JP2009188249A - Light-emitting diode and method of manufacturing the same, and light-emitting diode array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blue and violet light-emitting diode which has high luminous efficiency and a narrow spectrum line width by using a nitride semiconductor. <P>SOLUTION: The light-emitting diode comprises a lower clad layer, a light-emitting layer formed on the lower clad layer and made of the nitride semiconductor, an upper clad layer formed on the light-emitting layer, a lower ohmic electrode brought into contact with the lower clad layer, and an upper ohmic electrode brought into contact with the upper clad layer and having an optical window formed, wherein the lower clad layer, light-emitting layer and upper clad layer form a microcavity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention generally relates to light emitting diodes, and more particularly to a light emitting diode using a nitride semiconductor.

  Nitride semiconductors have a large band gap, and light emitting diodes with blue to violet wavelengths using such nitride semiconductors as light emitting layers have been realized.

  A light emitting diode is an element whose operation principle is spontaneous emission of photons generated in the light emitting layer. Conventionally, when a so-called optical microcavity is formed in a light emitting diode, the spontaneous emission rate of photons changes, As a result, it is known that favorable effects such as improved luminous efficiency and sharpened emission spectrum can be obtained.

An optical microcavity is a type of Fabry-Perot resonator, but the length of the resonator is as short as a few wavelengths, and as a result, the modes that occur in the resonator are restricted. When combined with, a forbidden band appears in the emission spectrum in which spontaneous emission of photons is suppressed. As a result, it is possible to obtain the effect of sharpening the emission spectrum or the effect of improving the light emission efficiency.
Japanese Patent No. 2735057 Patent No. 2780691 Patent No. 2890396 Japanese Patent No. 3135041 Japanese Patent No. 3538275 JD Joannopoulos et al., Photonic Crystals, Princeton University Press, Princeton, USA, 1995 EF Shubert, Light-Emitting Diodes Second Ed., P.257, Cambridge University Press, Cambridge, UK, 2006 EF Schubert et al., Science 265, 943, 1994 T. Ichinohe et al., Thin Solid Films 377-378, vol.87, 2000 D. Byrne, et al., Jpn. J. Appl. Phys. Vol. 42, (2003) pp.L1509-L1511

  However, even if such an optical microcavity is applied to a nitride light emitting diode that emits blue to blue-violet light, the conventional nitride light emitting diode is generally formed on a thick sapphire substrate as shown in FIG. Therefore, since the emission wavelength is as short as about 450 nm, it is impossible to realize a desired microcavity.

  Referring to FIG. 1, a conventional nitride light emitting diode includes a lower clad layer 12 made of GaN formed on a sapphire substrate 11 and a GaInN layer or GaInN / GaN formed on the lower clad layer 12. A light emitting layer 13 having a quantum well structure or the like, and an upper clad layer 14 made of GaN formed on the light emitting layer 13, and an upper electrode 16A is disposed on the upper clad layer 14 via a transparent conductive film 15. A lower electrode 16B is formed on a part of the lower cladding layer 12.

Further, a metal reflection film 17 is formed on the lower surface of the sapphire substrate 11, and output light is extracted upward from the upper clad layer 14 through the transparent conductive film 15.
In the conventional nitride light emitting diode having such a structure, the distance Lcav from the metal reflection film 17 to the upper end surface of the upper cladding layer 14 is inevitably several hundred microns or more, and various standing wave modes are possible. Therefore, the spontaneous emission generated in the light emitting layer 13 is not controlled, and a wide emission spectrum is generated. Along with this, the luminous efficiency also decreases.

  According to one aspect, the present invention solves the above problem by using a metal substrate having a reflective surface and forming a lower ohmic electrode, a lower clad layer formed on the reflective surface of the metal substrate, and the lower side. A light emitting layer made of a nitride semiconductor formed on the clad layer; an upper clad layer formed on the light emitting layer; an upper ohmic electrode in contact with the upper surface of the upper clad layer and having an optical window; The lower clad layer, the light emitting layer, and the upper clad layer form a microcavity between the upper surface of the upper clad layer and the reflective surface of the metal substrate, and the microcavity is the light emitting diode. This is solved by a light-emitting diode having a cavity length that is an integral multiple of ½ wavelength of the emission wavelength.

