JP2002335012A - Light emitting diode and dot matrix display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting diode wherein malfunction is not generated especially in a case that an LED display in which the diodes are connected in a matrix is constituted, and a light emitting element is not electrically damaged, regarding a light emitting diode using a nitride semiconductor light emitting element in which light emission is enabled from an ultraviolet region to a visible light. SOLUTION: This light emitting diode is provided with a light emitting element in which nitride semiconductor having Ga is used at least as a light emitting layer, and a semiconductor protecting element which is connected in parallel with the light emitting element and used for electrically protecting the light emitting element. Especially, the semiconductor protecting element which is connected in parallel with the light emitting element is switched on in both a forward direction and a backward direction by using a voltage higher than or equal to a forward voltage of the light emitting element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode using a nitride semiconductor light emitting device capable of emitting light from the ultraviolet region to visible light, and particularly to a case where an LED display connected in a matrix is constructed. The present invention relates to a light emitting diode in which a light emitting element is not electrically damaged without malfunction and a dot matrix display using the same.

[0002]

2. Description of the Related Art A nitride semiconductor (InxAlyGa1-x-yN,
Light emitting diodes utilizing 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) have been put to practical use. Accordingly, it has begun to be rapidly used in various fields such as a light source of a liquid crystal backlight and a writing light source of a printer. It is difficult to form a semiconductor having excellent crystallinity with good mass productivity, and a nitride semiconductor is currently formed on a sapphire substrate or a SiC substrate via a buffer layer. Therefore, a light-emitting element using a nitride semiconductor is considered to have a lower withstand voltage because of more crystal defects and poor crystallinity than a normal light-emitting element. In particular, the composition of the light-emitting layer contains Al and / or In elements, and is preferable as a light-emitting element using a nitride semiconductor having a light emission peak on a short wavelength side such as an ultraviolet region or a long wavelength side of visible light is formed. It tends to be difficult to form a film. Further, in a light-emitting element in which a nitride semiconductor is formed on an insulating substrate such as a sapphire substrate, the conductive semiconductor layer region has a total thickness of about 10%.
Since the thickness is less than μm, it tends to be broken when a voltage is applied.

Further, in order to further improve the luminous efficiency,
2. Description of the Related Art A light emitting layer is formed of an extremely thin film having a single quantum well structure or a multiple quantum well structure. Therefore, there is a problem that a light-emitting element using a nitride semiconductor having excellent characteristics having a small size, high efficiency, high output at a small current and high output is easily broken by a small electrostatic voltage.

For example, a light emitting diode whose normal light emitting layer is made of AlGaInP or the like and is capable of emitting red or infrared light has a withstand voltage of about 2 KV, while the light emitting layer is made of InG
The withstand voltage of a light-emitting element made of aN, which can emit blue, green, yellow, etc., is only about 0.5 KV or less. In particular,
In the case of a nitride semiconductor light emitting device capable of emitting ultraviolet light containing Al, the voltage is about 0.2 KV or less (the resistance to the light emitting device is almost 0 ohm, and 200p by switching.
A withstand voltage test was performed by passing a current from the capacitor of F to the light emitting element. ). As described above, unlike other semiconductor light emitting devices, a light emitting diode made of a group III nitride semiconductor is not only relatively low in reverse voltage but also forward voltage due to an electric shock due to an electric shock. Destruction is easy to occur.

[0005] As a countermeasure against static electricity and surge voltage, it is conceivable to provide a semiconductor protection element for restricting an excessive current for destroying the light emitting element from flowing. For example,
The Zener diode is connected in antiparallel with the light emitting element as a semiconductor protection element. This makes it possible to apparently increase the light resistance of the light emitting element against static electricity and surge. FIG. 7 shows a specific example. 7A, the LED chip 52 is arranged and fixed in the cup of the mount lead 51a using the die bond resin 56, and the LED chip 52 is connected to the mount lead 51a and the inner lead 51. FIG.
b and the wires 54 are used to make electrical connection. Further, a Zener diode 57 is arranged on the mount lead 51a as a semiconductor protection element. Zener diode 5
Reference numeral 7 fixes the mount lead 51a to the silver paste and electrically connects the other electrode of the Zener diode to the inner lead 51b with a wire. FIG. 7B shows an equivalent circuit diagram of FIG.

