JP2008034888A - Semiconductor light emitting device - Google Patents

Abstract

To improve light extraction efficiency.
A photonic crystal 801, a contact layer 802 of a first conductivity type provided on the photonic crystal, an electrode 807 provided on a partial region of the contact layer, and a region of another portion of the contact layer A first conductivity type cladding layer 803 provided on the active layer, an active layer 804 provided on the cladding layer, a second conductivity type cladding layer 805 provided on the active layer, A contact layer 809 of the second conductivity type provided on the electrode and an electrode 806 provided on the contact layer, and light emitted from the active layer is extracted outside through the photonic crystal.
[Selection] Figure 8

Description

  The present invention relates to a semiconductor light emitting device.

  A semiconductor light-emitting element is a device that utilizes light-emitting recombination of electrons and holes injected into a pn junction region. By changing the semiconductor material of the light emitting layer, light emission from infrared to ultraviolet can be realized.

  However, a semiconductor light emitting device has a critical angle due to a difference in refractive index between a semiconductor crystal and the atmosphere, and light absorption by a substrate capable of crystal growth. For this reason, only a few percent of the light emitted inside can be extracted outside.

  A configuration of a conventional semiconductor light emitting device is shown in FIG.

  On the p-type semiconductor substrate 1000, a multilayer reflective film 1001, a p-type contact layer 1002, a p-type cladding layer 1003, an active layer 1004 acting as a light emitting layer, an n-type cladding layer 1005, and an n-type contact layer 1006 are formed. An n-type electrode 1007 is formed on the contact layer 1002, and a p-type electrode 1008 is formed on the contact layer 1006.

  Of the light emitted from the active layer 1004, the light emitted to the n-type cladding layer 1005 side is extracted outside through the cladding layer 1005.

  On the other hand, the light emitted to the p-type cladding layer 1003 side is reflected by the multilayer reflective film 1001 and extracted outside through the n-type cladding layer 1005.

  According to this structure, the light emitted to the substrate 1000 side can be extracted outside by being reflected by the reflective film 1001.

  However, the reflectance of light that is not perpendicularly incident on the reflective film 1001 is low, the electrodes 1007 and 1008 that shield light are present on the light extraction surface, and the active layer 1004 is formed on the reflective film 1001. There were problems such as poor crystallinity and short life.

  Another conventional semiconductor light emitting device is shown in FIG. On an n-type GaP substrate 1101, an n-type InGaP buffer layer 1102, an n-type InAlP cladding layer 1103, an InGaAlP active layer 1104 acting as a light emitting layer, a p-type InAlP cladding layer 1105, a p-type GaAs contact layer 1106, and a contact layer 1106 A p-type electrode 1107 is formed thereon, and an n-type electrode 1100 is formed on the substrate 1101.

  Light emitted from the active layer 1104 is reflected by the n-electrode 1100 and the p-electrode 1107 and is extracted to the outside from the contact layer 1106 that is not shielded by the p-electrode 1107.

  However, in this structure, there is a problem that the light concentrated right below the electrode 1107 is blocked by the electrode 1107 and cannot be emitted to the outside.

  In the conventional device shown in FIG. 17, the light emitted from the active layer 1104 can be extracted outside only a few percent of the emitted light due to the refractive index difference between the crystal and air. There wasn't.

  By the way, the semiconductor light emitting element is a compound semiconductor light emitting element using a GaAs-based semiconductor material for emitting red to green light, and AlxGayln1-xyN for emitting light from the ultraviolet light region to the blue and green regions. Gallium nitride compound semiconductor light emitting devices using (0 ≦ x, y ≦ 1, x + y ≦ 1) have been put into practical use.

  However, since such a light emitting element generally has a high refractive index (GaN = 2.67, GaAs = 3.62), the critical angle (GaN = 21.9 degrees, GaAs = 16.0 degrees) is small, and light There was a problem that extraction efficiency was low.

  Further, in the GaAs system, light absorption at the substrate is large, and emitted light is absorbed by the substrate, so that light extraction efficiency is low.

  An example of a conventional gallium arsenide compound semiconductor light emitting device is shown in FIG.

  An n-GaAs buffer layer 1301, an n-1nGaAlP cladding layer 1302, an lnGaAlP active layer 1303, a p-lnGaA1P cladding layer 1304, and a p-AlGaAs current diffusion layer 1305 are sequentially grown on an n-GaAs substrate 1300. Further, a p-side electrode pad 1307 is formed on the p-AlGaAs current diffusion layer 1305, and an n-side electrode 1306 is formed on the n-GaN substrate 1300.

  In such a structure, the current flowing from the p-side electrode 1307 is spread by the p-AlGaAs current diffusion layer 1305, and a current is injected from the p-lnGaAlP cladding layer 1304 to the lnGaAlP active layer 1303 to emit light. It is taken out of the device through the p-AlGaAs current diffusion layer 1305.

  In the GaAs compound semiconductor light emitting device having such a structure, out of the light emitted from the active layer 1303, the light emitted to the substrate 1300 side is absorbed by the substrate 1300, and the light cannot be extracted outside the device. There was a problem. Specifically, 50% of the emitted light could not be extracted, which was fatal for achieving high brightness.

