JP2004006582A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device which can be operated with a higher drive voltage and a lower drive current. <P>SOLUTION: A plurality of LEDs 1 are formed in two dimensions on an insulated substrate 10 such as sapphire with the monolithic formation process and these LEDs are connected in series to form an LED array. Two sets of LED arrays are connected in the reverse polarities to the electrode 32. An air bridge wiring 28 is formed between the LEDs 1 and between the LED 1 and electrode 32. Many LEDs 1 are formed by allocating LED arrays in zig-zag in order to obtain a higher drive voltage and a lower drive current. Since two LED arrays are connected in the reverse polarities, an AC power supply may be used as the power source. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light emitting device in which a plurality of light emitting elements are formed on a substrate.
[0002]
[Prior art]
When a light emitting means such as a light emitting element (LED) is used for a display purpose or the like, the use conditions are a driving voltage of about 1 to 4 V and a driving current of about 20 mA. By the way, with the development of short-wavelength LEDs using GaN-based compound semiconductors in recent years, and the realization of solid-state light sources such as full-color and white, it has been studied to gradually apply LEDs to lighting applications. When an LED is applied to a lighting application, a situation may arise in which the LED is used under conditions different from the above-described use conditions of a drive voltage of 1 to 4 V and a drive current of 20 mA. For this reason, a scheme has been devised in which a large current flows through the LED to increase the light emission output. In order to allow a large current to flow, it is necessary to increase the pn junction area of the LED and reduce the current density.
[0003]
[Problems to be solved by the invention]
When an LED is used as a light source for illumination, it is convenient to use an alternating current as a power supply and to use it at a driving voltage of 100 V or more. If the same power is applied to obtain the same light emission output, applying a high voltage while maintaining a low current value can reduce power loss. However, in the conventional LED, the driving voltage cannot always be sufficiently increased.
[0004]
The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to provide a light-emitting device that can operate at a high driving voltage.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is characterized in that a plurality of light emitting elements are formed on an insulating substrate, and the plurality of light emitting elements are monolithically connected in series.
[0006]
Here, it is preferable that the plurality of light emitting elements are two-dimensionally arranged on the substrate.
[0007]
Further, it is preferable that the plurality of light emitting elements are divided into two sets and are connected in parallel to two electrodes so as to have opposite polarities.
[0008]
The connection between the plurality of light emitting elements is preferably an air bridge wiring.
[0009]
The electrical separation between the plurality of light emitting elements is preferably performed by sapphire used as the substrate.
[0010]
Further, the plurality of light emitting elements are divided into two sets each having the same number, the light emitting element arrays of each set are arranged in a zigzag shape, and the two light emitting element arrays are provided with two electrodes having opposite polarities. It is also preferable that they are connected in parallel, and the two sets of light emitting element arrays can be arranged alternately.
[0011]
Preferably, the light emitting element and the electrode have a substantially square or triangular planar shape.
[0012]
Further, it is preferable that the plurality of light emitting elements and the electrodes are arranged so that the overall shape is substantially square.
[0013]
In the present invention, the electrode may be an AC power supply electrode.
[0014]
Further, it is preferable that the two sets of light emitting element arrays have a common n-electrode.
[0015]
As described above, in the present invention, a plurality of light-emitting elements are formed monolithically, that is, on the same substrate, and these elements are connected in series, thereby enabling a high driving voltage. DC driving is possible by connecting a plurality of light emitting elements in one direction. However, the plurality of light emitting elements are divided into two sets, and each set of light emitting elements (light emitting element array) is connected to an electrode so that the polarities thereof are opposite to each other. The connection enables AC driving. The number of each set may be the same or different.
