JP4282743B2 - Gallium nitride compound semiconductor light emitting device - Google Patents

Description

  The present invention relates to a gallium nitride-based compound semiconductor light-emitting device, and more particularly to a gallium nitride-based compound semiconductor light-emitting device whose planar shape is a rectangle with different lengths of vertical and horizontal sides.

  In recent years, gallium nitride compound semiconductor materials have attracted attention as semiconductor materials for short-wavelength light emitting devices. Gallium nitride-based compound semiconductors include sapphire single crystals, various oxide substrates and III-V group compounds as substrates, and then an organic metal vapor deposition method (MOCVD method) or molecular beam epitaxy method (MBE method). ) Etc.

  In gallium nitride-based compound semiconductor light emitting devices, light from the light emitting layer is efficiently extracted to the outside using a transparent electrode such as an AuNi transparent electrode as a positive electrode and an ITO electrode. In order to improve the light extraction efficiency, various LED chips have been devised by designing the arrangement of the pad electrode on the transparent electrode and the electrode such as the negative electrode provided on the n-type layer (for example, Patent Document 1). reference).

  In addition, in the modularization of LED chips, in order to make space efficient, there is a growing need for a rectangular shape from a conventional square shape, particularly an irregular shape. The reason for this is that in the case of a square shape, a chip that emits light in the lateral direction is preferably a rectangular shape that is inefficient in mounting and can reduce the module height. However, such a rectangular LED chip has a situation in which the high light extraction efficiency of the LED chip, which has been conventionally achieved, is impaired due to the relationship between the distance between the electrodes and the electrode shape.

  For example, in Patent Document 2, in order to avoid an excessive concentration of current, an opaque diffusion electrode is formed on a transparent electrode that is originally provided for light extraction, thereby sacrificing the light emission output of the entire light emitting element. It has become.

JP 2005-19646 A JP 2004-221529 A

  An object of the present invention is to provide a gallium nitride-based compound semiconductor light-emitting device that solves the above-mentioned problems, has a high light extraction efficiency, and has a planar shape with a high light emission output and a rectangular shape with different vertical and horizontal sides. is there.

The present invention provides the following inventions.
(1) It has a gallium nitride compound semiconductor layer comprising a substrate and an n-type semiconductor layer, a light emitting layer and a p-type semiconductor layer laminated on the substrate, a negative electrode on the n-type semiconductor layer, and a transparent on the p-type semiconductor layer A gallium nitride compound semiconductor light emitting device provided with a conductive positive electrode and a positive electrode bonding pad, respectively, wherein the planar shape of the light emitting device is a rectangle with different lengths in the vertical and horizontal sides, and the positive electrode bonding pad has a rectangular long side A gallium nitride compound semiconductor, characterized in that it is within a range of ± 30% from the center, and the side surface on the rectangular long side of the gallium nitride compound semiconductor layer has a plane orientation other than the M plane in the gallium nitride single crystal lattice Light emitting element.

  (2) The gallium nitride compound semiconductor light-emitting element according to the above item 1, wherein the side surface on the long rectangular side of the gallium nitride compound semiconductor layer is an A plane in the gallium nitride single crystal lattice.

( 3 ) The gallium nitride-based compound semiconductor light-emitting element according to 1 or 2 above, wherein the length of the long side is 50 μm to 2000 μm.

( 4 ) The gallium nitride compound semiconductor light-emitting element according to the above item 3 , wherein the length of the long side is 200 μm to 600 μm.

(5) from the ratio 1:10 with a short side and the long side 4: 5 is the 1-4 wherein gallium nitride compound semiconductor light-emitting device according to any one of.

( 6 ) The gallium nitride compound semiconductor light-emitting element according to the above item 5 , wherein the ratio of the short side to the long side is from 1: 2 to 2: 3.

( 7 ) The gallium nitride compound semiconductor light-emitting element according to any one of the above items 1 to 6 , wherein unevenness is provided on a side surface of the long side of the rectangle of the gallium nitride compound semiconductor layer.