  According to another aspect, the present invention provides the above-described problem by forming a lower ohmic electrode having a reflective surface, a lower clad layer formed on the reflective surface of the metal substrate, and the lower clad layer. A light emitting layer made of a nitride semiconductor, an upper cladding layer formed on the light emitting layer, and an upper ohmic electrode in contact with an upper surface of the upper cladding layer and having an optical window formed thereon, The side cladding layer, the light emitting layer, and the upper cladding layer form a microcavity between the upper surface of the upper cladding layer and the reflective surface of the lower ohmic electrode, and the microcavity is an emission wavelength of the light emitting diode. A method of manufacturing a light-emitting diode having a cavity length that is an integral multiple of a half wavelength of the above, wherein the upper cladding layer is epitaxially formed on a support substrate by MOCVD. A step of epitaxially growing a light emitting layer on the upper cladding layer by an MOCVD method, a step of epitaxially growing the lower cladding layer on the light emitting layer by an MOCVD method, and the lower layer Forming a reflective film on the side cladding layer, forming the lower ohmic electrode on the reflective film, peeling the support substrate from the upper cladding layer, and the upper cladding layer Etching, and setting the film thickness of the upper clad layer to such a thickness that an optical cavity composed of the upper clad layer, the light emitting layer, and the lower clad layer forms a microcavity; Forming the upper ohmic electrode on the cladding layer. A method for manufacturing a light-emitting diode, comprising: To solve.

  According to the present invention, a microcavity can be formed even in a light emitting diode having a light emitting layer made of a nitride semiconductor, and a sharp light emission spectrum and high light emission efficiency can be realized. In this case, in the present invention, a light emitting diode having such a microcavity can be directly formed on a metal substrate constituting the lower ohmic electrode. For example, such a light emitting diode can be formed on an insulating crystal substrate such as sapphire. Compared with the case where it forms, it becomes possible to improve a heat dissipation characteristic markedly. For this reason, it becomes possible to construct a high-density light-emitting diode array by integrating a large number of light-emitting diodes of the present invention on a metal base. In particular, in the manufacturing method according to the present invention, even when the lower clad layer, the light emitting layer, and the upper clad layer are all formed by the MOCVD method, a multilayer reflection made of a dielectric multilayer film such as an oxide is formed on the upper clad layer. A film can be formed, and an efficient light-emitting diode using the MOCVD method can be manufactured.

[principle]
The fitness value (F value) representing the quality factor (Q) of the microcavity is expressed by the equation F = π (1−√R ₁ R ₂ ).
Given in. Here, R ₁ and R ₂ are the reflectivities of the two reflecting mirrors 1 and 2 constituting the Fabry-Perot interferometer shown in FIG.

Using the F value, the spectral half width of the microcavity is
Δλ = λcav / F
Given in. Where λcav is the resonance wavelength of the Fabry-Perot interferometer.

  The spontaneous emission emission control by the microcavity is based on the principle that the optical mode density in the cavity is much higher at the resonance wavelength and lower at the non-resonance wavelength than the value in free space. This effect becomes remarkable when the cavity length Lcav (distance between the reflecting mirrors 1 and 2) is close to the emission wavelength, and is highest in the case of λ / 2 (Lcav = λ / 2).

  Therefore, if this principle is used, there is a possibility that a light-emitting diode that is overwhelmingly more efficient than a conventional light-emitting diode can be realized. The present invention realizes an element exceeding the efficiency limit of a conventional light emitting diode by applying a microcavity to a blue light emitting diode or an ultraviolet light emitting diode.

  In the following, for example, the light emission wavelength of the GaN light emitting diode is 450 nm, and the gain is calculated when the cavity length of the microcavity is 900 nm (twice the light emission wavelength).

Gain (integrated enhancement ratio) Gint obtained when placing the light emitting layer of GaN light emitting diodes in the microcavity of FIG. 2, the formula Gint = (ξ / 2) ( 2 / π) (1-R 1) / ( 1− / R ₁ R ₂ ) √πln2 (λ / Δλn) (λcav / Lcav) (τcav / τ)
(Non-Patent Document 2).

