JP2009129941A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting device having a light emitting element using nanowires and capable of suppressing the incidence of side wall light emission to a substrate with a simple configuration.
A substrate, an insulating film formed on the substrate, a first conductivity type SiC film formed on the insulating film, and a first conductivity type semiconductor formed on the SiC film. A plurality of columnar crystal structures 8 in which a layer 5, a light emitting layer 6, and a second conductivity type semiconductor layer 7 are sequentially stacked; a first conductivity type side electrode 11 formed on a SiC film; A light emitting element 100 having a second conductivity type side electrode 9 formed on the columnar crystal structure, and the refractive index of the insulating film 2 is different from the refractive index of the SiC film 3. 2 is a thickness obtained by dividing the emission wavelength of the light emitting layer 6 by a numerical value that is not less than 3 times and not more than 5 times the refractive index of the insulating film 2, and the thickness of the SiC film 3 is the thickness of the light emitting layer 6. The thickness is obtained by dividing the emission wavelength by a numerical value that is not less than 3 times and not more than 5 times the refractive index of the SiC film 3.
[Selection] Figure 1

Description

  The present invention relates to a light-emitting device, and more particularly to a light-emitting device having a reflective film for light emitted from the light-emitting element.

  In recent years, light-emitting elements using GaN compound semiconductors that can emit light at short wavelengths (hereinafter referred to as GaN light-emitting elements) have been put into practical use. However, since GaN crystals are likely to generate dislocations, it is difficult and expensive to obtain good quality crystals. Therefore, various efforts are being made to solve such problems. For example, as a substrate for forming a GaN layer on the surface, a sapphire substrate, an SiC substrate, an SOI substrate (hereinafter referred to as an SiC / SOI substrate) on which an SiC film is formed on the surface, and the like have been studied.

  Among these, the SiC / SOI substrate is inexpensive, and as a composite semiconductor substrate for an electro-optical fusion device that can simultaneously integrate a Si integrated circuit fabricated on the SOI substrate and a GaN light emitting device fabricated on the SiC film. It attracts attention. For example, in Non-Patent Document 1, a SiC / SOI substrate is produced by carbonizing an SOI substrate having a Si film formed on the surface using Rapid Thermal Process, and a high-quality GaN layer is produced on the SiC film. A method is disclosed. Since SiC has a lattice constant close to that of GaN, it is suitable for growth of a GaN layer, and has an advantage of high heat conductivity and good heat dissipation. A disadvantage of SiC is that a thick buffer layer is required to obtain a GaN crystal, and cracks and dislocations are likely to occur.

  On the other hand, a light-emitting element using a columnar crystal structure called a GaN nanowire has been proposed as a new technique for improving luminance by reducing thread dislocations generated in a GaN crystal. It has been confirmed by TEM observation that GaN nanowires have few defects, and a high-luminance light-emitting element in which an MQD (Multiple Quantum Disk) made of GaN / InGaN is formed on this GaN nanowire has been realized (for example, non-patented) Reference 2).

  FIG. 3 is a cross-sectional view of the light emitting diode disclosed in Non-Patent Document 2. Note that the reference numerals in FIG. 3 are appropriately changed by the applicant. As shown in FIG. 3, in this light emitting diode, GaN nanowires are grown directly on a (111) Si substrate by using an RF-MBE method. In FIG. 3, 51 is an n-type Si substrate, 52 is an n-type side electrode made of Ti, 53 is an n-type GaN nanowire, 54 is an InGaN / GaN MQD active layer, 55 is a p-type GaN layer, and 56 is Ni / Au. A p-type transparent electrode 57, a Cu heat sink, and 58 an InGa liquid metal. The light-emitting diode using GaN nanowires manufactured in this manner has an advantage of high luminous efficiency because it can improve luminance and extract side wall light emission. Moreover, it is not necessary to form a GaN buffer layer.

  As a light emitting diode using a GaN nanowire, in addition to the one disclosed in Non-Patent Document 2, a GaN nanowire is grown on a GaN layer formed on a sapphire substrate using the MO-HVPE method. A high-luminance light-emitting element manufactured as described above and a manufacturing method thereof are known (for example, see Patent Document 1).

  FIG. 4 is a cross-sectional view of the light emitting diode disclosed in Patent Document 1. The reference numerals in FIG. 4 are appropriately changed by the applicant. 4, 69 is a sapphire substrate, 70 is a GaN buffer layer, 62 is an n-type side electrode, 63 is an n-type GaN nanowire, 64 is an InGaN / GaN MQD active layer, 65 is a p-type GaN layer, and 66 is a p-type side. A transparent electrode, 71 is a transparent insulating layer, and 72 is an electrode pad.

  A light emitting device disclosed in Non-Patent Document 3 is known as a technique related to the present invention in that a reflective film for light emitted from the light emitting layer is provided on the substrate side.