  In a gallium nitride-based compound semiconductor light-emitting device having a rectangular planar shape with different lengths in the vertical and horizontal directions, the amount of transmitted light on the side surface or the light reflected on the side surface is reduced by inclining the side surface of the semiconductor layer of the light-emitting device. The amount extracted from the other surface to the outside increases, and the light extraction efficiency is improved.

  Furthermore, by using a substrate whose main surface is a sapphire C-plane and making the side surface on the long rectangular side of the semiconductor layer have a plane orientation other than the M-plane in the gallium nitride single crystal lattice, the light extraction efficiency is further improved.

  In addition, a light-emitting element with less damage can be obtained by performing side surface processing of a gallium nitride-based compound semiconductor layer formed on a difficult-to-process substrate such as sapphire by wet etching.

  The present invention relates to a gallium nitride-based compound semiconductor light-emitting device having a rectangular planar shape with different vertical and horizontal side lengths, and has a device structure in which the side surface of the semiconductor layer is not perpendicular to the main surface of the substrate (hereinafter referred to as tilt). As a result, the light extraction efficiency has been dramatically improved. Another feature is that the long side surface is formed into a shape advantageous for light extraction by utilizing the difference in chemical etching difficulty of each crystal face of the gallium nitride compound semiconductor crystal.

Hereinafter, specific description will be given with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing an example of light travel in the gallium nitride-based compound semiconductor light emitting device of the present invention, in which the angle θ between the side surface of the semiconductor layer and the main surface of the substrate is smaller than 90 °. FIG. 2 is a cross-sectional view schematically showing an example of light travel in a gallium nitride-based compound semiconductor light-emitting device according to another embodiment of the present invention, and an angle θ between the side surface of the semiconductor layer and the main surface of the substrate is larger than 90 °. Is the case. In these figures, 204 is the main surface of the substrate (201), 205 is the side surface of the gallium nitride compound semiconductor layer (202), and the angle formed by these is θ. Reference numeral 203 denotes a path of light emitted at point A in the semiconductor layer.

  FIG. 3 is a cross-sectional view schematically showing an example of light travel in a conventional gallium nitride-based compound semiconductor light-emitting device, in which the side surface of the semiconductor layer is perpendicular to the main surface of the substrate. The numbers in the figure are the same as those in FIGS.

Although the reason why the light extraction efficiency is increased by the side surface of the semiconductor layer being inclined with respect to the main surface of the substrate as in the present invention is not clear, it can be considered as follows.
FIG. 3 shows a conventional gallium nitride-based compound semiconductor light emitting device. For example, when the light emitted at point A travels as shown by an arrow, the light incident on the side surface of the semiconductor layer is above the critical angle. Then, the light is reflected and further reflected on the upper surface of the semiconductor layer at a critical angle or more. As a result, the light extraction rate decreases.

  On the other hand, in the case of FIG. 1, the light is reflected on the side surface of the semiconductor layer, but is within the critical angle on the upper surface of the semiconductor layer, so that the light can be transmitted and extracted from the light emitting element. In FIG. 1, the inclination angle θ is smaller than 90 °. Preferably, θ is 10 ° or more and 80 ° or less, and more preferably 30 ° or more and 70 ° or less.

  In the case of FIG. 2, the incident light is within the critical angle on the side surface of the semiconductor layer, so that the light passes through the semiconductor layer.

  1 and 2, the light extraction efficiency is improved. However, when the angle θ between the side surface of the semiconductor layer and the main surface of the substrate is smaller than 90 ° as shown in FIG. The probability that light directed toward the side surface is reflected by the side surface and directed upward is higher than in the case of FIG. 2, which is preferable.

  As described above, in the present invention, the side surface of the light emitting element is used to improve the light extraction efficiency. Therefore, when the area of the light emitting elements (planar projection area) is the same, it is advantageous that the side surface area is large. In short, it is advantageous that the ratio of the peripheral length to the planar projection area of the light emitting element is large.