  As described above, there has been a problem that the light extraction efficiency is low conventionally.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a semiconductor light emitting device capable of improving light extraction efficiency and realizing high luminance.

  The semiconductor light emitting device of the present invention includes a photonics crystal, a first contact layer of a first conductivity type provided on the photonics crystal, and a first region provided on a partial region of the first contact layer. 1 electrode, a first cladding layer of a first conductivity type provided on a region of another part of the first contact layer, an active layer provided on the first cladding layer, A second conductivity type second cladding layer provided on the active layer; a second conductivity type second contact layer provided on the second cladding layer; and the second contact And a second electrode provided on the layer, wherein light emitted from the active layer is extracted outside through the photonic crystal.

  As described above, according to the present invention, the light extraction efficiency is improved and the brightness is increased by extracting light from the light-transmitting substrate, and the buffer layer is lattice-matched to the substrate. Good crystallinity and long life can be achieved.

  Furthermore, since the first and second electrodes are formed on the same surface side, by directly forming one of these electrodes on the heat sink, the luminance can be increased without saturating the light output up to a large current. Realized.

  By providing a concave region in the contact layer formed on a light-transmitting substrate, light from the light-emitting layer can be reflected off the side surface and effectively extracted outside the device, improving light extraction efficiency To do.

  Since the element shape is a polygonal column or cylinder, total reflection at the end face is reduced compared to the case of a quadrangular prism, and light inside the element can be effectively extracted from the end face to the outside. Extraction efficiency is improved.

  Alternatively, by providing a photonic crystal layer or a region having a refractive index distribution inside the semiconductor layer on one surface of the light emitting layer, light emitted from the light emitting layer is efficiently extracted outside the device. Extraction efficiency is improved and high brightness is realized.

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

(1) First Embodiment FIG. 1 shows a configuration of a semiconductor shipping element according to a first embodiment of the present invention.

  A buffer layer 101 made of In (x1) Ga (y1) A1 (1-x1-y1) P, In (x2) Ga (y2) Al (1-x2) over a light-transmitting semiconductor substrate 100 made of ZnSe. -Y2) n-type contact layer 102 made of P, n-type cladding layer 103 made of In (x3) Ga (y3) Al (1-x3-y3) P, In (x4) Ga (y4) Al (1-x4) -Active layer 104 made of y4) P, p-type cladding layer 105 made of In (x5) Ga (y5) Al (1-x5-y5) P, In (x6) Ga (y6) Al (1-x6-y6) ) A p-type contact layer 106 made of P is sequentially formed.

  Further, an n-type electrode 107 made of AuGe is formed on the n-type contact layer 102 partially removed by etching, and a p-type electrode 108 made of AuZn is formed on the P-type contact layer 106. Here, 0 = <x1, ..., x6, y1, ..., y6, x1 + y1, ... x6 + y6 <= 1.

  Here, it is desirable that the electrode material can be in ohmic contact with the contact layer and has a high light reflectance.

  The light emitted from the active layer 104 passes through the semiconductor substrate 100 and is extracted outside, and the light emitted toward the p-type electrode 108 is reflected by the electrode 108 and is also transmitted through the substrate 100 and extracted outside. . Since there are no obstacles on the light extraction surface, the light inside the element can be extracted effectively, so that the light extraction efficiency is improved.

  Further, ZnSe used for the substrate 100 has a lattice constant of 5.667 angstroms. However, the lattice constant can be controlled from 5.451 angstroms to 5.868 angstroms by changing the composition x and y of the In (x) Ga (y) Al (1-xy) P layer formed on the substrate 100. can do. Therefore, the light-emitting layer 104 lattice-matched to the ZnSe substrate 100 or the light-emitting layer 104 that is not lattice-matched but is within the critical thickness can be formed with good crystallinity.

  By adjusting the composition of the cladding layer 103 and the contact layer 106 so as to be larger than the band gap of the active layer 104, a structure without internal absorption can also be realized.

  Further, by changing the composition of the active layer 104, it is possible to realize from red to green. Furthermore, by using a single quantum well structure or a multiple quantum well structure using a quantum well layer having a thickness of several tens of angstroms, it is possible to improve the light emission efficiency and achieve a long lifetime.

  The n-type electrode 107 is formed by ion-implanting or diffusing n-type impurities into the p-type contact layer 106. Thereby, the p-type electrode 108 and the n-type electrode 107 are formed on the same plane. Thereby, the p-type electrode 108 can be directly bonded to the heat sink. Therefore, since the heat dissipation is improved, it is possible to operate up to a high current of several A without saturating the light output.

(2) Second Embodiment FIG. 2 shows a configuration of a semiconductor light emitting device according to a second embodiment of the present invention.

  On the semiconductor substrate 200 made of GaAs, the buffer layer 201 made of In (x1) Ga (y1) Al (1-x1-y1) P and the In (x2) Ga (y2) Al (1-x2-y2) P N-type contact layer 202, In (x3) Ga (y3) Al (1-x3-y3) P, n-type cladding layer 203, In (x4) Ga (y4) Al (1-x4-y4) P Active layer 204, p-type cladding layer 205 made of In (x5) Ga (y5) Al (1-x5-y5) P, p made of In (x6) Ga (y6) Al (1-x6-y6) P The mold contact layer 206 is formed sequentially.