[0016]
Although there are various methods for two-dimensionally arranging a plurality of light emitting elements, it is desirable to reduce the area occupied by the substrate as much as possible. For example, by arranging two light emitting element arrays in a zigzag shape, that is, arranging a plurality of light emitting elements on a bent straight line, and arranging the respective light emitting element arrays alternately, a large number of light emitting elements can be effectively used by utilizing the substrate area. A light-emitting element can be connected. By alternately arranging the two sets of light emitting element arrays, a crossing portion of the wiring may occur. However, by connecting the light emitting elements with an air bridge wiring, a short circuit at the crossing portion can be effectively prevented. The shapes of the light emitting element and the electrode are arbitrary. For example, when the planar shape is formed to be substantially square, the overall shape becomes substantially square, and a standard mounting structure can be used. Even when the light emitting element and the electrode are formed in a shape other than a square, for example, a triangle, a standard mount structure can be used similarly by combining these triangles to form a substantially square as a whole.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 shows a basic configuration of an LED 1 as a GaN-based compound semiconductor light emitting device in the present embodiment. In the LED 1, a GaN layer 12, a Si-doped n-type GaN layer 14, an InGaN light-emitting layer 16, an AlGaN layer 18, and a p-type GaN layer 20 are sequentially stacked on a substrate 10, and the p-type electrode 22 is in contact with the p-type GaN layer 20. , An n-electrode 24 is formed in contact with the n-type GaN layer 14.
[0019]
The LED shown in FIG. 1 is manufactured by the following process. That is, first, a sapphire c-plane substrate is heat-treated at 1100 ° C. for 10 minutes in a hydrogen atmosphere by an MOCVD apparatus. Then, the temperature is lowered to 500 ° C., and a silane gas and an ammonia gas are supplied for 100 seconds to form a discontinuous SiN film on the substrate 10. This process is for reducing the dislocation density in the device, and the drawing does not show the SiN film. Next, trimethylgallium and ammonia gas are supplied at the same temperature to grow a GaN layer to a thickness of 20 nm. The temperature is raised to 1050 ° C., and trimethylgallium and ammonia gas are supplied again to grow the undoped GaN (u-GaN) layer 12 and the Si-doped n-type GaN layer 14 to a thickness of 2 μm each. Thereafter, the temperature is lowered to about 700 ° C., and the InGaN light emitting layer 16 is grown to a thickness of 2 nm. The target composition is x = 0.15, that is, In _0.15 Ga _0.85 N. After the light emitting layer 16 is grown, the temperature is raised to 1000 ° C. to grow the AlGaN hole injection layer 18 and further to grow the p-type GaN layer 20.
[0020]
After the growth of the p-type GaN layer 20, the wafer is taken out from the MOCVD apparatus, and a 10 nm thick Ni and 10 nm thick Au are sequentially formed on the surface of the grown layer by vacuum evaporation. By performing the heat treatment at 520 ° C. in a nitrogen gas atmosphere containing 5% oxygen, the metal film becomes the p-type transparent electrode 22. After forming the transparent electrode, a photoresist is applied to the entire surface, and etching for forming an n-type electrode is performed using the photoresist as a mask. The etching depth is, for example, about 600 nm. A 5 nm thick Ti and 5 nm thick Al are formed on the n-type GaN layer 14 exposed by the etching, and heat-treated at 450 ° C. for 30 minutes in a nitrogen gas atmosphere to form an n-type electrode 24. Finally, the back surface of the substrate 10 is polished to 100 μm, and chips are cut out and mounted, whereby the LED 1 is obtained.
[0021]
In FIG. 1, one LED 1 is formed on a substrate 10, but in the present embodiment, a plurality of LEDs 1 are formed on the substrate 10 in a monolithic and two-dimensional array, and the LEDs are connected to form a light emitting device. (Chip).
[0022]
FIG. 2 shows an equivalent circuit diagram of the light emitting device. In FIG. 2, the light emitting element groups formed in a two-dimensional array are divided into two sets each having the same number (four in the figure), each set of LEDs 1 is connected in series, and two sets of LED columns are connected to electrodes (drive electrodes). ) Are connected in parallel so that they have opposite polarities. By connecting the LED strings in series in this manner, the LED 1 can be driven at a high voltage obtained by adding the respective drive voltages. In addition, since each LED string is connected in parallel to the electrodes so that their polarities are opposite to each other, even when an AC power supply is used, one of the LED strings always emits light during each cycle of the power supply. Therefore, efficient light emission can be performed.
[0023]
FIG. 3 is a partial plan view of a plurality of LEDs formed monolithically on the substrate 10. FIG. 4 is a sectional view taken along line IV-IV of FIG. 3, a p-electrode 22 and an n-electrode 24 are formed on the upper surface of the LED 1 as shown in FIG. The p-electrode 22 and the n-electrode 24 of the adjacent LED 1 are connected by an air bridge wiring 28, and a plurality of LEDs 1 are connected in series.
