JP2005294375A - Light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting element having a high directivity of a luminous flux taken out from the element and having a simple structure and an inexpensive structure.
In order to solve the above problems, the light-emitting element 1 of the present invention includes:
A light emitting layer portion 2 made of a compound semiconductor, a current diffusion layer 3, and an electrode 4 for applying a light emission driving voltage to the light emitting layer portion 3 are laminated in this order. The region where 4 is not formed is the light extraction surface PF,
In the current diffusion layer 3, a current blocking layer 5 that bypasses a current-carrying path between the electrode 4 and the light emitting layer portion 2 is buried immediately below the electrode 4, and the emitted light beam DL from the light emitting layer portion 2 is The light is extracted from the light extraction surface PF through a region located outside the current blocking layer 5 of the current spreading layer 3.
In addition, the current blocking layer 5 is made of a material that has a larger absorption capacity for the luminous flux from the light emitting layer portion 2 than that of the current diffusion layer 3, and is applied to the side surface of the current diffusion layer 3 directly or through reflection from the light emitting layer portion 2. It is characterized in that a part of the emitted luminous flux IL heading is absorbed by the current blocking layer 5.
[Selection] Figure 1

Description

  The present invention relates to a light emitting element.

The light-emitting layer portion is formed of (Al _x Ga _1-x ) _y In _1-y P mixed crystal (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1; hereinafter also referred to as AlGaInP mixed crystal or simply AlGaInP). The light emitting device has a high brightness by adopting a double hetero structure in which a thin AlGaInP active layer is sandwiched between an n-type AlGaInP clad layer having a larger band gap and a p-type AlGaInP clad layer. An element can be realized.

  For example, taking an AlGaInP light emitting device as an example, an n-type GaAs buffer layer, an n-type AlGaInP cladding layer, an AlGaInP active layer, and a p-type AlGaInP cladding layer are formed in this order in a heterogeneous form on an n-type GaAs substrate. The light emitting layer part which laminates | stacks and makes a double hetero structure is formed. Energization of the light emitting layer portion is performed through a metal electrode formed on the element surface. Here, since the metal electrode acts as a light shield, it is formed, for example, so as to cover only the central portion of the element surface, and light is taken out from the surrounding electrode non-formation region.

  In this case, reducing the area of the metal electrode as much as possible can increase the area of the light extraction surface formed around the electrode, which is advantageous from the viewpoint of improving the light extraction efficiency. Conventionally, attempts have been made to increase the light extraction amount by effectively spreading the current in the element by devising the electrode shape, but in this case as well, an increase in the electrode area is unavoidable anyway, and the light extraction area On the contrary, it falls into a dilemma where the amount of light extraction is limited by the decrease. In addition, the carrier concentration of the dopant in the clad layer, and thus the conductivity, is kept somewhat low in order to optimize the light emission recombination of carriers in the active layer, and the current tends not to spread in the in-plane direction. . This leads to concentration of current density in the electrode covering region and a substantial light extraction amount on the light extraction surface. Therefore, a method of forming a low resistivity current diffusion layer with an increased carrier concentration between the clad layer and the electrode is employed. Such a current diffusion layer is generally formed by setting the layer thickness to a certain extent in order to sufficiently spread the current in the in-plane direction, for example, by making the thickness larger than the light emitting layer portion.

Japanese Patent Laid-Open No. 11-046012 JP 08-167733 A

  By the way, the light emitting element may be used for a light source for an optical sensor in addition to an application such as illumination or display. In that case, the emitted light beam taken out from the element is required to have a certain degree of directivity. However, since the emitted light beam is emitted from the light emitting layer portion in all directions, an attempt has been made to impart directivity to the emitted light beam taken out from the element by improving the light emitting element itself or the surrounding structure. Yes. For example, as in Patent Document 1, a so-called current confinement type light emitting element in which the structure of the light emitting element is partially changed to enhance the directivity of the emitted light beam has been proposed. However, the current confinement type light emitting element has problems such as difficulty in controlling crystal growth for epitaxial growth and reduction in reliability due to a large current flowing in a part of the crystal. In addition, there is a problem that the structure is complicated and expensive compared to the conventional light emitting device. Further, for example, as described in Patent Document 2, in order to increase the directivity of the luminous flux of the light emitting element, an attempt is made to install and shape a reflector or absorber on the side surface of the element. However, in this case, there are problems that the light emitting element becomes expensive due to the installation and molding of the reflector or absorber, and that miniaturization is difficult.

