JP2015185831A - Nitride semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor light emitting element using an AlN single crystal substrate, which has higher chemical and physical resistance.SOLUTION: A nitride semiconductor light emitting element 1 is formed in a manner such that an angle formed between respective normal of lateral faces f1, f2 and faces f3, f4 opposite to the lateral faces f1, f2 of an AlN single crystal substrate 10 included in the nitride semiconductor light emitting element 1, and a normal of either of an a-plane or an m-plane of an AlN single crystal of the AlN single crystal substrate 10 is less than ±4° to show minimal inclination or a parallel state.

Description

  The present invention relates to a nitride semiconductor light emitting device, and more particularly to a nitride semiconductor light emitting device using an AlN single crystal substrate.

Conventionally, semiconductor light emitting devices have been widely used, but in recent years, development of high-power and long-life deep ultraviolet LEDs (hereinafter referred to as UVC-LEDs) that can be used particularly for sterilization applications having a wavelength of 280 nm or less is expected. . Currently, the main UVC-LED is manufactured by laminating an In _x Al _y Ga _1-xy N mixed crystal layer (0 ≦ x + y ≦ 1) on an AlN thin film heteroepitaxially grown on a sapphire substrate.

However, the thermal expansion coefficient of sapphire is 7.5 × 10 ⁻⁶ / K, whereas aluminum nitride is 4.15 × 10 ⁻⁶ / K, and the lattice constant mismatch is as large as 13%. For these reasons, the aluminum nitride thin film formed on sapphire contains many defects. By forming impurity levels due to this defect, the light emission efficiency of the LED is remarkably lowered, and the lifetime of the LED is also reduced due to current concentration at the defective part.

For example, in Patent Document 1, a mask layer with a window is provided on a base substrate such as a sapphire substrate, and then a growth condition is adjusted to form pits having a plurality of facets on the crystal growth surface. As a result, dislocations are concentrated in part, and regions of low dislocation density are formed in other parts.
Patent Document 2 relates to an AlN crystal substrate obtained by an AlN crystal surface treatment method and an AlN crystal surface treatment method used for a substrate of a semiconductor device such as a light emitting element, an electronic element, or a semiconductor sensor. In order to solve the problem in heteroepitaxial, three or more semiconductor layers homoepitaxially grown on one main surface side in the AlN crystal substrate including the AlN crystal substrate and the other main surface of the AlN crystal substrate are formed. A light-emitting element including the first electrode formed on the outermost semiconductor layer of the semiconductor layer, and a conductor on which the light-emitting element is mounted. The light-emitting element includes an AlN crystal substrate. The side is a light emitting surface side, the outermost semiconductor layer side is a mounting surface side, and the semiconductor layer is formed between a p-type semiconductor layer, an n-type semiconductor layer, and a p-type semiconductor layer and an n-type semiconductor layer. It is disclosed a semiconductor device including a light emitting layer is.

JP 2001-102307 A JP 2011-49610 A

  In the case of a semiconductor device using an AlN crystal as a substrate as in Patent Document 2, since the lattice matching with the semiconductor layer is high, the semiconductor layer has a low dislocation density compared to the semiconductor layer formed on the sapphire substrate. However, the problem of poor durability arises. Specifically, chemical and physical damage is received in the subsequent process of the light emitting element manufacturing process, and the performance as the light emitting element is deteriorated.

  The present invention has been made in view of such a problem, and provides a nitride semiconductor light emitting device having higher chemical and physical resistance in a nitride semiconductor light emitting device using an AlN single crystal substrate. Objective.

A nitride semiconductor light-emitting device according to one embodiment of the present invention includes an AlN single crystal substrate (for example, the AlN single crystal substrate 10 illustrated in FIG. 5) and a stacked structure portion (for example, FIG. 5 illustrated in FIG. 5). The laminated structure portion includes a first conductive type layer (for example, the first conductive type layer 21 shown in FIG. 5) and a light emitting layer (for example, the light emitting layer 22 shown in FIG. 5). ) And a second conductivity type layer (for example, the second conductivity type layer 23 shown in FIG. 5) are laminated on the AlN single crystal substrate in this order, and a normal of one side surface of the AlN single crystal substrate The angle between the normal line of any one of the AlN single crystal a-plane and the m-plane of the AlN single-crystal substrate is less than ± 4 °.
The amount of sedges on the side surface of the AlN single crystal substrate may be ± 25 μm or less.

