JP2007019488A - Semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance light take-out efficiency of a semiconductor light emitting element. <P>SOLUTION: The semiconductor light emitting element 10 comprises a buffer layer 14, an n-type GaN layer 16, an InGaN light emitting layer 18, and a p-type GaN layer 32 formed on a sapphire substrate 12. A ZnO layer 24 functioning as a transparent electrode is provided on the p-type GaN layer 32, and recesses are formed in the surface of the ZnO layer 24 at a two-dimensional interval. Assuming the wavelength of light from the InGaN light emitting layer 18 is λ in the air, the refractive index of the ZnO layer at that wavelength λ is n<SB>zλ</SB>, and the total reflection angle on the interface between the ZnO layer and a medium touching it is θ<SB>z</SB>, periodic interval L<SB>z</SB>of adjacent recesses is set in the following range; λ/n<SB>zλ</SB>≤L<SB>z</SB>≤λ/(n<SB>zλ</SB>×(1-sinθ<SB>z</SB>)). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device, and more particularly to a GaN-based semiconductor light emitting device.

  In recent years, semiconductor light emitting devices using GaN-based semiconductors are known as blue semiconductor light emitting devices. White LEDs, which are a combination of a blue semiconductor light emitting element and a yellow light emitter, are increasing in demand for LCD backlights for mobile phones and the like. In addition, since white LEDs have the characteristics of low power consumption and long life, they are expected to be used as light sources that are replaced with fluorescent lamps, incandescent lamps, and the like.

  A conventional GaN-based semiconductor light-emitting device has a structure in which a GaN buffer layer, an n-type GaN layer, a light-emitting layer, and a p-type GaN layer are sequentially grown on a sapphire substrate. However, in such a conventional structure, the difference between the refractive index of the p-type GaN layer and the refractive index of air or resin in contact with the p-type GaN layer is large. Since the total reflection angle at the interface with the resin becomes small, most of the light generated in the light emitting layer is totally reflected at the interface with the air and the resin in contact with the p-type GaN layer, and the light extraction efficiency is low. there were.

  For example, assuming that the semiconductor light emitting device emits light in the air, the refractive index of GaN is about 2.5 when the wavelength of light is 450 nm, and thus total reflection at the interface between the p-type GaN layer and air. The angle is as small as about 24 °. Light emitted from the light emitting layer and incident on the interface between the p-type GaN layer and air at an angle larger than the total reflection angle is totally reflected at the interface between the p-type GaN layer and air, and thus is extracted from the semiconductor light emitting device. I can't.

  To solve this problem, a method has been proposed in which irregularities are periodically formed in the p-type GaN layer at intervals of about the emission wavelength (for example, Patent Document 1). In this structure, the traveling direction of the light emitted from the light emitting layer is changed by the diffraction effect due to the irregularities formed periodically, and the light is diffracted at an angle that does not cause total reflection, thereby improving the light extraction efficiency of the semiconductor light emitting device. To do.

When such periodically formed irregularities are formed in the p-type GaN layer, a resist is first formed on the crystal-grown p-type GaN layer, and a resist pattern is formed by an interference exposure method or the like. Thereafter, a portion not covered with the resist pattern is removed by dry etching such as RIE, thereby forming irregularities in the p-type GaN layer.
Japanese Patent Laying-Open No. 2005-5679

  However, when the p-type GaN layer is etched by dry etching, nitrogen vacancies are generated on the surface of the etched p-type GaN layer due to plasma damage. Since this nitrogen vacancy acts as a donor, an n-type portion is generated on the surface of the etched p-type GaN layer. If there is an n-type portion on a part of the surface of the p-type GaN layer, the n / p junction is present and the portion is + biased from the n side, resulting in a reverse bias state. The forward voltage of the semiconductor light emitting device is increased. In addition, since the current injected into the light emitting layer is reduced in the n-type portion, and the resistance of the p-type GaN layer is high and there is no current spread, the effective light emitting region of the semiconductor light emitting element eventually decreases. .

  Therefore, it is necessary to remove the n-type portion of the p-type GaN layer by a method such as wet etching, but wet etching of GaN is difficult and difficult to remove completely, and the number of manufacturing processes increases. Therefore, the manufacturing cost increases.

  The present invention has been made in view of such a situation, and an object thereof is to provide a semiconductor light emitting device having improved light extraction efficiency.

In order to solve the above problems, a semiconductor light emitting device according to an aspect of the present invention is a semiconductor light emitting device in which an n-type GaN layer, a light emitting layer, and a p-type GaN layer are stacked on a substrate, A Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) is provided on the type GaN layer, and a two-dimensional surface is formed on the surface of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). Concave portions or convex portions are formed at periodic intervals.

According to this aspect, since the recesses or projections are formed on the surface of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at two-dimensional periodic intervals, light from the light emitting layer is not emitted. Diffracted. Of the diffracted light, diffracted light incident on the interface at a smaller angle than the total reflection angle at the interface between the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) and the medium in contact with the Mg _x Zn _1-x O layer is totally reflected. Without being taken out of the semiconductor light emitting device. Since recesses or protrusions are formed in the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5), not the p-type GaN layer, the plasma during dry etching is directly exposed to the p-type GaN layer. Therefore, the p-type GaN layer surface does not become n-type due to damage, so that the light extraction efficiency can be improved without increasing the forward voltage. In addition, since the wet etching process after dry etching, which has been conventionally required, becomes unnecessary, the manufacturing cost can be reduced.

The recesses or protrusions formed in the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) may be arranged in a square lattice shape or a triangular lattice shape. When arranged in a square lattice shape, concave portions or convex portions can be formed at two-dimensional periodic intervals. When arranged in a triangular lattice shape, the density of the concave portions or convex portions formed at two-dimensional periodic intervals can be increased, and the light extraction efficiency can be preferably improved.

  Another embodiment of the present invention is also a semiconductor light emitting device. This semiconductor light-emitting device is a semiconductor light-emitting device in which a p-type GaN layer, a light-emitting layer, and an n-type GaN layer are stacked, and has recesses or recesses on the surface of the n-type GaN layer at two-dimensional periodic intervals. A convex part is formed.

  According to this aspect, since the concave portions or the convex portions are formed on the surface of the n-type GaN layer at two-dimensional periodic intervals, the light from the light emitting layer is diffracted. Of the diffracted light, diffracted light that has entered the interface at an angle smaller than the total reflection angle at the interface between the n-type GaN layer and the medium in contact with the n-type GaN layer is extracted outside the semiconductor light emitting device without being totally reflected. Nitrogen vacancies are also generated by dry etching the n-type GaN layer, and the surface of the n-type GaN layer 16 becomes n-type. However, since the n-type GaN layer is originally n-type, a reverse bias is applied. The light extraction efficiency can be improved without entering the state and without increasing the forward voltage. In this case also, the manufacturing cost can be reduced because the wet etching step after the dry etching which has been conventionally required is not necessary.

  The concave portions or convex portions formed in the n-type GaN layer may be arranged in a square lattice shape or a triangular lattice shape. When arranged in a square lattice shape, concave portions or convex portions can be formed at two-dimensional periodic intervals. When arranged in a triangular lattice shape, the density of the concave portions or convex portions formed at two-dimensional periodic intervals can be increased, and the light extraction efficiency can be preferably improved.

  Yet another embodiment of the present invention is also a semiconductor light emitting device. This semiconductor light-emitting device is a semiconductor light-emitting device in which an n-type GaN layer, a light-emitting layer, and a p-type GaN layer are stacked on a substrate, and the substrate is a SiC substrate, on the surface of the SiC substrate, Concave portions or convex portions are formed at two-dimensional periodic intervals.

  According to this aspect, since the concave portions or the convex portions are formed on the surface of the SiC substrate at two-dimensional periodic intervals, the light emitted from the light emitting layer toward the SiC substrate is diffracted. Thereby, the light extraction efficiency can be improved. Even if the SiC substrate is dry-etched, the problem of an increase in forward voltage due to plasma damage does not occur, so that the processing is easy.