  Accordingly, an object of the present invention is to provide a light-emitting element that has high directivity of a luminous flux taken out of the element, has a simple structure, and is inexpensive.

Means for solving the problems / effects of the invention

In order to solve the above problems, in the light emitting device of the present invention,
A light emitting layer portion made of a compound semiconductor, a current diffusion layer, and an electrode for applying a light emission driving voltage to the light emitting layer portion are laminated in this order, and the electrode is formed on the main surface of the current diffusion layer. The unexposed area becomes the light extraction surface,
In the current diffusion layer, a current blocking layer that bypasses a current-carrying path between the electrode and the light-emitting layer portion is embedded immediately below the electrode, and a light flux from the light-emitting layer portion is diffused in the current diffusion layer. A layer is extracted from the light extraction surface through a region located outside the current blocking layer;
In addition, the current blocking layer is made of a material that has a larger absorption capacity for the luminous flux from the light emitting layer portion than the current diffusion layer, and is directly or reflected from the light emitting layer portion on the side surface of the current diffusion layer. A part of the emitted luminous flux is directed to be absorbed by the current blocking layer.

  According to the present invention, in the current diffusion layer, the current blocking layer that bypasses the energization path between the electrode and the light emitting layer portion is buried immediately below the electrode. Since the electrode acts as a light shield, when a voltage for driving the element is applied to this electrode, the current density in the element is high near the electrode and low around the electrode, which is the light extraction surface. Efficiency tends to decrease. Therefore, if the current blocking layer as described above is embedded in the current diffusion layer at a position immediately below the electrode of the electrode, the current blocking layer causes a current detour outside the region directly below the electrode, and the current density below the light extraction surface. Becomes higher. As a result, the luminous flux from the light emitting layer portion can be extracted from the light extraction surface through a region located outside the current blocking layer directly below the electrode in the current diffusion layer, and the light extraction efficiency can be increased. .

  Further, the current blocking layer is made of a material that has a greater ability to absorb light emitted from the light emitting layer than the current diffusion layer. A luminous flux is emitted from the light emitting layer portion in all directions, but the current blocking layer is made of a material having a large absorption capacity so that the light blocking layer 5 is changed from the light emitting layer portion 2 as shown in FIG. Is emitted directly to the light extraction surface PF through a region located outside the light source, that is, substantially perpendicular to the light emitting layer portion 2 (hereinafter, a direction perpendicular to the light emitting layer portion is referred to as an axial direction). The emitted light beam DL is easily extracted from the light extraction surface PF, whereas the emitted light beam IL emitted from the light emitting layer portion 2 as shown in FIG. A part of the luminous flux IL directed to the side surface 33 of the current diffusion layer 3 directly or through reflection is absorbed by the current blocking layer. Thereby, in the light emitting element 1, the emitted light beam taken out from the element has directivity in the axial direction.

  Next, in the light emitting device of the present invention, the current blocking layer can be formed so as to be included in the region immediately below the electrode. In this way, by forming the current blocking layer having a large absorption capacity so as to be included in the region immediately below the electrode that acts as a light shielding body, the luminous flux emitted from the light emitting layer portion in the substantially axial direction is converted into light. It is possible to take out as much as possible from the extraction surface.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram showing a light emitting device 1 according to an embodiment of the present invention. In the light emitting element 1, a light emitting layer portion 2 is formed on a first main surface of an n-type GaAs single crystal substrate (hereinafter simply referred to as a substrate) 6. Specifically, an n-type GaAs buffer layer 61 is formed in contact with the first main surface of the substrate 6, and the light emitting layer portion 2 is formed on the buffer layer 61. A current diffusion layer 3 is formed on the light emitting layer portion 2, and a first electrode 4 for applying a light emission driving voltage to the light emitting layer portion 2 is formed on the current diffusion layer 3. A second electrode 42 is formed on the entire surface of the substrate 6 on the second main surface side. The first electrode 4 is formed substantially at the center of the first main surface of the current diffusion layer 3, and the region around the first electrode 4 is a light extraction region PF from the light emitting layer portion 2. A bonding pad 45 made of Au or the like for bonding the electrode wire 46 is disposed at the center of the first electrode 4.