  According to the nitride semiconductor light emitting device of the present invention, a nitride semiconductor light emitting device having high chemical and physical resistance can be realized.

It is a schematic diagram for demonstrating the structure of an element side surface. It is a schematic diagram for demonstrating the crystal orientation of a nitride semiconductor. It is explanatory drawing for demonstrating the positional relationship of the side surface of an AlN single crystal substrate, a surface, and m surface. It is the schematic of the element side surface for demonstrating the amount of soges. It is a perspective view which shows typically an example of the nitride semiconductor light-emitting device in this embodiment. It is a characteristic view which shows the relationship between the angle which an element side surface and m surface make, and an etching rate. It is a characteristic view which shows the relationship between the angle which an element side surface and a surface make, and an etching rate.

Hereinafter, modes for carrying out the present invention will be described.
<Nitride semiconductor light emitting device>
The nitride semiconductor light emitting device of the present embodiment includes an AlN single crystal substrate and a stacked structure portion formed on the AlN single crystal substrate, and the stacked structure portion includes a first conductivity type layer, a light emitting layer, and The second conductivity type layer is laminated on the AlN single crystal substrate in this order, and the normal of one side surface of the AlN single crystal substrate and any one of the AlN single crystal a plane and the m plane of the AlN single crystal substrate. The angle formed by the normal of the surface is less than ± 4 °.

  That is, as shown in FIG. 1, the method of the surface of the AlN single crystal substrate 10 included in the nitride semiconductor light emitting device 1 and any one of the surfaces f3 and f4 facing the side surfaces f1 and f2 is used. When the line and the normal line of any one of the AlN single crystal a-plane and m-plane of the AlN single-crystal substrate 10 are parallel, or the direction in which one side of the a-plane or m-plane extends is the front-rear direction, the element Angle formed by the side surface of the element when the side surface is tilted in the front-rear direction, the left-right direction orthogonal to the front-rear direction, or the front-rear direction and the left-right direction, that is, the angle between the normals of these surfaces Is less than ± 4 ° and the a-plane or m-plane is parallel to the element side (when the angle between the normal of the a-plane or m-plane and the normal of the element side is 0 °) or completely Although not parallel to the a-plane or m-plane Side is formed so as to be slightly inclined state.

FIG. 2 is a unit cell showing the plane orientation of the AlN single crystal. Since the AlN single crystal is described in a hexagonal system and has 6-fold symmetry, the m plane and the a plane each have six equivalent planes as shown in FIG.
When the AlN single crystal is viewed from the (0001) plane, the a plane and the m plane of the AlN single crystal are planes that pass through one side of a hexagon composed of three nearest nitrogen atoms and three nearest aluminum atoms. The m-plane, and the plane that forms 90 ° with the m-plane is the a-plane.

  As shown in FIG. 3, the angle formed by the normal line Nf1 of the side surface f1 of the AlN single crystal substrate 10 and the normal line Na of one a-plane is less than ± 4 °, and the AlN single crystal substrate 10 The angle formed by the normal line Nf2 of the side surface f2 and the normal line Nm of one m-plane is less than ± 4 °. As described above, since the a-plane and the m-plane are shifted by 90 °, in the case of the rectangular AlN single crystal substrate 10, the normal of one side and the method of any one of the m-plane and the a-plane If the angle formed with the line is less than ± 4 °, the normal formed on the other side surface with respect to the normal of one of the m-plane and the a-plane is less than ± 4 °.

The angle formed between the normal line of the side surface of the AlN single crystal substrate 10 of the nitride semiconductor light emitting device 1 and the normal line of either the a-plane or the m-plane of the AlN single crystal is less than ± 4 °. The number of dangling bonds existing on the side surface and the step structure formed by cleavage when cleaving the element are reduced. Therefore, chemical and physical resistance can be improved.
The chemical resistance can be evaluated, for example, by measuring the etching rate on the side surface of the element with KOH (potassium hydroxide).

The physical resistance can be evaluated by, for example, the destruction probability of the element when the element is cleaved or the presence or absence of chipping.
Whether or not the angle formed by the normal of any element side surface of the AlN single crystal substrate 10 and the normal of any one of the AlN single crystal a-plane and m-plane is less than ± 4 ° is Although it is identified by crystal orientation measurement by a diffraction analysis method using a reciprocal lattice (for example, high-speed electron diffraction, low-energy electron diffraction, etc.), identification by XRD (X-ray diffraction) is preferable.