  Here, ξ is a parameter determined by the position of the active layer in the cavity, and when the position where the active layer hits the antinode of the standing wave formed in the cavity, a value of 2 is set. When the active layer is uniformly distributed, the value 1 is taken. In the following, assuming that the active layer can be installed at a position close to the antinode, a value of 1.5 is assumed as the value of the parameter ξ. Δλn is the half width of the emission spectrum. Further, τ and τcav are values of the lifetime in spontaneous emission and the lifetime in the cavity, respectively, and τcav / τ = 1 here.

The value of the gain Gint varies depending on the values of the reflectivities R ₁ and R _{2. In} the following, it is assumed that the reflector 2 is totally reflected and the value of the reflectivity R ₂ is 1.

If we calculate the first 0.5 reflectivity _{R 1} of the reflecting mirror 1, fitness value F is 10, the spectral half-width 45 nm, the gain gint is 9 (F = 10, Δλ = 45nm, Gint = 9) It becomes. If the value of the reflectance R ₁ is 0.8, the fitness value F is 30, the spectrum half width is 15 nm (F = 30, Δλ = 15 nm), and a value 11 (Gint = 11) is obtained as the gain Gint. . Naturally, the effect of the microcavity is increased when the value of R ₁ is large. Since the FWHM of the GaN-based light emitting diode is about 20 nm, the microcavity effect increases with a smaller value of Δλ. On the other hand, since the temperature dependence of the emission wavelength of the GaN-based light emitting diode is about 0.07 nm / ° C., if F is increased too much, a practical problem arises.

  A high-efficiency red light-emitting diode using the above principle has already been realized (Reference Document 3). The applicant has also tried to control light emission from silicon nanocrystals using a microcavity, and has confirmed sharpening of the spectrum and increase of light emission intensity (Reference 4).

  On the other hand, as described above, even if this principle is applied to the GaN light emitting diode of FIG. 1, the Fabry-Perot resonator includes the thick sapphire substrate 11 and cannot be realized.

  Recently, a technology for peeling a GaN-based semiconductor film from a sapphire substrate has been put into practical use, and a light-emitting diode using this technology is commercially available.

  Therefore, the present invention uses a light emitting diode peeled off from such a sapphire substrate, forms a metal reflecting mirror on one surface as the reflecting mirror R2, and etches the peeling surface which is the other surface to increase the cavity length. A technique for realizing a desired microcavity by setting a predetermined value is provided.

Preferably, a multilayer film reflecting mirror is formed on the etched surface as the reflecting mirror 1, and the reflectance R1 of the multilayer reflecting film 1 is less than the reflectance of the metal reflecting mirror 2 (about 0.95 or more for silver), 03 or more. The reflectance in this range is obtained by depositing _two kinds of dielectric films having different refractive indexes such as SiO ₂ and Ta ₂ 0 _{5 by} a thin film forming method capable of strictly controlling the film thickness such as an ion beam sputtering method. Can be easily realized.

  Advantages achieved by the technology of the present invention include:

  (1) Luminous efficiency is greatly improved by controlling spontaneous emission with a cavity structure.

  (2) By adopting the cavity structure, the emission direction of the output light is aligned in the vertical direction with respect to the reflecting mirror 1 and the directivity is improved.

  (3) As a result of the above (2), the light extraction efficiency from the surface is greatly improved.

  (4) As a result of (2), the loss of light in the lateral direction is reduced.

  Thus, the present invention makes it possible to realize a high-intensity purple-green light emitting diode that has not been realized in the past by the MOCVD method.

When the effect (2) is positively utilized, a light emitting diode array in which a number of micro light emitting diodes are formed in one chip can be formed.

[First Embodiment]
Next, a manufacturing process of the blue light-emitting diode according to the first embodiment of the present invention will be described with reference to FIGS. In the illustrated example, the emission wavelength of the blue light emitting diode is 450 nm. However, the present invention is not limited to such a specific emission wavelength, and the present invention can be applied to a green to violet light emitting diode having an emission wavelength in the range of 550 nm to 330 nm.

  First, referring to FIG. 3A, in this embodiment, a sacrificial layer 22 made of GaN is epitaxially formed to a thickness of, for example, 20 nm on a sapphire substrate 21 having a thickness of, for example, 300 μm by MOCVD.

