitting diode according to any one of the first to third aspects, the ohmic contact layer containing a conductivity-determining impurity at a high concentration contains Zn of 1 × 10 ¹⁹ / cm ³ or more. It is characterized by comprising Al _x Ga _1-x As (0 ≦ X ≦ 0.4).

  According to a sixth aspect of the present invention, in the light emitting diode according to any one of the first to fifth aspects, the current blocking layer made of the metal is made of any one of Ti, Ni, and AuBe.

  According to a seventh aspect of the present invention, in the light-emitting diode according to the second aspect, the area of the current blocking layer made of metal substantially immediately below the surface-side electrode is equal to or larger than that of the surface electrode. Features.

  According to an eighth aspect of the present invention, in the light emitting diode according to any one of the first to seventh aspects, the substrate is made of GaAs, and the light emitting portion is made of GaInP, AlInP, or AlGaInP.

  According to a ninth aspect of the present invention, in the light emitting diode according to any one of the first to eighth aspects, the ohmic contact layer has a thickness of 1 nm to 25 nm.

  According to a tenth aspect of the present invention, in the light emitting diode according to any one of the first to ninth aspects, the transparent conductive film is made of ITO and has a thickness of 200 nm to 600 nm.

  According to the present invention, since the current blocking layer made of metal is provided in the surface region portion between the light emitting portion and the transparent conductive film and not substantially coincident with the surface side electrode of the light emitting diode, the reverse voltage failure (forward In this way, it is possible to manufacture a light emitting diode with high yield. Accordingly, it is possible to obtain a light-emitting diode that has high yield, excellent reproducibility, is extremely inexpensive, has high luminance, high reliability, and low operating voltage.

  Hereinafter, embodiments of the present invention will be described mainly with reference to examples.

  FIG. 1 shows a configuration of a light emitting diode according to the first embodiment. The light-emitting diode is premised on a high concentration formed on the p-type clad layer 6 and a light-emitting portion sandwiching at least the active layer 5 between the n-type clad layer 4 and the p-type clad layer 6 on the substrate 1. An ohmic contact layer 7 containing a conductivity type determining impurity and a transparent conductive film 8 made of ITO formed on the ohmic contact layer 7 are provided, and further formed on the surface electrode 9 formed on the surface side and on the back surface side (substrate side). A back electrode 10 is provided. As a feature of the light emitting diode, a current blocking layer 11 made of metal is provided between the ohmic contact layer 7 and the transparent conductive film 8 and in a surface region portion that does not substantially coincide with the surface electrode 9 of the light emitting diode. It has.

  FIG. 2 shows a configuration of the light emitting diode according to the second embodiment. In this light emitting diode, a current blocking layer 11 made of metal is provided around the light emitting diode between the ohmic contact layer 7 and the transparent conductive film 8 made of ITO, and a current blocking layer 12 made of metal is further provided. This is a configuration of a high-intensity light-emitting diode that is provided at the same time in a location that substantially matches the surface electrode 9.

  In the embodiment of FIG. 2, the current blocking layer 12 is formed of metal in a structure in which the transparent conductive film 8 made of ITO is used as the current diffusion layer and the current blocking layer is further provided between the light emitting portion and the transparent conductive film. . Furthermore, when the current blocking layer 12 is formed, the current blocking layer 11 is also formed of metal around the light emitting diode, thereby preventing reverse voltage failure (leak current failure in the forward direction) and peeling of the transparent conductive film. Thus, it is possible to manufacture with a high yield. That is, it is possible to obtain a light emitting diode that has a high yield, excellent reproducibility, is extremely inexpensive, has high brightness, high reliability, and low operating voltage.

<Example 1>
As an example, a red band light emitting diode having an emission wavelength of about 630 nm and having the structure shown in FIG. 1 was manufactured. The production process is as follows.