  In addition, the width of the scribe groove for cleaving the element is usually smaller than about 20 μm, and when considering the scribe groove width and the amount of sedge when cleaved, if the amount of sedge exceeds 25 μm, the element itself or an adjacent element Lead to destruction. Further, in the case where an element is manufactured by increasing the interval between elements in order to prevent destruction of the element with respect to a soge exceeding 25 μm, the number of elements to be obtained is reduced. The nitride semiconductor light emitting device 1 of the present embodiment suppresses device destruction due to cleaving while ensuring a sufficient number of devices by making the amount of souge on the side surfaces f1 to f4 of the AlN single crystal substrate 10 ± 25 μm or less. be able to.

As shown in FIG. 4, the “sedge amount” means a squareness in the thickness direction of the split sections B <b> 1 and B <b> 2 with respect to the surface A of the element 1. That is, as shown in FIG. 4, the shifts ΔL1 and ΔL2 of the split sections B1 and B2 from the vertical plane corresponding to the planned cutting lines La and Lb are referred to as soge amounts.
In the nitride semiconductor light emitting device 1 of the present embodiment, the amount of soggy is, for example, between the most convex portion on the side surface and the most concave portion by length measurement from the side surface parallel direction of the device using an optical microscope or SEM (scanning electron microscope). It is evaluated by the distance. In addition, the measurement is performed on the outermost side of the element side surface, and the amount of sodge takes an average value.

  For example, in the schematic configuration diagram showing an example of the nitride semiconductor light emitting device 1 shown in FIG. 5, the outermost side portion C10 of the side surface f11 of the nitride semiconductor light emitting device 1 is measured from the direction parallel to the side surface f11. The length is measured from a direction parallel to the side surface f12. In the case of the nitride semiconductor light emitting device 1 having the configuration as shown in FIG. 5, the four outermost portions are measured from a total of eight locations from two directions, and the average value of the measurement results at the eight locations is obtained. The average value is evaluated as the amount of soge.

  Here, the case where the average value of the measurement results at the eight locations is obtained and the evaluation is performed using the average value as the amount of soda has been described, but each of the measurement results at eight locations may be evaluated as the amount of souge. . As described above, by evaluating the average value of the measurement results at the eight locations as the amount of soda, it is possible to evaluate the physical and chemical resistance of the entire device rather than a part of the device.

<Specific example>
Next, a more specific form of the nitride semiconductor light emitting device of this embodiment will be described with reference to the drawings.
FIG. 5 is a perspective view schematically showing an example of the nitride semiconductor light emitting device 1 of the present embodiment.
The nitride semiconductor light emitting device 1 includes an AlN single crystal substrate 10, a stacked structure portion 20 formed on the AlN single crystal substrate 10, and electrode portions 31 and 32 for supplying electrodes to the light emitting device.
The stacked structure unit 20 includes a first conductivity type layer 21, a light emitting layer 22, and a second conductivity type layer 23 having a conductivity type different from that of the first conductivity type layer 21 in this order on the AlN single crystal substrate 10. Being done.

  The first conductivity type layer 21 is composed of a rectangular bottom region 21a in a top view and a rectangular laminated portion 21b that is formed on the bottom region 21a in a convex shape and has an outer diameter smaller than that of the bottom region 21a. The laminated portion 21b is formed on one side in the longitudinal direction of the bottom region 21a, and the region on the other side is a region where the electrode portion 32 is formed. The stacked structure unit 20 includes, for example, a layer that becomes the first conductivity type layer 21, a layer that becomes the light emitting layer 22, and a layer that becomes the second conductivity type layer 23 in this order. In the region where 32 is to be formed, a mask is formed in a portion to be the stacked structure portion 20 without forming a mask, and the first conductivity type layer 21 is etched so that the stacked portion 21b remains.

Then, the electrode unit 31 is stacked on the second conductivity type layer 23.
Each side of the AlN single crystal substrate 10, that is, in the case of FIG. 5, the side surfaces f11, f12, f13 and the side surfaces f13, f14 facing the side surfaces f11, f12 are respectively normal to the side surfaces f11-f14. The angle formed by the normal line of either the a-plane or the m-plane of the AlN single crystal substrate 10 is less than ± 4 °.

