KR100992496B1 - Light-emitting diode - Google Patents

Abstract

The light emitting diode 10 has a main light extraction surface, and includes a compound semiconductor layer 13 including semiconductor layers 130 to 135, a light emitting part 12 included in the compound semiconductor layer, and a light emitting layer included in the light emitting part. 133, a transparent substrate 14 bonded to the compound semiconductor layer, and first and second electrodes of opposite polarities formed on the main light extraction surface on the opposite side to the transparent substrate. The second electrode is formed at a portion of the exposed compound semiconductor layer by removing the semiconductor layers 132 to 134 and has a circumference surrounded by the semiconductor layer. The main light extraction surface has an outer shape having a maximum width of 0.8 mm or more.

Light emitting diode, light extraction surface, compound semiconductor layer, light emitting portion, light emitting layer, transparent substrate

Description

Light Emitting Diodes {LIGHT-EMITTING DIODE}

This application claims 35 U.S.C. 35 U.S.C. of the date of filing of U.S. Provisional Patent Application 60 / 775,359, filed February 22, 2006 and Japanese Patent Application 2006-036169, filed February 14, 2006, in accordance with § 111 (b). 35 U.S.C. Claiming Benefits Under §119 (e) (1) An application filed under § 111 (a).

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to light emitting diodes, and more particularly, to large, high brightness light emitting diodes of transparent substrate junction type.

A light emitting diode (LED) capable of emitting red, orange, yellow or yellow green visible light, wherein aluminum phosphide-gallium-indium [(Al _X Ga _{1- X} ) _Y In _{1 - Y} P (where 0 ≦ _X ≦ 1, 0 ≦ Y ≦ 1)] is known in the art for compound semiconductor LEDs. With respect to the light emitted from the light-emitting layer of this type of LED as a light emitting portion generally optically opaque and formed of a substrate material such that the mechanical gallium arsenide (GaAs) strength is not large _{(Al X Ga 1 -X) Y} In 1 - _A light emitting layer formed of _Y P (where 0 ≦ _X ≦ 1 and 0 ≦ _Y ≦ 1) is provided.

Therefore, in recent years, in order to obtain a high brightness visible LED and also to further improve the mechanical strength of the device, it is possible not only to remove the opaque substrate material for the emitted light, but also to transmit the light, and also to increase the mechanical strength of the visible light. By newly installing a support layer (transparent substrate) formed of an excellent transparent material, a technique for constructing a bonded LED has been developed (for example, Japanese Patent No. 3230638, Japanese Patent Laid-Open No. 6-302857, and Japanese Patent Publication 2002). -246640, Japanese Patent 2588849 and Japanese Patent Laid-Open No. 2001-57441.

In order to obtain a high brightness visible LED, a method of improving light extraction efficiency by using an element shape has been used. Techniques for achieving high brightness using side shapes in the configuration of devices having electrodes formed on the surface and the back of a semiconductor light emitting diode are disclosed (for example, Japanese Patent Laid-Open No. 58-34985 and US Pat. No. 6229160). Publication).

Although junction LEDs have made it possible to provide high brightness LEDs, the demand for higher brightness LEDs still persists. Many shapes have been proposed for devices configured to form electrodes on the surface and back of the light emitting diode, respectively. The element of the configuration in which two electrodes are formed on the light extraction surface is complicated in shape and is not optimized in the lateral state and the electrode arrangement.

The present invention has been made to solve the above-described problem, and relates to a light emitting diode provided on a light extraction surface having two electrodes, and an object thereof is to provide a high brightness light emitting diode exhibiting high efficiency in light extraction.

As 1st Embodiment of this invention, this invention has a main light extraction surface, Comprising: The compound semiconductor layer containing a semiconductor layer, the light emitting part contained in the said compound semiconductor layer, the light emitting layer contained in the said light emitting part, and the said compound semiconductor layer A light emitting diode comprising a transparent substrate bonded to the substrate and first and second electrodes of opposite polarities formed on the main light extraction surface on the opposite side of the transparent substrate, wherein the second electrode is exposed by removing the semiconductor layer. It is formed at a part of the semiconductor layer and surrounded by a semiconductor layer, and the main light extraction surface has an outer shape having a maximum width of 0.8 mm or more.

2nd Embodiment of this invention is related with the light emitting diode furnace of 1st Embodiment, and the said transparent substrate is a board | substrate which permeate | transmits the light radiated | emitted from the light emitting part.

A third embodiment of the present invention relates to the light emitting diode furnace of the first or second embodiment, wherein the transparent substrate is formed on the first side of the light emitting portion side, which is substantially vertical, and on the side continuous from the first side and separated from the light emitting layer. And a second side having an inclined surface.

A fourth embodiment of the present invention relates to the light emitting diode furnace of the third embodiment, wherein the inclined surface of the second side has an inclination angle of 10 ° or more and less than 20 °, and the light emitting portion is projected onto the light emitting surface and is upward of the second side surface. Has some formed in it.

A fifth embodiment of the present invention relates to a light emitting diode according to any one of the first to fourth embodiments, wherein the transparent substrate has a bottom surface on which irregularities having a height difference in the range of 0.1 µm to 10 µm are formed.

A sixth embodiment of the present invention relates to the light emitting diode of any of the first to fifth embodiments, wherein the transparent substrate is formed of GaP.