  Next, in the step of FIG. 3A, an InGaN film 23 that acts as an etching marker for GaN is epitaxially formed on the GaN sacrificial layer 22 by MOCVD with a thickness of, for example, 10 nm. The first clad layer 24 made of n-type GaN is formed on the substrate 23 in the same manner as the sacrificial layer 22 except that the first cladding layer 24 is epitaxially formed with a thickness of 730 nm corresponding to 3/2 wavelength of the emission wavelength of the blue light emitting diode + 55 nm. To form.

  Next, in the step of FIG. 3A, the light emitting layer 25 having an InGaN / GaN quantum well structure on the first cladding layer 22 is alternately repeated with an InGaN film having a thickness of 7 nm and a GaN film having a thickness of 10 nm. By depositing, a film thickness of 110 nm, which is about ¼ wavelength of the emission wavelength, is formed as a whole. Further, a second cladding layer 26 made of p-type GaN is epitaxially formed on the light emitting layer 25 with a film thickness of 60 nm in the same manner as the first cladding layer 24.

  In the example of FIG. 3A, the first cladding layer 24, the light emitting layer 25, and the second cladding layer 26 form a microcavity Cav having a cavity length Lcav corresponding to two wavelengths as a whole. It is designed to be located at the antinode of the standing wave generated in the formed microcavity.

  Next, in the step of FIG. 3B, an Ag film 27 is formed as a reflective layer on the second cladding layer 26 of FIG. 3A to a thickness of, for example, 1000 nm, for example, by sputtering, and a Cu film is further formed on the Ag film 27. 28 is formed in an arbitrary film thickness by, for example, an electrolytic plating method. The Ag film 27 is in ohmic contact with the second cladding layer 26 under the Ag film 27, so that the Ag film 27 and the Cu film 28 form an ohmic electrode of the second cladding layer.

  Next, in the step of FIG. 3C, the structure of FIG. 3B is turned upside down, and further, the GaN sacrificial layer 22 is irradiated with a laser beam through the sapphire substrate 21, thereby the sapphire substrate 21 as shown in FIG. Is peeled and removed.

  Next, in the step of FIG. 3E, the GaN sacrificial layer 22 is removed by dry etching using chlorine gas or the like as an etching gas, and further, an element constituting the etching marker layer 23, for example, In, is etched while being monitored by a mass spectrometer. Then, the structure up to the etching marker layer 23 is etched and removed to obtain the structure in which the light emitting layer 25 is arranged in the microcavity shown in FIG. 3F.

  Further, the etching marker layer 23 exposed in this manner is etched and removed, for example, while monitoring the disappearance of In with a mass spectrometer, thereby arranging the light emitting layer 25 in the microcavity shown in FIG. 3F. A structure is obtained. The etching marker layer 23 may be left. In that case, the etching marker layer 23 is included in the subsequent structure.

Next, in the step of FIG. 3G, a multilayer reflective film 29 having a structure in which a 77 nm thick SiO ₂ film and a 52 nm thick Ta ₂ O ₅ film are alternately laminated on the structure of FIG. 3F is formed, In the step of FIG. 3H, a resist pattern R is formed to cover a part of the multilayer reflective film 29 at the center in the plan view.

Further, in the step of FIG. 3H, using the resist pattern R as a mask, Si or oxygen is applied at an acceleration voltage of 200 keV, for example, at a dose of 3 × 10 ¹⁴ cm ⁻² , mainly at the bottom of the microcavity Cav, Ions are implanted into the two cladding layers 26 to form a high resistance current confinement structure 24I in the periphery of the device.

  3I, the multilayer reflective film 29 is patterned using the resist pattern R as a mask, and the first cladding layer 24 is exposed in a ring shape at the periphery of the resist pattern R.

  Further, in the step of FIG. 3H, a ring-shaped ohmic electrode 30 is formed on the ring-shaped exposed portion of the first cladding layer 24, a 1.7 μm thick Al film, a 0.25 μm thick Ni film, and a thickness. It is formed in the form of a laminate of 0.5 μm Au film. In this embodiment, the ring-shaped ohmic electrode 30 defines an optical window 30A having a diameter of 0.2 mm, and blue light generated in the light emitting layer 25 passes through the optical window 30A. Outputs to the outside.