  Further, an n-type electrode 207 made of AuGe is formed on the n-type contact layer 202 partially removed by etching, and a p-type electrode 208 made of AuZn is formed on the P-type contact layer 206.

A light extraction window 209 is formed on the substrate 200 so that light can be extracted at a position facing the p-type electrode 208 with the active layer 204 interposed therebetween.
Here, 0 = <x1, ..., x6, y1, ..., y6, x1 + y1, ..., x6 + y6 <= 1.

  Light emitted from the active layer 204 is extracted outside through the light extraction window 209. Further, the light emitted to the p-type electrode 208 side is reflected by the electrode 208 and is transmitted through the window 209 and extracted outside.

  Further, although the size of the electrode 208, if the electrode 208 is larger than the light extraction window 209, a part of the light is absorbed by the substrate 200 and cannot be sufficiently extracted. Therefore, the electrode 208 is preferably smaller than the light extraction window 209. By doing so, light emitted from the active layer 204 can be effectively extracted, so that the light output of the element increases.

  According to the present embodiment, since there is no obstacle on the light extraction surface, the internal light can be extracted effectively. Further, by adjusting the compositions of the cladding layers 203 and 205 and the contact layers 202 and 206 so as to be larger than the band gap of the active layer 204, a structure without internal absorption can be realized.

  Further, by changing the composition of the active layer 204, light emission from red to green can be realized.

  Further, by making the structure of the active layer 204 a single quantum well structure or a multiple quantum well structure using a quantum well layer having a thickness of several tens of angstroms, an improvement in light emission efficiency and a long lifetime are realized.

  The n-type electrode 207 forms a region in which n-type impurities are ion-implanted and diffused from the p-type contact layer 206, so that the p-type electrode 208 and the n-type electrode 207 are formed on the same plane. As a result, the p-type electrode 208 can be directly bonded to the heat radiating plate, so that the operation can be performed without saturating the light output up to a high current of several angstroms.

(3) Third Embodiment FIG. 3 shows the configuration of an element according to a third embodiment of the present invention.

  On a substrate 300 made of n-type GaP, an n-type buffer layer 301 made of In (x1) Ga (y1) Al (1-xl-y1) P, In (x2) Ga (y2) Al (1-x2-y2) N-type cladding layer 302 made of P), active layer 303 made of In (x3) Ga (y3) Al (1-x3-y3) P, In (x4) Ga (y4) A1 (1-x4-y4) P A p-type clad layer 304 made of In and a p-type contact layer 305 made of In (x5) Ga (x5) Al (1-x5-y5) P are sequentially formed. An n-type electrode 306 made of AuGeNi is formed on the n-type GaP substrate 300. A light extraction window 308 is formed in the n-type electrode 306. Further, a p-type electrode 307 made of AuZn is formed on the p-type contact layer 305 whose surface has been etched away in a concave shape.

  Here, xa + ya <= 1, 0 <= xa, ya <= 1, and a is 1-5.

  The light emitted from the active layer 303 goes straight as indicated by an arrow A and is extracted from the light extraction window 308 on the p-type electrode 306 side to the outside of the element. Further, the light indicated by the arrow B is reflected under the p-type electrode 307 formed on the concave surface of the contact layer 305 and is extracted to the outside from the side surface.

  In the conventional device shown in FIG. 17, the light reflected by the p-type electrode 1107 is further reflected by the n-type electrode 1100, absorbed by impurities or the like inside the crystal, converted into heat, and taken out to the outside. could not. Since such light can be effectively extracted to the outside according to the present embodiment, the light extraction efficiency is improved.

  Here, by adjusting the composition of the clad layers 302 and 304 and the contact layer 305 to be larger than the band gap of the active layer 303, a structure without internal absorption can be realized.

  Further, by changing the composition of the active layer 303, light emission from red to green can be performed.

  In addition, the active layer 303 has a single quantum well structure using a quantum well layer having a thickness of several tens of angstroms or a multiple quantum well structure, thereby realizing improvement in luminous efficiency and long life. Can do.

(4) Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to the case where ZnSe is used as the semiconductor substrate.

  On the substrate 400 made of n-type ZnSe, an n-type buffer layer 401 made of In (x1) Ga (y1) Al (1-x1-y1) P lattice-matched to the substrate 400, In (x2) Ga (y2) Al N-type cladding layer 402 made of (1-x2-y2) P, active layer 403 made of In (x3) Ga (y3) Al (1-x3-y3) P, In (x4) Ga (y4) Al (1 A p-type cladding layer 404 made of -x4-y4) P and a p-type contact layer 405 made of In (x5) Ga (y5) Al (1-x5-y5) P are sequentially formed.

  Further, an n-electrode 406 made of AuGeNi is formed on the n-type ZnSe substrate 400, and a p-type electrode 407 made of AuZn is formed on the p-type contact layer 405 partially removed by etching.

