JP2006332365A - Group iii nitride based compound semiconductor light emitting element and light emitting device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a group III nitride based compound semiconductor light emitting element which can correspond to an increase of an injecting current, and can restrain a reduction of light emitting efficiency due to heat, and can materialize a light irradiation of a large amount of lights; and a light emitting device using the same. <P>SOLUTION: An MQW barrier layer 14 is formed with AlGaN, and its thickness and an amount of addition of Al are optimized, thereby restraining an occurrence of a carrier overflow with respect to an energization of a high injecting current, and enhancing the light emitting efficiency. Further, a heat loss can be suppressed by enhancement of the light emitting efficiency, and a reduction of a light emitting characteristic is hard to occur by heat generated by an LED element 1 itself, resulting in obtaining the LED element 1 indicating the stable light emitting characteristic even in consecutive energization. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a group III nitride compound semiconductor light-emitting device and a light-emitting device using the same, and in particular, can cope with an increase in injection current, and can realize light irradiation with a large amount of light while suppressing a decrease in light emission efficiency due to heat. The present invention relates to a group nitride compound semiconductor light emitting device and a light emitting device using the same.

  Conventionally, a group III nitride compound semiconductor light-emitting device is known as an LED (Light-Emitting Diode) device that emits light from blue to green. The group III nitride compound semiconductor light-emitting device is also used as an LED device that emits light having a wavelength shorter than visible light (near-ultraviolet to ultraviolet).

In recent years, with the expansion of LED applications, the demand for larger current type and higher output type LED elements is increasing. In response to such a demand, by increasing the thickness of the well layer and the barrier layer constituting the LED element, prevention of carrier leakage, prevention of diffusion of Mg from the p-side layer, and improvement of emission intensity by improving carrier confinement There is a group III nitride compound semiconductor light-emitting device as shown (for example, see Patent Document 1).
JP 2002-84000 A [0013]

  However, according to the conventional group III nitride compound semiconductor light emitting device, when the injection current for driving the LED device is increased, carrier overflow occurs and there is a limit to improvement in luminous intensity. In addition, there is a problem that the light emission efficiency is lowered by the heat of the LED element itself caused by light emission, and a large amount of light cannot be radiated stably.

  Accordingly, an object of the present invention is to provide a group III nitride compound semiconductor light-emitting element capable of coping with an increase in injection current and realizing a large amount of light irradiation while suppressing a decrease in light emission efficiency due to heat, and a light-emitting device using the same. It is to provide.

  In order to achieve the above object, the present invention provides a group III nitride compound semiconductor layer of a first conductivity type, a group III nitride compound semiconductor layer of a second conductivity type, the first and the first, Provided is a group III nitride compound semiconductor light-emitting device having a well layer and an MQW layer comprising a barrier layer containing 3 to 6% Al provided between two conductivity type group III nitride compound semiconductor layers .

  In order to achieve the above object, the present invention provides a group III nitride compound semiconductor layer of a first conductivity type, a group III nitride compound semiconductor layer of a second conductivity type, the first and A group III nitride compound provided between the second conductivity type group III nitride compound semiconductor layer and having a well layer made of InGaN and an MQW layer made of an AlGaN barrier layer containing 3 to 6% Al A semiconductor light emitting device is provided.

  In the group III nitride compound semiconductor light emitting device, the MQW layer includes a strain relaxation superlattice layer formed by alternately laminating an InGaN layer and an n-GaN layer in a predetermined number of pairs, and a p-InGaN layer. And a p-AlGaN layer may be provided between a clad layer formed by alternately laminating a predetermined number of pairs.

  In order to achieve the above object, the present invention provides a group III nitride compound semiconductor layer of a first conductivity type, a group III nitride compound semiconductor layer of a second conductivity type, the first and A group III nitride compound provided between the second conductivity type group III nitride compound semiconductor layer and having a well layer made of InGaN and an MQW layer made of an AlGaN barrier layer containing 3 to 6% Al A semiconductor light emitting element, an element mounting substrate configured to have a thermal expansion coefficient equivalent to that of the group III nitride compound semiconductor light emitting element, and the group III nitride compound semiconductor light emitting element and the element mounting substrate are equivalent. There is provided a light emitting device characterized by having an inorganic sealing portion configured to seal the group III nitride compound semiconductor light emitting element and the element mounting substrate.

  In the above light emitting device, the inorganic sealing portion is preferably made of low melting point glass. Further, the group III nitride compound semiconductor light-emitting device is preferably flip-mounted on the device mounting board.

  According to the present invention, it is possible to cope with an increase in injection current, and it is possible to realize a large amount of light irradiation while suppressing a decrease in light emission efficiency due to heat.

(First embodiment)
FIG. 1 is a cross-sectional view showing a layer structure of a group III nitride compound semiconductor light-emitting device according to the first embodiment of the present invention.