A seventh embodiment of the present invention relates to the light emitting diode furnace of the sixth embodiment, wherein the transparent substrate is formed of n-type GaP and has approximately (111) plane as its main surface.

An eighth embodiment of the present invention relates to a light emitting diode of any of the first to seventh embodiments, wherein the transparent substrate has a thickness in the range of 50 to 300 μm.

The ninth embodiment of the present invention relates to the light emitting diode of any one of the first to eighth embodiments, wherein the light emitting layer, the first electrode, and the second are provided under the condition that the light emitting diode has a light emitting surface appearance of 100% area. The electrodes have areas S _A , S ₁ , S ₂ that satisfy the relationship of 80% <S _A <90%, 10% <S ₁ <20%, and 5% <S ₂ <10%, respectively.

A tenth embodiment of the present invention relates to a light emitting diode according to any one of the first to ninth embodiments, wherein the second electrode extends in parallel with each other, and an imaginary line connecting the extreme points on each side is formed of the light emitting diode. Two or more straight lines of the same length having the extreme point on the opposite side approximately lying parallel to the side, and one connecting the extreme point of the near side of the two adjacent parallel straight lines in one of the opposite portions of the parallel straight line arbitrarily selected It consists of the above lines.

The eleventh embodiment of the present invention relates to the light emitting diode of any one of the third to tenth embodiments, wherein the second electrode is disposed outside the range of the inclined surface of the second side surface when projected onto the light emitting surface.

A twelfth embodiment of the present invention relates to a light emitting diode according to any one of the first to eleventh embodiments, wherein the distance E between the end of the second electrode and the end of the light emitting portion (μm) and the main emission wavelength ( λD) (nm) satisfies the relationship of 570 <λ _D <635 and 0.8 × λ _D -350 <E <1.6 × λ _D -750.

The thirteenth embodiment of the present invention relates to the light emitting diode of any one of the first to twelfth embodiments, wherein the first electrode is formed by combining lines having a width of 15 μm or less, and the spacing between adjacent lines ( D) (㎛) and a main emission wavelength (λD) (㎚) is 570 <λ _D <635, and satisfies the relationship _{0.4 × λ D -200 <D <} 0.8 × λ D -400.

A fourteenth embodiment of the present invention relates to a light emitting diode according to any one of the first to thirteenth embodiments, further comprising a transparent conductive film formed to cover at least a portion of the first electrode and the light extraction surface.

15th Embodiment of this invention is related with the light emitting diode in any one of 1st-14th embodiment, The said transparent conductive film is formed of ITO.

A sixteenth embodiment of the present invention relates to a light emitting diode of any one of the first to fifteenth embodiments, wherein the light emitting portion includes a GaP layer, and the second electrode is formed on the GaP layer.

A seventeenth embodiment of the present invention relates to a light emitting diode according to any one of the first to sixteenth embodiments, wherein the polarity of the first electrode is n-type, and the polarity of the second electrode is p-type.

The eighteenth embodiment of the present invention relates to the light emitting diode of any one of the first to seventeenth embodiments, wherein the compound semiconductor layer including the light emitting portion is (Al _x Ga _{1 -x} ) _Y In _{1 -Y} P (0). ≤ X ≤ 1, 0 <Y ≤ 1).

A nineteenth embodiment of the present invention relates to a light emitting diode of any one of the first to eighteenth embodiments, wherein the light emitting portion includes AlGaInP.

A twentieth embodiment of the present invention relates to a light emitting diode according to any one of the third to nineteenth embodiments, wherein the first side surface and the second side surface are formed by a dicing method.

According to the present invention, it is possible to further increase the light extraction efficiency from the light emitting portion of the LED, thereby providing a light emitting diode exhibiting high brightness.

These and other objects, specific features and advantages of the present invention will become apparent to those skilled in the art from the description given below with reference to the accompanying drawings.

1 is a plan view of a semiconductor light emitting diode according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor light emitting diode taken along line II-II of FIG. 1.

3 is a cross-sectional view of the epitaxial wafer according to Example 1 and Comparative Example 1 of the present invention.

4 is a plan view of a semiconductor light emitting diode lamp according to Example 1 of the present invention and Comparative Example 1. FIG.

5 is a cross-sectional view of the semiconductor light emitting diode lamp of FIG. 4.

6 is a plan view of a semiconductor light emitting diode according to a second embodiment of the present invention.

7 is a plan view of another semiconductor light emitting diode according to a second embodiment of the present invention.

8 is a plan view of a semiconductor light emitting diode according to Comparative Example 2. FIG.

9 is a plan view of a semiconductor light emitting diode according to a third embodiment of the present invention.

10 is a plan view of another semiconductor light emitting diode according to a third embodiment of the present invention.

11 is a plan view of another semiconductor light emitting diode according to a third embodiment of the present invention.

12 is a plan view of another semiconductor light emitting diode according to a third embodiment of the present invention.

13 is a plan view of another semiconductor light emitting diode according to a third embodiment of the present invention.

14 is a plan view of another semiconductor light emitting diode according to a third embodiment of the present invention.

15 is a plan view of another semiconductor light emitting diode according to a third embodiment of the present invention.

16 is a plan view of a semiconductor light emitting diode according to a fourth embodiment of the present invention.

17 is a cross-sectional view of the semiconductor light emitting diode taken along the line VII-VII of FIG. 16.