On a substrate 1 made of n-type GaAs, a buffer layer 2 made of n-type GaAs by an MOVPE method, an n-type Bragg reflection (DBR) layer 3, and an n-type clad made of n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P An active layer 5 made of undoped (Al _0.10 Ga _0.90 ) _0.5 In _0.5 P, a p-type cladding layer 6 made of p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, and an ohmic contact layer 7 made of p-type GaAs. Epitaxial wafers for light emitting diodes were produced by sequentially growing. Incidentally, the DBR layer 3 has a laminated structure composed of n-type AlInP (about 50 nm) and n-type GaAs (about 40 nm), and the number of pairs is 15 pairs.

  After carrying out the said light emitting diode epitaxial wafer from a MOVPE apparatus, the current block layer 11 which consists of metals was formed in the surface of this epitaxial wafer, ie, the ohmic contact layer 7 side. The method for forming the current blocking layer 11 is as follows.

  After carrying out the said light emitting diode epitaxial wafer from a MOVPE apparatus, the negative resist film was apply | coated to the whole surface using the spin coater on the surface of the epitaxial wafer for light emitting diodes, and was hardened.

  Next, using a mask aligner, exposure is performed so that a line having a width of 10 μm is formed in a portion corresponding to all of the peripheral portion of the light-emitting diode (periphery of the light-emitting diode: 4 sides), and further development is performed thereafter. The metal was patterned into a shape, and a metal to be the current blocking layer 11 was formed by a vacuum evaporation method, and the current blocking layer 11 having a width of 10 μm was formed by a lift-off method. At this time, three types of current blocking layers 11 of Ni, Ti, and AuBe were manufactured. At this time, the thickness of the current blocking layer 11 is 10 nm.

Further, a 300 nm-thick transparent conductive film 8 made of ITO was formed on the epitaxial wafer for light-emitting diodes on which the current blocking layer 11 was formed, by vacuum deposition. Incidentally, at this time, the glass substrate set in the same batch was taken out, cut into a size capable of Hall measurement, and the electrical characteristics of the transparent conductive film made of ITO were evaluated. The carrier concentration was 1.27 × 10 ²¹ / cm ^3. The mobility was 22.4 cm ² / Vs, and the resistivity was 2.31 × 10 ⁻⁴ Ω · cm. After the transparent conductive film 8 is formed, a circular surface electrode (p-side electrode) 9 having a diameter of 125 μm is formed on the upper surface of the transparent conductive film 8 so that the center is substantially coincident with the current blocking layer 11. It was formed by vapor deposition in a matrix using the method. For the surface electrode 9, nickel and gold were deposited in the order of 20 nm and 500 nm, respectively. Further, a back electrode (n-side electrode) 10 was formed on the entire bottom surface of the epitaxial wafer. The back electrode 10 was formed by depositing gold, germanium, nickel, and gold in the order of 60 nm, 10 nm, and 500 nm, respectively, and then alloying the electrodes was performed at 400 ° C. for 5 minutes in a nitrogen gas atmosphere.

  Thereafter, this epitaxial wafer was processed into a chip shape having a chip size of 300 μm square by dicing or the like, and then die bonding and wire bonding were performed to manufacture a light emitting diode chip.

  As a result of evaluating the LED characteristics of this light emitting diode chip, the light emission output when a current blocking layer made of Ni, a current blocking layer made of Ti, and a current blocking layer made of AuBe was formed was 2.51 ± 0.2 mW. It was. The forward operating voltage was also 2.0 V or less. For this reason, it has confirmed that a favorable LED characteristic was acquired. Furthermore, the peeling of the transparent conductive film 8 and the reverse voltage failure were less than 1%, and it was successful in producing a good yield.

  As described above, the current blocking layer 11 made of metal is provided at a position located below the transparent conductive film 8 that is the current diffusion layer, so that the light emitting diode without the conventional current blocking layer (FIG. 3). It was possible to manufacture a light-emitting diode with higher output than that with a high yield and reproducibility.

  As described above, the current block layer 11 made of metal is provided in the lower portion of the transparent conductive film 8 that is the current diffusion layer and around the light emitting diode, so that the conventional current block is provided. It was possible to manufacture with higher yield than a light emitting diode without a layer.