Note that the angle formed by the normals of all the side surfaces of the AlN single crystal substrate 10 and the normals of either the a-plane or the m-plane of the AlN single-crystal substrate 10 may not necessarily be less than ± 4 °. The angle formed by the normals of all side surfaces and the normal of the a-plane or m-plane is preferably less than ± 4 °.
Examples of a method for evaluating the angle formed between the side surfaces f11 to f14 and any one of the a-plane and m-plane of the AlN single crystal substrate 10 include the following methods. That is, first, the target element to be evaluated is polished to remove the electrode portions 31 and 32 and the mesa portion 25 having a laminated structure including the laminated portion 21b, the light emitting layer 22 and the laminated portion 21b. A flat surface made of the first conductivity type layer 21 is generated on the upper surface of the target element.

  Then, the crystal orientation is identified by a diffraction analysis method using a crystal reciprocal lattice on a flat surface. From the relationship between the element shape and the crystal orientation, the normal of the element side faces f11 to f14 and any one of the m plane and the a plane Evaluate the angle formed by the normal. That is, for each element side surface, the angle formed by the element side surface and either the m-plane or the a-plane is evaluated. XRD (X-ray diffraction method) is preferable as a diffraction analysis method using a crystal reciprocal lattice.

Next, each element included in the nitride semiconductor light emitting device 1 of the present embodiment will be described.
Each of these elements is applied independently or in combination in the nitride semiconductor light emitting device 1 of this embodiment.

[AlN single crystal substrate]
The method for producing the AlN single crystal substrate 10 is not particularly limited, but it is preferably produced by a sublimation method using aluminum nitride ceramics as a raw material from the viewpoint of obtaining a high quality AlN single crystal substrate 10. The dislocation density of the AlN single crystal substrate 10 is preferably less than 10 ⁷ cm ⁻² , particularly preferably less than 10 ⁵ cm ⁻² .

Since the incomplete surface treatment increases the dislocation density when the first conductivity type layer 21 is formed, the RMS (root mean square roughness) surface roughness of the AlN single crystal substrate 10 is 0 for an area of 10 μm × 10 μm. It is preferably less than 5 nm.
In the nitride semiconductor light emitting device 1 of the present embodiment, the AlN single crystal substrate 10 can be formed with the laminated structure portion 20 having the first conductive type layer 21, the light emitting layer 22, and the second conductive type layer 23 thereon. There is no particular limitation as long as it is correct. From the viewpoint of obtaining the laminated structure 20 with good crystallinity, the surface on which the laminated structure 20 is formed is preferably an Al surface. In addition, since the angle between the normal of the element side surface and the normal of any one of the a plane and the m plane is less than ± 4 °, the surface of the AlN single crystal substrate 10 is an Al plane (or N plane). It is preferable that the inclined substrate is less than 4 °.

(Laminated structure part)
In the nitride semiconductor light emitting device 1 of the present embodiment, the stacked structure unit 20 includes a first conductivity type layer 21, a light emitting layer 22, and a second conductivity type layer 23.
The first conductivity type layer 21 and the second conductivity type layer 23 are preferably composed of In _x Al _y Ga _1-xy N (0 ≦ x + y ≦ 1).

In a specific embodiment, the first conductivity type layer 21 is composed of a plurality of individual layers composed of In _x Al _y Ga _1-xy N (0 ≦ x + y ≦ 1), and the lattice parameter of the light emitting layer 22 It may be distorted in a pseudo-lattice matching so as to approach. The plurality of layers may include a plurality of layers having a gradient composition where x and y vary with thickness. In such a layer, the composition may be graded at individual stages or linearly. In a preferred embodiment, the In _x Al _y Ga _1-xy N layer has a composition approximately equal to the composition of the single crystal AlN at the interface of the AlN single crystal substrate 10. This promotes two-dimensional growth and suppresses the formation of inconvenient islands. By such island formation, for example, the first conductivity type layer 21 made of an Al _x Ga _1-x N layer and the subsequent layers are formed. Inadvertent elastic strain relaxation in the growth layer (light emitting layer 22, second conductivity type layer 23) is avoided.