(Configuration of LED element 1)
This face-up group III nitride compound semiconductor light-emitting element 1 (hereinafter referred to as “LED element 1”) is a blue LED element 1 that emits blue light having an emission wavelength of 460 to 470 nm. On the sapphire substrate 10, an AlN buffer layer 11, an n-GaN layer 12, a strain relaxation superlattice layer 13, an MQW layer 14, a cladding layer 15, a p ⁻ -GaN layer 16, and p ⁺ -GaN. The layer 17 and the contact layer 20 are laminated, and a pad electrode 18 made of Au is formed on the contact layer 20. In addition, an n-side electrode 19 made of Al is provided on the n-GaN layer 12 exposed by etching from the contact layer 20 to the n-GaN layer 12. In addition, in the same figure, in order to clarify the structure of each layer, each part is shown by the size different from an actual size.

  The strain relaxation superlattice layer 13 is formed by laminating 10 pairs of InGaN layers 130 and n-GaN layers 131 alternately.

  The MQW layer 14 is formed by laminating six pairs of InGaN layers 140 and AlGaN barrier layers 141 alternately.

  The clad layer 15 is formed by alternately stacking 5.5 pairs of p-InGaN layers 150 and p-AlGaN layers 151.

The contact layer 20 is made of ITO (Indium Tin Oxide) having a thermal expansion coefficient (α = 7 × 10 ⁻⁶ / ° C.) and light transmittance substantially the same as that of the GaN-based semiconductor compound. Current is diffused and supplied to the p ⁺ -GaN layer 17. When the LED element 1 is flip-mounted, rhodium (Rh) having light reflectivity can be used instead of ITO.

  Below, the manufacturing method of the LED element of this Embodiment is demonstrated.

First, the temperature of the wafer-like sapphire substrate 10 is raised to 1130 ° C. while flowing hydrogen gas (H ₂ ) into a reaction apparatus of a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus to clean the surface (a surface). After that, trimethylaluminum (TMA) and ammonia (NH ₃ ) are introduced at the substrate temperature, and an AlN buffer layer 11 having a thickness of 20 to 40 nm is grown by MOCVD. Next, with the substrate temperature maintained at 1130 ° C., trimethylgallium (TMG), nitrogen gas (N ₂ ), H ₂ , NH ₃ , and silane gas (SiH ₄ ) are introduced to grow the n-GaN layer 12. .

Next, the strain relaxation superlattice layer 13 is formed on the n-GaN layer 12. The strain relaxation superlattice layer 13 is first introduced with trixindium (TMI), TMG, N ₂ , H ₂ , NH ₃ , and SiH ₄ at a reactor internal temperature of 800 ° C., and In _x having a thickness of 20 to 50 mm. A Ga _1-x N layer (0.06 ≦ x ≦ 0.14) 130 is formed. Next, the temperature is raised to 850 ° C., TMG, N ₂ , H ₂ , NH ₃ , and SiH ₄ are introduced to form an n-GaN layer 131 having a thickness of 30 to 60 mm. By repeating this process, 10 pairs of InGaN layers 130 and n-GaN layers 131 are stacked.

Next, the MQW layer 14 is formed on the strain relaxation superlattice layer 13. The MQW layer 14 is first formed with an in-reactor temperature of 770 ° C., TMG, TMI, N ₂ , H ₂ , and NH ₃ are introduced to form an InGaN layer 140 with a thickness of 20 to 40 mm. Next, TMA, TMG, N ₂ , H ₂ , and NH ₃ are introduced at a temperature of 880 ° C., and an Al _0.5 Ga _0.95 N barrier layer 141 having a thickness of 20 to 80 mm is formed. By repeating this process, six pairs of InGaN layers 140 and AlGaN barrier layers 141 are laminated.

Next, a superlattice clad layer 15 is formed on the MQW layer 14. The cladding layer 15 is first introduced with TMI, TMG, N ₂ , H ₂ , NH ₃ , and cyclopentadinier magnesium (Cp ₂ Mg), and p-In _x Ga _1-x N having a thickness of 20 to 80 mm. A layer (0.05 ≦ x ≦ 0.12) 150 is formed. Next, TMA, TMG, N ₂ , H ₂ , NH ₃ , and Cp ₂ Mg were introduced, and a p-Al _x Ga _1-x N layer (0.25 ≦ x ≦ 0.40) having a thickness of 20 to 40 mm. ) 151 is formed. By repeating this process, 5.5 pairs of p-InGaN layer 150 and p-AlGaN layer 151 are laminated.

Next, the p ⁻ -GaN layer 16 is formed on the cladding layer 15. The p ⁻ -GaN layer 16 is formed by introducing TMG, N ₂ , H ₂ , NH ₃ , and Cp ₂ Mg at a reactor internal temperature of 1000 ° C. to form a p ⁻ -GaN layer 16 having a thickness of 800 mm.