  Here, it is necessary to adjust the composition ratios x1 to x5 and y1 to y5 in the respective layers 401 to 405 within a range in which lattice matching with the n-type ZnSe substrate 400 is possible. Further, by setting the band gaps of the p-type cladding layer 404 and the n-type cladding layer 402 to be larger than the band gap of the active layer 403, the double hetero effect can be obtained more effectively.

  According to the above configuration, the surface of the p-type contact layer 405 is etched away in a concave shape, as in the third embodiment. For this reason, the light emitted from the active layer 403 is reflected under the p-type electrode 407 and can be extracted from the end face, so that the extraction efficiency is improved.

  Regarding the dimensions of the element, the conventional element is generally 300 μm long × 300 μm wide. In the present embodiment, by setting the length to 100 μm × 100 μm, light absorption inside the element can be reduced and light extraction efficiency can be improved. Specifically, the light output of the entire device is improved about twice.

  By changing the composition ratios x3 and y3 of the active layer 403, light emission from red to green can be realized. Further, by using a quantum well structure having an element thickness of about several tens of angstroms, it is possible to reduce the influence of stress caused by the ZnSe substrate and achieve a long life.

(5) Fifth Embodiment FIG. 5 shows the configuration of the fifth embodiment of the present invention.

  On a semiconductor substrate 500 made of n-type GaP, an n-type buffer layer 501 made of In (xl) Ga (yl) Al (1-x1-y1) P, In (x2) Ga (y2) Al (1-x2- y2) n-type cladding layer 502 made of P, active layer 503 made of In (x3) Ga (y3> Al (1-x3-y3) P, In (x4) Ga (y4) Al (1-x4-y4) A P-type cladding layer 504 made of P, and a P-type contact layer 505 made of In (x5) Ga (y5) Al (1-x5-y5) P are sequentially formed.

  An n-type electrode 506 made of AuGeNi is formed on the n-type GaP substrate 500, and a P-type electrode 507 made of AuZn is formed on the P-type contact layer 505.

  Here, xa + ya <1, 0 <= xa, ya <= 1, and a is 1-5.

  And as an element shape, as shown in FIG. 5, the surface is processed into an octagonal prism having an octagonal shape. As a result, the light emitted to the four corners in the case of a quadrangular prism having a square surface as in the conventional element is also formed in a shape in which the four corners are cut off, so that the external light is not totally reflected. Can be taken out.

  Here, the element shape is not limited to an octagon but may be a pentagon or more. As the number of corners increases, the light extraction efficiency improves. Furthermore, when the element shape is a cylinder having a circular surface, the light extraction efficiency is further improved.

  By adjusting the composition of the cladding layers 502 and 504 and the contact layer 505 to be larger than the band gap of the active layer 503, a structure without internal absorption is realized. Further, light emission from red to green can be realized by changing the composition of the active layer 503.

  Further, by using a single quantum well structure or a multiple quantum well structure using a quantum well layer having a thickness of several tens of angstroms, it is possible to realize an improvement in light emission efficiency and a long lifetime.

(6) Sixth Embodiment FIG. 6 shows a sixth embodiment of the present invention.

  An n-type buffer layer 601 made of In (xl) Ga (y1) Al (1-xtoyl) N, In (x2) Ga (y2) A1 (1-x2-y2) on a substrate 600 made of n-type GaN. N-type cladding layer 602 made of N, active layer 603 made of In (x3) Ga (y3) A1 (1-x3-y3) N, In (x4) Ga (y4) A1 (1-x4-y4) N A P-type cladding layer 604 made of InP and a P-type contact layer 605 made of In (x5) Ga (y5) A1 (1-x5-y5) N are sequentially formed.

  An n-type electrode 606 made of TiAu is formed on the n-type GaN substrate 600, and a P-type electrode 607 made of NiAu is formed on the P-type contact layer 605.

  Here, xa + ya <= 1, 0 <= xa, ya <= 1, and a is 1-5.

  Then, as shown in FIG. 6, the light extraction efficiency is improved by processing the element shape into an octagonal prism whose surface is an octagon. The element shape is not limited to an octagon, and may be a polygon that is a pentagon or more. Further, the light extraction efficiency is improved by using a cylindrical shape.

  By adjusting the composition of the cladding layers 602 and 604 and the contact layer 605 to be larger than the band gap of the active layer 603, a structure without internal absorption can be realized.

  Further, by changing the composition of the active layer 603, light emission from ultraviolet to red can be realized.

  Furthermore, by using a single quantum well structure or a multiple quantum well structure using a quantum well layer having a thickness of several tens of amperes, it is possible to improve the light emission efficiency and achieve a long lifetime.

(7) Seventh Embodiment By the way, so-called photonic crystals have been put into practical use in recent years. The photonic crystal is a medium in which a periodic refractive index distribution is provided, and its effect increases as it becomes two-dimensional or three-dimensional, and exhibits characteristic optical characteristics.

  The characteristics of photonic crystals are due to the existence of a band gap. Since there is no light state in the band gap, light having photon energy corresponding to the band gap cannot exist in the crystal. Therefore, light incident on the crystal from the outside is reflected. In addition, when defects are introduced into the crystal in a linear form, photons are allowed to exist there. For this reason, an optical confinement effect and a waveguide are realized.

  An example of a photonic crystal is disclosed in the following literature by Noda et al. Using a wafer bonding technique.