FIG. 5 is a cross-sectional view of the light-emitting device disclosed in Non-Patent Document 3. Note that the reference numerals in FIG. 5 are appropriately changed by the applicant. In FIG. 5, 83 is a Si substrate, 84 is an n-AlN layer, 85 is an n-AlGaN layer, 86 is an n-GaN / n-AlN 20-period multilayer, 87 is an AlGaN / AlN DBR, and 88 is an n-GaN layer. , 89 is an InGaN / GaN MQD active layer, 90 is a p-AlGaN layer, 91 is a p-GaN layer, 92 is a heat sink, 93 is an n-type side electrode, and 94 is a p-type side electrode. In this light emitting device, a DBR (Distributed Bragg Reflector) 87 is formed between the active layer 89 of a normal light emitting element formed on the Si substrate 83 and the Si substrate 83, and the light emitted from the active layer 89 is emitted. The DBR 87 reflects the light, thereby improving the light extraction rate. Then, by growing three layers of n-Al _0.3 Ga _0.7 N / n-AlN (54 nm / 58 nm) DBR, the reflectance of light at a wavelength near 470 nm can be improved from 10% to 30%. The calculation result is obtained.
JP 2005-228936 A Applied Physics Letter 69 (15), October 1996, P.2264- "SiC raipid thermal carbonization of the (111) Si semiconductor-on-insulator structure and subsequent metalorganic chemical vapor deposition of GaN", AJ Steckl et al. Japanese Journal of Applied Physics, Vol. 43, No. 12A, 2004 NEDO Research Result Report, Project ID: 02A23024d “Practical research on gallium nitride based optical and electronic devices on silicon substrates” by Hiroyasu Ishikawa et al.

  In a conventional light-emitting device using GaN nanowires, light emitted from the active layer, particularly part of side-wall light emission, is absorbed by the substrate and cannot be extracted outside. In particular, when the substrate is made of Si, the band gap of Si is as small as 1.1 eV, and the loss is large because it absorbs from ultraviolet to visible light. Further, heat is generated as a result of this light absorption, and the influence of this heat generation extends to an electronic circuit (Si integrated circuit) integrated on the same substrate, which is not preferable in terms of reliability.

  Thus, in a light emitting device using GaN nanowires, it is conceivable to form a DBR on the nanowire itself, but even in such a case, sidewall emission is directly incident on the substrate and absorbed there, and the sidewall emission is taken out. I can't.

  In the light emitting device of Non-Patent Document 2, a DBR is formed on an n-type Si substrate 52 and a GaN nanowire 53 is formed on the DBR. In the light emitting device of Patent Document 1, a GaN buffer layer 70 is formed. It is conceivable to form a DBR on top and form a GaN nanowire 63 on the DBR. However, as is apparent from FIG. 5, a thick buffer layer such as the multilayer films 84 to 86 is required as the base of the DBR 87. For this reason, the advantage of the light emitting element using the nanowire that the light emitting element is formed without requiring a thick GaN buffer layer is lost.

  In addition, the light emitting element has a use that is required to be less expensive than a high performance (high reflectivity) reflective film provided on the substrate side, such as a lighting device.

  The present invention has been made to solve such a problem, and has a light-emitting device having a light-emitting element using nanowires and capable of suppressing the incidence of side-wall light emission on a substrate with a simple configuration. The purpose is to provide.

  In order to solve the above problems, a light-emitting device of the present invention includes a substrate, an insulating film formed on the substrate, a first conductivity type SiC film formed on the insulating film, and the SiC film. A plurality of columnar crystal structures formed by sequentially stacking a first conductivity type semiconductor layer, a light emitting layer, and a second conductivity type semiconductor layer, and the columnar crystal structure on the SiC film. A light-emitting element having a first conductivity type side electrode formed in a region where is not formed, and a transparent second conductivity type side electrode formed on the plurality of columnar crystal structures, The refractive index of the insulating film is different from the refractive index of the SiC film, and the thickness of the insulating film is the wavelength of light emitted from the light emitting layer (hereinafter referred to as the emission wavelength). Divided by a numerical value of 3 times or more and 5 times or less, and the thickness of the SiC film is The emission wavelength of the light-emitting layer, the thickness is divided by 3 times or more and 5 times or less of the value of the refractive index of the SiC film.

  With such a configuration, the insulating film and the SiC film constitute a reflective film that reflects the emission wavelength of the light emitting layer, so that the light emitted from the side wall of the light emitting layer is constituted by the insulating film and the SiC film. Reflected by the reflective film. Therefore, the extraction rate of side wall light emission of the light emitting layer can be improved, and incidence of the side wall light emission to the substrate can be suppressed with a simple configuration.