[0024]
In FIG. 4, each LED 1 is simply shown for convenience of explanation. That is, only the n-GaN layer 14, the p-GaN layer 20, the p-electrode 22, and the n-electrode 24 are shown. Needless to say, the InGaN light emitting layer 16 and the like actually exist as shown in FIG. The air bridge wiring 28 connects the p-electrode 22 to the n-electrode 24 via the air. This eliminates the need to dispose the electrodes along the etching grooves, as compared with a method in which an insulating film is applied to the element surface, electrodes are formed thereon, and the p-electrode 22 and the n-electrode 24 are electrically connected. Therefore, it is possible to avoid a problem that the LED 1 is deteriorated due to thermal cutoff of the wiring and elements constituting the insulating material from the insulating film to the n-layer and the p-layer due to thermal diffusion. The air bridge wiring 28 is used not only between the LEDs 1 but also between the LEDs 1 and electrodes (not shown).
[0025]
Further, as shown in FIG. 4, each LED 1 needs to be independent of each other and electrically insulated. For this reason, each LED 1 is configured to be separated on the sapphire substrate 10. Since sapphire itself is an insulator, each LED 1 can be electrically isolated. As described above, by using the sapphire substrate 10 as a resistor for electrically separating the LEDs, the electrical separation of the LEDs can be easily and reliably performed.
[0026]
The light emitting element may be an MIS in addition to an LED having a pn junction.
[0027]
FIG. 5 shows another equivalent circuit diagram of the light emitting device. In the figure, 20 LEDs 1 are connected in series to form one LED array, and two LED arrays (40 LEDs in total) are connected in parallel to a power supply. The driving voltage of LED1 is set to 5V, and the driving voltage of each LED array is 100V. The two LED arrays are connected in parallel to the power supply so as to have opposite polarities as in FIG. 2, and one of the LED arrays always emits light regardless of the polarity of the power supply.
[0028]
FIG. 6 specifically shows a two-dimensional array. This corresponds to the equivalent circuit diagram of FIG. In the figure, a total of 40 LEDs 1 are formed on a sapphire substrate 10, each of which is divided into two sets of 20 and connected in series by an air bridge wiring 28 to form two LED arrays. More specifically, the LEDs 1 are all the same square and of the same size, and one LED array is arranged on a straight line with 6, 7, and 7 from the top, respectively. ) And the second row (seven) are formed in opposite directions, and the second and third rows are also formed in opposite directions. The first and second rows and the second and third rows are spaced apart from each other. This is because the rows of the other LED array are inserted alternately as described later. The rightmost LED1 in the first column and the rightmost LED1 in the second column are connected by an air bridge wiring 28. The leftmost LED1 in the second column and the leftmost LED1 in the third column are also connected by the air bridge wiring 28 to form a zigzag arrangement. The leftmost LED1 in the first column is connected to an electrode (pad) 32 formed on the upper left of the substrate 10 by an air bridge wiring 28, and the rightmost LED1 in the third column is formed on the lower right of the substrate 10. The electrode (pad) 32 is connected to the air bridge wiring 28. The two electrodes (pads) 32 are also the same square as the LED 1. The other LED array is formed so as to be staggered in the gap between the one LED array. That is, the other LED array is arranged on the straight line with 7, 7, and 6 from the top, respectively, and the first column from the top is formed between the first and second columns of one LED array. The second column is formed between the second and third columns of one LED array, and the third column is formed below the third column of one LED array. The first and second columns and the second and third columns of the other LED array are also formed to be in opposite directions, and the rightmost LED 1 of the first column is the second column. The leftmost LED1 in the second row is connected to the rightmost LED1 via the airbridge wiring 28, and the leftmost LED1 in the third row is connected to the leftmost LED1 via the airbridge wiring 28 in a zigzag shape. The leftmost LED in the first column of the other LED array is connected to an electrode 32 formed on the upper left of the substrate 10 by an air bridge wiring 28, and the rightmost LED1 in the third column is formed on the lower right of the substrate 10. The electrode 32 is connected by an air bridge wiring 28. The polarities of the one LED array and the other LED array with respect to the electrodes 32 are opposite to each other. The overall shape of the light emitting device (chip) is rectangular. It should also be noted that the two electrodes 32 to which power is supplied are formed apart from each other at diagonal positions of a rectangle.