The light emitting layer portion 2 includes an active layer 21 made of a non-doped (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 0.55, 0.45 ≦ y ≦ 0.55) mixed crystal. , p-type _{(Al z Ga 1-z)} y In 1-y P ( except x <z ≦ 1) p-type cladding layer 23 and the n-type composed of _{(Al z Ga 1-z)} y In 1-y P ( However, it has a structure sandwiched between n-type cladding layers 22 made of x <z ≦ 1). In the light emitting device 1 of FIG. 1, a p-type AlGaInP cladding layer 23 is disposed on the first electrode 4 side, and an n-type AlGaInP cladding layer 22 is disposed on the second electrode 42 side. Therefore, the conduction polarity is positive on the first electrode 4 side. The term “non-doped” as used herein means “does not actively add a dopant”, and contains a dopant component inevitably mixed in a normal manufacturing process (for example, 10 ¹³ to 10 ¹⁶ / cm 3). It is not excluded that the upper limit is about ³ ). On the contrary, the p-type cladding layer 23 can be the second electrode 42 side and the n-type cladding layer 22 can be the first electrode side. In this case, the energization polarity is reversed, and the other members have a conductivity type opposite to that shown in the figure.

  In the current diffusion layer 3, a current blocking layer 5 is embedded immediately below the first electrode 4 to bypass a current path between the electrode 4 and the light emitting layer portion 2 as shown in FIG. As a result, the current density is increased around the region immediately below the electrode 4, that is, the region immediately below the light extraction surface PF, and the emitted light beam DL from the light emitting layer portion 2 is in the current blocking layer 3 immediately below the electrode. 5 is extracted from the light extraction surface PF through a region located outside of 5.

  In the present specification, “embedding” is not limited to a mode in which the current blocking layer 5 is surrounded by the current spreading layer 3, and any surface of the current blocking layer 5 is formed on the surface of the current spreading layer 3. Also includes exposed forms. For example, as shown in FIG. 5 (a), the current blocking layer 5 is exposed on the lower main surface of the current diffusion layer 3, that is, formed on the light emitting layer 2, or as shown in FIG. 5 (b). In addition, the current blocking layer 5 is exposed on the upper main surface of the current diffusion layer 3, that is, in contact with the electrode 4. However, in the case of FIG. 5B, the electrode 4 is required to be in contact with the current diffusion layer 3 as well. Further, as shown in FIG. 5C, when the electrode 4 is formed at the end of the upper main surface of the current diffusion layer 3 and the central portion is the light extraction surface PF, the current blocking layer 5 is A form exposed on the side surface of the current spreading layer 3 is also included.

  The current blocking layer 5 is made of a material that has a higher absorption capacity for the luminous flux from the light emitting layer portion 2 than the current diffusion layer 3, and the side surface 33 of the current diffusion layer 3 directly or through reflection from the light emitting layer portion 2. A part of the emitted light beam IL directed to is absorbed by the current blocking layer 5. Specifically, the current blocking layer 5 is composed of a compound semiconductor having a band gap energy smaller than the light energy corresponding to the peak emission wavelength of the emitted light beam so that the emitted light beam from the light emitting layer portion 2 can be absorbed. Is done. In the present embodiment, the current blocking layer 5 is made of GaAs capable of absorbing the luminous flux from the light emitting layer portion 2 made of AlGaInP mixed crystal.

  The current blocking layer 5 is formed so as to be included in a region immediately below the electrode 4. In the present embodiment, the current blocking layer 5 and the electrode 4 are configured in the same shape, and are disposed so that they overlap when the light emitting element 1 is viewed from the light extraction surface PF side as shown in FIG. When configured in this manner, it is possible to extract the light-emitting light beam DL emitted from the light-emitting layer portion 2 in the substantially axial direction from the light extraction surface PF to the maximum extent. Further, even if the current blocking layer 5 is included in the region immediately below the electrode 4, if the formation area (in a plane parallel to the light extraction surface PF) is extremely small, light emission toward the side surface 33 of the current diffusion layer 3 Since the effect of absorbing a part of the light beam IL may not be sufficiently obtained, it is preferable to set the formation area of the current blocking layer 5 to 70% or more with respect to the formation area of the electrode 4.