  Two or more light emitting elements having different emission wavelengths of each light emitting layer are formed on the insulating film, and the thickness of the insulating film is the shortest of the light emitting wavelengths of the light emitting layers of the two or more light emitting elements. Of the light emission wavelengths of the light emitting layers of the two or more light emitting elements, the longest light emission wavelength of the thickness obtained by dividing the light emission wavelength by the numerical value of 3 to 5 times the refractive index of the insulating film is 3 It may be a thickness between the thickness divided by a numerical value that is not less than twice and not more than five times.

  With such a configuration, even when a plurality of light emitting elements having different emission wavelengths are formed on one substrate, the thickness of the SiC film formed between each light emitting element and the substrate is equal to the emission wavelength of each light emitting element. Therefore, a reflective film that suitably reflects the side wall light emission of each light emitting element can be formed on the substrate side.

  A first conductivity type first SiC film formed on the insulating film; a first conductivity type first semiconductor layer formed on the first SiC film; and a first light emitting layer; A plurality of first columnar crystal structures formed by sequentially stacking first conductive type first semiconductor layers and the first columnar crystal structures on the first SiC film are not formed. The light emitting device comprising: a first first conductivity type side electrode formed in a region; and a transparent first second conductivity type electrode formed on the plurality of first columnar crystal structures. A first light emitting element, a first conductivity type second SiC film formed separately from the first first conductivity type SiC film on the insulating film, and the second SiC film A first conductive type second semiconductor layer formed thereon, a second light emitting layer for emitting light of a wavelength different from that of the first light emitting layer, and a second conductive layer. A plurality of second columnar crystal structures formed by sequentially laminating a second semiconductor layer of a type, and a region where the first columnar crystal structure is not formed on the second SiC film. A second light-emitting element comprising: a second first-conductivity-type side electrode; and a transparent second second-conductivity-type side electrode formed on the plurality of second columnar crystal structures. The thickness of the insulating film is obtained by dividing the emission wavelength of the first light emitting element by a value not less than 3 times and not more than 5 times the refractive index of the insulating film, A thickness between the thickness of the first light-emitting element and the thickness obtained by dividing the light emission wavelength of the second light-emitting element by a numerical value of 3 to 5 times the refractive index of the insulating film, A thickness obtained by dividing the emission wavelength of the first light emitting layer by a numerical value of 3 to 5 times the refractive index of the first SiC film; Even if the thickness of the second SiC film is a thickness obtained by dividing the emission wavelength of the second light emitting layer by a numerical value that is not less than 3 times and not more than 5 times the refractive index of the second SiC film. Good.

  With such a configuration, even when two light emitting elements having different emission wavelengths are formed on one substrate, a reflective film that suitably reflects the side wall light emission of each light emitting element can be configured on the substrate side.

Even if the semiconductor constituting the columnar crystal structure is a nitride semiconductor made of Ga _x In _1-x N (0 <x ≦ 1) or Al _y Ga _1-y N (0 ≦ y <1). Good.

The substrate may be made of Si, and the insulating film may be made of a SiO ₂ film. With such a configuration, an inexpensive SiC / SOI substrate can be used as the substrate, so that the cost can be reduced.

The thickness of the SiO ₂ film is preferably 40 nm to 160 nm, and the thickness of the SiC film is preferably 20 nm to 90 nm.

  The present invention is configured as described above, and has a light-emitting element using nanowires, and can provide a light-emitting device capable of suppressing incidence of side-wall light emission to a substrate with a simple configuration. There is an effect.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout the drawings, and redundant description thereof is omitted.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a configuration of a light-emitting device according to Embodiment 1 of the present invention.

[Constitution]
As shown in FIG. 1, the light emitting device 101 of the present embodiment includes a light emitting element 100 made of a light emitting diode and a SiC / SiO ₂ reflective film 4.

More specifically, the light emitting device 101 includes the Si substrate 1. An SiO ₂ film 2 as an insulating film is formed on the Si substrate 1. An n-type SiC film 3 is formed on the SiO ₂ film 2. The SiO ₂ film 2 and the n-type SiC film 3 constitute a SiC / SiO ₂ reflective film 4. The insulating film constituting the reflective film 4 needs to have a refractive index different from that of the n-type SiC film 3. Here, since the insulating film is composed of the SiO ₂ film 2, this requirement is satisfied. The SiO ₂ film 2 and the n-type SiC film 3 are each formed to a predetermined thickness. This predetermined thickness will be described in detail later.