  The concave portions or the convex portions formed on the SiC substrate may be arranged in a square lattice shape or a triangular lattice shape. When arranged in a square lattice shape, concave portions or convex portions can be formed at two-dimensional periodic intervals. When arranged in a triangular lattice shape, the density of the concave portions or convex portions formed at two-dimensional periodic intervals can be increased, and the light extraction efficiency can be preferably improved.

An Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) is provided on the p-type GaN layer, and a two-dimensional surface is formed on the surface of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). Concave portions or convex portions may be formed at periodic intervals. In this case, since recesses or projections are formed at two-dimensional periodic intervals on the surface of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5), the Mg _x Zn _{1− x} O layer (0 ≦ x ≦ 0.5) light emitted in the direction is diffracted. In the diffracted _light, Mg _{x Zn 1-x} O layer at an angle smaller than the total reflection angle at the interface between (0 ≦ x ≦ 0.5) and in contact therewith _medium, Mg _{x Zn 1-x} O layer (0 ≦ x ≦ 0.5) and the diffracted light incident on the interface between the medium and the medium adjacent thereto can be extracted outside the semiconductor light emitting element without being totally reflected.

The recesses or protrusions formed in the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) may be arranged in a square lattice shape or a triangular lattice shape. When arranged in a square lattice shape, concave portions or convex portions can be formed at two-dimensional periodic intervals. When arranged in a triangular lattice shape, the density of the concave portions or convex portions formed at two-dimensional periodic intervals can be increased, and the light extraction efficiency can be preferably improved.

Yet another embodiment of the present invention is also a semiconductor light emitting device. This semiconductor light-emitting device is a semiconductor light-emitting device in which an n-type GaN layer, a light-emitting layer, and a p-type GaN layer are stacked on a substrate, and Zn, In, Sn, and Mg are formed on the p-type GaN layer. A transparent conductive film layer made of an oxide layer containing at least one element selected from the group consisting of the above, or a stack of the oxide layer and a Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) The transparent conductive film layer is provided, and concave portions or convex portions are formed on the surface of the transparent conductive film layer at two-dimensional periodic intervals.

  According to this aspect, since the concave portions or the convex portions are formed on the surface of the transparent conductive film layer at two-dimensional periodic intervals, the light from the light emitting layer is diffracted. Of the diffracted light, diffracted light that has entered the interface at an angle smaller than the total reflection angle at the interface between the transparent conductive film layer and the medium in contact with the transparent conductive film layer is extracted outside the semiconductor light emitting device without being totally reflected. Since the concave or convex portions are formed in the transparent conductive film layer instead of the p-type GaN layer, plasma during dry etching is not directly exposed to the p-type GaN layer, and the surface of the p-type GaN layer due to damage is not exposed. Since n-type does not occur, light extraction efficiency can be improved without increasing the forward voltage. In addition, since the wet etching process after dry etching, which has been conventionally required, becomes unnecessary, the manufacturing cost can be reduced.

Yet another embodiment of the present invention is also a semiconductor light emitting device. This semiconductor light-emitting device is a semiconductor light-emitting device in which an n-type GaN layer, a light-emitting layer, and a p-type GaN layer are stacked on a substrate, and the substrate is a SiC substrate, on the surface of the SiC substrate, Concave portions or convex portions are formed at two-dimensional periodic intervals, and the p-type GaN layer is made of a transparent oxide layer containing at least one element selected from the group consisting of Zn, In, Sn, and Mg. A transparent conductive film layer in which a conductive film layer or an oxide layer thereof and a Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) are stacked is provided, and a two-dimensional surface is formed on the surface of the transparent conductive film layer. Concave portions or convex portions are formed at periodic intervals.

  According to this aspect, since the concave portions or the convex portions are formed on the surface of the SiC substrate at two-dimensional periodic intervals, the light emitted from the light emitting layer toward the SiC substrate is diffracted. Thereby, the light extraction efficiency can be improved. Even if the SiC substrate is dry-etched, the problem of an increase in forward voltage due to plasma damage does not occur, so that the processing is easy. Moreover, since the recessed part or the convex part is formed in the surface of the transparent conductive film layer at a two-dimensional periodic interval, the light emitted from the light emitting layer toward the transparent conductive film layer is diffracted. Of the diffracted light, diffracted light that has entered the interface at an angle smaller than the total reflection angle at the interface between the transparent conductive film layer and the medium in contact with the transparent conductive film layer is extracted outside the semiconductor light emitting device without being totally reflected. Since the concave or convex portions are formed in the transparent conductive film layer instead of the p-type GaN layer, plasma during dry etching is not directly exposed to the p-type GaN layer, and the surface of the p-type GaN layer due to damage is not exposed. Since n-type does not occur, light extraction efficiency can be improved without increasing the forward voltage. In addition, since the wet etching process after dry etching, which has been conventionally required, becomes unnecessary, the manufacturing cost can be reduced.

  According to the semiconductor light emitting device of the present invention, the light extraction efficiency can be improved.

(First embodiment)
FIG. 1 is a cross-sectional view of a semiconductor light emitting device according to a first embodiment of the present invention. As shown in FIG. 1, the semiconductor light emitting device 10 includes an n-type GaN layer 16 that is a contact layer, an InGaN light emitting layer 18, a p-type AlGaN layer 20 that is a cladding layer, and a p-type GaN 22 that is a contact layer. The p-type GaN layer 32 is a double heterostructure GaN-based semiconductor light emitting device. The light emission observation surface of the semiconductor light emitting device 10 according to the first embodiment is on the ZnO layer 24 side which is a transparent electrode. Each drawing is intended to explain the positional relationship of each layer and the like and does not necessarily represent an actual dimensional relationship. Further, in each embodiment, the same or corresponding components are denoted by the same reference numerals, and overlapping descriptions are omitted as appropriate.

  The semiconductor light emitting device 10 is formed by epitaxially growing a GaN-based semiconductor on the sapphire substrate 12.

  A buffer layer 14 is provided on the sapphire substrate 12. The buffer layer 14 is an AlGaN amorphous layer formed at a low temperature of about 550 ° C. using a PLD (Pulsed Laser Deposition) method. The buffer layer 14 has a thickness of about 10 to 20 nm. The buffer layer 14 is a base for growing a GaN film having good crystallinity on the sapphire substrate 12, and has a function as a buffer layer that prevents an increase in lattice defects due to lattice mismatch with the sapphire substrate 12. The buffer layer 14 may be a crystalline buffer layer. In this case, AlGaN is crystal-grown at about 800 to 1000 ° C. The thickness of the crystalline buffer layer is not particularly limited, but about 10 nm to 100 nm is sufficient.

  On the buffer layer 14, an n-type GaN layer 16 doped with Si using the MOCVD method is provided. The n-type GaN layer 16 functions as a contact layer. The dopant may be Ge. The temperature of the sapphire substrate 12 when the n-type GaN layer 16 is formed is maintained at about 1000 to 1200 ° C. If the n-type GaN layer 16 is thin, the sheet resistance of the n-type GaN layer 16 becomes high and increases the operating voltage. Therefore, the thickness of the n-type GaN layer 16 is preferably about 3 to 10 μm. The n-type GaN layer 16 also has a function as an n-type cladding layer.

  On the n-type GaN layer 16, an InGaN light emitting layer 18 is provided by using MOCVD. The temperature of the sapphire substrate 12 when the InGaN light emitting layer 18 is formed is maintained at about 700 to 1000 ° C. The InGaN light emitting layer 18 has a multiple quantum well (MQW) structure in which an InGaN layer and an InGaN layer having an In composition ratio smaller than that of the GaN layer or the emitting InGaN layer are alternately stacked. The number of wells may be about 5-10. The thickness of the InGaN layer is about 1 to 10 nm, and the InGaN layer is about 3 to 30 nm. For example, the InGaN layer is 3 nm and the GaN layer is 10 nm. Increasing the In composition ratio of the InGaN layer decreases the band gap energy and increases the emission peak wavelength. Therefore, the emission wavelength of the semiconductor light emitting element 10 can be controlled by changing the In composition ratio or the thickness of the InGaN layer.