  The current spreading layer 3 is composed of a compound semiconductor having a larger band gap energy than the light energy corresponding to the peak emission wavelength of the emitted light beam so that the emitted light beam from the light emitting layer portion 2 can be transmitted. Further, the current blocking layer 5 is made of a compound semiconductor having a conductivity type different from that of the current diffusion layer 3, thereby blocking a current-carrying path directly under the electrode 4 as shown in FIG. It is possible to make it. Specifically, the current spreading layer 3 has the same conductivity type as that of the p-type cladding layer 23 and the n-type cladding layer 22 located on the electrode 4 side, and the peak of the emitted light flux from the light emitting layer portion 2. It is composed of at least one of GaP, AlGaAs, and AlInP having a band gap energy larger than the light energy corresponding to the emission wavelength. These have good translucency with respect to the luminous flux from the light emitting layer portion 2 made of an AlGaInP mixed crystal.

In the present embodiment, the current diffusion layer 3 is made of GaP. Further, since the p-type cladding layer 23 is formed on the side of the electrode 4 in the light emitting layer portion 2, GaP of the current diffusion layer 3 is p-type and GaAs of the current blocking layer 5 is n-type. When AlGaAs (Al _{1 -a} Ga _a As) or AlInP (Al _{1 -b} In _b P) is used for the current diffusion layer 3, the light energy corresponding to the peak emission wavelength of the luminous flux from the light emitting layer portion 2 The mixed crystal ratio is such that the band gap energy becomes larger than that.

  The current spreading layer 3 is formed as a p-type GaP layer with Zn or Mg as a dopant. Further, the H and Zn content concentrations in the current diffusion layer 3 are made smaller than the H and Zn content concentrations in the p-type cladding layer 23, respectively. The formation thickness t1 of the current diffusion layer 3 is, for example, 5 μm or more and 20 μm or less (for example, 10 μm). The thickness of the current blocking layer 5 is 0.05 μm or more and 1 μm or less (for example, 0.1 μm).

In the surface layer portion including the main surface on the side where the first electrode 4 of the current diffusion layer 3 is formed, a high-concentration doping layer 37 having a Zn content concentration higher than that of the remaining portion in the current diffusion layer 3 is formed. ing. The Zn carrier concentration of the current diffusion layer 3 is 2 × 10 ¹⁸ / cm ³ or more and 5 × 10 ¹⁹ / cm ³ or less (for example, 1 × 10 ¹⁹ / cm ³ ) in the high-concentration doping layer 37, and the high-concentration doping is performed. It is set to 1 × 10 ¹⁷ / cm ³ or more and 2 × 10 ¹⁸ / cm ³ or less (for example, 8 × 10 ¹⁷ / cm ³ ) in a portion other than the layer 37.

  The thickness t2 of the high-concentration doping layer 37 is 1 μm or more and 4 μm or less (for example, 3 μm). The thickness t2 of the high-concentration doping layer 37 is such that the p-type dopant-containing concentration (Zn-containing concentration in this embodiment) in the surface layer portion of the current diffusion layer 3 where the dopant is the highest concentration is Nmax. When the concentration of the p-type dopant in the portion not affected by diffusion is Nmin, the position where it is approximately (Nmax + Nmin) / 2 in the layer thickness direction is the boundary position between the high-concentration doping layer 37 and the remaining portion. It is specified by defining. Note that the dopant-containing concentration and H concentration in each layer are those measured by secondary ion mass spectrometry (SIMS). The carrier concentration can be specified by well-known conductivity measurement.

  A portion of the current spreading layer 3 located between the p-type cladding layer 23 and the current blocking layer 5 is a first layer 35 formed by the MOVPE method. Further, on the opposite side of the first layer 35 with respect to the current blocking layer 5, a second layer 36 that forms the main part of the current spreading layer 3 is formed so as to cover the current blocking layer 5 together with the first layer 35. ing. The second layer 36 is formed by the HVPE method to be described later, and the surface layer portion on the first electrode 4 side is made the above-described high-concentration doped layer 37 by the additional diffusion of Zn.