The Journal of the Institute of Electronics, Information and Communication Engineers, March 1999, pp. 232 to 241 FIG. As shown in FIG. 18A, an AlGaAs layer 1201 and a GaAs layer 1202 are formed on a GaAs substrate 1200.

  As shown in FIG. 18B, the GaAs layer 1202 is patterned and processed into a lattice shape.

  A substrate subjected to such processing and a substrate composed of a GaAs substrate 1210, an AlGaAs layer 1211, and a GaAs layer 1212 having the same configuration are prepared, and a lattice-shaped GaAs layer 1202 as shown in FIG. And GaAs layer 1212 are fused while being aligned so as to be orthogonal to each other.

  Then, as shown in FIG. 18D, the one substrate 1210 and the AlGaAs layer 1211 are removed with a selective etchant.

  18 (a) to 18 (d) are further repeated to form a photonic crystal having a diffraction grating composed of a GaAs-based semiconductor material and air, as shown in FIG. 18 (e). Make it. Here, every other diffraction grating parallel to each other needs to be out of phase by a half period of the emitted light.

  A seventh embodiment of the present invention using such a photonic crystal will be described with reference to FIG.

  As shown in FIG. 7A, an n-GaAs buffer layer 701, a p-GaN contact layer 712, a p-InGaAlP cladding layer 702, an InGaAlP active layer 703, n, and the like are formed on a p-GaAs substrate 700 by MOCVD. The −lnGaAlP clad layer 704 is sequentially crystal-grown.

  Apart from this, the photonic crystal 705 is manufactured through the above-described steps, and is fused on the n-lnGaAlP cladding layer 704. An n-GaAs layer 706 is formed on the photonic crystal 705.

  The p-GaAs substrate 700 and the n-GaAs buffer layer 701 are removed. Further, as shown in FIG. 7B, an n-electrode 708 is formed on the n-GaAs layer 706 and a p-type transparent electrode 709 is formed on the p-lnGaAlP layer 703. Further, a part of the p-type transparent electrode 709 is removed to form a block layer 711, and a p-electrode pad 710 is formed from the p-type transparent electrode 709 to the block layer 711.

  With this configuration, the current injected from the p-electrode pad 710 is spread by the p-type transparent electrode 709, the light emitted by being injected into the active layer 703 is reflected by the photonic crystal 705, and the light is transmitted through the p-type transparent electrode 709. It is taken out.

  The photonic crystal 709 reflects 90% or more of light. As a result, when the current value is 20 mA, an optical output of 8 mW and an emission wavelength of 630 nm are obtained. This value is about twice that of the conventional device shown in FIG. 17, and the light extraction efficiency is greatly improved.

(8) Eighth Embodiment The configuration of an element according to an eighth embodiment of the present invention will be described with reference to FIG.

  This embodiment corresponds to a GaN-based compound semiconductor light emitting device in which a photonic crystal having threading dislocations is formed on a light extraction surface.

  A GaN buffer layer (not shown), an n-type GaN layer 802, an n-type AlGaN cladding layer 803, an lnGaN active layer 804, a p-AlGaN cladding layer 805, and a p-GaN contact layer 809 are sequentially grown on the sapphire substrate 801. I am letting.

  Further, the p-AlGaN cladding layer 805, the lnGaN active layer 804, and the n-type AlGaN layer 803 are partially removed by etching to expose the surface of the n-type GaN layer 802. A p-side electrode and a bonding electrode (not necessarily transparent) 806 are formed on the p-GaN contact layer 809, and an n-side electrode 807 is further formed on the n-type GaN layer 802.

  Separately from this, a photonic crystal made of, for example, GaN is prepared on a sapphire substrate. Here, many threading dislocations exist in GaN on the sapphire substrate. Such a photonic crystal 808 and the sapphire substrate 801 are fused. In this case, since the sapphire substrate 801 is transparent, the emitted light is not absorbed by the substrate 801.

  According to such a structure, the current flown from the p-side electrode 806 is emitted by injecting current from the p-type GaN contact layer 809 to the lnGaN light-emitting layer 804, and the light is emitted outside the device through the photonic crystal 808. It is taken out.

  The photonic crystal 808 has many threading dislocations as described above. Therefore, instead of reflecting light as in the photonic crystal 706 in the seventh embodiment, the light travels along threading dislocations, and the light is efficiently extracted out of the chip. This photonic crystal 808 also functions as a filter, and light emission with a narrow monochromatic width and a high monochromaticity can be obtained.

(9) Ninth Embodiment A ninth embodiment will be described with reference to FIG. This corresponds to an example in which no photonic crystal is introduced.

  The present embodiment is a GaN-based compound semiconductor light emitting device, and includes a GaN buffer layer (not shown), an n-type GaN contact layer 902, an n-type AlGaN cladding layer 903, and an InGaN active layer 904 on an n-GaN substrate 901. , P-AlGaN cladding layer 905 and p-GaN contact layer 911 are sequentially grown, and p-GaN contact layer 911, p-AlGaN cladding layer 905, lnGaN active layer 904, n-type AlGaN cladding layer 903, and n-type GaN contact. A part of the layer 902 is removed by etching to expose the surface of the n-type GaN layer 902.