Next, the p ⁺ -GaN layer 17 is formed on the p ⁻ -GaN layer 16. The p ⁺ -GaN layer 17 is formed by introducing TMG, N ₂ , H ₂ , NH ₃ , and Cp ₂ Mg at a reactor internal temperature of 1000 ° C. to form a p ⁺ -GaN layer 17 having a thickness of 300 mm.

  A contact layer 20 made of ITO is formed on the surface of the GaN-based semiconductor layer thus formed, and the n-GaN layer 12 is exposed by removing the contact layer 20 to the n-GaN layer 12 by wet etching. . Next, an n-side electrode 19 made of Al is formed on the exposed n-GaN layer 12. Next, a pad electrode 18 made of Au is formed on the surface of the contact layer 20. Next, it cuts into the LED element 1 of a predetermined size with a dicing saw. The wafer is not limited to being cut by a dicing saw, but may be cut by other cutting methods such as scribing.

  2 shows current-carrying characteristics of the LED element 1 having the AlGaN barrier layer shown in FIG. 1, (a) is a characteristic diagram showing changes in the current value when the thickness of the AlGaN barrier layer is changed, and (b). These are characteristic diagrams showing changes in luminous intensity with respect to changes in current.

  In this LED element 1, as shown in FIG. 2A, the Iv is 145 μW when the thickness of the AlGaN barrier layer 141 is 50 mm, and the case where the current is increased is also shown in FIG. It has been confirmed that a large amount of light can be obtained without causing the light intensity saturation seen in the GaN barrier shown in b).

(Effects of the first embodiment)
According to the first embodiment described above, the barrier layer of the MQW layer 14 is formed of AlGaN, and by optimizing the thickness and the amount of Al added, it is possible to suppress the occurrence of carrier overflow with respect to energization with a high injection current. It becomes possible, and luminous efficiency can be improved. Further, the heat loss can be suppressed by improving the light emission efficiency, and the LED element 1 that exhibits stable light emission characteristics even with continuous energization can be obtained.

  In the first embodiment, the barrier layer is made of AlGaN with an Al content of 5%. However, the current characteristics were examined by changing the amount of Al added when the film thickness was 50 mm. As shown in FIG. It can be seen that the Iv is 130 μW or more in the range of 3 to 6%, and that the Iv is 145 μW and the most favorable characteristic is obtained when the addition amount is 5%.

(Second Embodiment)
FIG. 4 is a cross-sectional view showing the light emitting device according to the second embodiment.

The light emitting device 21 uses the LED element 1 described in the first embodiment as a light source, and includes an Al ₂ O ₃ substrate 22 on which the LED element 1 is mounted, and the LED element 1 and the Al ₂ O ₃ substrate 22. And a glass sealing portion 26 made of low-melting glass for sealing.

The LED element 1 is mounted by flip mounting the LED element 1 shown in FIG. 1 on an Al ₂ O ₃ substrate 22 having a thermal expansion coefficient (α = 7 × 10 ⁻⁶ / ° C.) equivalent to that of the LED element 1. The pad electrode 18 and the n-side electrode 19 of the element 1 are electrically connected to a circuit pattern 23 formed of copper foil on the Al ₂ O ₃ substrate 22 through an Au stud pump 27. This circuit pattern 23 is connected to a circuit pattern 24 provided on the bottom surface opposite to the element mounting surface via a via pattern 25 provided in a via hole 220 formed in the Al ₂ O ₃ substrate 22.

The glass sealing portion 26 has a thermal expansion coefficient equivalent to that of the LED element 1 and the Al ₂ O ₃ substrate 22 and is formed of low melting point glass (refractive index n = 1.8) that can be hot-pressed at 350 ° C. And has a side surface 260 and an upper surface 261 to be a light extraction surface. In addition, by providing a thin yellow phosphor layer such as YAG (Yttrium Aluminum Garnet) on the surface of the glass sealing portion 26, the white light emitting device 21 that generates white light based on a mixture of blue and yellow can be obtained.

(Operation of the light emitting device 21)
By connecting the circuit pattern 24 of the light emitting device 21 to an external power supply unit (not shown) and applying a voltage, the MQW layer of the LED element 1 emits light. Blue light generated based on the light emission is incident on the glass sealing portion 26 mainly from the sapphire substrate 10 side of the LED element 1. Since the refractive index of the glass sealing portion 26 is larger than the refractive index (n = 1.7) of the sapphire substrate 10, blue light is incident on the glass sealing portion 26 without causing interface reflection with the sapphire substrate 10. , And is emitted from the side surface 260 and the upper surface 261.