By adopting the HVPE method, the H concentration in the current diffusion layer 3 can be set smaller than the H concentration of the p-type cladding layer 23 (usually about 15 × 10 ¹⁷ / cm ³ ) by the MOVPE method. In the present embodiment, only the first layer 35 of the current spreading layer 3 is formed by the MOVPE method, and the H concentration in this portion is somewhat higher. However, the H concentration of the second layer 36 is 7 × 10 ¹⁷ / cm ³ or less, and usually 2 × 10 ¹⁷ / cm ³ or less. Since the thickness of the first layer 35 is much smaller than the thickness of the second layer 36, in any case, the H concentration in the current diffusion layer 3 is sufficiently lower than the H concentration of the p-type cladding layer 23. Become. Of the second layer 36 constituting the main part of the current spreading layer 3, the portion excluding the high-concentration doping layer 37 is H and the Zn content concentration is set lower than the Zn content concentration of the p-type cladding layer. Since the amount of Zn to be inactivated by the bonding is small, sufficient conductivity can be ensured. As a result, the device life can be improved.

  Further, in the current diffusion layer 3, current diffusion in the in-plane direction proceeds mainly in the high concentration doping layer 37. Since the inner layer portion of the current diffusion layer 3 other than the high-concentration doping layer 37 has a low carrier concentration due to the dopant and a high resistivity in the in-plane direction, when the current enters the inner layer portion, re-diffusion in the in-plane direction occurs. It is difficult to occur and easily flows while detouring to the outer region of the electrode 4. As a result, the light extraction efficiency is improved.

  In the present embodiment, the first layer 35 and the second layer 36 are formed of the same compound semiconductor (specifically GaP), but may be formed of different compound semiconductors. For example, as shown in FIG. 4, the first layer 35 is made of AlGaAs (however, the mixed crystal ratio range in which the band gap energy is larger than the light energy corresponding to the peak emission wavelength of the light emitting layer), and the second layer 36 is made of GaP. And In this case, AlGaInP forming the p-type cladding layer 23, AlGaAs forming the first layer 35, and AlGaAs forming the first layer 35 and GaAs forming the current blocking layer 5 are lattice-matched. A good quality first layer 35 and current blocking layer 5 can be formed. Further, a p-type dopant is added to both the first layer 35 and the second layer 36. As the p-type dopant, both layers 35 and 36 can adopt Zn as in this embodiment, but the dopant of the first layer 35 formed by MOVPE diffuses to the p-type cladding layer 23 side. Mg and / or C, which are difficult to generate, may be used, and the dopant of the second layer 36 formed by HVPE may be Zn.

Hereinafter, a method for manufacturing the light-emitting element 1 of FIG. 1 will be described.
First, as shown in step (1) of FIG. 6, a GaAs single crystal substrate 6 is prepared. Then, as shown in the step (2), the n-type GaAs buffer layer 61 is, for example, 0.5 μm on the first main surface MP1 of the substrate 6, and then the light emitting layer portion 2 is formed as (Al _x Ga _1-x ) _y an in consisting _1-y P, 1 [mu] m of the n-type cladding layer 22 (n-type dopant is Si), 0.6 .mu.m active layer (non-doped) 21 and 1 [mu] m p-type cladding layer 23 (p-type dopant, the Mg : C from organometallic molecules can also contribute as a p-type dopant) in this order (first vapor phase growth step). Epitaxial growth of each of these layers is performed by a known MOVPE method. The following materials can be used as source gases for the source components of Al, Ga, In (indium), and P (phosphorus);
Al source gas; trimethylaluminum (TMAl), triethylaluminum (TEAl), etc .;
Ga source gas; trimethylgallium (TMGa), triethylgallium (TEGa), etc .;
In source gas; trimethylindium (TMIn), triethylindium (TEIn), etc.
P source gas: trimethyl phosphorus (TMP), triethyl phosphorus (TEP), phosphine (PH3), etc.

  Next, in the step (3) of FIG. 7, the first layer 35 made of p-type GaP (on the light emitting layer portion 2 already formed in the reaction vessel of the first vapor phase growth step ( A current blocking layer containing layer having a portion to be the current blocking layer 5 (see FIG. 1) later, which is made of n-type GaAs having an ability to absorb the luminous flux from the light emitting layer 2 5 ′ are sequentially formed by the MOVPE method. Next, the surface of the portion of the current blocking layer containing layer 5 ′ that remains as the current blocking layer 5 is covered with the photoresist layer 30. Then, when the process proceeds to step (4) and etching is performed with the first etching solution made of hydrochloric acid, the portion of the current blocking layer-containing layer 5 ′ that is not covered with the photoresist layer 30 is selectively etched. When the etching is completed, the photoresist layer 30 is removed after cleaning.