  A p-side transparent electrode 906 is formed on the p-type AlGaN layer 905, a current blocking layer 907 made of a current blocking insulating film is formed adjacent to the p-side transparent electrode 906, and on the current blocking layer 907, A p-side bonding electrode 908 connected to the p-side transparent electrode 906 is formed. Further, an N-side electrode 910 is formed on the n-type GaN contact layer 902.

  Here, after forming irregularities at the interface of the n-GaN layer 902, the n-AlGaN cladding layer 903 is grown to give a distribution in the refractive index. As a method of forming irregularities on the interface of the n-GaN layer 14, for example, the method shown in FIGS. 10A to 10D or FIGS. 11A to 11C may be used. Good.

  In the method shown in FIG. 10, first, a GaN buffer layer 2001 and an n-type GaN contact layer 2002 are sequentially formed on a sapphire substrate 2000 as shown in FIG.

  As shown in FIG. 10B, a resist is applied and patterning is performed using a photolithography method to form a resist film 2003.

  As shown in FIG. 10C, unevenness is formed on the surface of the n-type GaN contact layer 2002 using the resist film 2003 as a mask.

  Thereafter, as shown in FIG. 10D, a p-AlGaN cladding layer 2003 is formed to flatten the surface.

  Alternatively, in the method shown in FIG. 11, first, a GaN buffer layer 2101 and an n-type GaN contact layer 2102 are sequentially formed on a sapphire substrate 2100 as shown in FIG.

  As shown in FIG. 11B, for example, when the flow rate ratio of the etching gas in the reactive ion etching is set to BCl3: Cl2 = 1: 1, and the Cl2 gas ratio is increased, the n-type GaN contact layer 2102 Roughness occurs on the surface.

  Thereafter, as shown in FIG. 11C, a p-AlGaN cladding layer 2103 is formed to flatten the surface.

  According to the present embodiment, unevenness at the interface of the n-GaN layer 902 is formed, and the distribution of the refractive index with the n-AlGaN cladding layer 903 causes light to be reflected and scattered at the interface. The light extracted outside the device increases.

(10) Tenth Embodiment An element according to a tenth embodiment will be described with reference to FIG. As shown in FIG. 12A, a buffer layer, a clad layer 2201, an active layer 2202, and a clad layer 2203 (not shown) are sequentially formed on the substrate 2200, and on the surface opposite to the element formation surface of the substrate 2200. Then, a resist film 2204 is formed.

  As shown in FIG. 12B, when the resist film 2204 is heated, dripping occurs at the edge portion.

  As shown in FIG. 12C, when the resist film 2204 is used as a mask and etching is performed by an ion milling method, the edge portion of the semiconductor substrate 2200 is processed into a shape corresponding to the resist film 2204.

  As shown in FIG. 12D, a photonic crystal layer 2204 with high reflectivity is welded to the substrate 2200.

  According to this embodiment, as illustrated by arrows in FIG. 12D, light emitted from the active layer 2202 is reflected at various angles on the etched portion of the substrate 2200. The extraction efficiency is improved and the emission intensity is increased.

(11) Eleventh Embodiment By forming three light emitting elements having the same emission wavelength as the light emitting elements formed on the sapphire substrate on the photonic crystal, a light emitting element that emits light at three wavelengths is realized. Is done.

  As shown in FIG. 13, a blue light emitting element 2302 and a green light emitting element 2303 are formed on one surface of the photonic crystal layer 2300, and a red light emitting element 2301 is formed on the other surface.

  Short-wavelength light from the blue light-emitting element 2302 and the green light-emitting element 2303 passes through the photonic crystal layer 2300 so that the active layer of the red light-emitting element 2301 is not light-excited to emit light. On the other hand, a photonic crystal layer 2300 having a high reflectance is provided, and a red light emitting element 2301 that emits light having a long wavelength is fused to the back surface thereof. Thereby, blue, green, and red light are mixed and white is obtained.

  Here, the combination of the colors of the plurality of light emitting elements can be variously changed as necessary, and the mixed color changes accordingly.

(12) Twelfth Embodiment A twelfth embodiment of the present invention will be described with reference to FIG. The present embodiment is a GaN-based RC-LED (Resonance Cavity LED). On a GaN-based transparent semiconductor substrate 2400, an n-GaN buffer layer 2401, a DBR (Distributed Bragg Reflector) layer 2402 made of AlGaN / GaN and having a medium reflectivity are formed, and an InGaN-multiple quantum well structure ( MQW) active layer 2403, p-AlGaN cladding layer 2404, and p-InGaN adhesion layer 2405 are formed.

  Further, a separately prepared photonic crystal layer 2406 having a high reflectance is bonded to the clad layer 2404 through an adhesive layer 2405. Then, a p-electrode 2407 is formed on the upper surface of the photonic crystal layer 2406, and an n-electrode 2408 is formed on the upper surface of the semiconductor substrate 2400.

  If a GaN-based semiconductor material is used, it is difficult to obtain a DBR layer having a high reflectivity. Thus, by introducing the photonic crystal layer 2406, high light extraction efficiency can be realized.