In one embodiment, the light emitting layer 22 includes a multiple quantum well (MQW) layer, and is manufactured on the first conductivity type layer 21 composed of, for example, an Al _x Ga _1-x N layer. The MQW layer includes a plurality of quantum wells, each of which includes AlGaN or may consist essentially of AlGaN.
In one aspect, each period of the MQW layer includes an Al _x Ga _1-x N quantum well and an Al _y Ga _1-y N quantum well. Here, x is different from y. In a preferred embodiment, the difference between x and y is large enough to provide good confinement of electrons and holes in the active region, so that radiative recombination versus non-radiative recombination. The ratio can be increased. In one aspect, the difference between x and y is about 0.05, for example, x is about 0.35 and y is about 0.4. However, if the difference between x and y is excessively large, for example, greater than 0.3, inconvenient island formation occurs during the formation of the MQW layer.

The MQW layer may include a plurality of periods and may have a total thickness of less than 50 nm. The “total thickness” referred to here is the thickness of the light-emitting layer 22 when it is composed of one layer, and when it is composed of two or more layers, it is the thickness of all layers. Total.
In one aspect, the emissive layer 22 has an optional thin electron block (or hole block if an n-type contact is placed on top of the device) layer, which is a single layer such as, for example, Mg. It contains or consists essentially of Al _x Ga _1-x N doped with the above impurities. The electron block layer has a thickness of 20 nm, for example.

The Al _x Ga _1-x N layer as the second conductivity type layer 23 formed on the light emitting layer 22 is essentially an Al doped with at least one impurity such as one or more semiconductor materials, for example Mg. _x Ga _1-x N is included or consists essentially of it. The Al _x Ga _1-x N layer as the second conductivity type layer 23 is doped n-type or p-type, but what is the conductivity of the Al _x Ga _1-x N layer as the first conductivity type layer 21? It has the opposite conductivity. The thickness of the Al _x Ga _1-x N layer as the second conductivity type layer 23 is greater than 50 nm and less than 100 nm. In one aspect, the Al _x Ga _1-x N layer as the second conductivity type layer 23 comprises a cap layer comprising or consisting essentially of one or more semiconductor materials doped with the same conductivity. Yes. The cap layer includes GaN doped with Mg and has a thickness greater than 10 nm and less than 200 nm, preferably 50 nm.

  There may be one or more stacked structure units 20. From the viewpoint of improving the amount of light emission per unit area, it may be preferable to include a plurality of stacked structure units 20 connected in parallel. Further, the shape of the laminated structure 20 is not particularly limited, and examples thereof include a rectangular shape, a circle or an ellipse, a polygonal shape, and combinations thereof.

(Electrode part)
The nitride semiconductor light emitting device 1 of this embodiment includes electrode portions 31 and 32 for supplying power to the light emitting layer 22. Although arrangement | positioning in particular of the electrode parts 31 and 32 is not restrict | limited, When the laminated structure part 20 is a mesa structure, the example which arrange | positions an electrode at a mesa top part and a mesa bottom part, respectively is mentioned. In addition, there is an example in which electrodes are respectively arranged on the upper surface and the lower surface of the element.

  The electrode portions 31, 32 are, for example, Ni / Au alloys (typically used for p-type contacts) or Ti / Al / Ti / Au stacks (typically used for n-type contacts). For example, by sputtering or vapor deposition. The electrode portions 31 and 32 may also include an ultraviolet (UV) reflector. The UV reflector redirects photons emitted toward the electrode portions 31, 32 (so that the photons cannot escape from the laminated structure), and photons toward the desired light emitting surface, eg, the bottom surface. Is directed to improve the extraction efficiency of photons generated in the active region of the device. The material of the electrode portions 31 and 32 may be a conductive material such as gold, nickel, aluminum, titanium, or a combination thereof. The present invention is not limited to these examples.

<Others>
The nitride semiconductor light emitting device 1 of the present embodiment may have other configurations depending on the purpose. As an example, a protective layer made of SiO ₂ and / or SiN covering the surface of the laminated structure 20, a metal thin wire for supplying electric power from the outside, a sealing resin for making PKG, an antireflection film or a lens And an optical member such as a circuit unit and a sensor unit for controlling the operation of the nitride semiconductor light emitting device.
<Nitride Semiconductor Light-Emitting Device Manufacturing Method>
Next, an example of a method for manufacturing the nitride semiconductor light emitting device 1 of the present embodiment will be described.