  An undoped GaN layer (not shown) may be provided on the InGaN light emitting layer 18 by using MOCVD. The undoped GaN layer has a thickness of about 10 to 100 nm. The undoped GaN layer functions as a protective layer, and has a function of preventing the crystal of the InGaN light emitting layer 18 from deteriorating due to the high temperature of the InGaN light emitting layer 18 during the crystal growth process.

  On the InGaN light emitting layer 18, a p-type AlGaN layer 20 doped with Mg is provided. The p-type AlGaN layer 20 may be a p-type GaN layer. The p-type AlGaN layer 20 functions as a cladding layer. The temperature of the sapphire substrate 12 when the p-type AlGaN layer 20 is formed is maintained at about 1000 to 1200 ° C. The thickness of the p-type AlGaN layer 20 is 0.1 to 0.3 μm, for example, about 0.15 μm.

  On the p-type AlGaN layer 20, a p-type GaN layer 22 doped with Mg is provided. The p-type GaN layer 22 functions as a contact layer. The temperature of the sapphire substrate 12 when the p-type GaN layer 22 is formed is maintained at about 700 to 1000 ° C. The p-type GaN layer 22 has a thickness of about 20 nm to 0.2 μm.

On the p-type GaN layer 22, a ZnO layer 24 doped with Ga using a PLD method is provided. The ZnO layer 24 may be formed using a sol-gel method, a thermal CVD method, or the like. The thickness of the ZnO layer 24 is about 1 to 2 μm. The ZnO layer 24 has a high transmittance with respect to the emission wavelength band of the GaN-based semiconductor light-emitting element, and functions as a transparent electrode. The ZnO layer 24 may be a Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). Since the crystals of GaN and ZnO have the same wurtzite structure, a good interface can be obtained.

  A plurality of concave portions 30 are formed on the surface of the ZnO layer 24 at two-dimensional periodic intervals. The surface of the ZnO layer 24 refers to the surface facing the surface where the p-type GaN layer 22 and the ZnO layer 24 are in contact. FIG. 2 is a diagram illustrating an arrangement example of the recesses 30. FIG. 3 is a diagram illustrating another arrangement example of the recess 30. As shown in FIG. 2, the recesses 30 may be arranged in a square lattice pattern. When arranged in a square lattice, the recesses 30 can be formed at two-dimensional periodic intervals. Moreover, the recessed part 30 may be arrange | positioned and formed in the triangular lattice form, as shown in FIG. When arranged in a triangular lattice shape, the density of the concave portions 30 formed at two-dimensional periodic intervals can be increased, and the light extraction efficiency can be preferably improved.

  The shape of the recess 30 in plan view may be circular as shown in FIG. 2 or FIG. 3, for example, and may be quadrangular or hexagonal. The diameter and the length of one side may be about 100 nm. The depth of the recess 30 may be about 500 nm. A suitable periodic interval of the recess 30 will be described later.

  The recess 30 is formed by forming a resist on the ZnO layer 24, patterning the resist into a desired shape by a method such as an electron beam exposure method or a nanoimprint method, and performing dry etching such as an RIE method using the resist as a mask. To form.

  Thereafter, a part of the ZnO layer 24, the p-type GaN layer 22, the p-type AlGaN layer 20, the InGaN light emitting layer 18 and the n-type GaN layer 16 is removed by etching. Etching is performed halfway through the n-type GaN layer 16 to form an n-side electrode 28 on the exposed upper surface of the n-type GaN layer 16. The n-side electrode 28 is an ohmic contact, desirably has a small contact specific resistance and is thermally stable, and Al or Ti / Al can be suitably used. In order to obtain an ohmic contact, it is desirable to perform sintering at about 600 ° C. after forming the n-side electrode 28. The thickness of the n-side electrode 28 may be about 2500 mm.

  Finally, the p-side electrode 26 is formed in a part of the ZnO layer 24 where no recess is provided. For the p-side electrode 26, Al, Ti, Ag, or the like can be used to achieve ohmic contact. The thickness of the p-side electrode 26 may be about 1000 mm for Pt and about 3000 mm for Au. The p-side electrode 26 and the n-side electrode 28 can be formed using a vapor deposition method or a sputtering method.

  FIG. 4 is a diagram showing current-luminance characteristics of the semiconductor light emitting device. 4 represents the forward current of the semiconductor light emitting element 10, and the vertical axis represents the luminance. A curve 34 shows current-luminance characteristics when the recess 30 is not formed on the surface of the ZnO layer 24, and a curve 36 shows current-luminance characteristics when the recess 30 is formed on the surface of the ZnO layer 24. As shown in FIG. 4, the luminance is improved by forming the recess 30 on the surface of the ZnO layer 24. This means that the light extraction efficiency of the semiconductor light emitting device 10 is improved.

Since the semiconductor light emitting device 10 according to the first embodiment has recesses formed on the surface of the ZnO layer 24 at two-dimensional periodic intervals, the light from the InGaN light emitting layer 18 is diffracted. Of the diffracted light, diffracted light that has entered the interface at an angle smaller than the total reflection angle θ _z at the interface between the ZnO layer 24 and air is extracted without being totally reflected, so that the light The extraction efficiency can be improved.

  In the semiconductor light emitting device 10 according to the first embodiment, since the recess is formed in the ZnO layer 24 instead of the p-type GaN layer 22, the n-type on the surface of the p-type GaN layer 22 due to plasma damage during dry etching. Therefore, the light extraction efficiency can be preferably improved without increasing the forward voltage.

FIG. 5 is a diagram for explaining the periodic intervals of the recesses 30. The period interval of the recesses 30 refers to the interval between the centers of the recesses adjacent in the vertical or horizontal direction in a two-dimensional plane. The periodic interval is L _z , the peak wavelength in the air of light from the InGaN light emitting layer 18 is λ, the refractive index of the ZnO layer 24 at the wavelength λ is _nzλ , and at the interface between the ZnO layer 24 and the air layer. The total reflection angle when light from the light emitting layer is incident is θ _z . Since the total reflection angle θ _z is θ _z = sin ⁻¹ (1 / n _zλ ), for example, the refractive index _nzλ of ZnO at a wavelength λ = 450 nm is 2.3, and the refractive index of air is 1. Assuming 0, the total reflection angle θ _z is about 25.8 °.

と表すことができる。ｍは整数であり回折光の次数を意味する。（１）式において、左辺は回折光５０と回折光５２の位相差を表している。位相差が２πの整数倍であるときに、回折光５０と回折光５２は互いに強め合う。（１）式をＬ_ｚについて変形すると、

のように表すことができる。 In FIG. 5, the condition that the diffracted light 50 and the diffracted light 52 diffracted in the direction of θ _m from the light 48 guided in the lateral direction through the ZnO layer 24 in the direction normal to the ZnO layer 24 is as follows.

It can be expressed as. m is an integer and means the order of diffracted light. In the formula (1), the left side represents the phase difference between the diffracted light 50 and the diffracted light 52. When the phase difference is an integral multiple of 2π, the diffracted light 50 and the diffracted light 52 strengthen each other. When the equation (1) is transformed with respect to L _z ,

It can be expressed as

の範囲にあるとき、互いに強め合う回折光５０と回折光５２は半導体発光素子１０の外部に放出される。実質的には１次の回折光の強度が最も強いので、ｍ＝１として周期間隔Ｌ_ｚを設定してよい。すなわち、

を満たすような周期間隔Ｌ_ｚに設定することが望ましい。たとえば、波長λ＝４５０ｎｍ、ＺｎＯの屈折率ｎ_ｚλ＝２．３、ｍ＝１、θ_ｚ＝２５．８°として上記の（４）式を用いて周期間隔Ｌ_ｚを計算すると、１９６ｎｍ≦Ｌ_ｚ≦３４６ｎｍとなる。 When the angle θ _{m at} which the diffracted light 50 and the diffracted light 52 reinforce each other is smaller than the total reflection angle θ _z , that is, when θ _m is in the range of 0 ≦ θ _m ≦ θ _z , the diffracted light 50 and the diffracted light reinforce each other. 52 is not totally reflected at the interface between the ZnO layer 24 and air and can be taken out of the semiconductor light emitting device 10. That is, the period interval L _z is

When in this range, the diffracted light 50 and the diffracted light 52 that strengthen each other are emitted to the outside of the semiconductor light emitting device 10. Since the intensity of the first-order diffracted light is the strongest, the periodic interval L _z may be set with m = 1. That is,

It is desirable to set the periodic interval L _z which satisfies. For example, when the period interval L _z is calculated using the above equation (4) with the wavelength λ = 450 nm, the refractive index of ZnO n _zλ = 2.3, m = 1, and θ _z = 25.8 °, 196 nm ≦ L _z ≦ 346 nm.