  Here, the material of each layer is not limited to the above materials, and may be other GaN-based semiconductor materials, or GaAs-based semiconductor materials. However, when a GaAs-based material is used, the light emitted by GaAs is absorbed, so it is necessary to remove the substrate and fuse the light-emitting layer to a GaP substrate or the like.

  The element according to the present embodiment can also be applied to a VCSEL (Vertical Cavity Surface Emitting Laser).

  Next, a method for forming a GaN-based photonic crystal will be described with reference to FIG.

  As shown in FIG. 15A, the buffer layer 2501 and the InxAlyGa (1-xy) N (0 ≦ x, y ≦ 1) layer 2502 are formed on the GaN substrate 2500.

  As shown in FIG. 15B, the InxAlyGa (1-xy) N layer 2502 is patterned and processed into a lattice shape.

  A substrate that has been subjected to such processing and a substrate composed of a GaN substrate 2600 having the same configuration, a buffer layer 2601, and an InxAlyGa (1-xy) N layer 2602 are prepared, as shown in FIG. Thus, the lattice-like layer 2502 and the layer 2602 are fused while being aligned so as to be orthogonal to each other.

  Then, as shown in FIG. 15D, one substrate 2600 is peeled off by laser light irradiation.

  Further, as shown in FIG. 15E, the buffer layer 2601 is removed by reactive ion etching.

  The photonic crystal having a diffraction lattice is produced by further repeating the steps shown in FIGS. 15A to 15E. Here, every other diffraction grating parallel to each other needs to be out of phase by a half period of the emitted light.

  According to the seventh to twelfth embodiments described above, the photonic crystal region or the region having a predetermined refractive index distribution is provided on at least one surface of the light emitting layer of the compound semiconductor light emitting device.

  In particular, the photonic crystal acts as a highly reflective film because there is no light corresponding to the band gap. Moreover, since it has a high reflectance with respect to components other than normal incidence, the light extraction efficiency can be improved by introducing it as a reflective layer.

  Alternatively, in the GaN-based compound semiconductor light emitting device, many threading dislocations exist in the GaN layer. When a photonic crystal is manufactured using such a crystal, many threading dislocations exist in the photonic crystal fused to the substrate. For this reason, light advances along this dislocation, and light is efficiently extracted outside the device. Since the photonic crystal in this case also functions as a filter, light emission with high monochromaticity with a narrow wavelength half width can be obtained.

  In addition, by forming a light emitting element having a light emission wavelength different from that of the light emitting element formed on the sapphire substrate on the photonic crystal, a light emitting element that emits light at two wavelengths can be obtained.

  Alternatively, by forming irregularities at the interface of the semiconductor layer, there is a refractive index distribution inside the semiconductor layer, and light is reflected and scattered at this interface, so that light can be extracted more effectively outside the device. Can do.

  Distribution of the refractive index inside such a semiconductor layer may be realized by combining semiconductor layers having different refractive indexes.

  As described above, in the region having the refractive index distribution, the light extracted from the active layer is reflected more in the chip and the light is extracted on the light extraction surface side, thereby greatly improving the light extraction efficiency. It becomes possible to achieve high brightness.

  In addition, the increased luminance can reduce the injected current, which contributes to the improvement of the reliability of the element.

1 is a longitudinal sectional view showing a sectional structure of a semiconductor light emitting device according to a first embodiment of the present invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 2nd Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 3rd Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 4th Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 5th Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 6th Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 7th Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 8th Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 9th Embodiment of this invention. The longitudinal cross-sectional view which showed the method of forming an unevenness | corrugation in the surface of the GaN layer in the semiconductor light-emitting device by the said 9th Embodiment. The longitudinal cross-sectional view which showed the other method of forming an unevenness | corrugation in the surface of the GaN layer in the semiconductor light-emitting device by the said 9th Embodiment. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 10th Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 11th Embodiment of this invention. The longitudinal cross-sectional view which showed the cross-section of the semiconductor light-emitting device by the 12th Embodiment of this invention. The longitudinal cross-sectional view which shows the procedure of the manufacturing method of the photonics crystal using GaN. The longitudinal cross-sectional view which showed the cross-section of the conventional semiconductor light-emitting device. The longitudinal cross-sectional view which showed the cross-section of the other conventional semiconductor light-emitting device. The longitudinal cross-sectional view which shows the procedure of the manufacturing method of the photonics crystal using GaN. The longitudinal cross-sectional view which showed the cross-section of other conventional semiconductor light-emitting devices.