[0029]
FIG. 7 shows the circuit diagram of FIG. Each LED array is connected in series while bending in a zigzag manner, and it will be apparent that the two LED arrays are formed with each zigzag row between each other. With such an arrangement, a large number of LEDs 1 can be arranged on the small substrate 10. Since only two electrodes 32 are required for 40 LEDs 1, the use efficiency of the substrate 10 can be improved in this respect as well. Further, when the LEDs 1 are individually formed in order to separate the LEDs 1, it is necessary to cut and separate the wafer. On the other hand, in the present embodiment, the separation of the LEDs 1 can be performed by etching. Can be narrowed. Thereby, the size of the sapphire substrate 10 can be further reduced. Separation between the LEDs 1 is achieved by using a photoresist, reactive ion etching, and wet etching in combination to etch away the areas other than the LEDs 1 until they reach the substrate 10. Since each LED array emits light alternately, luminous efficiency can be improved and heat radiation characteristics can be improved. Also, by changing the number of LEDs 1 connected in series, the driving voltage as a whole can be changed. When the area of the LED 1 is reduced, the driving voltage per LED can be increased. When 20 LEDs 1 are connected in series, an emission output of about 150 mW can be obtained when driven by a commercial power supply (100 V, 60 Hz). The drive current in this case is about 20 mA.
[0030]
As can be seen from FIG. 7, when the two LED arrays are alternately arranged in a zigzag manner, a crossing portion 34 is inevitably generated in the air bridge wiring 28. For example, when the first column and the second column of the other LED array are connected, they cross the wiring portion for connecting the first column and the second column of one LED array. However, since the air bridge wiring 28 of the present embodiment does not adhere to the substrate 10 as described above and passes through the air away from the substrate 10, the air bridge wirings 28 come into contact with each other at the intersection portion 34 and are short-circuited. Can be easily avoided. This is one of the advantages of using the air bridge wiring 28. The air bridge wiring 28 is formed, for example, as follows. That is, a photoresist having a thickness of 2 μm is applied to the entire surface, and a hole is formed in the shape of the air bridge wiring, followed by post-baking. On top of this, 10 nm of Ti and 10 nm of Au are deposited in this order by vacuum deposition. Further, a photoresist is applied again on the entire surface with a thickness of 2 μm, and holes are formed only in portions where air bridge wiring is to be formed. Then, Au having a thickness of 3 to 5 μm is attached to the entire surface of the electrode by ion plating (plating) in an electrolytic solution using Ti and Au as electrodes. Thereafter, the sample is immersed in acetone, and the photoresist is dissolved and removed by ultrasonic cleaning, whereby the air bridge wiring 28 is completed.
[0031]
By arranging the plurality of LEDs 1 in a two-dimensional array in this manner, it is possible to effectively use the substrate area and drive the device with a high drive voltage, particularly a commercial power supply. Various other patterns are also possible. Generally, it is desirable that the two-dimensional array pattern has the following conditions.
[0032]
(1) In order to uniformly supply a current to each LED and obtain uniform light emission, it is desirable that each LED has the same shape and electrode position.
[0033]
(2) In order to cut the wafer into chips, it is desirable that the sides of each LED be straight.
[0034]
(3) In order to improve light extraction efficiency and utilize reflection from the periphery using a standard mount, it is desirable that the LED has a planar shape close to a square.
[0035]
(4) The size of the two electrodes (bonding pads) is about 100 μm square and desirably separated from each other.
[0036]
(5) For effective utilization of the wafer area, it is desirable that the ratio of the wiring and the pad is small.
[0037]
Of course, these are not essential, and for example, a planar triangle may be used as the shape of each LED. Even if the shape of each LED is triangular, the overall shape can be made substantially square by combining them. Hereinafter, some examples of the two-dimensional array pattern will be described.