As an example of the manufacturing method of the nitride semiconductor light emitting device 1 of the present embodiment, an Al _x Ga _1-x N layer (0 ≦ x ≦ 1) as the first conductivity type layer 21 on the AlN single crystal substrate 10, a light emitting layer 22 and an Al _x Ga _1-x N layer as the second conductivity type layer 23 are laminated in this order, and the normal line on either side of the AlN single crystal substrate 10 and the AlN single crystal a of the AlN single crystal substrate 10 There is a method of cleaving the element so that the angle formed with the normal line of any one of the surface and the m-plane is a surface of less than ± 4 °.

As an example of the method of cleaving the element, for example, the following method can be given. That is, when dividing into substantially rectangular elements, the first scribe groove extending in a direction parallel to a pair of opposing sides of the element after division and a direction parallel to the other pair of sides when viewed from above It is necessary to form a second scribe groove extending in the direction.
That is, first, first scribe grooves are formed in parallel at regular intervals. At this time, laser irradiation is performed so that the angle formed by the normal of the surface formed inside the groove by the first scribe groove and the normal of the m-plane of the AlN single crystal is less than ± 4 °. For example, forming a first scribe groove substantially parallel to one side of a hexagon forming a part of the m plane when the hexagonal column representing the crystal structure of the AlN single crystal substrate 10 is viewed from the (0001) plane, In addition, laser irradiation is performed so that the extending direction of the m-plane viewed from the (0001) plane is substantially parallel to the laser irradiation direction.

  Next, the laser irradiation direction is rotated by 90 °, and second scribe grooves orthogonal to the first scribe grooves are formed in parallel at regular intervals. At this time, laser irradiation is performed so that the angle formed between the normal line of the surface formed inside the groove by the second scribe groove and the normal line of the AlN single crystal a surface is less than ± 4 °. For example, when the hexagonal column representing the crystal structure of the AlN single crystal substrate 10 is viewed from the (0001) plane, it is a side that forms part of the a plane and is orthogonal to one side that forms part of the m plane. A second scribe groove is formed substantially parallel to the side, and laser irradiation is performed so that the direction in which the a-plane viewed from the (0001) plane extends and the laser irradiation direction are substantially parallel.

Thereafter, the element is cleaved along the first and second scribe grooves by pressing and applying a blade from the surface opposite to the surface on which laser irradiation has been performed.
As an example of the cleaving method, a combination of a laser and a scriber is described here, but other combinations such as a stealth dicing and an expander using a laser, a blade dicing using a diamond cutter, or a combination of a scriber, a chopper and an expander can be given.

  Further, in order to make the normals of the four side surfaces of the element after cleaving and the normals of any one of the m-plane and a-plane parallel, the element formation direction and the AlN single crystal substrate 10 It is necessary to match the extending direction of the m-plane and the a-plane. In order to match the element formation direction, it is preferable to form an orientation flat parallel to the m-plane or the a-plane on the AlN single crystal substrate 10.

Examples are shown below.
<Example 1>
Single crystal AlN grown using the sublimation method is processed into a wafer shape with a wire saw or the like so that the (0001) surface is the front surface and the (000-1) surface is the back surface, and the surface is mechanically ground and chemically and physically An AlN single crystal substrate 10 having a flat Al surface at the atomic level was prepared by polishing using a polishing method.

After the prepared AlN single crystal substrate 10 was introduced into the organometallic vapor phase epitaxy reactor, hydrogen and ammonia mixed gas were introduced into the reactor, and the AlN single crystal substrate 10 was heated to 1100 ° C.
Subsequently, trimethylaluminum (TMA) was introduced, and an AlN buffer layer (thickness 0.3 μm) was grown on the AlN single crystal substrate 10.

Subsequently, reducing the TMA gas flow rate, increasing the trimethylgallium (TMG) gas flow rate, inclination _Al x _{Ga 1-x} N layer is grown, _Al x Ga ₁ x is linearly inclined in the thickness direction (gradient) _{A −xN} transition layer was grown to 0.1 μm.
As the first conductivity type layer 21, an AlGaN layer of the first conductivity type doped with Si was grown on the transition layer with a thickness of 500 nm.