As a result, the Zener diode is electrically connected to the LED chip in anti-parallel. LE
The tips of the mount leads and the inner leads on which the D chips are arranged and electrically connected are sealed with an epoxy resin 58 or the like, so that a light emitting diode can be formed. FIG. 8 shows the current-voltage characteristics of the semiconductor light emitting element (broken line) and the Zener diode (solid line), respectively. When a forward current is applied to turn on the light emitting element, substantially no current flows because the Zener diode, which is a semiconductor protection element, is connected in anti-parallel. Therefore, the LED chip, which is a light emitting element, can emit light efficiently with the driving voltage of the light emitting diode. On the other hand, when a surge voltage that destroys the light emitting element is applied in the forward direction,
The Zener diode limits the voltage to a voltage VZ lower than the surge voltage at which the light emitting element is destroyed. That is, a current flows through the Zener diode at a rising voltage selected to a voltage lower than the voltage at which the LED chip is destroyed, and a constant voltage is generated.
No large voltage is applied to the ED chip.

[0007]

However, it has been found that a new problem arises when an LED display in which light-emitting diodes whose light-emitting elements are protected by such zener diodes are arranged in a matrix is used. FIG. 9 shows a schematic circuit configuration of an LED display arranged in a matrix for dynamic driving using the light emitting diodes. In FIG. 9, LED chips and light-emitting diodes in which zener diodes are connected in opposite directions are arranged in a matrix like L1 to L12. The light emitting diode is connected for each column and row, and only the light emitting diode of which column and row is selected can emit light. When a light emitting diode in which the above-mentioned zener diode is incorporated as a protection element is arranged in this circuit, a current flows into another circuit via the semiconductor protection element, and an unintended light emitting diode emits light.

[0008] Such unintended lighting of the light emitting diodes not only lowers the lighting brightness of the desired light emitting diodes L1 and L7, but also causes a reduction in the contrast and malfunction of the entire LED display. Therefore, a Zener diode or a normal silicon diode is not suitable for a display having a circuit configuration in a matrix form, and is substantially unusable. In addition, when a defect check of a light emitting element is performed based on the presence or absence of a reverse leakage current, simply connecting a protection element such as a zener diode in parallel causes the reverse direction of the light emitting diode to pass through the protection element due to the characteristics of the protection element. Inconveniently, it is not possible to perform a defect check because the current is supplied. Therefore, an object of the present invention is to provide a light emitting diode that protects a light emitting element against static electricity and surge voltage and does not malfunction. It is another object of the present invention to provide a light emitting diode that can easily check for a defect in a light emitting element.

[0009]

According to the present invention, there is provided a light emitting diode having a light emitting element in which at least a light emitting layer is a nitride semiconductor containing Ga, and a semiconductor protection element for electrically protecting the light emitting element. . In particular, the semiconductor protection element connected in parallel with the light emitting element conducts at a voltage higher than the forward voltage of the light emitting element in both directions. More specifically, the semiconductor protection element connected in parallel with the light emitting element conducts bidirectionally symmetrically or asymmetrically at a voltage higher than the forward voltage of the light emitting element, or has a negative resistance characteristic. Thus, destruction and malfunction of the light emitting element can be suppressed. Further, in a region where the voltage is low, a current flows substantially without passing through the protection element, so that the defect check of the light emitting element can be easily performed.