と表すことができる。ｎ_{ｚ（λ−Δλ）}は波長λ−ΔλにおけるＺｎＯ層の屈折率を、ｎ_{ｚ（λ＋Δλ）}は波長λ＋ΔλにおけるＺｎＯ層の屈折率を表す。ここでも、実質的には１次の回折光の強度が最も強いので、ｍ＝１として周期間隔Ｌ_ｚを設定してよい。すなわち、

を満たすような周期間隔Ｌ_ｚに設定してよい。この場合、たとえば、波長λ＝４５０ｎｍ、半値幅Δλを１５ｎｍ、θ_ｚ＝２５．８°とし、波長λにおけるＺｎＯの屈折率ｎ_ｚλと波長λ±Δλでの屈折率ｎ_{ｚ（λ±Δλ）}が等しく２．３であるとすると、（６）式から、１８９ｎｍ≦Ｌ_ｚ≦３５８ｎｍとなる。 In addition, since the emission spectrum of the semiconductor light emitting element is broad unlike the semiconductor laser, the periodic interval L _z may be set in consideration of the half width Δλ in air. That is, even if the period interval _Lz is set in accordance with the wavelength λ ± Δλ shifted by Δλ from the emission peak wavelength λ, the light emission efficiency is improved. Here, the half-value width Δλ is a wavelength width from the emission peak wavelength λ to a wavelength at which the emission intensity becomes ½. The range of the periodic interval L _z when considering the half width Δλ is

It can be expressed as. _{nz (λ−Δλ)} represents the refractive index of the ZnO layer at the wavelength λ−Δλ, and _{nz (λ + Δλ)} represents the refractive index of the ZnO layer at the wavelength λ + Δλ. Again, since the intensity of the first-order diffracted light is substantially strong, the periodic interval L _z may be set with m = 1. That is,

May be set to periodic interval L _z which satisfies. In this case, for example, the wavelength λ = 450 nm, the half width Δλ is 15 nm, θ _z = 25.8 °, and the refractive index _nzλ of ZnO at the wavelength λ and the refractive index _nz at the wavelength λ ± Δλ _{(λ ± Δλ).} Are equally 2.3, from equation (6), 189 nm ≦ L _z ≦ 358 nm.

と表すことができる。ここでも、実質的には１次の回折光の強度が最も強いので、ｍ＝１として周期間隔Ｌ_ｚを設定してよい。すなわち、

を満たすような周期間隔Ｌ_ｚに設定してよい。この場合、波長λ＝４５０ｎｍ、半値幅Δλを１５ｎｍ、θ_ｚ＝２５．８°とし、波長λにおけるＺｎＯの屈折率ｎ_ｚλと波長λ±Δλでの屈折率ｎ_{ｚ（λ±Δλ）}が等しく２．３であるとすると、（８）式から、１８９ｎｍ≦Ｌ_ｚ≦９３５ｎｍとなる。 Further, as described above, it is most desirable when the angle θ _{m at} which the diffracted light 50 and the diffracted light 52 are strengthened is smaller than the total reflection angle θ _z , but substantially θ _m is twice as large as θ _z . Even if it is smaller, it has the effect of improving the luminous efficiency. That is, θ _m may be in a range of 0 ≦ θ _m ≦ 2θ _z . At this time, the range of the period interval L _z is

It can be expressed as. Again, since the intensity of the first-order diffracted light is substantially strong, the periodic interval L _z may be set with m = 1. That is,

May be set to periodic interval L _z which satisfies. In this case, the wavelength λ = 450 nm, the half width Δλ is 15 nm, θ _z = 25.8 °, and the refractive index _nzλ of ZnO at the wavelength λ is equal to the refractive index _{nz (λ ± Δλ)} at the wavelength λ ± Δλ. Assuming 2.3, from equation (8), 189 nm ≦ L _z ≦ 935 nm.

In the first embodiment, the case where the concave portion is formed on the surface of the ZnO layer 24 has been described. However, even if the convex portion instead of the concave portion is formed, the light extraction efficiency is similarly improved. In the above description, the semiconductor light emitting element 10 emits light in the air. However, the semiconductor light emitting element 10 may be covered with a phosphor or a light transmissive resin. In this case, when determining the total reflection angle theta _z, rather than the refractive index of air, by using the refractive index of the phosphor and the light transmitting resin is a medium ZnO layer 24 is in contact, (3) to ( Equation 8) can be applied.

(Second Embodiment)
FIG. 6 is a cross-sectional view of a semiconductor light emitting device according to the second embodiment of the present invention. As shown in FIG. 6, the semiconductor light emitting device 60 includes a p-type GaN layer 32 composed of a p-type GaN 22 as a contact layer and a p-type AlGaN layer 20 as a cladding layer, an InGaN light-emitting layer 18, and a contact layer. This is a double heterostructure GaN-based semiconductor light-emitting device in which an n-type GaN layer 16 is stacked. The light emission observation surface of the semiconductor light emitting device 60 according to the second embodiment is on the n-type GaN layer 16 side.

  In the semiconductor light emitting device 60 according to the second embodiment, first, an n-type GaN layer 16, an InGaN light emitting layer 18, a p-type AlGaN layer 20, and a p-type GaN layer 22 are stacked on a sapphire substrate. Up to this point, the process is the same as that of the semiconductor light emitting device 10 according to the first embodiment. Thereafter, the sapphire substrate and the buffer layer are peeled off by laser lift-off. As the laser, a KrF laser having a wavelength of 248 nm can be used.

  A plurality of recesses 30 are formed at two-dimensional periodic intervals on the surface of the n-type GaN layer 16 exposed by peeling the sapphire substrate and the buffer layer. The surface of the n-type GaN layer 16 refers to a surface facing the surface where the InGaN light-emitting layer 18 and the n-type GaN layer 16 are in contact. As shown in FIG. 2, the recesses 30 may be arranged in a square lattice pattern. Moreover, the recessed part 30 may be arrange | positioned and formed in the triangular lattice form, as shown in FIG.

  The shape of the recess 30 in plan view may be circular as shown in FIG. 2 or FIG. 3, for example, and may be quadrangular or hexagonal. The diameter and the length of one side may be about 100 nm. The depth of the recess 30 may be about 500 nm.

  The recess 30 can be formed by performing dry etching such as RIE as in the semiconductor light emitting device 10 according to the first embodiment. Nitrogen vacancies are also generated by dry etching the n-type GaN layer 16 and the surface of the n-type GaN layer 16 becomes n-type. However, since the n-type GaN layer 16 is originally n-type, a reverse bias is applied. The forward voltage does not rise.

  After forming the recess 30, a part of the p-type GaN layer 22, the p-type AlGaN layer 20, the InGaN light emitting layer 18 and the n-type GaN layer 16 is removed by etching. Etching is performed halfway through the n-type GaN layer 16 to form an n-side electrode 28 on the exposed upper surface of the n-type GaN layer 16.

  Thereafter, the p-side electrode 26 is formed on the p-type GaN layer 22. Since the light emitting observation surface of the semiconductor light emitting device 60 is on the n-type GaN layer 16 side, it is not necessary to form a transparent electrode layer of ZnO on the p-type GaN layer 22, and a p-side electrode directly on the n-type GaN layer 16. 26 is formed. The p-side electrode 26 is preferably made of Pt / Au or the like. The thickness of the p-side electrode 26 may be about 1000 mm for Pt and about 3000 mm for Au.