<Comparative example>
As a comparative example, a red light emitting diode having a structure shown in FIG. The production process is as follows.

On a substrate 1 made of n-type GaAs, a buffer layer 2 made of n-type GaAs, an n-type DBR layer 3, an n-type cladding layer 4 made of n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, and undoped by an MOVPE method. An active layer 5 made of (Al _0.10 Ga _0.90 ) _0.5 In _0.5 P, a p-type cladding layer 6 made of p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P, and an ohmic contact layer 7 made of p-type GaAs are grown in order. An epitaxial wafer for a light emitting diode was produced. Incidentally, the DBR layer 3 has a laminated structure composed of n-type AlInP (about 50 nm) and n-type GaAs (about 40 nm), and the number of pairs is 15 pairs.

After carrying out the said light emitting diode epitaxial wafer from a MOVPE apparatus, the 300 nm-thick transparent conductive film 8 which consists of ITO was formed by the vacuum evaporation method on the surface of this epitaxial wafer, ie, the ohmic contact layer 7 side. At this time, the glass substrate set in the same batch was taken out, cut into a size capable of Hall measurement, and the electrical characteristics of the transparent conductive film were evaluated. The carrier concentration was 1.27 × 10 ²¹ / cm ³ , The mobility was 22.4 cm ² / Vs, and the resistivity was 2.31 × 10 ⁻⁴ Ω · cm.

  A circular surface electrode 9 having a diameter of 125 μm was formed on the upper surface of the light emitting diode epitaxial wafer by evaporation in a matrix form. The surface electrode 9 was formed by depositing nickel and gold in the order of 20 nm and 500 nm, respectively.

  Further, a back electrode 10 was formed on the entire bottom surface of the epitaxial wafer. The back electrode 10 was formed by depositing gold, germanium, nickel, and gold in the order of 60 nm, 10 nm, and 500 nm, respectively, and then alloying the electrodes was performed at 400 ° C. for 5 minutes in a nitrogen gas atmosphere.

  Thereafter, this epitaxial wafer was processed into a chip shape having a chip size of 300 μm square by dicing or the like, and then die bonding and wire bonding were performed to manufacture a light emitting diode chip.

  As a result of evaluating the LED characteristics of this light emitting diode chip, a light emission output of 2.49 mW was obtained. However, the yield was 80% due to reverse voltage failure and peeling of the transparent conductive film.

<Example 2>
In the first embodiment of the present invention, the current blocking layer 11 made of metal is provided between the ohmic contact layer 7 and the transparent conductive film 8 made of ITO and around the light emitting diode. However, as shown in FIG. 2, the current blocking layer 12 made of metal is further provided at the same time between the ohmic contact layer 7 and the transparent conductive film 8 made of ITO and at a location substantially coincident with the surface electrode 9. Similarly, the effect of improving the peeling of the transparent conductive film and the deterioration of the reverse direction characteristic can be obtained. The current blocking layer 12 can be provided as part of the process of forming the current blocking layer 11.

<Reason for optimal conditions>
(1) About the current blocking layer 11 provided around the light emitting diode First, the width of the current blocking layer provided around the light emitting diode has an optimum value.

  When the width of the current blocking layer provided around the light emitting diode is larger, the reverse voltage failure and the peeling of the transparent conductive film are reduced, and the yield is improved. However, if it is too large, it becomes a slight light absorption layer. The forward voltage also increases. For this reason, it is not desirable to make it too large or too small. Therefore, it is preferably 3 μm to 50 μm, more preferably 5 μm to 30 μm.

  Second, there is an optimum value for the film thickness of the current blocking layer provided around the light emitting diode. This is because if the current blocking layer provided around the light emitting diode is too thick, it is difficult to extract emitted light. Moreover, it is because a reverse voltage defect and the peeling defect of a transparent conductive film will increase when it is made too thin. Therefore, the film thickness of the current blocking layer 11 provided around the light emitting diode is preferably 2 to 25 nm, and more preferably 5 to 15 nm.