According to a second aspect of the present invention, there is provided a light emitting diode using a nitride semiconductor having at least a light emitting layer containing In and Ga, and a light emitting element connected in parallel with the light emitting element to electrically protect the light emitting element. And a semiconductor protection element. In particular, the semiconductor protection element has at least one selected from a trigger diode, a transistor having an open base, a varistor, and a zener diode connected in series in the reverse direction.

In a light emitting diode according to a third aspect of the present invention, the light emitting device has p-type and n-type nitride semiconductors on a sapphire substrate with at least a light emitting layer interposed through a nitride semiconductor containing Ga.

The dot matrix display according to a fourth aspect of the present invention is a dot matrix display having a configuration in which a light emitting diode having a specific protection element is dynamically driven to thereby prevent a malfunction or the like. be able to.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has conducted various experiments,
A light-emitting diode that is protected against static electricity and surge voltage in both the forward and reverse directions of a light-emitting diode using a nitride semiconductor light-emitting element without being substantially affected by loss or a drive circuit. The present invention has been accomplished.

That is, the present invention incorporates the circuit shown in FIG. 1 in a light emitting diode, so that the light emitting diode alone protects the LED chip against static electricity and surge voltage without impairing the characteristics inherent to the LED chip. A light emitting diode was obtained.

A trigger diode as a semiconductor protection element used in the present invention has a voltage-current characteristic as shown in FIG. In FIG. 2, the voltage is plotted on the horizontal axis and the current is plotted on the vertical axis, and when the voltage is applied in each direction, the breakdown voltage V
There is a characteristic that the impedance becomes low at the border of BO and the current suddenly flows. In FIG. 2, the nitride semiconductor light emitting device is indicated by a dotted line, and the trigger diode is indicated by a solid line.
Since the trigger diode has no polarity, it exhibits substantially symmetric characteristics in each direction.

In the light emitting diode in which the trigger diode is connected in parallel to the LED chip, the trigger diode is arranged in the forward and reverse directions of the light emitting element.
Acts as a voltage limiter for voltages greater than | VBO |. By selecting and using a trigger diode whose breakdown voltage | VBO | is higher than the driving voltage of the LED chip, the trigger diode acts as a voltage limiter when static electricity or surge voltage is applied to the light emitting diode. It acts as a bypass protection. Therefore, a voltage exceeding the breakdown voltage | VBO | is not applied to the light emitting element, and the light emitting element is not destroyed.

In addition, since it does not conduct to the breakdown voltage even in the reverse direction and has a current blocking capability, it functions to prevent malfunctions due to current sneak in each of the light emitting diodes connected in a matrix. Furthermore, the leakage current of the trigger diode up to the breakdown voltage VBO is sufficiently small and negligible in view of the LED chip characteristics.
Therefore, even during the steady driving of the LED device, the characteristics unique to the light emitting element are not impaired.

When a transistor is used, for example, an npn-type transistor having an open base has a voltage-current characteristic as shown in FIG. 10 (here, the transistor of the present invention is to be interpreted in a broad sense). And not only those having three exposed terminals, but also n
(Including a semiconductor protection element in which only two terminals are exposed to a pn junction or a pnp junction semiconductor.) A wavy line in FIG. 10A indicates a light-emitting element, and a solid line indicates a transistor. This characteristic is obtained by connecting the anode of the LED 1001, which is a light emitting element, to the emitter of the transistor 1002 and the cathode of the LED to the collector of the transistor.
In the forward direction, it has the same characteristics as the Zener diode,
In the reverse direction, it functions as a protection circuit having the same characteristics as the trigger diode. Generally, a GaN-based LED is weak due to an overvoltage in the reverse direction, and has good matching as a protection circuit. FIG.
FIG. 10B shows an equivalent circuit diagram of FIG.

When a transistor is used, it has a greater advantage than other protection elements. That is, an LED chip which is an actual light emitting element, a Zener diode, a trigger diode, and a transistor which are mass-produced are mounted. In this case, a troublesome problem may occur depending on the structure, polarity, and mounting method of the semiconductor element. Zener diodes and transistors using silicon are n
A mold substrate is easily obtained, and the use of an n-type substrate is advantageous in terms of characteristics and cost. For this reason, most diodes have an n-type semiconductor substrate and a p-type semiconductor bonding electrode.