  FIG. 4 shows the microcavity Cav in more detail.

  Referring to FIG. 4, the microcavity Cav has a resonator length of 2λ as a whole, and the center of the light emitting layer 25 is positioned at the antinode of the standing wave formed in the microcavity. Is formed. Here, the center of the light emitting layer 25 may be formed at another antinode of the standing wave formed in the microcavity, and the microcavity length Lcav is an integral multiple of 1 / 2λ. However, if the cavity length Lcav is increased, light emission in a large number of modes is possible. In such a microcavity with a short resonator length, the possible modes are limited as described above, so that energy is concentrated in the fundamental mode, a sharp emission spectrum is obtained, and at the same time, luminous efficiency is greatly improved. To do. Further, the directivity of the output light emitted through the multilayer reflective film 29 is improved, and the output light is emitted with high directivity in the direction perpendicular to the multilayer reflective film 29.

The multilayer reflective film 29 preferably has a transmittance of 30 to 90%. For example, if the number of repetitions of the SiO ₂ film and the Ta ₂ O ₅ film in the multilayer reflective film 29 is set to 2 times, the transmittance of 30% can be obtained, whereas if the number of repetitions is set to 6 times, the rate of 90% Transmittance is obtained. Alternatively, the multilayer reflective film 29 can be omitted.

For example, if the refractive indexes of the two types of dielectric films constituting the multilayer reflective film 29 are n ₁ and n ₂ , respectively, the reflectance of the multilayer reflective film 29 with respect to light of wavelength λ is set to be equal to that of one dielectric film. This can be maximized when the film thickness L ₁ is λ / 4n ₁ and the film thickness L ₂ of the other dielectric film is λ / 4n ₂ (Non-patent Document 2). Therefore, since the refractive index of the Ta ₂ O ₅ film with a refractive index of the SiO ₂ film is 1.46 is 2.16, for example, in the case of light emitting diodes having a wavelength to emit light of 450 nm, of the SiO ₂ film By setting the film thickness to 77 nm and the film thickness of the Ta ₂ O ₅ film to 52 nm, the reflectance of the multilayer reflective film 29 can be maximized.

  In the illustrated example, the light emitting layer 25 has a multiple quantum well structure. However, the present invention is not limited to such a specific configuration, and the light emitting layer 25 may be a single quantum well layer or a bulk InGaN. It is also possible to use layers. Furthermore, the InGaN layer in the light emitting layer may contain other elements such as Al.

  In this embodiment, the case where the emission wavelength is 450 nm has been described. However, by adjusting the concentration of In in the InGaN / GaN light emitting layer 25, it is possible to emit light at other wavelengths. In that case, the film thickness of the cladding layers 24 and 26 and the film thickness of the light emitting layer 25 vary from the above values, but the relationship described with reference to FIG. 4 needs to be maintained.

  In the present invention, it should be noted that the multilayer reflective film 29 is formed after the main body portion of the light emitting diode, that is, the laminated structure of the first cladding layer 24, the light emitting layer 25, and the second cladding layer 26 is formed. It is. Therefore, in the present invention, the formation process of the multilayer reflective film 29 does not affect the formation process of the first cladding layer 24, the light emitting layer 25, and the second cladding layer 26, and the first cladding layer 24, the light emitting layer 25 and the second cladding layer 26 can be efficiently formed using the MOCVD method with high film formation efficiency.

  On the other hand, in the technique of Non-Patent Document 4, for example, a blue light emitting diode having a microcavity structure is formed directly on a sapphire substrate, so that a multilayer reflective film is formed on the lower cladding forming the main body of the blue light emitting diode. It is necessary to provide between the layer and the underlying sapphire substrate. For this reason, in the technique of Non-Patent Document 4, the main body portion of the light emitting diode is formed on the multilayer reflective film and then formed as a multilayer reflective film so that the main body portion of the light emitting diode can be formed by epitaxial growth. It is necessary to use a nitride semiconductor. However, in order to obtain a high reflectance with a multilayer reflective film using a nitride semiconductor, the multilayer reflective mirror needs to be formed by stacking a GaN film and an AlGaN film having a large Al composition. However, if the AlGaN film is grown by the MOCVD method when the Al composition becomes large, it will contain a large amount of defects, so the MOCVD method cannot be used. For this reason, in Non-Patent Document 4, film formation is performed by the MBE method, which has a low growth rate and poor crystallinity, resulting in low luminous efficiency.