18 is a diagram showing a relationship between the emission wavelength (nm) and the emission distance E (μm) from the electrode.

FIG. 19 is a diagram showing a relationship between the interval D (µm) of the first electrode and the emission wavelength (nm). FIG.

The light emitting portion according to the present invention is a compound semiconductor laminate structure having a pn junction including a light emitting layer. The light emitting layer may be composed of compound semiconductors of any conductivity type of n-type and p-type. Compound semiconductor is represented by the general formula _{(Al x Ga 1 -X) Y} In 1 - is preferably represented by _Y P (0≤X≤1, 0≤Y≤1). The light emitting unit may be any structure of a double hetero, single quantum well (SQW), multi-quantum well (MQW), but the MQW structure is selected for obtaining monochromatic light emission. It is desirable to. The composition of the barrier layer constituting the quantum well (QW) and (Al _x Ga _{1- X} ) _Y In _{1 - Y} P (0 ≦ _X ≦ 1, 0 ≦ _Y ≦ 1) forming the well layer is determined by the expected wavelength. A quantum level that induces luminescence is determined to be formed in the well layer.

The so-called light emitting portion includes a light emitting layer and a cladding layer disposed on opposite sides of the light emitting layer so as to be opposite to each other for the purpose of being able to " entrapping " the carrier and the emitted light which may cause radiation recombination. To form a double hetero (DH) structure. This is most advantageous for securing high intensity light emission. The cladding layer is preferably formed of a semiconductor material having a broader forbidden band and exhibiting a higher refractive index than the compound semiconductor forming the light emitting layer. For example, capable of emitting a yellow green light wavelength of about 570㎚ (Al _{0 .4} Ga _{0 .6)} cladding layer with respect to the light-emitting layer formed by a composition formula of In _{0.5 0 .5} P is (Al _0.7 Ga _{0.3) 0.5} In _It is formed by the composition formula of _0.5 P [Y. Hosokawa et al., J. Crystal Growth, 221 (2000), 652-656. An intermediate layer may be interposed to suitably change the band discontinuity between the two layers between the light emitting layer and each clad layer. In this case, the intermediate layer is preferably formed of a semiconductor material having a forbidden bandwidth intermediate between the light emitting layer and the cladding layer.

According to the present invention, a substrate having excellent characteristics is produced by bonding a transparent substrate to a light emitting portion including a light emitting layer grown on a semiconductor substrate in order to improve brightness, heat dissipation and mechanical strength. The transparent substrate may be, for example, a group III-V compound semiconductor crystal such as potassium phosphide (GaP) or aluminum gallium arsenide (AlGaAs), a group II-VI semiconductor crystal such as zinc sulfide (ZnS) or zinc selenide (ZnSe), And group IV semiconductor crystals such as hexagonal or cubic silicon carbide (SiC).

The transparent substrate preferably has a thickness of about 50 μm or more so as to mechanically support the light emitting portion with sufficient strength. It is also desirable to have a thickness that does not exceed about 300 μm to facilitate mechanical processing after bonding. For example, in a compound semiconductor LED providing a light emitting layer formed of (Al _x Ga _{1 -X} ) _Y In _{1 - Y} P (0 ≦ _X ≦ 1, 0 ≦ _Y ≦ 1), about 50 μm or more and about 300 μm or less It is most suitable to have a transparent substrate formed of n-type GaP single crystal having a thickness.

In particular, a transparent substrate is gallium phosphide as a material which is good for transmitting light emitted from a light emitting layer formed of (Al _x Ga _{1- X} ) _Y In _{1 - Y} P (0 ≦ _X ≦ 1, 0 ≦ _Y ≦ 1) to the outside. When (GaP) is selected, the bonding to the GaP surface having the same material has an advantage of obtaining a good state such as high mechanical strength and coinciding thermal expansion coefficient.

The present invention has a great effect when the outer shape of the main light extraction surface has a maximum width of 0.8 mm or more. "Maximum width" refers to the longest part of the surface contour. For example, in the case of a rectangle or a rectangle, the diagonal becomes the maximum width. The adoption of this structure is necessary for light emitting diodes suitable for high current use, which are required in recent years. As the size increases, special device configurations from the electrode design are important in order to enable a uniform flow of current.

In addition, in the present invention, the second electrode needs to be formed at a position where the periphery thereof is surrounded by the semiconductor layer. By adopting such a structure, the distance of the second electrode from the semiconductor layer can be made uniform, and the area of the second electrode can be minimized without making the flow of current uniform and adding resistance. Since the second electrode is formed in the remaining region after removing the light emitting layer, the minimization of the area causes a high brightness effect.

In particular, the present invention preferably has a structure in which the light emitting portion includes a GaP layer and the second electrode is formed on the CaP layer. The adoption of this configuration as well as the fact that GaP is a transparent material can lead to the formation of ohmic electrodes with low contact resistance to the metal and cause the effect of resistance blocking.

The transparent substrate to be bonded is preferably mass-produced to be a substrate showing stable quality, and particularly preferably composed of GaP single crystals which are available at low cost. It is preferable that the substrate has a (100) plane or a (111) plane. In particular, it is preferable to use an n-type GaP single crystal having an approximately (111) plane as the main surface. Compared to the p-type substrate, the n-type substrate has a high transmittance for the same impurity concentration, which is preferable for obtaining high luminance. This is because the (111) plane has a property of easily forming irregularities.