In the case of a rectangle, the ratio of the peripheral length to the area is larger for rectangles with opposite side lengths than for squares with equal side lengths.
Therefore, the effect of improving the light extraction efficiency by inclining the side surface of the semiconductor layer of the light emitting element with respect to the main surface of the substrate is increased when the planar shape of the light emitting element is a rectangle having different lengths of the vertical and horizontal sides, that is, a rectangle. .

  The planar shape of the light emitting element of the present invention is not particularly limited as long as it is a rectangle having different lengths in the vertical and horizontal sides, that is, a rectangle. In short, an arbitrary shape can be obtained in accordance with an electronic device or the like in which a light emitting element is incorporated.

  The ratio of the short side to the long side of the rectangle is preferably as large as possible. This is because the ratio of the peripheral length to the area increases as the ratio of the short side to the long side increases. However, if this ratio becomes too large, the light emitting element becomes too long, and as a result, it becomes difficult to dispose the positive electrode and the negative electrode, or the drive voltage increases. Therefore, the ratio of the short side to the long side of the light emitting device of the present invention is preferably 1:10 to 4: 5. More preferably, it is 1: 2 to 2: 3.

  Considering the arrangement of the positive electrode and the negative electrode, workability in manufacturing the light emitting element, current distribution, and the like, the absolute length of the long side is preferably 50 to 2000 μm, more preferably 200 to 600 μm. Moreover, as absolute length of a short side, 40-1000 micrometers is preferable, More preferably, it is 100-300 micrometers.

  As the layer structure of the gallium nitride compound semiconductor light emitting device, for example, the layer structure as shown in FIG. 4 is well known, and the layer structure of the gallium nitride compound semiconductor light emitting device of the present invention also has such a well known layer structure. Any layer structure can be used. In FIG. 4, 1 is a substrate, 2 is a buffer layer, and 3 is an n-type semiconductor layer. The n-type semiconductor layer includes an underlayer (3c), an n-type contact layer (3a), and an n-type cladding layer (3b). 4 is a light emitting layer, and 5 is a p-type semiconductor layer. The p-type semiconductor layer is composed of a p-type cladding layer (5b) and a p-type contact layer (5a). Reference numeral 10 denotes a positive electrode, which includes a translucent positive electrode (11) and a positive electrode bonding pad (12). 20 is a negative electrode.

In the present invention, the substrate 1 includes a sapphire single crystal (Al ₂ O ₃ ; A plane, C plane, M plane, R plane), spinel single crystal (MgAl ₂ O ₄ ), ZnO single crystal, LiAlO ₂ single crystal, Oxide single crystal substrates such as LiGaO ₂ single crystal, MgO single crystal or Ga ₂ O ₃ single crystal, and borides such as Si single crystal, SiC single crystal, GaAs single crystal, AlN single crystal, GaN single crystal or ZrB ₂ A known substrate material selected from non-oxide single crystal substrates such as single crystals can be used without any limitation. Among these, sapphire single crystal or SiC single crystal is preferable. Moreover, a just board | substrate may be sufficient and the board | substrate which provided the off angle may be sufficient.

When a sapphire single crystal is used for the substrate, the gallium nitride compound semiconductor single crystal grown on the substrate conforms to the sapphire single crystal (Al ₂ O ₃ ; A plane, C plane, M plane, R plane). It is known that crystals grow in the orientation.

  When a plane perpendicular to the C plane of a gallium nitride compound semiconductor single crystal grown using the C plane of a sapphire single crystal as a substrate is etched from the C-axis direction, the crystal apex is exposed on a plane other than the M plane, for example, the A plane. As a result, irregularities are easily formed, and the M-plane tends to be flat. In the present invention, since the side surface of the light emitting element is used for improving the light extraction efficiency, if the side surface is uneven, the surface area of the side surface is increased, and the light extraction efficiency is further improved. Therefore, in the light emitting device of the present invention, it is preferable that the long side of the rectangle be a surface other than the M surface, for example, the A surface.