[0038]
FIG. 8 shows an example in which a total of six LEDs 1 are arranged two-dimensionally, and FIG. 9 shows a circuit diagram thereof. The arrangement shown in FIG. 8 is basically the same as the arrangement shown in FIG. 6. The total of six LED arrays are divided into two sets each of the same number, and each is composed of three LEDs connected in series. One LED array is arranged in a zigzag shape, and one LED 1 is formed in the first row and two LEDs 1 are formed in the second row from the top. The LEDs in the first column and the rightmost LEDs 1 in the second column are connected in series by an air bridge wiring 28, and the two LEDs 1 in the second column are also connected in series by an air bridge wiring 28. Electrodes (pads) 32 are formed on the upper left and lower left of the substrate 10, the first row of LEDs 1 is connected to the upper left electrode 32 by air bridge wiring, and the leftmost LED 1 in the second row is lower left. Connected to electrode 32. The other LED array is also arranged in a zigzag manner, and two LEDs 1 are formed in the first column and one LED 1 is formed in the second column from the top. The first column of the other LED array is formed between the first column and the second column of the one LED array, and the second column of the other LED array is the second column of the one LED array. Formed below the eyes. The LED 1 at the right end in the first column is connected in series to the LED 1 in the second column by an air bridge wiring 28, and the two LEDs 1 in the first column are also connected in series by the air bridge wiring 28. The leftmost LED 1 in the first column is connected to the upper left electrode 32 by an air bridge wiring 28, and the second column LED 1 is connected to the lower left electrode 32 by an air bridge wiring 28. As can be seen from FIG. 9, also in this example, the two LED arrays are connected to the electrode 32 in parallel with each other, and are connected so as to have opposite polarities to each other. Therefore, when the AC power is supplied, the two LED arrays emit light alternately.
[0039]
FIG. 10 shows an example in which a total of 14 LEDs are two-dimensionally arranged, and FIG. 11 shows a circuit diagram thereof. The total of 14 LED arrays are divided into two sets, each of which is composed of 7 LEDs connected in series. One LED array is arranged in a zigzag shape, and three LEDs 1 are formed in the first row and four LEDs 1 are formed in the second row from the top. The left end LED in the first column and the left end LED 1 in the second column are connected in series by an air bridge wiring 28, and the three LEDs in the first column and the four LEDs 1 in the second column are also connected. They are connected in series by an air bridge wiring 28. Electrodes (pads) 32 are formed on the upper right and lower right portions of the substrate 10, the rightmost LED1 in the first column is connected to the upper right electrode 32 by air bridge wiring, and the rightmost LED1 in the second column is connected to the right. Connected to lower electrode 32. The other LED array is also arranged in a zigzag manner, with four LEDs 1 being formed in the first row and three LEDs 1 being formed in the second row. The first column of the other LED array is formed between the first column and the second column of the one LED array, and the second column of the other LED array is the second column of the one LED array. Formed below the eyes. The leftmost LED 1 in the first column is connected in series to the leftmost LED 1 in the second column by an air bridge wiring 28. The four LEDs 1 in the first column and the three LEDs 1 in the second column are also connected in series. The rightmost LED1 in the first column is connected to the upper right electrode 32 by an air bridge wiring 28, and the rightmost LED1 in the second column is connected to the lower right electrode 32 by an air bridge wiring 28. As can be seen from FIG. 11, also in this example, the two LED arrays are connected to the electrode 32 in parallel with each other, and are connected so as to have opposite polarities to each other. Therefore, when the AC power is supplied, the two LED arrays emit light alternately.
[0040]
The features common to the two-dimensional patterns of FIGS. 6, 8 and 10 are that each LED 1 is substantially the same shape and size as a square, and the two electrodes (pads) are also substantially square and are not formed adjacent to each other. (Separately formed), a combination of two LED arrays, two LED arrays are formed so as to be bent and intersect each other on a chip, and the two LED arrays have opposite polarities. Connected to the electrodes as described above.