A large number of nanowires (columnar crystal structures) 8 are formed on the n-type SiC film 3 so as to extend in the thickness direction of the n-type SiC film 3. In each nanowire 8, an n-type GaN layer 5 as an n-type semiconductor layer (lower cladding layer) is formed on the n-type Sic film 3, and an InGaN / GaN MQD activity as a light emitting layer is formed on the n-type GaN layer 5. A layer 6 is formed, and a p-type GaN layer 7 as a p-type semiconductor layer (upper clad layer) is formed on the InGaN / GaN MQD active layer 6. The n-type semiconductor layer and the p-type semiconductor layer are composed of Ga _x Al _1-x N (0 <x ≦ 1), the composition is appropriately selected, and the required conductivity type is imparted by appropriately doping impurities. . Here, as described above, the n-type semiconductor layer and the p-type semiconductor layer are both made of GaN, and are given n-type and p-type conductivity types, respectively. The light-emitting layer, the Ga _x In _1-x N single layer made of (0 <x ≦ 1) or Ga _x In _1-x N (0 <x ≦ 1) materials having different compositions from each other a composed material from It is comprised by the multilayer which laminates two layers which become. The composition and layer thickness of the light emitting layer are selected according to the light emission wavelength, light emission efficiency, and the like. Here, the light emitting layer, the n-type semiconductor layer, and the p-type semiconductor layer are double heterojunction. In addition, the light emitting layer is formed of an InGaN / GaN multilayer as described above.

In addition, a transparent insulating layer 12 is formed on the n-type SiC film 3 so as to fill the spaces between the numerous nanowires 8. The transparent insulating layer 12 is made of, for example, SiO ₂ .

  A transparent p-type side electrode 9 is formed on the upper ends of the nanowires 8 and the transparent insulating layer 12. The p-type side electrode 9 is made of, for example, Ni / Au.

  An electrode pad 10 made of a metal such as Ti / Al is formed on the p-type side electrode 9.

  Furthermore, an n-type side electrode 11 is formed on the n-type SiC film 3 so as to be located in a region where a large number of nanowires 8 are not formed. Here, the n-type side electrode 11 is made of Ni.

  The n-type SiC film 3, the n-type GaN layer 5, the InGaN / GaN MQD active layer 6, the p-type GaN layer 7, the p-type side electrode 9, the electrode pad 10, and the n-type side electrode 11 constitute the light emitting element 100. is doing.

[Thickness setting of SiO ₂ film 2 and n-type SiC film 3]
Next, the thickness setting (design) of the SiO ₂ film 2 and the n-type SiC film 3 characterizing the present invention will be described.

Since the light emitting element 100 configured as described above emits light having a wavelength corresponding to approximately visible light from near ultraviolet light, the SiC / SiO ₂ reflective film 4 is required to reflect light having these wavelengths. .

In order for the SiC / SiO ₂ reflective film 4 to have a practical reflectance, the thicknesses of the n-type SiC film 3 and the SiO ₂ film 2 satisfy the following expressions (1) and (2), respectively. Is preferred. Here, λ represents the wavelength of light emitted from the light emitting element 100, t1 represents the thickness of the n-type SiC film 3, and n1 represents the refractive index of SiC. T2 represents the thickness of the SiO ₂ film 2 (insulating film), and n2 represents the refractive index of SiO ₂ (material constituting the insulating film).

λ / (3 × n1) ≦ t1 ≦ λ / (5 × n1) (1)
λ / (3 × n2) ≦ t2 ≦ λ / (5 × n2) (2)
In the formulas (1) and (2), the coefficients of the refractive index n1 of SiC and the refractive index n2 of SiO ₂ are set to 3 to 5 because the coefficient is 4 when the effect is most effective and the reflectance is high. Considering that the thickness of the n-type SiC film 3 and the SiO ₂ film 2, the emission wavelength of the light emitting element 100, and the desired reflectance vary when the light emitting device 101 is manufactured, the optimum The thickness is approximately 7% with respect to the thickness (thickness when the coefficient is 4). That is, if the deviation of the thickness of the n-type SiC film 3 and the SiO ₂ film 2 from the theoretically optimum thickness is within 7%, the reflectance of the SiC / SiO ₂ reflective film 4 is within a practical range. It is assumed that it will fit. When the coefficient is 4, the highest reflectance of the SiC / SiO ₂ reflective film 4 is derived as follows. When two types of films having different refractive indexes are stacked, the light reflected on the surface of the film and the light reflected on the boundary surface of the film are combined to form reflected light. At this time, if all the reflected lights have the same phase, they can overlap to obtain high reflection characteristics. On the other hand, the phase shift of reflected light at the boundary surface from the high refractive index to the low refractive index is zero, and the phase shift of reflected light at the boundary surface from the low refractive index to the high refractive index is 180 °. It becomes. Therefore, when the film thickness is set so that the optical path difference between the two reflected lights is 180 °, the reflected lights have the same phase and overlap each other. Therefore, the film thickness for obtaining the highest reflection characteristic is as shown in Expression (3) and Expression (4). Here, m and l are integers.