As the gallium nitride-based compound semiconductor constituting the buffer layer, the n-type semiconductor layer, the light emitting layer, and the p-type semiconductor layer, the general formula Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y <1, Semiconductors having various compositions represented by 0 ≦ x + y ≦ 1) are known. Even in the group III nitride semiconductor constituting the buffer layer, the n-type semiconductor layer, the light emitting layer, and the p-type semiconductor layer in the present invention, the general formula Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y Semiconductors having various compositions represented by <1, 0 ≦ x + y ≦ 1) can be used without any limitation.

  Examples of methods for growing these group III nitride semiconductors include metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and hydride vapor deposition (HVPE). Desirably, the composition control is easy and the MOCVD method with mass productivity is suitable, but it is not necessarily limited to this method.

When the MOCVD method is employed as a method for growing the semiconductor layer, trimethyl gallium (TMGa) or triethyl gallium (TEGa), which is an organometallic material, is used as a group III Ga material. Trimethylaluminum (TMAl) or triethylaluminum (TEAl) is mainly used. Further, for In which is a constituent material of the light emitting layer, trimethylindium (TMI) or triethylindium (TEI) is used as a raw material. Ammonia (NH ₃ ) or hydrazine (N ₂ H ₄ ) or the like is used as a Group V N source.

Si or Ge is used as a dopant material for the n-type semiconductor layer. Monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used as the Si raw material, and germane (GeH ₄ ) or an organic germanium compound is used as the Ge raw material. In the p-type semiconductor layer, Mg is used as a dopant. For example, biscyclopentadienyl magnesium (Cp ₂ Mg) or bisethylcyclopentadienyl magnesium ((EtCp) ₂ Mg) is used as the raw material.

  In order to stack a gallium nitride compound semiconductor on the above substrate, it is disclosed in the low temperature buffer method disclosed in Japanese Patent No. 3026087 and Japanese Patent Laid-Open No. 4-29723, or in Japanese Patent Laid-Open No. 2003-243302. A lattice-mismatched crystal epitaxial growth technique called the Seeding Process (SP) method can be used.

When a lattice mismatch crystal epitaxial growth technique such as a low-temperature buffer method or an SP method is used, a gallium nitride compound semiconductor as an underlayer to be stacked thereon is undoped or low-doped GaN of about 5 × 10 ¹⁷ cm ^−3. It is desirable that The film thickness of the underlayer is desirably 1 to 20 μm, and more preferably 5 to 15 μm.

An n-type contact layer made of n-type GaN is grown on the underlying layer in contact with the negative electrode to supply current. The n-type GaN is grown while supplying an n-type dopant so as to be 1 × 10 ¹⁸ cm ⁻³ to 1 × 10 ¹⁹ cm ⁻³ . Generally, Si or Ge is selected as the n-type dopant. Regarding doping, there may be a case of uniformly doping or a structure in which a lightly doped layer and a highly doped layer are periodically repeated. In particular, the latter intermittent doping is effective in suppressing pits generated during crystal growth.

  It is preferable to provide an n-type cladding layer between the n-type contact layer and the light emitting layer. The n-type cladding layer can be formed of AlGaN, GaN, InGaN, or the like. Needless to say, it is desirable that the composition be larger than the band gap of InGaN in the active layer when using InGaN. The carrier concentration of the n-type cladding layer may be the same as that of the n-type contact layer, or may be large or small.

  The light emitting layer on the n-type cladding layer preferably has a quantum well structure. A single quantum well structure having only one well layer or a multiple quantum well structure having a plurality of well layers may be used. Among them, the multi-quantum well structure is suitable as a device structure using a gallium nitride compound semiconductor because it can have both high output and low driving voltage. In the case of a multiple quantum well structure, the entire well layer (active layer) and barrier layer together are referred to as a light emitting layer in this specification.

  The p-type semiconductor layer is usually 0.01 to 1 μm thick, and is composed of a p-type cladding layer in contact with the light emitting layer and a p-type contact layer for forming a positive electrode. The p-type cladding layer and the p-type contact layer can be combined. The p-type cladding layer is formed using GaN, AlGaN, or the like, and doped with Mg as a p-dopant.