[0041]
FIG. 12 shows an example in which LEDs having a triangular planar shape are two-dimensionally arranged, and FIG. 13 shows a circuit diagram thereof. In FIG. 12, a total of six LEDs 1a, 1b, 1c, 1d, 1e, and 1f are formed such that their planar shapes are triangular. The LED 1a and the LED 1e face each other on one side of the triangle and are arranged so as to form a substantially square shape, and the LEDs 1b and 1f are arranged so as to face each other and form a substantially square shape. Further, the LED 1d and the electrode 32 are connected to face each other, and the LED 1c and the electrode 32 are connected to face each other. The two electrodes 32 also have a triangular planar shape similarly to the LED, and are similarly arranged to be substantially square. The opposing sides of the LEDs constitute the n-electrode 24, that is, the two opposing LEDs share the n-electrode 24. The LED and the electrode 32 also have an n-electrode connection. Also in this arrangement, a total of six LEDs are divided into two sets as in the above-described example. One LED array is an array composed of LEDs 1a, 1b, and 1c. The p-electrode 22 of the LED 1a is connected to the electrode 32 by an air bridge wiring 28, and the n-electrode 24 is connected to the p-electrode 22 of the LED 1b by the air bridge wiring 28. Connected. The n-electrode 24 of the LED 1b is connected to the p-electrode 22 of the LED 1c by an air bridge wiring 28. The n-electrode 24 of the LED 1c is connected to the electrode 32. The other LED array is composed of LED1d, LED1e, and LED1f. The electrode 32 and the p-electrode 22 of LED1f are connected by an air bridge wiring 28, and the n-electrode 24 of LED1f is connected to the p-electrode 22 of LED1e by an air bridge wiring 28. The n-electrode 24 of the LED 1e and the p-electrode 22 of the LED 1d are connected by an air bridge wiring 28, and the n-electrode 24 of the LED 1d is connected to the electrode 32.
[0042]
In FIG. 13, an n-electrode of an LED 1a forming one LED array and an n-electrode of an LED 1e forming the other LED array are connected, and an n-electrode of an LED 1b forming one LED array and an LED 1f forming the other LED array. Note that is connected. Circuit wiring can be reduced by sharing some n-electrodes of the two sets of LED arrays. Also in this example, the two LED arrays are connected to the electrodes 32 in parallel and connected to have opposite polarities. In addition, each LED has the same shape and the same size, and the LEDs 32 are formed in a triangular shape while facing each LED on one side, so that the LEDs and the electrodes can be formed at a high density to reduce the required substrate area. it can.
[0043]
FIG. 14 shows another example in which LEDs having a triangular planar shape are two-dimensionally arranged, and FIG. 15 is a circuit diagram thereof. In this example, a total of 16 LEDs 1a to 1r are formed two-dimensionally. The LEDs 1a and 1j, 1b and 1k, 1c and 1m, 1d and 1n, 1e and 1p, 1f and 1q, 1g and 1r face each other on one side of the triangle. An n-electrode 24 is commonly formed on the opposing sides. The LED 1i faces the electrode 32, and the LED 1h faces the electrode 32. One LED array includes LEDs 1a, 1b, 1c, 1d, 1e, 1f, 1g, and 1h, and the other LED array includes LEDs 1r, 1q, 1p, 1n, 1m, 1k, 1j, and 1i. The n-electrode 24 of the LED 1b is connected to the p-electrode 22 of the LED 1c by an air bridge wiring 28, and the n-electrode 24 of the LED 1e is also connected to the p-electrode 22 of the LED 1f by the air bridge wiring 28. The n-electrode 24 of the LED 1q is also connected to the p-electrode 22 of the LED 1p by the air bridge wiring 28, and the n-electrode 24 of the LED 1m is also connected to the p-electrode 22 of the LED 1k by the air bridge wiring 28. In FIG. 14 as well, crossover portions occur as in FIG. 12, but a short circuit can be avoided by the air bridge wiring 28. Also in this example, the necessary wiring is reduced by using some of the n-electrodes 24 of the two sets of LED arrays in a shared structure. Also in this example, the two LED arrays are connected in parallel to the electrodes 32 with polarities opposite to each other, and can be driven by AC. FIG. 12 shows a case of a total of six LEDs, and FIG. 14 shows a case of a total of sixteen LEDs. However, other numbers of LEDs can be similarly arranged two-dimensionally. The present applicant has also created a light emitting device in which 38 LEDs are two-dimensionally arranged.
[0044]
Although the case of the AC drive has been described above, it goes without saying that the DC drive is also possible. In this case, instead of connecting the LED arrays to the electrodes so as to have opposite polarities, the LED arrays may be connected in the forward direction according to the direction of the polarity of the DC power supply. High voltage driving is possible by connecting a plurality of LEDs in series. Hereinafter, the case of DC drive will be described.
[0045]
FIG. 16 shows an example in which two LEDs are connected in series, and FIG. 17 shows a circuit diagram thereof. Each LED 1 has a rectangular planar shape, and the two LEDs are connected by an air bridge wiring 28. The electrode 32 is formed near each LED1, and the electrode 32 and the LED1 form a rectangular area. That is, the electrode 32 occupies a part of the rectangular area, and the LED 1 is formed in another area of the rectangular area.