Proceeding to step (5) in FIG. 8, a second layer 36 (which is an HVPE layer portion) made of p-type GaP is grown by HVPE so as to enclose the current blocking layer 5 (second vapor phase growth step). . Specifically, in the HVPE method, GaCl, which is a group III element, is heated and held at a predetermined temperature in a container, and hydrogen chloride is introduced onto the Ga, thereby causing GaCl by the reaction of the following formula (1). And is supplied onto the substrate together with the H ₂ gas that is a carrier gas.
Ga (liquid) + HCl (gas) → GaCl (gas) + 1 / 2H ₂ (1)
In the case of GaP, the growth temperature is set to about 800 to 860 ° C., for example. Moreover, P is a Group V element is supplied to the substrate PH3 with H ₂ as a carrier gas. Further, Zn which is a p-type dopant is supplied in the form of DMZn (dimethylzinc). GaCl is excellent in reactivity with PH3, and the second layer 36 that forms the main part of the current diffusion layer 3 can be efficiently grown with Ga by the reaction of the following formula (2):
GaCl (gas) + PH ₃ (gas)
→ GaP (solid) + HCl (gas) + H ₂ (gas) (2)

When the growth of the second layer 36 is completed, the process proceeds to step (6), transferred to another container, and heated at, for example, 650 to 750 ° C. (for example, 700 ° C.) while being group V element compound (Zn ₃ As ₂ , Zn _3). It was circulated vapor P _2, etc.), and vacuum diffusion. Then, the Zn component is additionally diffused in the electrode formation side portion of the second layer 36, and the high concentration doping layer 37 is formed. The diffusion time is adjusted according to how much the formation thickness t2 of the high-concentration doping layer 37 is set. Note that the p-type dopant used for the p-type cladding layer 23 uses Mg and / or C having a relatively small diffusion coefficient, so that when the current diffusion layer 3 is formed by the HVPE method, The diffusion of the p-type dopant from the p-type cladding layer 23 to the active layer 21 due to heating can be suppressed, which contributes to the improvement of the emission intensity.

  When the above steps are completed, the first electrode 4 and the second electrode 42 are formed by a vacuum deposition method, and the bonding pad 45 is disposed on the first electrode 4, and baking for electrode fixing is performed at an appropriate temperature. Apply. Then, the second electrode 42 is fixed to a terminal electrode (not shown) that also serves as a support using a conductive paste such as an Ag paste, while an Au wire 46 is formed so as to straddle the bonding pad 45 and another terminal electrode. The light emitting element 1 is obtained by bonding and further forming a resin mold. Note that the bonding of the wire 46 is performed by an automatic bonding apparatus by photographing an image of the first surface of the element with a camera, identifying the bonding pad 45 region by a known image processing method.

FIG. 9 shows that the main part of the current diffusion layer 3 is formed of GaP, and only the electrode forming side portion of the current diffusion layer 3 is formed as the GaAsP layer 38, and the high concentration of Zn in the GaAsP layer 38 as a dopant. In this example, the doping layer 37 is formed by the above-described additional diffusion. Since the diffusion rate of Zn in GaAsP is larger than that in GaP, the high-concentration doping layer 37 can be formed in a shorter time. Further, according to the HVPE method, changing the composition during the growth of the current diffusion layer 3 (in this case, GaP → GaAsP) can be easily performed by changing the mixing ratio of the group V element gas (AsH ₃ and PH ₃ ). (Especially than the LPE method).

  In the above embodiment, the light emitting layer portion 2 is formed directly on the substrate 6 via the buffer layer 61. However, in order to improve the light extraction efficiency between the substrate 6 and the light emitting layer portion 2. A reflective layer may be interposed. As the reflective layer, for example, a layer in which a plurality of compound semiconductor layers having different refractive indexes as disclosed in JP-A-7-66455 is stacked can be used. That is, as shown in FIG. 13, compound semiconductor layers 9 a and 9 b having different refractive indexes are alternately stacked on the main surface 2 b opposite to the light extraction surface PF side of the light emitting layer portion 2. A reflection layer 9 is formed that reflects the emitted light beam RL from the portion 2 by giving a directivity in the direction of the light extraction surface PF by Bragg reflection. The reflective layer 9 is hereinafter referred to as a DBR (Distributed Bragg Reflector) layer 9.