In the semiconductor light emitting device 60 according to the second embodiment, since the recesses are formed on the surface of the n-type GaN layer 16 at two-dimensional periodic intervals, the light from the InGaN light emitting layer 18 is diffracted. Of the diffracted light, diffracted light that has entered the interface at an angle smaller than the total reflection angle θ _g at the interface between the n-type GaN layer 16 and air is taken out of the semiconductor light emitting device 60 without being totally reflected. The light extraction efficiency can be improved.

を満たす範囲で設定することが望ましい。λはＩｎＧａＮ発光層１８からの光の空気中でのピーク波長を、ｎ_ｇλはその波長λにおけるｎ型ＧａＮ層１６の屈折率を表す。 The period interval L _g of the recess 30 is

It is desirable to set in a range that satisfies the above. λ represents the peak wavelength of light from the InGaN light-emitting layer 18 in the air, and _ngλ represents the refractive index of the n-type GaN layer 16 at the wavelength λ.

By forming the recess 30 in the surface of the n-type GaN layer 16 at periodic intervals L _g which satisfies the expression (9), it is possible to take out the diffracted light to the outside of the semiconductor light emitting element 60, it is possible to improve the light extraction efficiency it can. For example, the wavelength lambda = 450 nm, the refractive index _{n gλ} = 2.5 of the n-type GaN layer 16, when calculating the periodic interval _{L g} using total reflection angle θ _g = 23.6 ° as above (9), 180 nm ≦ L _g ≦ 300 nm.

の範囲にあってもよい。ｎ_{ｇ（λ−Δλ）}は波長λ−Δλにおけるｎ型ＧａＮ層１６の屈折率を、ｎ_{ｇ（λ＋Δλ）}は波長λ＋Δλにおけるｎ型ＧａＮ層１６の屈折率を表す。 Further, similarly to the first embodiment, the light extraction efficiency can be improved even if the periodic interval _Lg is set in consideration of the half width Δλ of the semiconductor light emitting element 60. That is, the periodic interval L _g between adjacent recesses 30 is

It may be in the range. _{ng (λ−Δλ)} represents the refractive index of the n-type GaN layer 16 at the wavelength λ−Δλ, and _{ng (λ + Δλ)} represents the refractive index of the n-type GaN layer 16 at the wavelength λ + Δλ.

の範囲にあってもよい。 Further, similarly to the first embodiment, the light extraction efficiency can be improved even if the angle θ _{m at} which the diffracted light strengthens is in the range of 0 ≦ θ _m ≦ 2θ _g . That is, the periodic interval L _g between adjacent recesses 30 is

It may be in the range.

  FIG. 7 is a view showing a modification of the semiconductor light emitting device according to the second embodiment of the present invention. In the semiconductor light emitting device 62 shown in FIG. 7, the surface of the n-type GaN layer 16 exposed by etching from the ZnO layer 24 side to the middle of the n-type GaN layer 16 without peeling off the sapphire substrate 12 and the buffer layer 14. Thus, the recess 30 is formed in a place other than the region where the n-side electrode 28 is formed. In FIG. 7, since the size of the concave portion 30 is enlarged, only one concave portion 30 is drawn, but a plurality of concave portions 30 are actually formed.

  When the light emitted from the InGaN light emitting layer 18 and reflected by the interface between the buffer layer 14 and the sapphire substrate 12 enters the region where the concave portion 30 is formed, this light is diffracted by the concave portion 30, so the traveling direction changes, It can be taken out of the semiconductor light emitting device 62 without being totally reflected. Also in the semiconductor light emitting device 62, since the recess 30 is formed in the n-type GaN layer 16, the forward voltage does not increase when the surface of the n-type GaN layer 16 becomes n-type.

In the second embodiment, the case where the concave portion is formed on the surface of the n-type GaN layer 16 has been described. However, even if the convex portion is formed on the surface of the n-type GaN layer 16 instead of the concave portion, the light extraction efficiency is similarly improved. Has an improvement effect. In the above description, the semiconductor light emitting element 60 or 62 emits light in the air. However, the semiconductor light emitting element 60 or 62 may be covered with a phosphor or a light-transmitting resin. Good. In this case, when the total reflection angle θ _g is obtained, if the refractive index of the phosphor or light-transmitting resin that is the medium in contact with the n-type GaN layer 16 is used instead of the refractive index of air, the above (9) Equation (11) can be applied.

(Third embodiment)
FIG. 8 is a cross-sectional view of a semiconductor light emitting device according to the third embodiment of the present invention. As shown in FIG. 8, the semiconductor light emitting device 70 includes an n-type GaN layer 16 that is a contact layer, an InGaN light emitting layer 18, a p-type AlGaN layer 20 that is a cladding layer, and a contact layer on a SiC substrate 40. This is a double heterostructure GaN-based semiconductor light emitting device in which a p-type GaN layer 32 composed of p-type GaN 22 is stacked. The light emission observation surface of the semiconductor light emitting device 70 is the ZnO layer 24 side or the SiC substrate 40 side. In the case where the ZnO layer 24 side is the light emission observation surface, a reflector (not shown) made of, for example, silver (Ag) is provided between the SiC substrate 40 and the mounting substrate when the semiconductor light emitting device 70 is used. Good. By providing the reflecting plate, the light emitted from the SiC substrate 40 side can be reflected to the ZnO layer 24 side which is a light emission observation surface.

  The semiconductor light emitting device 70 according to the third embodiment is formed by epitaxially growing a GaN-based semiconductor on the SiC substrate 40, and then the recess 30 is formed on the surface of the SiC substrate 40. A ZnO layer 24 that functions as a transparent electrode is provided on the ZnO layer 24, but no recess is formed in the ZnO layer 24.

  Since SiC is conductive unlike sapphire, the p-type GaN layer, the InGaN light emitting layer, etc. are etched to form the n-side electrode connected to the n-type GaN layer 16 as in the first or second embodiment. The process is unnecessary, and the manufacturing process can be simplified and the reliability can be improved.

  A plurality of concave portions 30 are formed on the surface of the SiC substrate 40 at two-dimensional periodic intervals. The surface of SiC substrate 40 refers to a surface facing the surface where n-type GaN layer 16 and SiC substrate 40 are in contact. As shown in FIG. 2, the recesses 30 may be arranged in a square lattice pattern. Moreover, the recessed part 30 may be arrange | positioned and formed in the triangular lattice form, as shown in FIG.

  The shape of the recess 30 in plan view may be circular as shown in FIG. 2 or FIG. 3, for example, and may be quadrangular or hexagonal. The diameter and the length of one side may be about 100 nm. The depth of the recess 30 may be about 500 nm.

  The recess 30 can be formed by performing dry etching such as RIE as in the semiconductor light emitting device 10 according to the first embodiment. Even if the SiC substrate 40 is dry-etched, the problem of an increase in forward voltage due to plasma damage does not occur.

  An n-side electrode 28 is provided in a part of the SiC substrate 40 where the recess 30 is not formed. The n-side electrode 28 is desirably formed near the center of the surface of the SiC substrate 40. The n-side electrode 28 also functions as a reflective layer, and Ni, Ti, Ni / Ti / Au, NiTi alloy, or the like can be used. The thickness of the n-side electrode 28 may be about 2500 mm.

  A p-side electrode 26 is formed in a partial region on the ZnO layer 24. When the SiC substrate 40 is used as the substrate, it is desirable to form the p-side electrode 26 near the center of the surface of the ZnO layer 24. The p-side electrode 26 is preferably made of Pt / Au or the like. The thickness of the p-side electrode 26 may be about 1000 mm for Pt and about 3000 mm for Au.

In the semiconductor light emitting device 70 according to the third embodiment, since the recesses are formed on the surface of the SiC substrate 40 at two-dimensional periodic intervals, the light emitted from the InGaN light emitting layer 18 toward the SiC substrate 40. Is diffracted at the interface between the SiC substrate 40 and air. The light diffracted in an angle direction smaller than the total reflection angle θ _{s with} respect to the normal line of the SiC substrate 40 is taken out of the semiconductor light emitting device 70 without being totally reflected at the interface between the SiC substrate 40 and air. Light extraction efficiency can be improved.