[0046]
FIG. 18 shows an example in which a total of four LEDs are two-dimensionally arranged, and FIG. 19 shows a circuit diagram thereof. The LED 1 shown in FIG. 16 is divided into two parts, which are connected in parallel. It can also be said that two sets of LED arrays each composed of two LEDs are connected in parallel in the forward direction. The LEDs 1a and 1b constitute one LED array, and the LEDs 1c and 1d constitute another LED array. The LED 1a and the LED 1c share the p-electrode 22 and the n-electrode 24, and the LED 1b and the LED 1d also share the p-electrode 22 and the n-electrode 24. According to this configuration, there is an effect that the current is made uniform as compared with FIG.
[0047]
FIG. 20 shows an example in which a total of three LEDs are two-dimensionally arranged, and FIG. 21 shows a circuit diagram thereof. The LEDs 1a, 1b, and 1c are not the same shape, and an electrode 32 is formed on a part of the LED 1a. The n-electrode 24 of the LED 1a and the p-electrode of the LED 1b are connected by an air bridge wiring 28 extending over the LED 1b. By devising the shape and arrangement of each LED, the overall appearance of the light emitting device (chip) can be made substantially square even with three LEDs.
[0048]
FIG. 22 shows an example in which a total of six LEDs are two-dimensionally arranged, and FIG. 23 shows a circuit diagram thereof. The LEDs 1a to 1f have the same shape and the same size. The LEDs 1a to 1f are connected in series. The LEDs 1a to 1c are arranged on a straight line, and the LEDs 1d to 1f are arranged on another straight line. The LED 1c and the LED 1d are connected by an air bridge wiring 28. Also in this example, the overall shape of the chip can be made substantially square.
[0049]
FIG. 24 shows an example in which a total of five LEDs are two-dimensionally arranged, and FIG. 25 shows a circuit diagram thereof. The LEDs 1a to 1e have the same shape (rectangle) and the same size. Also in this example, the overall shape can be substantially square.
[0050]
Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made. In particular, a pattern in the case where a plurality of light emitting elements (eg, LEDs) are two-dimensionally arranged can be other than the above-described pattern. In this case, the electrodes may be shared between adjacent light emitting elements to reduce the number of wirings, the whole shape may be square or rectangular, a plurality of light emitting element arrays may be connected in parallel to the electrodes, It is preferable that the sets of light emitting element arrays have opposite polarities, and that a plurality of sets of light emitting element arrays are bent in a zigzag shape and combined.
[0051]
26 to 31 illustrate some of these modifications. FIG. 26 shows a two-dimensional arrangement in the case of AC driving, in which a total of 40 LEDs are arranged. FIG. 27 is a circuit diagram thereof. The difference from FIG. 6 is that some of the two sets of LED arrays share the n-electrode 24 (see FIG. 5). For example, the n-electrode 24 of the LED (indicated by α in the drawing) located second from the right end of the first column of one LED array is connected to the LED (β in the drawing) located at the right end of the first column of the other LED array. ) Is shared with the n-electrode 24. The air bridge wiring 28 at the end of the LED array (the γ portion in the figure) is commonly formed without crossing.
[0052]
FIG. 28 shows a two-dimensional arrangement in the case of AC driving, in which a total of 14 LEDs are arranged. FIG. 29 is a circuit diagram thereof. The difference from FIG. 10 is that some of the two sets of LED arrays share the n-electrode 24. For example, the n-electrode 24 of the leftmost LED (indicated by α in the drawing) of the first column of one LED array is the second LED (shown by β in the drawing) located from the right end of the first column of the other LED array. ) Is shared with the n-electrode 24. Further, the air bridge wiring 28 at the end portion (the γ portion in the drawing) is formed in common.
[0053]
FIG. 30 shows a two-dimensional arrangement in the case of AC driving, in which a total of six LEDs are arranged. FIG. 31 is a circuit diagram thereof. Also in this example, the air bridge wiring 28 at the end (γ portion) is commonly formed. Also in this configuration, it can be said that the n-electrode 24 in one LED array and the n-electrode 24 in the other LED array are shared.
[0054]
【The invention's effect】
As described above, according to the present invention, light can be emitted by driving at a high driving voltage.
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram of a light emitting element (LED).