  As the negative electrode, negative electrodes having various compositions and structures are well known, and these known negative electrodes can be used without any limitation. As a contact material for the negative electrode that contacts the n-type contact layer, in addition to Al, Ti, Ni, Au and the like, Cr, W, V, and the like can be used. Needless to say, the entire negative electrode can have a multilayer structure to provide bonding properties and the like. In particular, it is preferable to cover the outermost surface with Au in order to facilitate bonding.

As the positive electrode, positive electrodes having various compositions and structures are well known, and these known positive electrodes can be used without any limitation.
The translucent positive electrode material may include Pt, Pd, Au, Cr, Ni, Cu, Co, and the like. Further, it is known that the translucency is improved by using a structure in which a part thereof is oxidized. Moreover, there is no problem in using a conductive oxide such as ITO, IZO, IWO or the like that is common as the transparent electrode. In addition to the above materials, Rh, Ag, Al, or the like can be used as the reflective positive electrode material.

  Usually, after forming a light transmissive or reflective positive electrode, a positive electrode bonding pad constituting a bonding pad portion on a part of the surface is prepared. The positive electrode is composed of the positive electrode bonding pad. Various materials are known as materials for the positive electrode bonding pad, and these well-known materials can be used in the present invention without any particular limitation. In addition to Al, Ti, Ni, and Au used for the negative electrode material, Cr, W, and V can be used without any limitation. However, it is desirable to use a material having good adhesion to the light transmissive or reflective positive electrode used. It is necessary to make the thickness sufficiently thick so as not to damage the light transmitting or reflecting positive electrode against the stress at the time of bonding. The outermost layer is preferably made of a material having good adhesion to the bonding ball, for example, Au.

  Further, at the position of the positive electrode bonding pad, in order to extract light emitted from the lower part of the positive electrode bonding pad to the maximum from the lateral direction, it is desirable that the positive electrode bonding pad be formed near the center of the rectangular long side. Further, by disposing the positive electrode bonding pad at the center of the rectangular long side, for example, at a position of ± 30% from the center, the current diffusion path can be shortened and the driving voltage of the element can be lowered.

  A wafer in which a gallium nitride compound semiconductor, a negative electrode, and a positive electrode are stacked on a substrate is divided into light-emitting elements, and a side surface of the semiconductor layer is inclined so as to cover the positive electrode, the negative electrode, and the exposed p-type semiconductor layer. A resist pattern is formed.

  At that time, when the side surface orientation is the M plane of the gallium nitride compound semiconductor crystal, the side surface shape becomes flat. On the other hand, when the surface orientation of the side surface is a surface other than the M plane of the gallium nitride compound semiconductor crystal, the side surface shape is uneven. By setting the long side of the rectangle to a surface other than the M-plane, a light-emitting element having excellent light extraction efficiency can be obtained.

  The resist may be positive or negative. Lithography is performed according to a general procedure using a photomask having an appropriate pattern so that the boundaries of individual elements including the positive electrode and the negative electrode are exposed. Alternatively, if the resist covers the electrodes and the p-type semiconductor layer described above and individual elements can be identified, the lithograph is not necessarily required. The film thickness is preferably 0.1 μm to 20 μm. If the film thickness is thin, the film is likely to be peeled off during wet etching, and if it is thick, a problem of lithographic resolution occurs and it is difficult to recognize the lower pattern. The thickness is preferably 0.5 μm to 10 μm, more preferably 1 μm to 5 μm.

The removal of the gallium nitride compound semiconductor until it reaches the substrate is preferably performed by a laser. By selecting a laser having a wavelength shorter than the absorption edge of the gallium nitride compound semiconductor, the processing position is limited to the laser irradiation position because of the high absorption coefficient of 10 ⁵ cm ⁻¹ of the gallium nitride compound semiconductor. By appropriately selecting a laser optical system, processing with a width narrower than 10 μm is possible, and the device yield can be improved. The laser processing depth of the substrate can be arbitrarily selected within a range of 1 μm or more. However, if the processing depth is small, a shape defect in the subsequent division process tends to occur. If it is 10 μm or more, the occurrence of defects is suppressed, but if it is 20 μm or more, it is more desirable.