t1 = (m / 2 + 1/4) λ / n1 (3)
t2 = (l / 2 + 1/4) λ / n2 (4)
Here, if m = l = 0, t1 = λ / (4 × n1) (5)
t2 = λ / (4 × n2) (6)
Thus, the reflectance is highest when the coefficient is 4. This indicates that a high reflectance can be obtained by optically laminating a quarter wavelength film.
Further, in the formula (3) and the formula (4), when m ≠ 0 and l ≠ 0 are considered, the formula (1) and the formula (2) can be replaced as the formula (7) and the formula (8). Of these, a film thickness that is easy to fabricate can be selected.

mλ / (2 × n1) + λ / (3 × n1) ≦ t1 ≦ mλ / (2 × n1) + λ / (5 × n1) (7)
lλ / (2 × n1) + λ / (3 × n2) ≦ t2 ≦ lλ / (2 × n1) + λ / (5 × n2) (8)
Specifically, assuming that light over the entire visible light region from near ultraviolet light is incident on the substrate 1, the thickness of the n-type SiC film 3 is in the range of approximately 20 nm to 90 nm according to the equation (1). According to the formula (1), the thickness of the SiO ₂ film 2 is set to a thickness in the range of about 40 nm to 160 nm. For example, when the light emitting element 100 is a red light emitting element, the thickness of the n-type SiC film 3 is set to about 65 nm, and the thickness of the SiO ₂ film 2 is set to about 120 nm. When the light emitting element 100 is a green light emitting element, the thickness of the n-type SiC film 3 is set to about 50 nm, and the thickness of the SiO ₂ film 2 is set to about 90 nm. When the light emitting element 100 is a blue light emitting element, the thickness of the n-type SiC film 3 is set to about 45 nm, and the thickness of the SiO ₂ film 2 is set to about 80 nm.

  The inventor has confirmed that the reflection film formed based on the expressions (1) and (2) can obtain a reflectance of approximately 30% in calculation.

[Production method]
Next, a manufacturing method of the light emitting device 101 configured as described above will be described with reference to FIG.

In FIG. 1, first, a SiC / SOI substrate composed of a Si substrate 1, a SiO ₂ film 2 and an n-type SiC film 3 is produced. The SiC / SOI substrate is manufactured using, for example, a technique described in Non-Patent Document 1 or the following publicly known document. This known document is described in Proc. Of International Meeting for Future of Electron Devices, Kansai, pp.59-60, 2004, "Metamorphosis of Ultra-Thin Top Si Layer of SOI Substrate into 3C-SiC Using a Rapid Thermal Process", H .Iikawa et al.

  Refer to these documents for the detailed manufacturing method of the SiC / SOI substrate. Here, this will be briefly described.

For example, an SOI substrate is prepared in which a buried oxide film layer made of SiO ₂ and a Si (111) layer are sequentially formed on bulk Si (100). Then, the Si (111) layer on the surface of this SOI substrate is 1200 ° C. to 1450 ° C. in accordance with the thickness of the Si layer for several seconds to several minutes in an atmosphere of C ₃ H ₈ —H ₂ mixed gas. At temperature, it is carbonized using the Rapid Thermal Process. Thereby, a SiC film is formed on the buried oxide film layer, and as a result, a SiC / SOI substrate is manufactured.

Next, the SiC film is doped with nitrogen to form an n-type SiC film 3. Thus, the Si substrate 1, the SiO ₂ film 2, and the n-type SiC film 3 are formed. This n-type SiC film also functions as an n-type contact layer for forming an n-type side electrode 11 described later. The n-type SiC film 3 can be controlled to have a desired thickness by epitaxially growing nitrogen-doped SiC on the carbonized SiC film or by etching the SiC film. it can. When the n-type SiC film 3 is grown by epitaxial growth on the carbonized SiC film, the carbonized SiC film may be left undoped.

  Next, a large number of nanowires 8 are formed on the n-type SiC film 3 by using, for example, the RF-MBE method. Since the crystal growth method using the RF-MBE method on the SiC film of the GaN nanowire array having the MQD active layer is disclosed in Non-Patent Document 2, refer to Non-Patent Document 2 for details. Here, this will be briefly described.

  First, Ga nuclei are formed on the n-type SiC layer 3 by irradiating a Ga beam from a Ga element source at 500 ° C. for 30 seconds, for example. Thereafter, nitrogen excited by RF plasma is irradiated on the n-type SiC layer 3 for 60 seconds, for example, to form GaN dots.

  Next, the SiC / SOI substrate on which the GaN dots are formed is heated to, for example, about 890 ° C. and placed in a nitrogen atmosphere to grow GaN nanowires. In this process, the n-type GaN layer 5 is formed by doping the GaN layer with Si. Thereafter, the InGaN / GaN MQW active layer 6 and the p-type GaN layer 7 are successively grown at a low temperature of 650 ° C. In this process, the p-type GaN layer 7 is formed by doping the GaN layer with Mg. The diameter of the nanowire 8 formed in this way is, for example, 70 nm to 100 nm, and the height of the nanowire 8 is 1 μm to 1.5 μm. The interval between the nanowires 8 is about 100 nm.