Explanation of symbols

100 ZnSe substrate 101 Buffer layer 102 made of In (x1) Ga (y1) Al (1-x1-y1) P n-type contact layer 103 made of In (x2) Ga (y2) Al (1-x2-y2) P N-type cladding layer 104 made of In (x3) Ga (y3) Al (1-x3-y3) P 104 active layer 105 In (x5) made of In (x4) Ga (y4) Al (1-x4-y4) P P-type cladding layer 106 made of Ga (y5) Al (1-x5-y5) P In-type contact layer 107 made of In (x6) Ga (y6) Al (1-x6-y6) P n-type electrode 108 p-type Electrode 200 GaAs semiconductor substrate 201 Buffer layer 202 made of In (x1) Ga (y1) Al (1-x1-y1) P 202 n-type core made of In (x2) Ga (y2) Al (1-x2-y2) P Tact layer 203 n-type cladding layer 204 made of In (x3) Ga (y3) Al (1-x3-y3) P 204 Active layer 205 In made of In (x4) Ga (y4) Al (1-x4-y4) P (X5) p-type cladding layer 206 made of Ga (y5) Al (1-x5-y5) P 206 p-type contact layer 207 made of In (x6) Ga (y6) AI (1-x6-y6) P n-type electrode 208 p-type electrode 300 n-type GaP substrate 301 buffer layer 302 made of In (x1) Ga (y1) Al (1-x1-y1) P 302 In (x3) Ga (y3) Al (1-x2-y2) P N-type cladding layer 303 active layer 304 made of In (x4) Ga (y4) Al (1-x3-y3) P 304 p-type cladding made of In (x5) Ga (y5) Al (1-x5-y5) P Layer 305 In x6) p-type contact layer 306 made of Ga (y6) AI (1-x6-y6) P n-type electrode 307 p-type electrode 308 light extraction window 400 ZnSe substrate 401 n-InGaAlP buffer layer 402 n-InGaAlP cladding layer 403 InGaAlP Active layer 404 p-InGaAlP cladding layer 405 P-InGaAlP contact layer 406 n-type electrode 407 p-type electrode 500 Substrate 501 made of n-type GaP n made of In (x1) Ga (y1) Al (1-x1-y1) P N-type cladding layer 503 made of In (x2) Ga (y2) Al (1-x2-y2) P Active layer 504 made of In (x3) Ga (y3) Al (1-x3-y3) P P-type cladding layer 505 I made of In (x4) Ga (y4) Al (1-x4-y4) P (X5) p-type contact layer 506 made of Ga (y5) Al (1-x5-y5) P n-type electrode 507 made of AuGeNi p-type electrode made of AuZn 600 substrate 601 made of n-type GaN In (xl) Ga ( yl) n-type buffer layer 602 made of Al (1-xl-y1) N n-type cladding layer 603 made of In (x2) Ga (y2) A1 (1-x2-y2) N 603 In (x3) Ga (y3) Active layer 604 made of A1 (1-x3-y3) N In-type cladding layer 605 In (x5) Ga (y5) A1 (1- (In (x4) Ga (y4) A1 (1-x4-y4) N) p-type contact layer 606 made of x5-y5> N n-type electrode 607 made of TiAu p-type electrode 700 made of NiAu p-GaAs substrate 701 p-GaN buffer layer 702 p-ln aAlP cladding layer 703 InAlGaP active layer 704 n-InGaA1P cladding layer 705 Photonic crystal layer 706 n-GaAs layer 708 N electrode 709 p transparent electrode 710 p electrode pad 711 Block layer 712 p-GaN contact layer 801 Sapphire substrate 802 n-GaN contact Layer 803 n-AlGaN layer 804 InGaN active layer 805 p-A1 GaN cladding layer 806 p-electrode pad 807 N-electrode 808 photonics crystal layer 809 p-GaN contact layer 901 n-GaN substrate 902 n-GaN contact layer 903 n-AlGaN cladding layer 904 InGaN active layer 905 p-AlGaN cladding layer 906 p transparent electrode 908 p bonding electrode pad 909 Refractive index distribution layer 910 with unevenness formed n electrode 911 p GaN contact layer 2000 sapphire substrate 2001 GaN buffer layer 2001
2002 n-type GaN contact layer 2003 resist film 2100 sapphire substrate 2101 GaN buffer layer 2102 n-type GaN contact layer 2103 p-AlGaN cladding layer 2200 substrate 2201 cladding layer 2202 active layer 2203 cladding layer 2204 resist film 2300 photonics crystal layer 2301 red light emitting element 2302 Blue light emitting element 2303 Green light emitting element 2400 Semiconductor substrate 2401 n-GaN buffer layer 2402 DBR layer 2403 InGaN-multi-quantum well structure (MQW) active layer 2404 p-AlGaN cladding layer 2404
2405 p-InGaN adhesion layer 2406 photonic crystal layer 2407 p-electrode 2408 n-electrode 2500 GaN substrate 2501 buffer layer 2502 InxAlyGa (1-xy) N (0 ≦ x, y, z ≦ 1) layer 2600 GaN substrate 2601 buffer layer 2602 InxAlyGa (1-xy) N layer

Claims (2)

Photonics crystals,
A first contact layer of a first conductivity type provided on the photonic crystal;
A first electrode provided on a partial region of the first contact layer;
A first cladding layer of a first conductivity type provided on a region of another part of the first contact layer;
An active layer provided on the first cladding layer;
A second conductivity type second cladding layer provided on the active layer;
A second contact layer of a second conductivity type provided on the second cladding layer;
A second electrode provided on the second contact layer;
With
A semiconductor light-emitting element, wherein light emitted from the active layer is extracted outside through the photonic crystal. A transparent substrate provided between the photonic crystal and the first contact layer;
2. The semiconductor light emitting device according to claim 1, wherein light emitted from the active layer is extracted outside through the substrate and the photonic crystal.

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