The light emitting portion may be formed on a surface of a group III-V compound semiconductor single crystal substrate such as gallium arsenide (GaAs), indium phosphide (InP), or gallium phosphide (GaP), or a silicon (Si) substrate. The light emitting portion is preferably formed of a double hetero (DH) structure capable of "intrapping" the light emitted in connection with the carrier to induce radiation recombination. Thereafter, the light emitting layer is preferably formed of an SQW structure or a multi-quantum well (MQW) structure in order to obtain light emission with excellent monochromatic properties. As examples of the means for forming the constituent layer of the light emitting portion, organometallic chemical vapor deposition (MOCVD) means, molecular beam epitaxial (MBE) means and liquid phase epitaxial (LPE) means can be cited.

Between the substrate and the light emitting portion, a buffer layer that supports the function of mitigating the lattice mismatch between the material of the substrate and the constituent layers of the light emitting portion, a Bragg reflective layer that reflects the emitted light from the light emitting layer to the outside of the device, an etching used for selective etching A stop layer is interposed. Next, a contact layer for reducing the contact resistance of the ohmic electrode on the constituent layer of the light emitting part, a current diffusion layer for diffusing the device driving current to the entire plane of the light emitting part, and a current blocking layer for limiting the region through which the device driving current can pass, and the current A constriction layer or the like may be installed.

The present invention is characterized in that a first electrode and a second electrode having a different polarity from the first electrode are formed on the main light extraction surface of the light emitting diode. The "main light extraction surface" used in the present invention is the surface of the light emitting portion lying on the opposite side of the surface to which the transparent substrate is bonded.

By forming an electrode in this structure in the present invention, there is no need to apply a current to the transparent substrate to be joined. Therefore, a material having a high transmittance can be selected from various materials such as an insulator and a high resistance semiconductor, and bonding of a substrate having a high transmittance can obtain high brightness.

In addition, the present invention uses a first side of the transparent substrate which is substantially perpendicular to the light emitting surface of the light emitting layer at the portion of the side close to the light emitting layer, and a second side that is inclined with respect to the light emitting surface at the portion away from the light emitting layer. It is desirable to. The second side is continuous to the first side. The inclination is preferably directed toward the inside of the semiconductor layer. The reason why the present invention adopts such a configuration is that light emitted from the light emitting layer toward the transparent substrate side can be efficiently extracted to the outside. That is, some of the light emitted from the light emitting layer toward the transparent substrate side is reflected on the first side surface and extracted through the second side surface. Light reflected on the second side is extracted through the first side. The synergistic effect of the first side and the second side may increase the light extraction probability.

In this invention, it is preferable that a 2nd electrode is formed in the position other than the upper position (as seen by projection) of the inclined structure of a 2nd side surface. The inclination angle of the second side surface is more than 10 degrees and less than 20 degrees. It is preferable that a part of the light emitting portion is formed above the second side when projected onto the light emitting surface. In the present invention, by forming the second electrode at such a position, high brightness can be obtained and light extraction efficiency is improved through the inclined surface.

In the present invention, the second electrode extends in parallel to each other, at least two straight lines of the same length and parallel straight lines having their extreme points in which an imaginary line connecting the extreme points on each side lies approximately in parallel with the side of the chip. It is preferable that it consists of one or more lines connecting the extreme points of the adjacent side of two adjacent parallel straight lines from the arbitrary selection of the opposite side of (refer FIG. 1, FIG. 6, FIG. 7, FIG. 9). By adopting such a shape, the second electrode can cover the entire light emitting portion and minimize its inherent area. Increasing the number of parallel lines may correspond to larger chips. It is most preferable that the line connecting the end points of the parallel lines can minimize the electrode area. Since the second electrode needs to provide the pad portion necessary for the wire bonding, the line may be a curved line or a curved line in that it increases the degree of freedom in positioning the pad portion. Increasing the degree of freedom of pad position positioning results in facilitating the fabrication of chips.

In order to spread the current evenly in the light emitting portion, it is necessary to arrange the second electrode evenly with respect to the light emitting portion. If the distance between the electrode and the part furthest from the electrode of the light emitting portion is too large, the current does not diffuse to the entire light emitting portion. If the distance is too small, diffusion of current is not a problem, but the number (area) of the electrode is increased so that the light extraction area is reduced and the brightness is lowered. The distance that allows diffusion of the current from the electrode is changed by the emission wavelength. In the light emitting layer of AlGaInP (light emission wavelength: 570 nm or more and 635 nm or less), the diffusion distance of an electric current increases with wavelength. Therefore, the distance between the electrode and the part furthest from the electrode of the light emitting portion has an optimum range with respect to the light emission wavelength. With respect to the second electrode, the present invention relates to the distance between the end of the second electrode (approximately closest to the element periphery of the electrode) and the end of the light emitting part (approximately the closest part to the element periphery of the light emitting part), denoted by E (µm). And a main emission wavelength represented by λ _D (nm) is formed in a structure satisfying the relationship of 0.8 × λ _D -350 <E <1.6 × λ _D -750 with respect to the emission wavelength of 570 <λ _D <635. Do.