On the AlGaN layer of the first conductivity type, a multiple quantum well (MQW) layer having a total thickness of 50 nm was grown as the light emitting layer 22.
An AlGaN electron block layer having a thickness of 50 nm was formed on the MQW layer.
As the second conductivity type layer 23, a second conductivity type GaN layer doped with Mg and having a thickness of 200 nm was formed on the AlGaN electron block layer.

  An AlN single crystal in which the multilayer structure 20 composed of the first conductivity type AlGaN layer, the multiple quantum well (MQW) layer, the AlGaN electron block layer, and the second conductivity type GaN layer thus formed is formed. The crystal orientation of the substrate 10 is measured by XRD, and the angle formed by the normal of any element side surface after cleaving and the normal of any m-plane is 0 °, 1 °, 2 °, 3 °, The element direction was determined so as to be 4 ° and 5 °, and electrode portions 31 and 32 for supplying power to the light emitting layer 22 were formed.

  For the element cleaving, a laser ablation method is used to form a scribe groove, and the element is cleaved using a semiconductor singulation device using a zirconia ceramic blade. Each of the nitride semiconductor light emitting devices 1 having angles of 0 °, 1 °, 2 °, 3 °, 4 °, and 5 ° with the normal line of any mN plane of the AlN single crystal was produced.

  The side surface of the element after cleaving was observed with an optical microscope, and measurement of chipping and measurement of the amount of sedge were performed to confirm that the amount of sedge on the side surface of the element was ± 25 μm or less. Moreover, the etching rate was calculated by the length measurement by the SEM of the side surface before and behind the process which performed the etching process with strong alkali aqueous solution (20% of concentration KOH aqueous solution) using the produced element. In the etching process, it is necessary to remove decomposition products generated by laser ablation. Generally, the generated decomposition products are removed by etching with the above-mentioned strong alkaline aqueous solution for about 10 minutes. However, if etching is performed for a long time, the surface shape for optical improvement is lost, so the etching amount must be such that the surface shape for optical improvement is not lost. The etching amount is preferably 280 nm or less, and therefore, the etching rate needs to be about 1.7 μm / hour.

Each element formed so that the angle formed by the normal of any m-plane and the normal of any element side has an angle of 0 °, 1 °, 2 °, 3 °, 4 °, 5 ° About the chipping generation | occurrence | production condition of the element at the time of cleaving was confirmed. Chipping means chipping of the element, and chipping reaching the electrode portions 31 and 32 is defined as chipping. Table 1 shows the measurement results of chipping.
Table 1 shows the angle of the element side surface with respect to the m plane, that is, the angle formed by the normal line of any m plane and the normal line of any element side surface, and the occurrence of chipping at each angle. Is.

  From Table 1, when the angle formed by the normal of the m-plane and the normal of the element side surface is less than 4 °, no chipping occurs at the time of cleaving, but the normal of the m-plane and the element side surface When the angle formed by the normal is 4 ° or more, it can be seen that chipping occurs at the time of cleaving, and physical vulnerability appears.

<Example 2>
The first conductivity type AlGaN layer as the first conductivity type layer 21 formed in the same manner as in Example 1, the multiple quantum well (MQW) layer as the light emitting layer 22, the AlGaN electron block layer, and the second conductivity type layer 23, the crystal orientation of the AlN single crystal substrate 10 on which the laminated structure portion 20 composed of the second conductivity type GaN layer is formed is measured by XRD, and the normal on either side of the element after cleaving, The element direction is determined so that the angle formed by the normal of the a-plane is 0 °, 1 °, 2 °, 3 °, 4 °, 5 °, and power is supplied to the light emitting layer 22. Electrode portions 31 and 32 for supply were formed.

The element is cleaved in the same manner as in Example 1, and the angle formed between the normal line of the element side surface after cleaving and the normal line of any surface of the AlN single crystal a plane is 0 °, 1 °, 2 °, Nitride semiconductor light emitting devices 1 of 3 °, 4 °, and 5 ° were respectively produced.
The side surface of the element after cleaving was observed with an optical microscope, and measurement of chipping and measurement of the amount of sedge were performed to confirm that the amount of sedge on the side surface of the element was ± 25 μm or less. Moreover, the etching rate was calculated by the length measurement by the SEM of the side surface before and behind the process which performed the etching process with strong alkali aqueous solution (20% of concentration KOH aqueous solution) using the produced element.