(Effect of the second embodiment)
According to the second embodiment described above, the light-emitting device 21 with a large amount of light based on the preferable effect of the LED element 1 described in the first embodiment can be obtained. Further, since the LED element 1 is sealed with glass, the sealing property of the LED element 1 is better and more reliable than sealing with a resin material such as epoxy and silicone, so that the blue light emitted from the LED element 1 can be reduced. On the other hand, the glass sealing portion 26 made of an inorganic material does not deteriorate, and the light emitting device 21 having stable optical characteristics can be obtained over a long period of time. Since silicone is superior to epoxy resin in heat resistance, sealing property and heat resistance can be improved as compared with epoxy resin by using LED element 1 having a large calorific value.

  Moreover, since the deterioration of the glass sealing portion 26 made of an inorganic material does not occur with respect to the blue light emitted from the LED element 1, the light emitting device 21 having a large amount of light with stable light emission characteristics over a long period of time can be obtained. Further, the heat resistance of the entire light emitting device 21 including the LED element 1 is good. Further, since glass has a smaller coefficient of thermal expansion than that of the resin material, disconnection due to factors such as thermal expansion and contraction of the sealing material can theoretically not occur. For this reason, it can be configured to withstand the heat generated when the energization current is increased. can get.

It is sectional drawing which shows the layer structure of the group III nitride compound semiconductor light-emitting device based on the 1st Embodiment of this invention. 1 shows current-carrying characteristics of an LED element having an AlGaN barrier layer shown in FIG. 1, (a) is a characteristic diagram showing a change in current value when the thickness of the AlGaN barrier layer is changed, and (b) is a change in current. It is a characteristic view which shows the change of the luminous intensity with respect to. It is a current characteristic figure when changing the addition amount of Al with a fixed film thickness (50 kg). It is sectional drawing which shows the light-emitting device concerning 2nd Embodiment.

Explanation of symbols

1 ... LED element, 10 ... sapphire substrate, 11 ... AlN buffer layer, 12 ... n-GaN layer, 13 ... strain relaxing superlattice layer, 14 ... MQW layer, 15 ... clad layer, 16 ^... p - -GaN layer, 17 layer ^... p + -GaN layer, 18 ... pad electrode, 19 ... n-side electrode, 20 ... contact layer, 21 ... light-emitting device, 22 ... _Al 2 _{O 3} substrate, 23 ... circuit pattern, 24 ... circuit pattern, 25 ... via Pattern, 26 ... Glass sealing part, 27 ... Stud pump, 130 ... InGaN layer, 131 ... n-GaN layer, 140 ... InGaN layer, 140 ... InGaN layer, 141 ... AlGaN barrier layer, 150 ... p-InGaN layer, 151p -AlGaN layer, 220 ... via hole, 260 ... side surface, 261 ... upper surface,

Claims (6)

A group III nitride compound semiconductor layer of a first conductivity type;
A group III nitride compound semiconductor layer of a second conductivity type;
III, comprising a well layer and an MQW layer comprising a barrier layer containing 3 to 6% Al, provided between the first and second conductivity type group III nitride compound semiconductor layers. Group nitride compound semiconductor light emitting device. A group III nitride compound semiconductor layer of a first conductivity type;
A group III nitride compound semiconductor layer of a second conductivity type;
A well layer made of InGaN and an MQW layer made of an AlGaN barrier layer containing 3 to 6% Al, provided between the group III nitride compound semiconductor layers of the first and second conductivity types; A group III nitride compound semiconductor light emitting device characterized in that:   The MQW layer includes a strain relaxation superlattice layer formed by alternately stacking InGaN layers and n-GaN layers in a predetermined number of pairs, and a predetermined pair of p-InGaN layers and p-AlGaN layers alternately. The group III nitride compound semiconductor light-emitting device according to claim 1, wherein the light-emitting device is provided between a clad layer constituted by a number of layers. Group III nitride compound semiconductor layer of first conductivity type, Group III nitride compound semiconductor layer of second conductivity type, Group III nitride compound semiconductor of first and second conductivity types A III-nitride compound semiconductor light emitting device having a well layer made of InGaN and an MQW layer made of an AlGaN barrier layer containing 3 to 6% Al provided between the layers;
An element mounting substrate configured to have a thermal expansion coefficient equivalent to that of the group III nitride compound semiconductor light emitting element;
Inorganic sealing for sealing the group III nitride compound semiconductor light emitting device and the device mounting substrate, wherein the group III nitride compound semiconductor light emitting device and the device mounting substrate have the same coefficient of thermal expansion And a light emitting device.   The light emitting device according to claim 4, wherein the inorganic sealing portion is made of low-melting glass.   5. The light emitting device according to claim 4, wherein the group III nitride compound semiconductor light emitting element is flip-mounted on the element mounting substrate.

Images