As shown in Fig. 18, the above-described relational expression derived by plotting the diffusion region of current through the entire light emitting portion with respect to the light emission wavelength assigned to the horizontal axis and the distance between the end of the second electrode and the end of the light emitting portion assigned to the vertical axis. Indicates that the left term represents the lower limit of the region, and the right term represents the upper limit of the region, and the range of the distance extends as the emission wavelength is increased. By adopting the above-described shape, the diffusion of the current through the entire light emitting portion not only suppresses the addition of the electrode area, but also prevents the luminance decrease due to the reduction of the light extraction area and can obtain high luminance. Moreover, the said condition that a 2nd electrode should be arrange | positioned other than the upper side of the inclined side is also satisfied.

Similarly, the first electrode has an optimum range of the current spreading distance with respect to the light emission wavelength. According to the present invention, the first electrode is formed by combining a line having a width of 15 μm or less, the space between adjacent lines is represented by D (μm), and the main emission wavelength is represented by λ _D (nm). as shown in, it is formed from a _{570 <λ D <635, 0.4} × λ D -200 <D < structure satisfying the relationship 0.8 × λ _D -400 is preferred. The above relation represents an area in which a current can be uniformly diffused in the light emitting portion. If the spacing between the first electrodes is too wide, a portion that does not allow diffusion of current occurs. If too narrow, the electrode area needs to be increased. By adopting such a structure, the diffusion of current through the entire light emitting portion can suppress the addition of the electrode area, prevent the decrease in luminance due to the reduction of the light extraction area, and obtain high brightness.

In this invention, it is preferable that the angle between a 2nd side surface and a 1st side surface exists in the range of 10 degrees or more and less than 20 degrees. By adopting such a range, it is possible to efficiently extract light reflected to the bottom of the transparent substrate to the outside.

Then, in this invention, it is preferable that the width | variety (thickness direction) of a 1st side surface exists in the range of 30 micrometers-100 micrometers. The light reflected by the bottom of the transparent substrate by having the width of the first side within this range can be efficiently returned to the light emitting surface at the portion of the first side, and can be released through the main light extraction surface, so that light emission by the light emitting diode The result is that the efficiency can be obtained successfully.

In the present invention, it is preferable to form a light emitting portion having a structure including a GaP layer, and to form a second electrode on the GaP layer. The adoption of this configuration can achieve the effect of lowering the operating voltage. By forming the second electrode on the GaP layer, good ohmic contact can be obtained and the operating voltage can be lowered.

It is preferable to form this invention with the 1st electrode of n type polarity, and the 2nd electrode of p type polarity. The adoption of this structure results in a high brightness effect. When the first electrode is formed in the p-type, the electrical resistance is high, resulting in deterioration of current spreading and deterioration of luminance. Forming the first electrode in the n-type improves current spreading and obtains high luminance.

It is preferable that this invention roughens the inclined surface of a transparent substrate. Adoption of such a structure can obtain the effect of improving the light extraction efficiency through the inclined surface. By roughening the inclined surface, total reflection on the inclined surface can be suppressed and the light extraction efficiency can be improved. Cotton may be roughened by chemical etching with a mixed solution consisting of phosphoric acid, hydrogen peroxide and water plus hydrochloric acid.

Next, it is preferable that this invention forms the unevenness | corrugation which has a height difference within the range of 0.1 micrometer-10 micrometers on the bottom face of a transparent substrate. The adoption of this structure results in the effect that light interlaced on the chip is diffusely reflected and efficiently extracted out of the chip.

It is preferable that this invention forms a 2nd side surface by the dicing method. The adoption of this production method has the effect of improving the yield. The formation of the second aspect can be obtained by a combination of methods such as wet etching, dry etching, scribing method, laser processing method, etc., but the dicing method is most preferable because of the controllability of the shape and high productivity.

It is preferable that this invention forms a 1st side surface by the dicing method. Adoption of this production method can lower the production cost. Specifically, as a result, a large number of light emitting diodes can be produced and production costs can be lowered. Adoption of such a production method can improve light extraction efficiency and obtain high brightness through the first aspect.

According to the present invention, an area of the light emitting layer represented by S _A , S ₁ , and S ₂ , an area of the first electrode, and an area of the second electrode are 80% under the condition that the light emitting surface appearance of the light emitting diode has an area of 100%. It is preferable to form the light emitting diode in a structure satisfying the relationship of <S _A <90%, 10% <S ₁ <20%, and 5% <S ₂ <10%. Adoption of such a shape can achieve high luminance because a small electrode area satisfies efficient light emission from a large light emitting area.

The present invention preferably has a transparent conductive film formed to cover the first electrode and a part of the light extraction surface. The adoption of this shape allows the transparent conductive film to facilitate the diffusion of current and to produce LED chips of low operating voltage. In addition, the present invention preferably forms a transparent conductive film of ITO. ITO exhibits low resistance and high transmittance, resulting in the effect of lowering the operating voltage without disturbing the extraction of light.

Example 1:

Example 1 specifically illustrates an example of manufacturing a light emitting diode according to the present invention.

1 and 2 are views showing a semiconductor light emitting diode manufactured in Example 1, FIG. 1 is a plan view, and FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 3 is a cross-sectional view of a laminated structure of a semiconductor epitaxial wafer used for a semiconductor light emitting diode.

The semiconductor light emitting diode 10 produced in Example 1 was a red LED having an AlGaInP light emitting portion.