  Or the method by the dicer which is a mechanical method is also possible. In this case, the selection of the blade used for cutting is made suitable, and the chipping and cracking of the element can be suppressed by keeping the amount of biting into the substrate as small as possible. Although it chooses arbitrarily in the range of 1 micrometer-50 micrometers, what is necessary is just to select 1 micrometer-20 micrometers, More preferably, 1 micrometer-10 micrometers.

Next, wet etching is performed on the divided portions to form concave portions (split grooves). Wet etching is performed using orthophosphoric acid. Orthophosphoric acid is added to a beaker placed in a predetermined heating device, and heated to 100 ° C to 400 ° C. If the heating temperature is low, the etching rate is slow, and if it is too high, the mask peels off. Desirably 150 ° C. to 300 ° C., more desirably 180 ° C. to 240 ° C., a sufficient balance between etching speed and mask resistance can be obtained. By this wet etching, the side surface of the semiconductor layer inclined with respect to the main surface of the substrate is obtained.
Then, it is divided into each light emitting element.

  As a form of the light emitting element, a so-called face-up (FU) type in which light emission is extracted from the semiconductor side using a transparent positive electrode may be used, or a so-called flip chip (FC) in which light emission is extracted from the substrate side using a reflection type positive electrode. ) Good as a mold.

  The gallium nitride compound semiconductor light emitting device of the present invention can be formed into a lamp by providing a transparent cover by means well known in the art, for example. In addition, a white lamp can be produced by combining the gallium nitride compound semiconductor light emitting device of the present invention and a cover having a phosphor.

  In addition, since the lamp manufactured from the gallium nitride compound semiconductor light emitting device of the present invention has high light output and low driving voltage, electronic devices such as mobile phones, displays, and panels incorporating the lamp manufactured by this technology, Mechanical devices such as automobiles, computers, and game machines incorporating the electronic devices can be driven with low power and can achieve high characteristics. In particular, the battery-powered devices such as mobile phones, game machines, toys, and automobile parts exhibit power saving effects.

  EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to only these examples.

Example 1
A sapphire (Al ₂ O ₃ ) C-plane substrate was used as a substrate, and a buffer layer made of AlN was laminated thereon according to the method described in JP-A-2003-243302. Next, an underlayer made of undoped GaN is 6 μm on the buffer layer, and an n-type contact layer made of GaN having an average carrier concentration of 1 × 10 ¹⁹ cm ⁻³ by periodically doping Ge is 4 μm. An n-type cladding layer made of In _0.1 Ga _0.9 N with a thickness of 12.5 nm, a barrier layer made of GaN with a thickness of 16 nm and a well layer made of In _0.2 Ga _0.8 N with a thickness of 2.5 nm are alternately stacked five times. After that, a light emitting layer having a multi-quantum well structure provided with a barrier layer and a p-type contact layer made of Mg-doped (concentration 8 × 10 ¹⁹ / cm ³ ) Al _0.03 Ga _0.97 N and having a thickness of 0.15 μm are sequentially formed. A gallium nitride compound semiconductor layer on the substrate was laminated.
These laminations were performed by a normal MOCVD method.

  In the manufacture of the light emitting element, an indium tin oxide (ITO) film having a thickness of 0.25 μm was formed on the surface of the gallium nitride-based compound semiconductor layer using a sputtering apparatus to obtain a transparent electrode. Thereafter, the indium tin oxide (ITO) film portion was formed into a predetermined rectangular shape using a known lithographic technique and ITO etching technique. At that time, in the direction of each side of the rectangular shape, the vertical and horizontal directions of the light-emitting element correspond to the surface orientation of the sapphire C-plane substrate, and the long side of the rectangle is parallel to the A-plane (11-20) of the GaN crystal. The direction was aligned.