Next, a transparent insulating layer 12 made of, for example, SiO ₂ is formed on the n-type SiC layer 3 so as to fill the spaces between the many nanowires 8 and cover the n-type SiC layer 3.

  Next, a part of the transparent insulating layer 12 is removed so that a predetermined region (region where the n-type side electrode 11 is to be formed) of the n-type SiC film 3 is exposed, and Ni is deposited on the exposed n-type SiC film 3. An n-type side electrode 11 made of is formed. In addition, a part of the transparent insulating layer 12 is removed so that the upper ends of many nanowires 8 are exposed, and a transparent p-type side electrode 9 made of, for example, Ni / Au is covered so as to cover the exposed upper ends of the nanowires 8. Is formed.

  Thereafter, an electrode pad 10 made of a metal such as Ti / Al is formed on the p-type transparent electrode 6.

  In this way, the light emitting device 101 is manufactured.

[Operation and effect]
Next, operations and effects of the light emitting device of the present embodiment configured and manufactured as described above will be described.

When a predetermined voltage is applied between the p-type side electrode 9 and the n-type side electrode 11, light having a predetermined wavelength is emitted from the side wall of the InGaN / GaN MQD active layer 6 of the nanowire 8 of the light emitting device 100. . The emitted light is emitted (taken out) to the outside through the transparent p-type electrode 9 and the transparent insulating layer 12. On the other hand, a part of the light emitted from the side wall of the InGaN / GaN MQD active layer 6 is directed to the Si substrate 1, and about 30% of this light is reflected by the SiC / SiO ₂ reflective film 4. For this reason, side wall light is prevented from entering the substrate 1 and being absorbed there.

  Thereby, the extraction rate of the side wall light is improved, and the influence of heat generation due to the absorption of the side wall light in the Si substrate 1 is suppressed from being applied to the electronic circuit (Si integrated circuit) integrated on the same substrate, thereby improving reliability. improves. In particular, when the substrate 1 is made of Si as in the present embodiment, since the band gap is small, the substrate 1 just absorbs light having a wavelength around the visible light, particularly in the vicinity of green light. Cheap. Therefore, when the light emitting element 100 emits green light, the effect of the present invention becomes more remarkable.

  In addition, in the light emitting device disclosed in Non-Patent Document 3 (FIG. 5), a DBR of three layers is formed on a Si substrate by complex epitaxial growth to obtain a reflectance of 30%. According to the present embodiment, it can be seen that a reflective film having a similar reflectance can be obtained with a simple configuration. Therefore, it is suitable for applications that require a reflective film provided on the substrate side to be less expensive than high performance (high reflectance), such as a lighting device.

  Further, according to the present embodiment, an inexpensive SiC / SOI substrate can be used as the substrate, so that the cost can be reduced.

In the above description, Si is used as the material for the substrate 1 and an SiO ₂ film is used as the insulating film on the substrate 1 because it is preferable from the viewpoint of cost, stability, and integration with the Si integrated circuit. However, the present invention is not limited to this. For example, an insulating film such as a SiN film can be used instead of the SiO ₂ film. The substrate 1 can be made of a material other than Si. In addition, after the light emitting device 100 is formed on the substrate 1, the substrate 1 can be removed and mounted. This is because the reflective film 4 is composed of the insulating film 2 and the SiC film 3.

In the above, a simple example using GaN and GaInN as a semiconductor constituting the nanowire 8 has been shown. For example, an overflow suppression layer for preventing leakage of carriers from the active layer 6 is formed in the vicinity of the active layer. The overflow suppression layer may be made of Al _y Ga _1-y N (0 ≦ y <1). In addition, various configurations of known light emitting diodes can be selected and applied to the configuration of the light emitting element 100.

  Moreover, although the light emitting diode which consists of the nitride semiconductor material which can light-emit three primary colors was illustrated as the light emitting element 100 above, the light emitting element 100 is comprised with the light emitting element which consists of another material according to a use. can do. Thereby, the light of the desired wavelength can be light-emitted from the light emitting element 100, and the reflective film 4 which reflects the light of this desired wavelength can be comprised. Even with such a configuration, the same effect as described above can be obtained.

(Embodiment 2)
FIG. 2 is a cross-sectional view showing the configuration of the light-emitting device according to Embodiment 2 of the present invention.

As shown in FIG. 2, in this embodiment, the light-emitting device 201 includes a plurality of (here, two) light-emitting elements 100A and 100B having different emission wavelengths, and a plurality (here, two) corresponding to these. SiC / SiO ₂ reflective films 4A and 4B are formed on one substrate 1. The other points are the same as in the first embodiment.