(2) Regarding the current blocking layer 12 provided immediately below the electrode of the light emitting diode Third, the size, that is, the diameter of the current blocking layer provided immediately below the electrode is approximately equal to the diameter of the electrode formed on the surface electrode, that is, the transparent conductive film. It is preferable to make them equal or larger.

  This is because if the diameter of the current blocking layer is smaller than the diameter of the surface electrode, there is a portion where the current flowing directly under the electrode cannot be shielded, and the increase in the light emission output due to the current confinement effect is reduced. It is.

  Further, it is necessary to optimize the diameter of the current blocking layer according to the distance of the semiconductor layer from the current blocking layer to the active layer. For example, in the case of the above embodiment, the distance from the active layer to the current block layer is about 1 μm, and if this is the case, the current flowing around the current block layer bypasses the semiconductor layer below the current block layer. Therefore, it is possible to achieve high brightness due to the highly efficient current confinement effect. On the contrary, when the distance of the semiconductor layer from the current block layer to the active layer is as long as about 10 μm, the current flowing around the current block layer flows again to the position immediately below the electrode by the semiconductor layer to the active layer. As a result, light emission directly under the electrode increases, and a significant improvement in luminance cannot be expected. A countermeasure for such a case is solved by making the diameter of the current blocking layer larger than the diameter of the electrode.

  Fourth, the film thickness of the current blocking layer provided immediately below the electrode of the light emitting diode has an optimum value. This is because it becomes difficult to extract emitted light if the current blocking layer is too thick. On the other hand, if the thickness is too thin, the current blocking effect is reduced and the light emission output is not improved. Therefore, the film thickness of the current blocking layer is preferably 2 to 25 nm, and more preferably 5 to 15 nm.

  Fifth, it is desirable to use a metal that easily oxidizes as the metal of the current blocking layer provided immediately below the electrode of the light emitting diode. This is because the current blocking effect is more effective when oxidized. Further, it is transparent to the emitted light, so that the light extraction is improved and the light emission output is further increased.

(3) Ohmic contact layer Sixth, the ohmic contact layer 7 in contact with the transparent conductive film is mainly composed of Al _x Ga _1-x As (0 ≦ X ≦ 0.4) or main doped with Zn at a high concentration. Further, Ga _x In _1-x P (0 ≦ X ≦ 0.7) in which Mg is added at a high concentration is desirable.

  A transparent conductive film made of ITO basically belongs to an n-type semiconductor material, and a light emitting diode is generally manufactured by p-side up. For this reason, the light emitting diode in which the transparent conductive film made of ITO is attached to the current diffusion layer has a conductivity type of n / p / n junction from the substrate side. For this reason, in the light emitting diode, a large potential barrier is generated at the interface between the transparent conductive film made of ITO and the p-type semiconductor layer, and the light emitting diode usually has a very high operating voltage. In order to solve this problem, the p-type semiconductor layer requires an ohmic contact layer having a very high carrier concentration.

For this purpose, AlGaAs having a low Al mixed crystal ratio to GaAs mainly doped with Zn at a high concentration is suitable. Specifically, it has a carrier concentration of 1 × 10 ¹⁹ / cm ³ or more. It is preferable. Alternatively, Ga _x In _1-x P (0 ≦ X ≦ 0.7) in which Mg is mainly added at a high concentration as described above is suitable, and more specifically, 1 × 10 ¹⁹ / cm ³ or more. It preferably has a carrier concentration.

  Seventh, the ohmic contact layer 7 is, for example, GaAs to AlGaAs having a low Al mixed crystal ratio, and the thickness of the ohmic contact layer is preferably in the range of 1 nm to 50 nm.