On the other hand, a GaN-based LED which is a nitride semiconductor
May be formed on a sapphire substrate, and there is basically no polarity when an insulating substrate such as sapphire is used. However, for example, when a Zener diode is mounted on a common conductive substrate, the polarity is naturally determined. That is, in this case, the frame (conductive base) on which the light emitting element is mounted is determined as the anode (positive electrode). However, this connection can raise significant reliability issues. Silver plating may be applied to the frame of the LED, which is a light emitting element, in order to improve the reflection efficiency. When a positive voltage is applied to this, there is a risk of reacting with moisture that has entered from the outside and short-circuiting due to the migration action of silver. In addition, in the GaN-based LED, the n-type semiconductor layer is on the sapphire side, and a forward voltage is applied between the frame and the exposed n-type semiconductor layer, which matches the direction in which migration occurs. It is preferable that the polarity is reversed, but the zener diode determines this polarity.

Here, np using the same n-type semiconductor substrate
A look at the n-transistor shows that the frame can be mounted on the negative electrode. In other words, a protection circuit using transistors has great advantages in terms of reliability in addition to protection ability and prevention of malfunction.

From the above, a semiconductor protection element having a bidirectional protection function is connected in parallel with an LED, and the LED is driven within the voltage of the semiconductor protection element. From this, LE
The light emitting element can be protected from static electricity and surge voltage without impairing the characteristics inherent to the D chip, and malfunction of the light emitting diode can be prevented. The semiconductor protection element is
As long as it has the above-described bidirectional protection function, a trigger diode, a transistor having an open base, a varistor, a zener diode connected in series in the reverse direction, and an IC or LSI including these characteristics can also be used. . Hereinafter, the present invention will be described in more detail with reference to Examples, which are embodiments of the present invention. However, it goes without saying that the present invention is not limited to this.

[0023]

[Example 1] A nitride semiconductor is deposited on a sapphire substrate which has been washed in advance by MOCVD to form an LED as a light emitting element. A sapphire substrate is placed in a reaction vessel of an MOCVD apparatus, and baked at 800 ° C. while flowing hydrogen gas. Next, a TMG (trimethyl gallium) gas as a source gas, a hydrogen gas as a nitrogen gas and a carrier gas are flown, and GaN as a buffer layer having a thickness of 150 is formed on a sapphire substrate at a substrate temperature of 550 ° C.
The film is formed by Å.

After the formation of the buffer layer, the flow of the raw material gas is stopped, the film forming temperature is raised to 1050 ° C., and TM is used as the raw material gas.
A non-doped n-type GaN is formed to a thickness of 1.5 μm by flowing a hydrogen gas as a G gas, a nitrogen gas and a carrier gas. An n-type GaN layer for forming an n-type electrode is formed on the n-type GaN. While maintaining the film forming temperature, a TMG gas and a nitrogen gas as source gases, and a hydrogen gas and a silane gas as a carrier gas are flowed to form an n ⁺ -type GaN having a thickness of 2.3 μm.
To form a film. While maintaining the film forming temperature, n ⁺ Ga
A TMG gas as a source gas, a nitrogen gas and a hydrogen gas as a carrier gas are flowed over N, and undoped GaN and S
An n-type multilayer film in which i-doped GaN is formed in 20 cycles is formed. Note that modulation doping is performed in which the impurity concentration of the GaN layer is different.

Subsequently, AlInGaN is formed on the modulation-doped GaN layer as an active layer. Specifically, the film forming temperature is lowered to 800 ° C. TMA as raw material gas
An active layer is formed by flowing (trimethylaluminum) gas, TMI (trimethylindium) gas, TMG gas, nitrogen gas and hydrogen gas as carrier gas.