More specifically, one SiO ₂ film 2 is formed on one substrate 1, and the first n-type SiC film 3A and the second n-type having different thicknesses are formed on the SiO ₂ film 2. SiC film 3B is formed. The SiO ₂ film 2 and the first n-type SiC film 3A constitute a first SiC / SiO ₂ reflective film 4A, and the SiO ₂ film 2 and the second n-type SiC film 3B constitute a second SiC. / SiO ₂ reflective film 4B is formed.

  A first light emitting element 100A is formed on the first n-type SiC film 3A. The first light emitting device 100A includes a plurality of first nanowires 8A, a first n-type GaN layer 5A, a first InGaN / GaN MQD active layer 6A, and a first p-type GaN layer 7A. It consists of a p-type side electrode 9A, a first electrode pad 10A, and a first n-type side electrode 11A. Since the interrelationship between the constituent elements of the first light emitting element 100A is the same as that of the light emitting element 100 of Embodiment 1, the description thereof is omitted.

  A second light emitting element 100B is formed on the second n-type SiC film 3B. The second light emitting device 100B includes a plurality of second nanowires 8B, a second n-type GaN layer 5B, a second InGaN / GaN MQD active layer 6B, and a second p-type GaN layer 7B. It is composed of a p-type side electrode 9B, a second electrode pad 10B, and a second n-type side electrode 11B. Since the interrelationship between the components of the second light emitting element 100B is the same as that of the light emitting element 100 of Embodiment 1, the description thereof is omitted.

  The first InGaN / GaN MQD active layer 6A, the second light emitting element 100B, and the second InGaN / GaN MQD active layer 6B of the first light emitting element 100A have different emission wavelengths from each other. Correspondingly, the compositions of the materials constituting each are different. Corresponding to the difference in the emission wavelength, the first n-type GaN layer 5A and the first p-type GaN layer 7A of the first light-emitting element 100A and the second n-type of the second light-emitting element 100B are used. The GaN layer 5B and the second p-type GaN layer 7B are different from each other in the composition of the materials constituting them.

  The thickness of the first n-type SiC film 3A and the thickness of the second n-type SiC film 3B are set according to the formula (1), and are different from each other. Specifically, the thickness of the first n-type SiC film 3A is set to a thickness corresponding to the emission wavelength of the first InGaN / GaN MQD active layer 6A of the light-emitting element 100A, and the second n-type SiC film The thickness of the film 3B is set to a thickness corresponding to the emission wavelength of the second InGaN / GaN MQD active layer 6B of the light emitting element 100B.

The thickness of the SiO ₂ film 2 is calculated according to the formula (2) with respect to the emission wavelength of the first InGaN / GaN MQD active layer 6A of the light emitting device 100A, and the second InGaN of the light emitting device 100B. / GaN MQD active layer 6B is set to a thickness (selected as appropriate) between the thickness calculated according to the equation (2) with respect to the emission wavelength.

When three or more light emitting elements having different emission wavelengths are formed on one Si substrate, the thickness of the SiO ₂ film 2 is the shortest emission wavelength among the three or more light emitting elements. On the other hand, the thickness between the thickness calculated according to the formula (2) and the thickness calculated according to the formula (2) with respect to the longest emission wavelength of the three or more light emitting elements is appropriately selected. Is set. In particular, when three light emitting elements that emit three primary colors of red, blue, and green are integrated on a Si substrate, the thickness of the SiO ₂ film 2 is set to a green emission wavelength (530 nm) that is easily absorbed by the Si substrate. ) Is preferably set to a reflective thickness, that is, about 90 nm.

  According to the above configuration, even when a plurality of light emitting elements having different emission wavelengths are formed on one substrate, the n-type SiC film 3 formed between each light emitting element and the Si substrate 1 is formed on each light emitting element. By forming a predetermined thickness according to the emission wavelength, a reflective film that favorably reflects the side wall emission of each light emitting element can be formed on the Si substrate 1 side. As a result, even when a plurality of light-emitting elements having different emission wavelengths are formed on one substrate, the same effect as in Embodiment 1 can be obtained.

  The light-emitting device of the present invention is useful as a light-emitting device including a light-emitting element and a reflective film that is provided on the substrate side and reflects light emitted from the light-emitting element. Useful as.

It is sectional drawing which shows the structure of the light-emitting device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the structure of the light-emitting device which concerns on Embodiment 2 of this invention. It is sectional drawing of a light emitting diode provided with the conventional GaN nanowire. FIG. 3 shows a cross-sectional view of a light emitting diode comprising another conventional GaN nanowire. It is sectional drawing of the light emitting device provided with the conventional GaN light emitting element and a reflecting film.