Example 1 demonstrates this invention concretely, citing the case where a light emitting diode is manufactured by bonding a GaP substrate to the epitaxial laminated structure (epitaxial wafer) arrange | positioned on a GaAs substrate as an example.

The LED 10 includes an epitaxial wafer which provides a semiconductor layer 13 sequentially stacked on a semiconductor substrate 11 formed of an Si-doped n-type GaAs single crystal having a surface inclined 15 ° from the (100) plane. Made using. The semiconductor layer is formed of a Si-doped n-type GaAs buffer layer (130), Si-doped n-type multilayer (Al Ga _{0 .5 0 .5),} contact layer 131 is formed of In _{0.5 0 .5} P, Si the doped n-type _{(Al 0 .7 Ga 0 .3)} 0.5 in 0 .5 P lower cladding layer 132 formed of, an undoped 20 pairs of _{(Al 0 .2 Ga 0 .8)} 0.5 in 0. ₅ p and _{(Al 0 .7 Ga 0 .3)} 0.5 in 0 .5 light emitting layer (133), Mg-doped p-type formed of a _{p (Al 0 .7 Ga 0 .3} ) formed of in _0.5 p _{0 .5} Top clad layer 134 and p-type GaP layer 135 doped with Mg.

In Example 1, the constituent semiconductor layers 130 to 135 include trimethyl aluminum [(CH ₃ ) ₃ Al], trimethyl gallium [(CH ₃ ) ₃ Ga], and trimethyl indium [(CH ₃ ) ₃ In]. The epitaxial wafer was formed by laminating | stacking on the GaAs board | substrate 11 by the reduced-pressure organometallic chemical vapor deposition method (MOCVD method) used as a raw material of the. Biscyclopentadiethyl magnesium [bis- (C ₅ H ₅ ) ₂ Mg] was used as a raw material for Mg doping. Disilane (Si ₂ H ₆ ) was used as a raw material for Si doping. And phosphine (PH ₃ ) or arsine (AsH ₃ ) was used as a raw material of group V constituent elements. The GaP layer 135 was grown at 750 ° C, and other constituent semiconductor layers 130 to 134 forming the semiconductor layer 13 were grown at 730 ° C.

GaAs buffer layer 130 had a carrier concentration of 2 × 10 ¹⁸ cm ⁻³ and a layer thickness of 0.2 μm. Contact layer 131 _{(Al 0 .5 Ga 0 .5)} 0.5 In 0 .5 was formed to P, had a layer thickness of 2 × 10 ¹⁸ cm ^-3 and the carrier concentration of 1.5㎛. The n-clad layer 132 had a carrier concentration of 8 × 10 ¹⁷ cm ⁻³ and a layer thickness of 1 μm. The light emitting layer 133 was an undoped layer of 0.8 mu m thickness. The p-clad layer 134 had a carrier concentration of 2 × 10 ¹⁷ cm ⁻³ and a layer thickness of 1 μm. GaP layer 135 had a carrier concentration of about 3 × 10 ¹⁸ cm ⁻³ and a layer thickness of 9 μm.

The region of the p-type GaP layer 135 reaching the depth of 1 mu m from the surface was polished and mirror-finished. The surface of the p-type GaP layer 135 was given a roughness of 0.18 nm by mirror polishing. On the other hand, the n-type GaP substrate 14 attached to the mirror-finished surface of the p-type GaP layer 135 was prepared. Si was added to the GaP substrate 14 prepared for attachment until a carrier concentration of 2 × 10 ¹⁷ cm ⁻³ . A single crystal having a plane orientation of (111) was used. The GaP substrate 14 waiting for attachment had a diameter of 50 nm and a thickness of 250 μm. This GaP substrate 14 has a mirror polished surface before being bonded to the p-type GaP layer 135 and has a square mean value of 0.12 nm.

The GaP substrate 14 and the epitaxial wafer are taken into the processing apparatus and evacuated inside the apparatus until it is vacuumed. Thereafter, the surfaces of the GaP substrate 14 and the epitaxial wafer were irradiated with an accelerated Ar beam to remove surface contamination. The two components were then joined at room temperature.

Next, the GaAs substrate 11 and the GaAs buffer layer 130 were selectively removed from the bonded wafer by the A ammonia-based etchant.

In order to form the n-type ohmic electrode 15 on the surface of the contact layer 131, 0.15 mu m thick AuGe (Ge mass ratio 12%), 0.05 mu m thick Ni, and 1 mu m thick Au were formed by vacuum deposition. Was deposited. This electrode is patterned by finishing according to a common photolithography method. The n-type ohmic electrode is formed in a lattice shape measured at a width of 10 μm and at an interval of 60 μm (FIG. 1).

Next, the GaP layer 135 was exposed by selectively removing portions of the epitaxial layers 131 to 134 in the region for forming the p electrode. In order to form the p-type ohmic electrode 16 on the surface of the GaP layer, AuBe was deposited to a thickness of 0.2 µm and Au to a thickness of 1 µm by vacuum deposition. The p-type ohmic electrode 16 was formed in two stacked shapes each constituting three sides of a quadrangle having a width of 25 mu m (FIG. 1). At this time, the distance from the end of the light emitting portion to the end of the p-type ohmic electrode was 130 µm. The resulting bonded layer was then heat treated for alloying at 450 ° C. for 10 minutes to form low resistance p-type and n-type ohmic electrodes.