Next, on the active layer, a superlattice p-type clad layer in which Mg-doped AlGaN having a thickness of 40 ° and Mg-doped InGaN having a thickness of 25 ° are repeated five times is formed as a p-type clad layer. Let it form. More specifically,
While maintaining the film formation temperature at 1050 ° C., TMG gas, TMA (trimethylaluminum) gas,
A p-type clad layer is formed by introducing a nitrogen gas, a hydrogen gas as a carrier gas and a Cp ₂ Mg (cyclopentadienyl magnesium) gas as a p-type dopant.

Finally, while maintaining the film formation temperature at 1050 ° C., the source gas is TMG gas, nitrogen gas, hydrogen gas as the carrier gas and Cp ₂ Mg as the impurity gas, and Mg-doped GaN is formed as the p-type contact layer. Let it.
After forming the nitride semiconductor wafer, the active layer and the like are removed by RIE so that the n-type contact layer can be partially exposed. Thereafter, an electrode is formed on each of the p-type and n-type contact layers by using sputtering. A plurality of LED chips are formed as light emitting elements by scribing the nitride semiconductor wafer. Thus, an active layer having a quantum well structure is formed on the sapphire substrate, and a light emitting element which is a nitride semiconductor having a double hetero structure is formed. The active layer serving as a light emitting layer is a light emitting element capable of emitting ultraviolet light of a nitride semiconductor containing Ga. A light emitting diode is formed using this light emitting element as shown in FIG.

FIG. 3 is a schematic view showing a light emitting diode of a can type package according to an embodiment of the present invention. The LED chip 31 obtained as described above is joined to the accommodation portion of the silver-plated stem 33 with a silver paste 36.
Next, the trigger diode chip 32 which has an npn junction and is an n-type substrate at the flat portion of the periphery of the storage portion of the stem is joined with a silver paste 36. In this case, the stem is on the cathode side and the inner lead is on the anode side. More specifically, the inner lead 33a and the LED chip 3
No. 1 p-side extraction electrode (anode side), and the mount lead 33b and the n-side extraction electrode (cathode side) of the LED chip 31 are connected by a gold wire 35 by wire bonding. The inner lead 33a of the stem is electrically insulated from the storage part of the stem 33 and the mount lead 33b. Next, the n-side extraction electrode serving as the upper surface of the trigger diode and the inner lead 33a are connected by wire bonding with a gold wire 35.

Finally, the cap 34 and the flange of the stem 33 are welded and sealed by resistance welding in an N ₂ atmosphere, so that the mount lead 33b is used as a cathode, the inner lead 33a is used as an anode, and the trigger diode chip 32 is used as an LED chip. A light-emitting diode connected in parallel to 31 can be formed.

The withstand voltage of the light emitting diode thus obtained is evaluated. FIG. 6 shows a test circuit of the device used for the evaluation. The specification of the power supply V is a DC voltage with a maximum voltage of 3 kV and a maximum current of 3 mA.
F and the resistance R were set to 0Ω. The capacitor C was designed to withstand the test voltage sufficiently, and the changeover switch S was designed to have high insulation resistance, low contact resistance and no chattering. The wiring between the test apparatus and the test sample was made as short as possible, and the stray capacitance was set to 5% or less of the capacitance of the capacitor C. In the test method, the switch S of the device is set to the power supply V side, and the test voltage is charged in the capacitor C. The changeover switch S is set to the sample side to discharge.