  This is because the ohmic contact layer 7 has a band gap that serves as an absorption layer for the light emitted from the active layer 5, so that the light emission output decreases as the film thickness increases. . Therefore, the upper limit of the film thickness of the ohmic contact layer 7 is set to about 50 nm. However, it is more preferably up to 30 nm. Further, when the film thickness of the ohmic contact layer 7 is less than 1 nm, it becomes difficult to tunnel between the transparent conductive film 8 made of ITO and the ohmic contact layer 7, so the operating voltage is lowered. This makes it difficult to stabilize the operating voltage. Accordingly, the film thickness of the ohmic contact layer 7 in contact with the transparent conductive film 8 made of ITO has an optimum value, which is 1 nm to 50 nm.

(4) About the transparent conductive film 8 made of ITO Eighth, the method of forming the transparent conductive film 8 made of ITO is preferably a vacuum deposition method. The reason will be described below for each manufacturing method.

  First, in the sputtering method, the equipment cost of the sputtering apparatus itself is high, and furthermore, the number of charged sheets per batch is small, so throughput is a problem.

  Next, in the spray method using the MOD solution, first, the resistivity of the transparent conductive film made of ITO cannot be lowered unless the surface temperature of the substrate is heated to 500 ° C. or higher. The influence of heat is large, and the surface of the ohmic contact layer is oxidized, resulting in a problem that a tunnel junction cannot be achieved. In addition, since the transparent conductive film made of ITO is formed at a high temperature, the carrier concentration of ITO is lowered, which makes it difficult to make a tunnel junction. Furthermore, it is difficult to charge a large number of sheets, that is, to manufacture a manufacturing facility with high throughput, and it is difficult to perform stable mass production.

  Next, in the coating method, it is very difficult to lower the resistivity as compared with the spray method, the sputtering method, and the vacuum deposition method. This makes it very difficult to make a tunnel junction with the ohmic contact layer. Furthermore, since a transparent conductive film made of ITO is formed from about 200 nm to about 500 nm, it is necessary to repeatedly perform steps such as coating, drying, and baking, so that the throughput is very poor.

  For the above reasons, the vacuum deposition method, which is a method with a low manufacturing apparatus price, excellent stability, and high throughput, is preferable as a method for forming the transparent conductive film 8 made of ITO.

  Ninth, the film thickness of the transparent conductive film 8 made of ITO is preferably in the range of 200 nm to 500 nm.

  The reason why the lower limit is 200 nm is that a film thickness of about 200 nm is necessary to obtain a sufficient current dispersion effect. Next, since the upper limit is 500 nm, when the film thickness of the transparent conductive film 8 made of ITO becomes about 500 nm when formed by vacuum deposition, the transparency of the transparent conductive film 8 made of ITO, that is, transmission This is because the rate gradually deteriorates. Further, since a sufficient current dispersion effect can be obtained by the transparent conductive film 8 made of ITO having a thickness of about 200 nm to 300 nm, the manufacturing cost is only increased even if it is made too thick.

  Therefore, the film thickness of the transparent conductive film 8 made of ITO is preferably in the range of 200 nm to 500 nm, more preferably about 200 nm to 400 nm.

<Modification 1>
In the embodiments of the present invention, the AlGaInP-based light emitting diode has been described in detail. However, the present invention is intended for the periphery of the light emitting diode and from the metal between the semiconductor layer and the transparent conductive film made of ITO. This is a technique for providing a current blocking layer, which is not limited to an AlGaInP light emitting diode. That is, the present invention can be applied to other materials such as AlGaAs light emitting diodes and InGaAsP long wavelength light emitting diodes.

<Modification 2>
In the embodiment of the present invention, the light emitting part is constituted by the n-type cladding layer 4, the active layer 5, and the p-type cladding layer 6. For example, a semiconductor layer (diffusion suppression layer) for suppressing diffusion of conductivity type determining impurities. Can be additionally provided above and below the active layer, or on either the upper side or the lower side. Even under such a configuration, the effect of improving the peeling of the transparent conductive film and the deterioration of the reverse direction characteristic can be obtained. This diffusion suppression layer may be undoped or a low concentration semiconductor layer. In any case, the present invention can be applied regardless of the presence or absence of a diffusion suppression layer for suppressing the diffusion of the conductivity type determining impurity.