を満たす範囲で設定することが望ましい。λはＩｎＧａＮ発光層１８からの光の空気中でのピーク波長を、ｎ_ｓλはその波長λにおけるＳｉＣ基板４０の屈折率を、θ_ｓはＳｉＣ基板と空気との界面での全反射角を表す。 The periodic interval L _s of the recess 30 is

It is desirable to set in a range that satisfies the above. λ represents the peak wavelength of light from the InGaN light-emitting layer 18 in the air, n _sλ represents the refractive index of the SiC substrate 40 at the wavelength λ, and θ _s represents the total reflection angle at the interface between the SiC substrate and air. .

By forming the recess 30 in the periodic interval L _s satisfying (12), it is possible to take out the diffracted light to the outside of the semiconductor light emitting element 70, it is possible to improve the light extraction efficiency. For example, when the periodic interval L _s is calculated using the above equation (12) with the wavelength λ = 450 nm, the refractive index n _sλ = 2.65 of the SiC substrate 40, and θ _s = 22.2 °, 170 nm ≦ L _s ≦ 273 nm.

の範囲にあってもよい。ｎ_{ｓ（λ−Δλ）}は波長λ−ΔλにおけるＳｉＣ基板４０の屈折率を、ｎ_{ｓ（λ＋Δλ）}は波長λ＋ΔλにおけるＳｉＣ基板４０の屈折率を表す。 Further, the light extraction efficiency can be improved even if the periodic interval L _s is set in consideration of the half width Δλ of the semiconductor light emitting element 70. That is, the periodic interval L _s between adjacent recesses 30 is

It may be in the range. _{ns (λ−Δλ)} represents the refractive index of the SiC substrate 40 at the wavelength λ−Δλ, and ns _{(λ + Δλ)} represents the refractive index of the SiC substrate 40 at the wavelength λ + Δλ.

の範囲にあってもよい。 Furthermore, the light extraction efficiency can be improved even if the angle θ _{m at} which the diffracted light strengthens is in the range of 0 ≦ θ _m ≦ 2θ _s . That is, the periodic interval L _s between adjacent recesses 30 is

It may be in the range.

  In the third embodiment, the case where the concave portion is formed on the surface of the SiC substrate 40 has been described. However, even if the convex portion instead of the concave portion is formed on the surface of the SiC substrate 40, the light extraction efficiency is similarly improved. . In the above description, the semiconductor light emitting element 70 emits light in the air. However, the semiconductor light emitting element 70 may be covered with a phosphor or a light transmissive resin. In this case, the above formulas (12) to (14) can be applied by using not the air but the refractive index of the phosphor or light-transmitting resin that is the medium in contact with the SiC substrate 40.

(Fourth embodiment)
FIG. 9 is a cross-sectional view of a semiconductor light emitting device according to the fourth embodiment of the present invention. As shown in FIG. 9, the semiconductor light emitting device 80 includes an n-type GaN layer 16 that is a contact layer, an InGaN light-emitting layer 18, a p-type AlGaN layer 20 that is a cladding layer, and a contact layer on a SiC substrate 40. This is a double heterostructure GaN-based semiconductor light emitting device in which a p-type GaN layer 32 composed of p-type GaN 22 is stacked. The light emission observation surface of the semiconductor light emitting device 80 according to the fourth embodiment is the ZnO layer 24 side or the SiC substrate 40 side. As in the third embodiment, a reflector may be provided when mounting.

  The semiconductor light emitting device 80 according to the fourth embodiment is different from the semiconductor light emitting device 70 according to the third embodiment in that a recess 38 is formed on the surface of the ZnO layer 24 provided on the p-type GaN layer 22. . A recess 30 is formed on the surface of the SiC substrate 40 as in the third embodiment.

A plurality of concave portions 38 are formed on the surface of the ZnO layer 24 at two-dimensional periodic intervals. The surface of the ZnO layer 24 refers to the surface facing the surface where the ZnO layer 24 and the p-type GaN layer 22 are in contact. The arrangement, shape, and the like of the recesses 38 are the same as those of the semiconductor light emitting device 10 according to the first embodiment, and the periodic interval L _z can be set by applying the equations (3) to (8). However, when the SiC substrate 40 is used as the substrate, it is desirable to form the p-side electrode 26 near the center of the surface of the ZnO layer 24.

In the semiconductor light emitting device 80 according to the fourth embodiment, since the recesses 38 are formed on the surface of the ZnO layer 24 at two-dimensional periodic intervals, the light emitted from the InGaN light emitting layer 18 toward the ZnO layer 24. Is diffracted. In the diffracted light, diffracted light incident on the interface at an angle smaller than the total reflection angle theta _z at the interface between the ZnO layer 24 and the air may be taken out of the semiconductor light emitting element 80 without being totally reflected. The effect of the recess 30 formed on the surface of the SiC substrate 40 is the same as that of the semiconductor light emitting device 70 according to the third embodiment.

  Also in the semiconductor light emitting device 80 according to the fourth embodiment, since the recess is formed in the ZnO layer 24 instead of the p-type GaN layer 22 as in the first embodiment, plasma damage during dry etching is caused. Since the n-type of the surface of the p-type GaN layer 22 does not occur, the forward voltage does not increase. Similarly to the third embodiment, even if the SiC substrate 40 is dry-etched, the forward voltage does not increase due to plasma damage.

(Fifth embodiment)
The semiconductor light emitting device according to the fifth embodiment is at least selected from the group consisting of Zn, In, Sn, and Mg instead of the ZnO layer 24 of the semiconductor light emitting device 10 according to the first embodiment shown in FIG. In the semiconductor light emitting device, an oxide layer containing one element is formed on a p-type GaN layer. Other configurations of the semiconductor light emitting device according to the fifth embodiment are the same as those of the semiconductor light emitting device 10 according to the first embodiment.

An oxide layer containing at least one element selected from the group consisting of Zn, In, Sn, and Mg, that is, an ITO-based oxide (ITO, In ₂ O ₃ , SnO ₂ , InZnO composite oxide) layer, It is formed by magnetron sputtering. The Sn content of ITO may be about 2 to 20%. The InZnO composite oxide may have a Zn content of about 5 to 40%. If the thickness of the ITO-based oxide layer is too thin, the current does not spread into the ITO-based oxide layer. Therefore, the thickness of the ITO-based oxide layer is preferably 500 mm or more. The thicker the ITO-based oxide layer, the more light can be taken out from the lateral direction, and it is desirable. However, since the thickness of the ITO-based oxide layer is high, it is preferable that the thickness be 10 μm or less.

  Since p-type GaN is vulnerable to plasma damage, it is necessary to adjust the sputtering conditions so as not to cause damage. For example, if the target has a size of 4 inches, it is desirable that the sputtering power to be input is 600 W or less. The ITO-based oxide layer has a high transmittance with respect to the emission wavelength band of the GaN-based semiconductor light-emitting element, and functions as a transparent conductive film layer.

  In order to avoid plasma damage more effectively, a method of vapor deposition using a vacuum vapor deposition method can be employed. Alternatively, two-stage film formation may be performed in which the magnetron sputtering method is performed after the vacuum deposition method is performed. In this case, an electrode layer with higher transparency can be formed than when the vacuum deposition method is used alone.

Concave portions or convex portions are formed on the surface of the ITO-based oxide layer at two-dimensional periodic intervals. The surface of the ITO-based oxide layer refers to the surface facing the surface where the ITO-based oxide layer and the p-type GaN layer are in contact. The arrangement, shape, and the like of the recesses or protrusions are the same as those of the semiconductor light emitting device 10 according to the first embodiment, and the periodic interval L _z can be set by applying the equations (3) to (8). . Note that (3) when applying to (8), the refractive index _{n Zramuda} of ZnO layer is replaced with the refractive index _{n Airamuda} of ITO-based oxide layer, from the light emitting layer at the interface between the ZnO layer and the air layer The total reflection angle θ _{z at} the time of the incident light is replaced with the total reflection angle θ _I when the light from the light emitting layer is incident on the interface between the ITO-based oxide layer and the air layer.