Thereafter, by using the vacuum vapor deposition method, Au was deposited on a portion of the n-type ohmic electrode until it had a thickness of 1 µm to form a bonding pad. In addition, the semiconductor layer was covered with a deposited SiO ₂ film until it became a thickness of 0.3 mu m and used as a protective film.

Next, a V-shaped groove was inserted into the GaP substrate 14 from the rear surface by using a dicing saw so that the angle of the inclined surface (indicated by reference numeral 20 in FIG. 2) was 15 °. Thereafter, the surface of the light emitting diode protected the resist, and the back surface 23 of the GaP substrate 14 was roughened by etching with a mixture of phosphoric acid, hydrogen peroxide and water + hydrochloric acid. The back of the GaP substrate 14 had an average square (rms) of 500 nm.

Next, the wafer was cut into chips at intervals of 1 mm using a dicing saw from the surface side. The first side 21 has a length of 80 μm and lies approximately perpendicular to the light emitting layer.

The crushed layer was removed by dicing, and the contamination was removed by etching with a mixture of sulfuric acid and hydrogen peroxide to produce a semiconductor light emitting diode (chip) 10.

Regarding the LED chip 10 manufactured as described above, as shown schematically in Figs. 4 and 5, a light emitting diode lamp 42 has been assembled. The LED lamp 42 quickly mounts the LED chip with silver (Ag) paste on the mounting substrate 45, and the n-type ohmic electrode 15 of the LED chip 10 and the n installed on the surface of the mounting substrate 45. The electrode terminal 43, the p-type ohmic electrode 16, and the p-electrode terminal 44 were wire-bonded with a gold wire 46, and then manufactured by sealing a bonding corner with a general epoxy resin 41.

When a current flows between the n-type and p-type ohmic electrodes 15 and 16 through the n-electrode terminal 43 and the p-electrode terminal 44 disposed on the surface of the mounting substrate 45, a main wavelength of 620 nm is applied. Red light having emitted. The forward voltage Vf during the passage of 400 mA of current in the forward direction reached 2.3 V, which is a magnitude reflecting the good ohmic characteristics of the ohmic electrodes 15 and 16. When the forward current is set to 400 mA, the light emission intensity is a size of 4000 mcd, which reflects the structure of the light emitting unit having high light emission efficiency and the fact that the extraction efficiency to the outside is improved by removing the fracture layer with a chip during separation of the wafer. High brightness is reached.

Comparative Example 1:

Example 1 has a chip side that includes a first side that is approximately perpendicular to the light emitting surface and a second side that is inclined with respect to the light emitting surface, while Comparative Example 1 changes the side shape and is approximately perpendicular to the light emitting surface. It had a side including only the first side. Comparative Example 1 had the same process as in Example 1 until formation of p-type and n-type ohmic electrodes, and the side was prepared by etching without inserting a V-shaped groove from the back side using a dicing saw into the GaP substrate. The chips were produced by cutting at intervals of 1 mm using a dicing saw from the surface side without cotton. The chip side was formed so as to lie approximately perpendicular to the light emitting layer. Next, the chip | tip was produced by removing the crushing layer and the contamination by dicing with the liquid mixture of a sulfuric acid and hydrogen peroxide. When the chip was evaluated in the same manner as in Example 1, the light extraction efficiency was lowered through the chip side surface and the emission intensity was only 2500 mcd.

Example 2:

The light emitting diode was manufactured according to the process of Example 1, changing the shape of a p-type ohmic electrode. The relevant shape is shown in FIG. 6. The light emitting diode thus obtained had the advantages of low resistance and high brightness as in the product of Example 1 even if one of the letters on the three sides of the square of the p-type ohmic electrode was inverted left and right as shown in FIG. In addition, the p-type ohmic electrode can have a number of different shapes and patterns. Further addition of the size of the LED chip may correspond to increasing the number of letters on the three sides of the rectangle (FIG. 7).

Comparative Example 2:

Except for arranging the p-type ohmic electrode near the end of the light emitting portion, according to the process of Example 1 (FIG. 8), the light extraction efficiency was lowered because there was no light emitting portion above the inclined surface of the GaP substrate. The emission intensity was only 3500 mcd when the product was evaluated in the same manner as in Example 1. By arranging the p-type ohmic electrode near the center, the light extraction efficiency could be increased.

Example 3:

The light emitting diode was produced according to the process of Example 1, forming the p-type ohmic electrode and the n-type ohmic electrode in the shapes shown in FIGS. 9 to 15. This product had the same advantages of low resistance and high brightness as in Example 1.

Example 4:

In Example 4 from Example 4, a light emitting diode chip having a transparent conductive film was prepared using the same substrate and epitaxial wafer. 16 and 17 show a semiconductor light emitting diode manufactured in Example 4, FIG. 16 is a plan view thereof, and FIG. 17 is a sectional view taken along the line VII-VII of FIG. 16. In order to form an n-type ohmic electrode on the surface of the contact layer, 0.15 μm thick AuGe (12% by mass of Ge) and Ni having a thickness of 0.05 μm were deposited by vacuum deposition. Patterning the resulting stack using a common photolithography method formed a circular electrode with a diameter of 30 μm. The center distance between the nearest n-type ohmic electrodes was set to 0.25 mm. A p-type ohmic electrode was then formed and alloyed by heat treatment at 450 ° C. for 10 minutes.