Explanation of symbols

Reference Signs List 1 Si substrate 2 SiO ₂ film 3 n-type SiC film 3A first n-type SiC film 3B second n-type SiC film 4 SiC / SiO ₂ reflective film 4A first SiC / SiO ₂ reflective film 4B second SiC / SiO ₂ reflective film 5 n-type GaN layer 5A first n-type GaN layer 5B second n-type GaN layer 6 InGaN / GaN MQD active layer 6A first InGaN / GaN MQD active layer 6B second InGaN / GaN MQD active layer 7 p-type GaN layer 7A first p-type GaN layer 7B second p-type GaN layer 8 nanowire 8A first nanowire 8B second nanowire 9 p-type side electrode 9A first p-type side electrode 9B Second p-type side electrode 10 Electrode pad 10A First electrode pad 10B Second electrode pad 11 n-type side electrode 11A First n-type side electrode 11B Second n-type side electrode 12 Transparent insulating layer 12A First Transparent Edge layer 12B second transparent insulating layer 100 light-emitting element 100A first light emitting element 100B second light emitting element 101, 201 light emitting devices

Claims (6)

A substrate,
An insulating film formed on the substrate;
A first conductive type SiC film formed on the insulating film, a first conductive type semiconductor layer formed on the SiC film, a light emitting layer, and a second conductive type semiconductor layer are sequentially stacked. A plurality of columnar crystal structures formed on the SiC film; a first conductivity type side electrode formed in a region where the columnar crystal structures are not formed; and a plurality of columnar crystal structures formed on the plurality of columnar crystal structures. A transparent light-emitting element having a transparent second conductivity type side electrode,
The refractive index of the insulating film is different from the refractive index of the SiC film;
The thickness of the insulating film is a thickness obtained by dividing the wavelength of light emitted from the light emitting layer (hereinafter referred to as a light emitting wavelength) by a value that is not less than 3 times and not more than 5 times the refractive index of the insulating film,
The light emitting device, wherein the thickness of the SiC film is a thickness obtained by dividing the light emission wavelength of the light emitting layer by a numerical value of 3 to 5 times the refractive index of the SiC film. On the insulating film, two or more light emitting elements having different light emission wavelengths from each other are formed.
The thickness of the insulating film is a thickness obtained by dividing the shortest emission wavelength among the emission wavelengths of the light emitting layers of the two or more light emitting elements by a numerical value of 3 to 5 times the refractive index of the insulating film; 2. The thickness between a thickness obtained by dividing the longest emission wavelength among the emission wavelengths of the light-emitting layers of the two or more light-emitting elements by a numerical value of 3 to 5 times that of the insulating film. The light-emitting device described. A first conductivity type first SiC film formed on the insulating film; a first conductivity type first semiconductor layer formed on the first SiC film; and a first light emitting layer; A plurality of first columnar crystal structures formed by sequentially stacking first conductive type first semiconductor layers and the first columnar crystal structures on the first SiC film are not formed. The light emitting device comprising: a first first conductivity type side electrode formed in a region; and a transparent first second conductivity type electrode formed on the plurality of first columnar crystal structures. A first light emitting device as
A first conductivity type second SiC film formed on the insulating film separately from the first first conductivity type SiC film, and a first conductivity type formed on the second SiC film. A plurality of second semiconductor layers of a type, a second light-emitting layer that emits light having a wavelength different from that of the first light-emitting layer, and a second semiconductor layer of a second conductivity type are sequentially stacked. A second columnar crystal structure; a second first-conductivity-type-side electrode formed in a region where the first columnar crystal structure is not formed on the second SiC film; A second light emitting element as the light emitting element having a transparent second second conductivity type side electrode formed on the two columnar crystal structures,
The thickness of the insulating film is a thickness obtained by dividing the emission wavelength of the first light emitting element by a value that is not less than 3 times and not more than 5 times the refractive index of the insulating film, and the emission wavelength of the second light emitting element. , And a thickness divided by a numerical value not less than 3 times and not more than 5 times the refractive index of the insulating film,
The thickness of the first SiC film is a thickness obtained by dividing the emission wavelength of the first light emitting layer by a numerical value that is not less than 3 times and not more than 5 times the refractive index of the first SiC film,
The thickness of the second SiC film is a thickness obtained by dividing the emission wavelength of the second light emitting layer by a numerical value that is not less than 3 times and not more than 5 times the refractive index of the second SiC film. Item 3. A light emitting device according to Item 2. The semiconductor constituting the columnar crystal structure is a nitride semiconductor made of Ga _x In _1-x N (0 <x ≦ 1) or Al _y Ga _1-y N (0 ≦ y <1). Item 4. The light emitting device according to any one of Items 1 to 3. The light emitting device according to claim 1, wherein the substrate is made of Si, and the insulating film is made of a SiO ₂ film. The light emitting device according to claim 5, wherein the SiO ₂ film has a thickness of 40 nm to 160 nm, and the SiC film has a thickness of 20 nm to 90 nm.

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