In the semiconductor light emitting device according to the fifth embodiment, since the concave or convex portions are formed at two-dimensional periodic intervals on the surface of the ITO-based oxide layer functioning as the transparent conductive film layer, the InGaN light emitting layer The light emitted from the direction toward the ITO-based oxide layer is diffracted. Of the diffracted light, diffracted light incident on the interface at an angle smaller than the total reflection angle θ _I at the interface between the ITO-based oxide layer and air can be extracted outside the semiconductor light emitting element without being totally reflected. .

  In the semiconductor light emitting device according to the fifth embodiment, as in the first embodiment, since the recess is formed in the ITO-based oxide layer instead of the p-type GaN layer, plasma damage during dry etching is caused. Since the n-type surface of the p-type GaN layer does not occur, the forward voltage does not increase. In addition, since the wet etching process after dry etching, which has been conventionally required, becomes unnecessary, the manufacturing cost can be reduced.

Although the ITO-based oxide does not have the same crystal structure as GaN like ZnO, it can be used as an ohmic electrode for p-GaN. The specific resistivity of ZnO is about 2 × 10 ⁻⁴ Ωcm, whereas the specific resistivity of ITO-based oxide is about 9 × 10 ⁻⁵ to 1 × 10 ⁻⁴ Ωcm. This means that the current of the ITO-based oxide is easier to spread than that of ZnO. Therefore, when the ITO-based oxide layer is formed on the p-type GaN layer, the film thickness is larger than when the ZnO layer is formed. Can be thinned.

(Sixth embodiment)
The semiconductor light emitting device according to the sixth embodiment is at least selected from the group consisting of Zn, In, Sn and Mg instead of the ZnO layer 24 of the semiconductor light emitting device 80 according to the fourth embodiment shown in FIG. In the semiconductor light emitting device, an oxide layer containing one element is formed on a p-type GaN layer. Other configurations of the semiconductor light emitting device according to the sixth embodiment are the same as those of the semiconductor light emitting device 80 according to the fourth embodiment.

Formation of an oxide layer containing at least one element selected from the group consisting of Zn, In, Sn, and Mg, that is, an ITO-based oxide (ITO, In ₂ O ₃ , SnO ₂ , InZnO composite oxide) layer The method, thickness, and the like may be the same as those of the semiconductor light emitting device according to the fifth embodiment. A concave portion or a convex portion is formed on the surface of the SiC substrate as in the third and fourth embodiments.

Concave portions or convex portions are formed on the surface of the ITO-based oxide layer at two-dimensional periodic intervals. The surface of the ITO-based oxide layer refers to the surface facing the surface where the ITO-based oxide layer and the p-type GaN layer are in contact. The arrangement, shape, and the like of the recesses or protrusions are the same as those of the semiconductor light emitting device 10 according to the first embodiment, and the periodic interval L _z can be set by applying the equations (3) to (8). . Note that (3) when applying to (8), the refractive index _{n Zramuda} of ZnO layer is replaced with the refractive index _{n Airamuda} of ITO-based oxide layer, from the light emitting layer at the interface between the ZnO layer and the air layer The total reflection angle θ _{z at} the time of the incident light is replaced with the total reflection angle θ _I when the light from the light emitting layer is incident on the interface between the ITO-based oxide layer and the air layer.

In the semiconductor light emitting device according to the sixth embodiment, since recesses or projections are formed at two-dimensional periodic intervals on the surface of the ITO-based oxide layer functioning as a transparent conductive film layer, an InGaN light emitting layer The light emitted from the direction toward the ITO-based oxide layer is diffracted. Of the diffracted light, diffracted light incident on the interface at an angle smaller than the total reflection angle θ _I at the interface between the ITO-based oxide layer and air can be extracted outside the semiconductor light emitting element without being totally reflected. . Moreover, the effect of the recessed part or convex part formed in the surface of a SiC substrate is the same as that of the case of the semiconductor light-emitting device which concerns on 3rd, 4th embodiment.

  Also in the semiconductor light emitting device according to the sixth embodiment, as in the first embodiment, since the recess is formed in the ITO-based oxide layer instead of the p-type GaN layer, plasma damage during dry etching is caused. Since the n-type surface of the p-type GaN layer does not occur, the forward voltage does not increase. Further, as in the fifth embodiment, the ITO-based oxide film can be made thinner than when the ZnO layer is formed. In addition, since the wet etching process after dry etching, which has been conventionally required, becomes unnecessary, the manufacturing cost can be reduced.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. By the way.

In the fifth and sixth embodiments, the ITO-based oxide layer is formed on the p-type GaN layer, but the ITO-based oxide layer and the Mg _x Zn _1-x O layer (0 ≦ 0) are formed on the p-type GaN layer. x ≦ 0.5) may be formed, and concave portions or convex portions may be formed at two-dimensional periodic intervals with respect to the transparent conductive layer. Also in this case, the light extraction efficiency can be improved as in the fifth and sixth embodiments.

Since both the ITO-based oxide layer and the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) are in ohmic contact, the p-type GaN layer, the Mg _x Zn _1-x O layer ( 0 ≦ x ≦ 0.5), an ITO-based oxide layer may be laminated in this order, or a p-type GaN layer, an ITO-based oxide layer, and an Mg _x Zn _1-x O layer (0 ≦ x ≦ 0. You may laminate in the order of 5). When the p-type GaN layer, the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5), and the ITO-based oxide layer are stacked in this order, GaN and Mg _x Zn _1-x O layer (0 ≦ x ≦ Since the crystal of 0.5) has the same wurtzite structure, a good bonding interface can be obtained.

Further, when the p-type GaN layer, the ITO-based oxide layer, and the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) are stacked in this order, there is an advantage that the two-dimensional structure process is simplified. The Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) is easily dissolved in acid, particularly HCl, and the ITO-based oxide is much less soluble in HCl than that. Accordingly, if a two-dimensional pattern is formed on the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) and wet etching is performed, the ITO-based oxide becomes a pseudo etching stop layer, and a desired two-dimensional structure is obtained. Can be made easily.

In the above embodiment, the ZnO layer or the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) is used in the first to fourth embodiments, and the ITO-based oxidation is used in the fifth to sixth embodiments. The physical layer has a function as a current spreading layer. In the GaN-based semiconductor light emitting device, the current spreading layer is essential. When there is no current spreading layer, p-type GaN, which is a contact layer on the semiconductor side, has a very high specific resistance of several Ωcm. Therefore, just by attaching a 100 μm diameter pad electrode to the contact layer like a red semiconductor light emitting device. Current does not reach the entire active layer, and light is emitted almost directly below the pad electrode. Considering a 300 μm square chip, the thickness of the p-type GaN layer for spreading the current over the entire chip is on the order of several mm, which is not realistic. Therefore, in the GaN-based semiconductor light emitting device, it is necessary to spread the current before the p-type GaN layer. In the first to fourth embodiments, the ZnO layer or the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0. 5) However, the ITO-based oxide layer plays a role in the fifth to sixth embodiments. Therefore, as shown in FIG. 1, even when a recess or a protrusion is formed, a ZnO layer, a Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5), an ITO-based layer is formed immediately above the semiconductor layer. The oxide layers are preferably connected continuously. The thickness of the thinned portion after forming the concave portion or the convex portion is preferably about 500 mm, although it depends on the driving current. By leaving about 500 mm of the thickness of the thinned portion, it can effectively function as a current spreading layer.