Next, a transparent conductive film formed of kdium tin (ITO) covering the light emitting surface of the upper clad layer and the n-type ohmic electrode was deposited to a thickness of 300 nm by a general magnetron sputtering method. The transparent conductive film has a specific resistance of 2 × 10 ⁻⁴ Ω · cm and exhibits a transmittance of 94% with respect to light of the emission wavelength.

Next, Au was deposited to a thickness of 1 탆 on a part of the transparent conductive film by a vacuum deposition method to form a bonding pad. The semiconductor layer was covered with a deposited SiO ₂ film until it became 0.3 [mu] m thick and used as a protective film. Thereafter, a light emitting diode chip was obtained in accordance with the process of Example 1.

When this light emitting diode was evaluated in the same manner as in Example 1, the transparent conductive film had the effect of uniformly diffusing the current and the effect of extracting the light of the emission wavelength with little loss. Had the same advantages.

INDUSTRIAL APPLICABILITY The present invention can provide a large sized light emitting diode which exhibits high brightness and low operating voltage, which has not been achieved until now by the electrode arrangement and the optimization of the chip shape, and has high reliability, and can be used for various display lamps.

Claims (20)

Having a main light extraction surface; A compound semiconductor layer including a semiconductor layer; A light emitting part included in the compound semiconductor layer; A light emitting layer included in the light emitting unit; A transparent substrate bonded to the compound semiconductor layer; And A light emitting diode comprising first and second electrodes of opposite polarities formed on a main light extraction surface on a side opposite to said transparent substrate: The second electrode is formed at a portion of the compound semiconductor layer exposed by removing the semiconductor layer, and the periphery of the second electrode is all surrounded by the semiconductor layer; The main light extraction surface has a light emitting diode having an outer shape having a maximum width of 0.8mm or more. The method of claim 1, The transparent substrate is a light emitting diode, characterized in that the substrate for transmitting the light emitted from the light emitting portion. The method according to claim 1 or 2, And the transparent substrate comprises a first side on the side of the vertical light emitting portion, and a second side having a slanted surface formed on the side continuous from the first side and away from the light emitting layer. The method of claim 3, wherein The inclined surface of the second side has an inclination angle of 10 ° or more and less than 20 °; A light emitting diode, wherein a part of the light emitting portion is formed above the second side when projected onto the light emitting surface. The method according to claim 1 or 2, The transparent substrate has a light emitting diode, characterized in that the bottom surface is formed with irregularities having a height difference in the range of 0.1㎛ ~ 10㎛. The method according to claim 1 or 2, The transparent substrate is a light emitting diode, characterized in that formed of GaP. The method of claim 6, The transparent substrate is formed of n-type GaP, and has a (111) plane as a main surface thereof. The method according to claim 1 or 2, The transparent substrate is a light emitting diode, characterized in that having a thickness in the range of 50 ~ 300㎛. The method according to claim 1 or 2, The light emitting layer, the first electrode, and the second electrode were 80% <S _A <90%, 10% <S ₁ <20%, and 5% <, respectively, under the condition that the light emitting diode had a light emitting surface appearance of 100% area. _A light emitting diode having an area S _A , S ₁ , S ₂ satisfying a relationship of S ₂ <10%. The method according to claim 1 or 2, At least two linear electrodes having the same length parallel to each other, and having an imaginary line connecting the extreme ends of both sides thereof parallel to the side surface of the light emitting diode; On either side of the parallel straight electrode, it is composed of one or more linear electrodes connecting the extreme points on the near side of the adjacent parallel straight electrode, All of the parallel straight electrodes are integrally connected by the connecting linear electrodes. The method of claim 3, wherein And the second electrode is disposed outside the range of the inclined surface of the second side surface when projected onto the light emitting surface. The method according to claim 1 or 2, The distance E (μm) and the main emission wavelength λ _D (nm) between the end of the second electrode and the end of the light emitting portion are 570 <λ _D <635 and 0.8 × λ _D -350 <E <1.6 × λ A light emitting diode that satisfies the relationship of _D- 750. The method according to claim 1 or 2, The first electrode is formed by combining lines having a width of 15 μm or less; The distance D between the adjacent lines (μm) and the main emission wavelength λD (nm) satisfy the relationship of 570 <λ _D <635 and 0.4 × λ _D -200 <D <0.8 × λ _D -400. A light emitting diode characterized in that. The method according to claim 1 or 2, And a transparent conductive film formed to cover at least a portion of the first electrode and the light extraction surface. The method of claim 14, The transparent conductive film is a light emitting diode, characterized in that formed of ITO. The method according to claim 1 or 2, The light emitting portion comprises a GaP layer; And the second electrode is formed on the GaP layer. The method according to claim 1 or 2, The polarity of the first electrode is n-type; The polarity of the second electrode is a p-type light emitting diode. The method according to claim 1 or 2, The compound semiconductor layer including the light emitting part is formed of a composition formula of (Al _x Ga _1-x ) _Y In _1-Y P (0 ≦ _X ≦ 1, 0 < _Y ≦ 1). The method according to claim 1 or 2, The light emitting diodes of claim 1, wherein the light emitting unit comprises AlGaInP. The method of claim 3, wherein The first side surface and the second side surface are formed by a dicing method.

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