Next, the same operation is repeated while changing the polarity of the test voltage. Test voltage is 100V step, maximum 2.5k
V was set. The evaluation result of the withstand voltage test of the light emitting diode obtained in this example is 2.5 kV in both the forward and reverse directions.
Can withstand. That is, the LED chip can be driven in the same manner as when no semiconductor protection element is added, and becomes constant at the breakdown voltage of the trigger diode above the rated voltage. [Embodiment 2] FIG. 4 is a schematic view of a surface mount type light emitting diode as an example of the present invention. 4 is a front view, and the lower figure is a cross-sectional view. This light emitting diode uses an LED chip made of a nitride semiconductor. The nitride semiconductor is formed on a sapphire substrate that has been cleaned in advance by using the MOCVD method. The sapphire substrate is placed in the reaction vessel of the MOCVD apparatus, and the hydrogen gas is flowed for 800.
Baking at ℃. Next, TMG (trimethyl gallium) gas as a source gas, hydrogen gas as a nitrogen gas and a carrier gas were flown, and GaN was formed as a buffer layer to a thickness of 150 ° on a sapphire substrate at a substrate temperature of 550 ° C.

After the formation of the buffer layer, the flow of the raw material gas is stopped, the film forming temperature is raised to 1050 ° C., and TM is used as the raw material gas.
A non-doped n-type GaN having a thickness of 1.5 μm was formed by flowing a hydrogen gas as a G gas, a nitrogen gas and a carrier gas. Subsequently, an n-type GaN layer is formed as an n-type contact layer for forming an n-type electrode on the n-type GaN. Specifically, TM is used as a source gas while maintaining the film forming temperature.
G ⁺ gas, nitrogen gas, and hydrogen gas and silane gas as a carrier gas are flowed to form an n ⁺ -type GaN film having a thickness of 2.3 μm. Next, a multilayer film in which TMG gas, nitrogen gas and hydrogen gas are flown as a source gas and a non-doped GaN and a Si-doped GaN are formed in 20 cycles on the n ⁺ -type GaN while maintaining the film formation temperature. To form
Note that modulation doping is performed in which the impurity concentration of the GaN layer is different.

Subsequently, on the modulation-doped GaN layer, 250 ° GaN and 30 ° thick InGaN were formed as active layers.
Are repeated six times, and the both ends are G
An active layer of aN is formed. Specifically, while maintaining the film formation temperature at 1050 ° C., TMG as a source gas, hydrogen gas as a nitrogen gas and a carrier gas are flowed over the modulation-doped GaN layer to form a non-doped GaN film at 30 °. Next, while flowing only the carrier gas,
The film forming temperature is lowered to 800 ° C. After the temperature is stabilized, a TMI (trimethyl indium) gas, a TMG gas, a nitrogen gas, and a hydrogen gas as a carrier gas are flowed again as source gases, and non-doped InGaN is deposited at 250 ° C.
To form a film. After repeating this for 6 cycles, finally, the film formation temperature is set to 1050 ° C., TMG as a source gas, hydrogen gas as a nitrogen gas and a carrier gas are flown, and non-doped GaN is formed at 30 ° to form an active layer.

Next, a superlattice p-type cladding layer in which Mg-doped AlGaN having a thickness of 40 ° and Mg-doped InGaN having a thickness of 25 ° are repeated five times is formed as a p-type cladding layer on the active layer. Let it form. Film forming temperature 105
While maintaining at 0 ° C., TMG gas, TM
A (trimethylaluminum) gas, nitrogen gas, hydrogen gas as carrier gas and Cp ₂ M as p-type dopant
g (cyclopentadienyl magnesium) gas is introduced to form a p-type AlGaN film at 40 °.

Finally, while maintaining the film formation temperature at 1050 ° C., TMG gas, nitrogen gas, hydrogen gas as a carrier gas, and Cp ₂ Mg as an impurity gas are flowed, and Mg-doped GaN is formed as a p-type contact layer. Let it.
After forming the nitride semiconductor wafer, the active layer and the like are removed by RIE so that the n-type contact layer can be partially exposed. Thereafter, an electrode is formed on each of the p-type and n-type contact layers by using sputtering. Each LED chip is formed by scribing the nitride semiconductor wafer. Thus, an active layer having a multiple quantum well structure is formed on the sapphire substrate, and a light emitting device which is a nitride semiconductor having a double hetero structure is formed. The active layer serving as a light emitting layer is a nitride semiconductor containing Ga which is capable of emitting blue light. By using this light emitting element, a light emitting diode capable of emitting white light is formed as shown in FIG.