  On the other hand, the present invention makes it possible to manufacture a light emitting diode efficiently and inexpensively using the MOCVD method, which is a film forming method with a high growth rate and excellent crystallinity.

  In the present embodiment, as shown in FIG. 5, the multilayer reflective film 29 can be omitted if necessary. In this case, the upper surface of the first cladding layer 24 acts as a reflecting mirror.

Further, in the present embodiment, as shown in FIG. 6, a transparent conductive film 30B such as ITO (In ₂ O ₃ .SnO ₂ ) is provided between the first cladding layer 24 and the multilayer reflective film 29 so as to form the ohmic electrode. It can also be provided as a part of 30. According to such a configuration, it becomes possible to perform more uniform current injection than the ohmic electrode 30.

[Second Embodiment]
FIG. 7 shows a configuration of a light-emitting diode array according to the second embodiment of the present invention. However, in the figure, the same reference numerals are given to the parts described above, and the description will be omitted.

  Referring to FIG. 7, the laminated body in which the second clad layer 26, the light emitting layer 25, and the first clad layer 24 are laminated to form the microcavity Cav is formed with an insulating film 62 on a support base 61 made of Cu, for example. .., And element regions I, II, III,... Are defined in the laminate.

  Further, in each of the element regions I, II, III,..., The ring-shaped electrode 30 and the ring-shaped current confinement structure 25I are formed, and the Ag reflection film 27 is perpendicular to the paper surface of FIG. A wiring pattern in which the Cu electrode film 28 is laminated extends continuously.

  In each element region I, II, III,..., A current confinement structure 25I is formed in a ring shape corresponding to the ring electrode 30.

  In the light-emitting diode array having such a configuration, the light-emitting diodes described in the previous embodiment are arranged in a matrix, but by selecting one wiring pattern and selecting one ring-shaped electrode 30, any element can be selected. The light emitting diode in the region can emit light.

  If such a light emitting diode array is used, a minute proximity image transmission device can be realized.

  FIG. 8 shows a modification of the light emitting diode array of FIG.

  Referring to FIG. 8, in this embodiment, the support base 61 and the insulating film 62 are omitted, and the lower electrode 28 also serves as the support base 61 instead.

  The lower electrode 28 uniformly carries an Ag reflecting film 27 on the upper surface thereof, and a large number of the light emitting diodes described in the first embodiment are formed on each element region.

  In such a configuration, heat generated in the light emitting diode is efficiently absorbed by the lower electrode that also serves as the support base, and even when the light emitting diodes are arranged at a high density and are driven simultaneously, The temperature rise of the light emitting diode can be effectively suppressed. That is, in the present embodiment, the lower electrode 28 not only functions as a support base but also functions as an effective heat sink.

  As mentioned above, although this invention was described about preferable embodiment, this invention is not limited to this specific embodiment, A various deformation | transformation and change are possible within the summary described in the claim.

It is a figure which shows the structure of the conventional GaN light emitting diode. It is a figure explaining the principle of a microcavity. It is FIG. (1) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (2) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (3) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (4) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (5) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (6) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (7) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (8) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (9) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is FIG. (10) explaining the manufacturing process of the light emitting diode by the 1st Embodiment of this invention. It is a figure which shows the detail of the light emitting diode by the said 1st Embodiment. It is a figure which shows the structure of the light emitting diode by the modification of 1st Embodiment. It is a figure which shows the structure of the light emitting diode by the modification of 1st Embodiment. It is a figure which shows the structure of the light emitting diode array by the 2nd Embodiment of this invention. It is a figure which shows the structure of the modification of the light emitting diode array by the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Reflector 21 Sapphire substrate 22 1st clad layer 23 Etching marker layer 24 2nd clad layer 25 Light emitting layer 25I Current confinement structure 26 3rd clad layer 27 Ag reflecting film 28 Lower electrode 29 Multilayer reflecting film 30 Upper electrode 30A Optical window 30B Transparent conductive film 61 Support base 62 Insulating film