FIG. 2 is an equivalent circuit diagram of the light emitting device.
FIG. 3 is a plan view of two LEDs.
FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;
FIG. 5 is another equivalent circuit diagram of the light emitting device.
FIG. 6 is an explanatory diagram in which forty LEDs are two-dimensionally arranged.
FIG. 7 is a circuit diagram of FIG. 6;
FIG. 8 is an explanatory diagram in which six LEDs are two-dimensionally arranged.
FIG. 9 is a circuit diagram of FIG.
FIG. 10 is an explanatory diagram in which 14 LEDs are two-dimensionally arranged.
FIG. 11 is a circuit diagram of FIG.
FIG. 12 is an explanatory diagram in which six LEDs are two-dimensionally arranged.
FIG. 13 is a circuit diagram of FIG.
FIG. 14 is an explanatory diagram in which 16 LEDs are two-dimensionally arranged.
FIG. 15 is a circuit diagram of FIG. 14;
FIG. 16 is an explanatory diagram in which two LEDs are arranged.
FIG. 17 is a circuit diagram of FIG.
FIG. 18 is an explanatory diagram in which four LEDs are two-dimensionally arranged.
FIG. 19 is a circuit diagram of FIG. 18;
FIG. 20 is an explanatory diagram in which three LEDs are two-dimensionally arranged.
FIG. 21 is a circuit diagram of FIG. 20;
FIG. 22 is an explanatory diagram in which six LEDs are two-dimensionally arranged.
FIG. 23 is a circuit diagram of FIG. 22;
FIG. 24 is an explanatory diagram in which five LEDs are two-dimensionally arranged.
FIG. 25 is a circuit diagram of FIG. 24;
FIG. 26 is an explanatory diagram of another two-dimensional arrangement.
FIG. 27 is a circuit diagram of FIG. 26;
FIG. 28 is an explanatory diagram of another two-dimensional arrangement.
FIG. 29 is a circuit diagram of FIG. 28;
FIG. 30 is an explanatory diagram of another two-dimensional arrangement.
FIG. 31 is a circuit diagram of FIG. 30;
[Explanation of symbols]
10 substrate (wafer), 12 u-GaN layer, 14 n-type GaN layer, 16 InGaN light emitting layer, 18 AlGaN layer, 20 p-GaN layer, 22 p-electrode, 24 n-electrode.

Claims (13)

A plurality of light emitting elements are formed on an insulating substrate, and the plurality of light emitting elements are monolithically connected in series. The device of claim 1,
The light emitting device, wherein the plurality of light emitting elements are two-dimensionally arranged on the substrate. The apparatus according to any one of claims 1 and 2,
The light-emitting device, wherein the plurality of light-emitting elements are divided into two sets, and are connected in parallel to two electrodes so as to have opposite polarities. The device according to any one of claims 1 to 3,
The light emitting device according to claim 1, wherein the connection between the plurality of light emitting elements is an air bridge wiring. The apparatus according to any one of claims 1 to 4,
The light emitting device according to claim 1, wherein the electrical separation between the plurality of light emitting elements is performed by sapphire used as the substrate. The device according to claim 2,
The plurality of light-emitting elements are divided into two groups each having the same number, the light-emitting element arrays of each set are arranged in a zigzag pattern, and the two light-emitting element arrays are connected in parallel to two electrodes so as to have opposite polarities. A light emitting device characterized by being performed. The device according to claim 6,
The light emitting device, wherein the two sets of light emitting element arrays are alternately arranged. The apparatus according to any one of claims 6 and 7,
The light emitting device is characterized in that the light emitting element and the electrode have a substantially square planar shape. The apparatus according to any one of claims 6 and 7,
The light emitting device is characterized in that the light emitting element and the electrode have a triangular planar shape. The device according to claim 2,
The light emitting device according to claim 1, wherein the plurality of light emitting elements and the electrodes are arranged so that the overall shape is substantially square. The device according to claim 10,
The light emitting device according to claim 1, wherein the light emitting element array including the plurality of light emitting elements is arranged in a zigzag shape. The device according to any one of claims 6 to 9,
The light emitting device, wherein the electrode is an electrode for an AC power supply. The device according to any one of claims 6 to 9,
A light-emitting device, wherein the two sets of light-emitting element arrays have a common n-electrode.

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