First, a silver-plated copper lead frame 4
1 is formed by punching, and a package 42 serving as an outer frame of the light emitting diode is formed on the lead frame 41 by an injection molding method. Next, the LED chip 43, which is a gallium nitride-based compound semiconductor, is inserted into the plastic package 4
2 epoxy resin 4 on the exposed part of the lead frame 41
Join at 6. Further, the lead electrode 4 of the package 42
An n-substrate transistor chip 44 having an npn junction on 1 is joined with a silver paste 47. The lead frame 41 joined to the LED chip 43 of the package 42 and the lead electrode 41 joined to the transistor chip 44 are electrically insulated by the package material. The lead electrode 41 to which the LED chip 43 is bonded and the n-side extraction electrode (cathode side) of the LED chip 43, and the surface electrode of the transistor chip 44 and the other lead electrode 41 are wire-bonded with a gold wire. Similarly, the p-side extraction electrode (anode side) of the LED chip 43 is connected to the gold wire 45 by wire bonding.

Next, a transparent epoxy resin containing YAG: Ce as a phosphor capable of absorbing blue light and emitting light of a complementary color by injection molding on the package 42 is LE.
It is formed on a D chip and a transistor diode.
The lead frame 41 protruding from the outer frame of the package 42 is cut into an optimum shape, and finally the lead is bent along the outer frame of the plastic package 42. From the above, L
A surface-mount type white light-emitting diode in which a transistor chip 44 was connected in parallel with the ED chip 43 was formed.

With respect to the thus obtained light emitting diode of this example, the withstand voltage was evaluated by the same method as in Example 1. As a result, as in Example 1, it was confirmed that the light emitting diode withstands 2.5 kV in both the forward and reverse directions. . That is, the LED chip can be driven in the same manner as when no semiconductor protection element is added, and becomes constant at the breakdown voltage of the transistor above the rated voltage. When a Zener diode is die-bonded with an Ag paste, Ag tends to migrate from the anode side to the cathode side. Therefore, there is a case where Ag migrates and short-circuits with the driving of the LED chip or the Zener diode connected in parallel. is there. However, when the semiconductor protection element of the present invention is used, the above-mentioned problem can be avoided because the LED chip and the transistor diode can be connected with the same polarity on the lead electrode. further,
When the LED is used in a matrix LED display that is dynamically driven by using the light emitting diode, it is possible to substantially eliminate the light emitting diode that is turned on. [Embodiment 3] Fig. 5 is a sectional view of a light emitting diode of a shell type. First, a silver-plated copper lead frame 5
1 is formed by punching and pressing. The formed lead frame 51 is provided with LE at the tip of the mount lead 51a.
It has a cup which is a storage portion for the D chip 52, and a flat portion below the cup to which the trigger diode chip 53 can be joined.

An LED chip 52, which is a gallium nitride-based compound semiconductor, is die-bonded to a storage portion of the lead frame 51 with an epoxy resin 56. Subsequently, in order to prevent the emitted light from the LED chip from being absorbed by the trigger diode, it is arranged between the lead frames on the bottom surface of the cup. That is, as shown in FIG. 5, the SMD trigger diode chip 53 is joined between the inner lead 51b and the mount lead 51a by welding. Unlike an LED chip that is substantially protected by a cup, the SMD trigger diode is easily affected by shrinkage of a sealing resin to be formed later, and is thus joined by welding that can be firmly joined.

Inner lead 51b and LED chip 52
And the mount lead 51a and the p-side extraction electrode (anode side) of the LED chip 52 are wire-bonded with a gold wire 54, respectively. The inner lead 51b is electrically insulated from the mount lead 51a.