Subsequently, a resist protective film was formed by a known lithographic technique for the purpose of protecting the rectangular transparent conductive film.
Thereafter, the n-type contact layer of the boundary portion of each light emitting element and the negative electrode formation region (portion not protected by the resist) was exposed using an RIE apparatus.

  Subsequently, a negative electrode was formed on the n-type contact layer in the negative electrode formation region by a known lithographic technique. Similarly, a positive electrode bonding pad was formed on the transparent electrode by a known lithographic technique. Both the negative electrode and the positive electrode bonding pad have a structure in which Cr (400 Å) / Ti (1000 Å) / Au (10000 Å) are laminated from the semiconductor layer side, and these laminations were performed by a known vapor deposition technique.

  FIG. 5 is a schematic view showing a planar arrangement of electrodes of a light emitting element manufactured in this example. The outer shape of the light emitting element was a rectangle having a short side of 250 μm and a long side of 500 μm, the position of the positive electrode bonding pad was the center of the long side, and the distance from the negative electrode was 235 μm. The size of the positive electrode bonding pad is 95 μm in diameter.

  After the electrode manufacturing process for each light emitting element is completed, a photoresist used for lithography is applied to the wafer. Thereafter, the substrate was exposed only at the boundary portions of the individual light emitting elements by lithography again.

  Laser was used as means for removing the gallium nitride compound semiconductor layer until it reached the substrate. A laser groove having a wavelength of 266 nm, a frequency of 50 kHz, an output of 1.6 W, a processing speed of 70 mm / second and a depth of 20 μm was first formed in the X-axis direction on the substrate. The stage was rotated 90 °, and split grooves were formed in the same manner in the Y-axis direction. The width of the dividing groove was 2 μm.

  The substrate after the formation of the split grooves was immersed in a quartz beaker containing orthophosphoric acid heated to 240 ° C. using a heating apparatus for 20 minutes to perform wet etching. The etching amount of the gallium nitride compound semiconductor layer was 5.2 μm. The substrate and the gallium nitride compound semiconductor layer after the wet etching were washed with water in an ultrasonic wave, and the etching mask made of resist was removed by organic washing.

  The substrate and the gallium nitride compound semiconductor layer after the etching treatment were further thinned by polishing on the substrate side until the thickness of the substrate became 80 μm, and then separated into individual light emitting elements by a breaking device.

  When the output of the separated light emitting element was evaluated with an integrating sphere, it was 7.1 mW when 20 mA was applied. When the drive voltage was measured, the voltage when 20 mA was applied was 3.35V.

  When the side surface of the light emitting element was observed by SEM, the side surface of the gallium nitride-based compound semiconductor layer had an angle (θ) between the side surface and the main surface of the substrate as shown in FIG. °. Further, as shown in FIG. 6, the shape of the side surface of the light emitting element was substantially flat on the short side, but was uneven on the long side.

(Example 2)
A gallium nitride-based compound semiconductor light-emitting device was fabricated in the same manner as in Example 1 except that the position of the positive-electrode bonding pad was changed, and the obtained light-emitting device was evaluated in the same manner as in Example 1. The relationship between the distance and the characteristics of the light emitting element was examined.
The results are shown in FIG. From this figure, it can be seen that the light emission output gradually increases as the distance between the positive electrode bonding pad and the negative electrode is increased. On the other hand, it can be seen that the drive voltage also increases as the distance between the positive electrode bonding pad and the negative electrode is increased, and particularly when the drive voltage exceeds 250 μm, the increase width increases. Therefore, from the balance of light emission output and drive voltage, the position of the positive electrode bonding pad is preferably near the center of the long side of the light emitting element.