<Modification 3>
In the embodiment of the present invention, a light emitting diode structure was formed on a substrate 1 made of GaAs, and a current blocking layer 11 and a transparent conductive film 8 made of ITO were sequentially formed thereon. Thus, a light emitting diode was obtained. For example, when the substrate is made of Ge, or as in the embodiment, a light emitting diode structure is once formed on a substrate made of GaAs, and then, using the various wafer fusion techniques, the initially formed light emitting diode structure is utilized. Even in a light-emitting diode attached to a different substrate, a current confinement type light-emitting diode composed of a metal current blocking layer and a transparent conductive film made of ITO shown in the present invention is used as a substrate material. Nevertheless, the present invention can be applied and the intended effect of the present invention can be obtained.

<Modification 4>
In the embodiment of the present invention, a simple double hetero structure in which the active layer is sandwiched between the clad layers is used. However, even if the active layer has a quantum well structure, for example, the intended effect of the present invention can be obtained. .

1 is a cross-sectional structure diagram of an AlGaInP-based red light emitting diode according to an embodiment of the present invention. It is a cross-section figure of the AlGaInP type red light emitting diode concerning other embodiments of the present invention. It is a cross-section figure of the AlGaInP type red light emitting diode concerning a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Buffer layer 3 Bragg reflective layer 4 N-type clad layer 5 Active layer 6 P-type clad layer 7 Ohmic contact layer 8 Transparent conductive film 9 Surface electrode 10 Back electrode 11 Current block layer 12 Current block layer

Claims (10)

A light emitting part having at least an active layer sandwiched between n-type and p-type conductivity clad layers on a substrate, an ohmic contact layer containing a conductivity-determining impurity at a high concentration thereon, and a transparent conductive film thereon In the light emitting diode having a structure in which electrodes are formed on the front side and the back side,
A light-emitting diode, wherein a current blocking layer made of metal is provided in a surface region portion between the light-emitting portion and the transparent conductive film and not substantially coinciding with the surface-side electrode of the light-emitting diode. The light emitting diode according to claim 1.
A light-emitting diode characterized in that a current blocking layer made of metal is also provided almost directly below the surface-side electrode. The light emitting diode according to claim 1.
A light-emitting diode, characterized in that a current blocking layer made of metal provided in a surface region portion that does not substantially coincide with the surface-side electrode of the light-emitting diode is provided around the light-emitting diode. The light emitting diode according to any one of claims 1 to 3,
The ohmic contact layer containing a conductivity-determining impurity at a high concentration comprises Ga _x In _1-x P (0 ≦ X ≦ 0.7) containing 1 × 10 ¹⁹ / cm ³ or more of Mg. A light emitting diode. The light emitting diode according to any one of claims 1 to 3,
The ohmic contact layer containing a conductivity-determining impurity at a high concentration is composed of Al _x Ga _1-x As (0 ≦ X ≦ 0.4) containing Zn of 1 × 10 ¹⁹ / cm ³ or more. A light emitting diode. The light emitting diode according to any one of claims 1 to 5,
The light-emitting diode, wherein the current blocking layer made of the metal is made of Ti, Ni, or AuBe. The light emitting diode according to claim 2, wherein
The light emitting diode according to claim 1, wherein an area of a current blocking layer made of a metal substantially immediately below the surface side electrode is equal to or larger than that of the surface electrode. The light emitting diode according to any one of claims 1 to 7,
The light emitting diode according to claim 1, wherein the substrate is made of GaAs, and the light emitting portion is made of GaInP, AlInP, or AlGaInP. The light emitting diode according to any one of claims 1 to 8,
The light-emitting diode, wherein the ohmic contact layer has a thickness of 1 nm to 25 nm. The light emitting diode according to any one of claims 1 to 9,
The light-emitting diode, wherein the transparent conductive film is made of ITO and has a thickness of 200 nm to 600 nm.

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