For the purpose of protecting the LED chip 52 and the SMD trigger diode chip 54 from external stress, moisture, dust and the like, and obtaining appropriate light distribution characteristics, they are molded with an epoxy resin having excellent light transmittance. The sealing resin, which is a molding member, can be formed by inserting a lead frame into a cavity serving as a shell-shaped mold frame containing epoxy resin so that the LED chip and the SMD trigger diode chip can be resin-sealed, and then heat-cured. . As described above, a bullet-type light emitting diode in which the trigger diode chip 53 is connected in antiparallel to the LED chip 52 is formed.

With respect to the thus obtained light emitting diode of this example, the withstand voltage was evaluated by the same method as in Example 1. As a result, as in Example 1, it was confirmed that the light emitting diode could withstand 2.5 kV in both the forward and reverse directions. . That is, the LED chip can be driven in the same manner as when no semiconductor protection element is added, and becomes constant at the breakdown voltage of the trigger diode above the rated voltage.

[0043]

As described above, according to the present invention, L
A semiconductor protection element that satisfies a specific relationship with the ED chip is L
By connecting in parallel to the ED chip, it is possible to obtain a light emitting diode that is protected from static electricity and surge voltage and does not impair the characteristics inherent to the LED chip.

[Brief description of the drawings]

FIG. 1 shows a circuit diagram of a light emitting diode of the present invention.

FIG. 2 shows a voltage-current characteristic diagram of a trigger diode and an LED chip.

FIG. 3 is a perspective view of a light emitting diode which is a can type package according to the first embodiment.

FIGS. 4A and 4B are a front view and a cross-sectional view of a surface-mount type light emitting diode according to a second embodiment. FIGS.

FIG. 5 is a schematic sectional view of a light emitting diode of a shell type resin mold type according to a third embodiment.

FIG. 6 shows a circuit diagram of a withstand voltage evaluation test apparatus.

FIG. 7A is a schematic sectional view of a light emitting diode of a shell type resin mold type shown for comparison with the present invention, and FIG. 7B shows an equivalent circuit thereof.

FIG. 8 shows a voltage-current characteristic diagram of a Zener diode and an LED chip.

FIG. 9 is a schematic partial circuit diagram of a dot matrix display using light emitting diodes.

FIG. 10 (A) shows n with the base open.
FIG. 10B shows a voltage-current characteristic diagram of a pn-type transistor and an LED chip, and FIG. 10B shows an equivalent circuit thereof.

[Explanation of symbols]

 21, 31, 43, 52 ... LED chip 22, 32, 44, 53 ... trigger diode chip 35, 45, 54 ... gold wire 41, 51 ... lead frame 33 ... stem 34 ..Cap 42 ... Plastic package 58 ... Mold resin 36,47 ... Ag paste 46,56 ... Epoxy resin 57 ... Metal piece by welding

Claims (4)

[Claims] 1. A light-emitting diode having a light-emitting element in which at least a light-emitting layer is a nitride semiconductor containing Ga and a semiconductor protection element for electrically protecting the light-emitting element, wherein the light-emitting diode is connected in parallel with the light-emitting element. Semiconductor protection element
A light-emitting diode, which conducts at a voltage higher than a forward voltage of a light-emitting element in both directions. 2. A light emitting diode comprising a light emitting element using a nitride semiconductor having at least a light emitting layer containing In and Ga, and a semiconductor protection element connected in parallel with the light emitting element for electrically protecting the light emitting element. Wherein the semiconductor protection element has at least one selected from a trigger diode, a transistor having an open base, a varistor, and a zener diode connected in series in a reverse direction. 3. The light-emitting diode according to claim 1, wherein the light-emitting element has p-type and n-type nitride semiconductors on a sapphire substrate with at least a light-emitting layer interposed through a nitride semiconductor containing Ga. 4. A dot matrix display for dynamically driving the light emitting diode according to claim 1.