1 is a cross-sectional view of a semiconductor light emitting element according to a first embodiment of the present invention. It is a figure which shows the example of arrangement | positioning of a recessed part. It is a figure which shows the other example of arrangement | positioning of a recessed part. It is a figure which shows the electric current-luminance characteristic of a semiconductor light-emitting device. It is a figure for demonstrating the periodic space | interval of a recessed part. It is sectional drawing of the semiconductor light-emitting device based on the 2nd Embodiment of this invention. It is a figure which shows the modification of the semiconductor light-emitting device concerning the 2nd Embodiment of this invention. It is sectional drawing of the semiconductor light-emitting device based on the 3rd Embodiment of this invention. It is sectional drawing of the semiconductor light-emitting device which concerns on the 4th Embodiment of this invention.

Explanation of symbols

  10 semiconductor light emitting device, 12 sapphire substrate, 14 buffer layer, 16 n-type GaN layer, 18 InGaN light emitting layer, 24 ZnO layer, 26 p-side electrode, 28 n-side electrode, 30 recess, 32 p-type GaN layer.

Claims (17)

A semiconductor light-emitting device in which an n-type GaN layer, a light-emitting layer, and a p-type GaN layer are stacked on a substrate,
An Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) is provided on the p-type GaN layer,
A semiconductor light emitting device, wherein concave portions or convex portions are formed at two-dimensional periodic intervals on the surface of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). The wavelength of light from the light emitting layer in air is λ, the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength λ is _nzλ, and the Mg _x Zn _When the total reflection angle at the interface between the _1-xO layer (0 ≦ x ≦ 0.5) and the medium in contact therewith is θ _z , the periodic interval between adjacent concave portions or the periodic interval L _z between adjacent convex portions But,

The semiconductor light emitting element according to claim 1, wherein the semiconductor light emitting element is in the range of The wavelength of light from the light emitting layer in the air is λ, the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength λ is _nzλ, and from the light emitting layer And the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength _{λ−Δλ is nz (λ−Δλ)} , the wavelength The refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at _{λ + Δλ is nz (λ + Δλ),} and the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). When the total reflection angle at the interface with the medium in contact with it is θ _z , the periodic interval of adjacent concave portions or the periodic interval L _z of adjacent convex portions is

The semiconductor light emitting element according to claim 1, wherein the semiconductor light emitting element is in the range of The wavelength of light from the light emitting layer in the air is λ, the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength λ is _nzλ, and from the light emitting layer And the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength _{λ−Δλ is nz (λ−Δλ)} , the wavelength The refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at _{λ + Δλ is nz (λ + Δλ),} and the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). When the total reflection angle at the interface with the medium in contact with it is θ _z , the periodic interval of adjacent concave portions or the periodic interval L _z of adjacent convex portions is

The semiconductor light emitting element according to claim 1, wherein the semiconductor light emitting element is in the range of 5. The concave portion or the convex portion formed in the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) is arranged in a square lattice shape or a triangular lattice shape. The semiconductor light emitting element in any one. A semiconductor light-emitting device in which a p-type GaN layer, a light-emitting layer, and an n-type GaN layer are stacked,
A semiconductor light emitting device, wherein recesses or projections are formed on the surface of the n-type GaN layer at two-dimensional periodic intervals. The wavelength of light from the light emitting layer is λ, the refractive index of the n-type GaN layer at the wavelength λ is _ngλ, and the total reflection angle at the interface between the n-type GaN layer and the medium in contact therewith Is θ _g , the periodic interval between adjacent concave portions or the periodic interval L _g between adjacent convex portions is

The semiconductor light emitting device according to claim 6, which is in the range of The wavelength of light from the light emitting layer in the air is λ, the refractive index of the n-type GaN layer at the wavelength λ is _ngλ, and the half width of the light from the light emitting layer in the air is Δλ, The refractive index of the n-type GaN layer at the wavelength λ−Δλ is _{ng (λ−Δλ)} , the refractive index of the n-type GaN layer at the wavelength λ + Δλ is _{ng (λ + Δλ),} and the n-type GaN layer is in contact with it. When the total reflection angle at the interface with the medium is θ _g , the periodic interval between adjacent concave portions or the periodic interval L _g between adjacent convex portions is

The semiconductor light emitting device according to claim 6, which is in the range of The wavelength of light from the light emitting layer in the air is λ, the refractive index of the n-type GaN layer at the wavelength λ is _ngλ, and the half width of the light from the light emitting layer in the air is Δλ, The refractive index of the n-type GaN layer at the wavelength λ−Δλ is _{ng (λ−Δλ)} , the refractive index of the n-type GaN layer at the wavelength λ + Δλ is _{ng (λ + Δλ),} and the n-type GaN layer is in contact with it. When the total reflection angle at the interface with the medium is θ _g , the periodic interval between adjacent concave portions or the periodic interval L _g between adjacent convex portions is

The semiconductor light emitting device according to claim 6, which is in the range of   10. The semiconductor light emitting device according to claim 6, wherein the concave portions or the convex portions formed in the n-type GaN layer are arranged in a square lattice shape or a triangular lattice shape. A semiconductor light-emitting device in which an n-type GaN layer, a light-emitting layer, and a p-type GaN layer are stacked on a substrate,
The substrate is a SiC substrate;
Concave portions or convex portions are formed on the surface of the SiC substrate at two-dimensional periodic intervals,
An Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) is provided on the p-type GaN layer,
A semiconductor light emitting device, wherein concave portions or convex portions are formed at two-dimensional periodic intervals on the surface of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). The wavelength of light from the light emitting layer in air is λ, the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength λ is _nzλ, and the Mg _x Zn _When the total reflection angle at the interface between the _1-xO layer (0 ≦ x ≦ 0.5) and the medium in contact therewith is θ _z , the periodic interval between adjacent concave portions or the periodic interval L _z between adjacent convex portions But,

The semiconductor light emitting device according to claim 11, which is in the range of The wavelength of light from the light emitting layer in the air is λ, the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength λ is _nzλ, and from the light emitting layer And the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength _{λ−Δλ is nz (λ−Δλ)} , the wavelength The refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at _{λ + Δλ is nz (λ + Δλ),} and the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). When the total reflection angle at the interface with the medium in contact with it is θ _z , the periodic interval of adjacent concave portions or the periodic interval L _z of adjacent convex portions is

The semiconductor light emitting device according to claim 11, which is in the range of The wavelength of light from the light emitting layer in the air is λ, the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength λ is _nzλ, and from the light emitting layer And the refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at the wavelength _{λ−Δλ is nz (λ−Δλ)} , the wavelength The refractive index of the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) at _{λ + Δλ is nz (λ + Δλ),} and the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5). When the total reflection angle at the interface with the medium in contact with it is θ _z , the periodic interval of adjacent concave portions or the periodic interval L _z of adjacent convex portions is

The semiconductor light emitting device according to claim 11, which is in the range of 15. The recesses or protrusions formed in the Mg _x Zn _1-x O layer (0 ≦ x ≦ 0.5) are arranged in a square lattice shape or a triangular lattice shape. The semiconductor light emitting element in any one. A semiconductor light-emitting device in which an n-type GaN layer, a light-emitting layer, and a p-type GaN layer are stacked on a substrate,
On the p-type GaN layer, a transparent conductive film layer made of an oxide layer containing at least one element selected from the group consisting of Zn, In, Sn and Mg, or the oxide layer and Mg _x Zn _{1− x O} layer (0 ≦ x ≦ 0.5) and a transparent conductive film layer formed by laminating is provided,
A semiconductor light emitting device, wherein concave portions or convex portions are formed on the surface of the transparent conductive film layer at two-dimensional periodic intervals. A semiconductor light-emitting device in which an n-type GaN layer, a light-emitting layer, and a p-type GaN layer are stacked on a substrate,
The substrate is a SiC substrate;
Concave portions or convex portions are formed on the surface of the SiC substrate at two-dimensional periodic intervals,
On the p-type GaN layer, a transparent conductive film layer made of an oxide layer containing at least one element selected from the group consisting of Zn, In, Sn and Mg, or the oxide layer and Mg _x Zn _{1− x O} layer (0 ≦ x ≦ 0.5) and a transparent conductive film layer formed by laminating is provided,
A semiconductor light emitting device, wherein concave portions or convex portions are formed on the surface of the transparent conductive film layer at two-dimensional periodic intervals.

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