The angle formed by the normal of any one of the a-planes and the normal of any of the side surfaces of the element is 0 °, 1 °, 2 °, 3 °, 4 °, and 5 °. About each element, the chipping generation | occurrence | production situation of the element at the time of cleaving was confirmed.
Table 2 shows the angle of the element side surface with respect to the a plane, that is, the angle formed by the normal of the a plane and the normal of the element side surface, and the occurrence of chipping at each angle.

  From Table 2, when the angle formed between the normal of the a-plane and the normal of the element side is less than 4 °, no chipping occurs during cleaving, but the normal of the a-plane and the element side When the angle formed by the normal is 4 ° or more, it can be seen that chipping occurs at the time of cleaving, and physical vulnerability appears.

<Example 3>
In the same manner as described in Example 1, the angle with respect to the m-plane, that is, the angle formed between the normal of the m-plane and the normal of the element side surface is a value between 1 ° and 5 °. The nitride semiconductor light-emitting device 1 obtained by cleaving the surface with the angle shifted by 1 ° is wet-etched with a strong alkali solution (20 wt% KOH aqueous solution), and the etching rate of the device side surface is confirmed. went. The result is shown in FIG. From FIG. 6, when the angle formed between the normal of the m-plane and the normal of the element side is less than 4 °, the etching does not proceed so rapidly, but the etching is not performed on the side of the element that is 4 ° or more. It is understood that the chemical fragility appears rapidly and the etching rate exceeds 1.7 μm / hour, that is, exceeds the etching rate at which the surface shape for optical improvement is lost.
In FIG. 6, the horizontal axis represents the amount of deviation of the angle of the element side surface from the m-plane, that is, the angle [°] formed by the m-plane (normal line) and the element side surface (normal line). Is the etching rate [μm].

<Example 4>
In a method similar to the method described in Example 2, the angle with respect to the a-plane, that is, the angle formed between the normal of the a-plane and the normal of the element side surface is a value between 1 ° and 5 °. The nitride semiconductor light-emitting device 1 obtained by cleaving the surface with the angle shifted by 1 ° is wet-etched with a strong alkali solution (20 wt% KOH aqueous solution), and the etching rate of the device side surface is confirmed. went. FIG. 7 shows the result. From FIG. 7, when the angle formed between the normal of the a-plane and the normal of the element side is 4 ° or less, the etching does not proceed so rapidly, but the etching is not performed on the side of the element that is 5 ° or more. It is understood that the chemical fragility appears rapidly and the etching rate exceeds 1.7 μm / hour, that is, exceeds the etching rate at which the surface shape for optical improvement is lost.

In FIG. 7, the horizontal axis represents the amount of deviation of the angle of the element side surface from the a plane, that is, the angle [°] formed by the a plane (normal line) and the element side surface (normal line). Is the etching rate [μm].
As described above, according to the present invention, it has been confirmed that a nitride semiconductor light emitting device using the AlN single crystal substrate 10 and improved in chemical and physical resistance can be realized.

  The scope of the present invention is not limited to the exemplary embodiments and examples shown and described. Based on the knowledge of those skilled in the art, design changes or the like may be added to each embodiment or example, and each embodiment or example may be arbitrarily combined, and is equivalent to the purpose of the present invention. Also includes all embodiments that provide an effect. Further, the scope of the invention can be defined by any desired combination of particular features among all the disclosed features.

DESCRIPTION OF SYMBOLS 1 Nitride semiconductor light-emitting device 10 AlN single crystal substrate 20 Laminated structure part 21 1st conductivity type layer 22 Light emitting layer 23 2nd conductivity type layer 31, 32 Electrode part f11-f14 Side surface

Claims (2)

An AlN single crystal substrate;
A laminated structure formed on the AlN single crystal substrate,
The laminated structure portion is formed by laminating a first conductivity type layer, a light emitting layer, and a second conductivity type layer in this order on the AlN single crystal substrate,
Nitride whose angle formed between the normal line of one side surface of the AlN single crystal substrate and the normal line of any one of the AlN single crystal a plane and m plane of the AlN single crystal substrate is less than ± 4 ° Semiconductor light emitting device.   The semiconductor light emitting element according to claim 1, wherein the amount of sedges on the side surface of the AlN single crystal substrate is ± 25 μm or less.

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