Claims (13)

A metal substrate having a reflective surface and forming a lower ohmic electrode;
A lower clad layer formed on the reflective surface of the metal substrate;
A light emitting layer made of a nitride semiconductor formed on the lower cladding layer;
An upper cladding layer formed on the light emitting layer;
An upper ohmic electrode in contact with the upper surface of the upper cladding layer and formed with an optical window;
Including
The lower clad layer, the light emitting layer, and the upper clad layer form a microcavity between the upper surface of the upper clad layer and the reflective surface of the metal substrate,
The light emitting diode according to claim 1, wherein the microcavity has a cavity length that is an integral multiple of a half wavelength of the light emitting wavelength of the light emitting diode.   Furthermore, a multilayer reflective film is provided on a portion of the upper surface of the upper cladding layer where the upper ohmic electrode forms the optical window, and the microcavity includes an interface between the upper cladding layer and the multilayer reflective film, The light emitting diode according to claim 1, wherein the light emitting diode is formed between the reflective surface on the metal substrate.   3. The light emitting diode according to claim 2, wherein the multilayer reflective film is made of a stack of oxide films. The light emitting diode according to claim 1, wherein the upper ohmic electrode includes a transparent conductive film that covers the upper surface of the upper cladding layer in the optical window.   The light emitting diode according to claim 4, wherein a reflective film having a transmittance of 30 to 90% is formed on the transparent conductive film.   6. The light emitting diode according to claim 1, wherein a current confinement structure for confining carriers introduced from the upper ohmic electrode is provided in the upper clad layer.   7. The light emitting diode according to claim 6, wherein the current confinement structure is a high resistance region containing oxygen atoms. A metal base carrying an insulating film;
A plurality of light emitting diode elements formed on the metal base through the insulating film;
The light emitting diode array according to claim 1, wherein each of the plurality of light emitting diode elements comprises the light emitting diode according to claim 1. A lower ohmic electrode having a reflective surface; a lower clad layer formed on the reflective surface of the metal substrate; a light emitting layer made of a nitride semiconductor formed on the lower clad layer; and the light emitting layer An upper clad layer formed on the upper clad layer; and an upper ohmic electrode in contact with the upper surface of the upper clad layer and having an optical window formed thereon, wherein the lower clad layer, the light emitting layer, and the upper clad layer are A microcavity is formed between the upper surface of the upper clad layer and the reflective surface of the lower ohmic electrode, and the microcavity has a cavity length that is an integral multiple of half the wavelength of the light emitting diode. A method of manufacturing a light emitting diode characterized by comprising:
Epitaxially growing the upper cladding layer on a support substrate by MOCVD;
A step of epitaxially growing a light emitting layer on the upper cladding layer by MOCVD;
Epitaxially growing the lower cladding layer on the light emitting layer by MOCVD;
Forming a reflective film on the lower cladding layer;
Forming the lower ohmic electrode on the reflective film;
Peeling the support substrate from the upper cladding layer;
Etching the upper cladding layer and setting the film thickness of the upper cladding layer to such a thickness that an optical cavity composed of the upper cladding layer, the light emitting layer, and the lower cladding layer forms a microcavity; When,
Forming the upper ohmic electrode on the upper cladding layer;
The manufacturing method of the light emitting diode characterized by the above-mentioned.   The method of manufacturing a light emitting diode according to claim 9, wherein the upper cladding layer includes an etching marker layer, and the etching step includes a step of stopping etching at the etching marker layer.   The method of manufacturing a light emitting diode according to claim 10, further comprising a step of removing the etching marker layer after the etching step.   The method for manufacturing a light-emitting diode according to any one of claims 9 to 11, wherein the step of peeling the base includes a step of irradiating the base with laser light.   13. The method according to claim 9, further comprising a step of forming a multilayer reflective film on the upper cladding layer by stacking first and second oxide films having different refractive indexes after the etching process. A method for producing a light-emitting diode according to any one of the above.