(Comparative Example 1)
A gallium nitride-based compound semiconductor light-emitting device was fabricated in the same manner as in Example 1 except that the orientation was aligned so that the long side of the rectangle was parallel to the M-plane (10-10) of the GaN crystal.
When the obtained light emitting device was evaluated in the same manner as in Example 1, the output when 20 mA was applied was 6.4 mW, and the drive voltage was 3.30 V. When the side surface of the light emitting element was observed by SEM, the angle (θ) between the side surface and the main surface of the substrate was 70 ° as shown in FIG. Moreover, as for the shape of the side surface of the gallium nitride-based compound semiconductor layer, irregularities were formed on the short side, but the long side was almost flat.

(Example 3)
A gallium nitride-based compound semiconductor light-emitting device was fabricated in the same manner as in Example 1 except that wet etching was not performed.
When the obtained light emitting device was evaluated in the same manner as in Example 1, the output when 20 mA was applied was 5.1 mW, and the drive voltage was 3.32 V. When the side surface of the light emitting element was observed by SEM, the side surface of the gallium nitride-based compound semiconductor layer was perpendicular to the main surface of the substrate, like the side surface of the substrate. Moreover, the shape of the side surface of the gallium nitride compound semiconductor layer was almost flat on both the short side and the long side.

  The gallium nitride-based compound semiconductor light-emitting device of the present invention has a high light emission output, and its planar shape is a rectangle with different vertical and horizontal sides, so that it can be efficiently incorporated into various electronic devices, The above utility value is extremely large.

It is sectional drawing which shows typically an example of the progress of the light in the gallium nitride type compound semiconductor light-emitting device of this invention. It is sectional drawing which shows typically an example of the progress of the light in the gallium nitride type compound semiconductor light-emitting device of another aspect of this invention. It is sectional drawing which shows typically an example of the progress of the light in the conventional gallium nitride type compound semiconductor light-emitting device. It is the figure which showed typically the general layer structure of the gallium nitride type compound semiconductor light emitting element. 3 is a schematic diagram showing a planar arrangement of electrodes of a gallium nitride-based compound semiconductor light-emitting device fabricated in Example 1. FIG. 3 is a schematic diagram illustrating a side shape of a gallium nitride-based compound semiconductor light emitting device manufactured in Example 1. FIG. It is the figure which showed the relationship between the positive electrode bonding pad-negative electrode distance and the light emitting element characteristic which were obtained in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Buffer layer 3 N-type semiconductor layer 4 Light emitting layer 5 P-type semiconductor layer 10 Positive electrode 11 Translucent positive electrode 12 Positive electrode bonding pad 20 Negative electrode 201 Substrate 202 Gallium nitride compound semiconductor layer 203 Light emitted at point A in the semiconductor layer Path of light 204 Main surface of substrate 205 Side surface of gallium nitride compound semiconductor layer

Claims (6)

A substrate and a gallium nitride compound semiconductor layer comprising a n-type semiconductor layer, a light emitting layer and a p-type semiconductor layer laminated on the substrate, a negative electrode on the n-type semiconductor layer, a transparent positive electrode on the p-type semiconductor layer, and A gallium nitride-based compound semiconductor light-emitting device provided with a positive electrode bonding pad, wherein the planar shape of the light-emitting device is a rectangle with different lengths in length and width, and the rectangular long side of the gallium nitride-based compound semiconductor layer A side surface of the gallium nitride compound semiconductor light emitting device, wherein the gallium nitride single crystal lattice is an A plane . The gallium nitride compound semiconductor light-emitting element according to claim 1, wherein the long side has a length of 50 μm to 2000 μm. The gallium nitride compound semiconductor light-emitting element according to claim 2, wherein the long side has a length of 200 μm to 600 μm. The gallium nitride compound semiconductor light emitting element according to any one of claims 1 to 3, wherein the ratio of the short side to the long side is from 1:10 to 4: 5. The gallium nitride-based compound semiconductor light-emitting device according to claim 4, wherein the ratio of the short side to the long side is 1: 2 to 2: 3. The gallium nitride compound semiconductor light-emitting element according to any one of claims 1 to 5, wherein irregularities are provided on a side surface of the long side of the rectangular side of the gallium nitride compound semiconductor layer.

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