  In the light emitting device 1 of FIG. 13, the DBR layer 9 is composed of a multilayer film (AlGaN / GaN multilayer film in this embodiment) in which compound semiconductor layers 9a and 9b having different refractive indexes are alternately stacked. The light emitting layer portion 2 is formed on the GaAs substrate 6 with the GaAs buffer layer 6 interposed therebetween. According to this structure, the emitted light beam from the light emitting layer part 2 is reflected by the DBR layer 9, and the reflected emitted light beam RL is superimposed on the emitted light beam DL directly going from the light emitting layer part 2 to the light extraction surface PF side. Since the light is extracted from the light extraction surface PF, the light extraction efficiency is improved. Moreover, since it can form by consistently growing epitaxially on a board | substrate with the DBR layer 9 and the light emitting layer part 2, there exists an advantage by which a manufacturing process is simplified.

  In addition, since the DBR layer 9 uses Bragg reflection, the incident angle of the reflected luminous flux (defined by the angle with respect to the normal of the reflecting surface) is limited. Among them, since the emitted light beam having an incident angle of approximately 0 ° is totally reflected, the emitted light beam RL that is perpendicularly incident on the DBR layer 9 as shown in FIG. 13, that is, the vertical direction from the light emitting layer portion 2 to the DBR layer 9 side ( The emitted light beam RL emitted in the direction opposite to the axis a in the figure is totally reflected by the DBR layer 9. On the other hand, a luminous flux (not shown) that is incident from a direction that is not perpendicular to the DBR layer 9 is not reflected (except for a part where the incident angle corresponds to the black angle). In this way, the emitted light beam RL reflected by the DBR layer 9 has directivity in the light extraction surface PF direction (axis a direction).

Hereinafter, experiments conducted for confirming the effects of the present invention will be described.
As an example, the light emitting device 1 of the above-described embodiment of FIG. 1 was produced. On the other hand, as a comparative example, as shown in FIG. 11, a light emitting element 1 ′ in which a current blocking layer was not formed was manufactured (the other parts are the same as in the example). Then, as shown in FIG. 10, two electrodes 101 and 102 are prepared, mounted on one electrode 101 so that the light extraction surface PF is on the upper side, and the electrode wire 46 is attached to the other electrode 102. Connected. The current-carrying characteristics are negative on the electrode 101 side and positive on the electrode 102 side. In addition, the direction of the arrow in the figure, that is, the direction extending in the direction perpendicular to the light extraction surface PF (light emitting layer portion 2) was defined as the axial direction a.

  Then, about the Example and the comparative example, the directly above luminous intensity and integrating sphere luminous intensity of the emitted light beam obtained from each were measured using the photometer. The on-axis luminous intensity is the luminous intensity obtained in the axial direction a, and the integrating sphere luminous intensity is obtained by total luminous intensity measurement using an integrating sphere.

  In the example, although the integrating sphere luminous intensity is reduced to about 0.8 times that of the comparative example, the axial luminous intensity is about twice that of the comparative example. That is, it can be seen that the embodiment is a light emitting element with high directivity in which the amount of the emitted light beam leaking from the side surface is suppressed and the emitted light beam is mainly extracted from the light extraction surface PE. In addition, the integrating sphere luminous intensity decreased compared to the comparative example is due to the absorption effect of the luminous flux by the current blocking layer, and the axial luminous intensity increased due to the effect of bypassing the energization path by the current blocking layer. It is estimated that

  As described above, it is possible to provide a light-emitting element with high directivity of emitted light flux, simple structure, and low cost.

Schematic diagram showing an example of a light-emitting element of the present invention in a laminated structure Schematic view of the light-emitting element of FIG. 1 viewed from the light extraction surface side Schematic diagram showing the current path in the current spreading layer The figure which shows the 1st modification of the light emitting element of FIG. The figure showing the modification of the embedding form of a current blocking layer The figure which shows the manufacturing process of the light emitting element of FIG. Figure following Figure 6 Figure following Figure 7 The figure which shows the 2nd modification of the light emitting element of FIG. The figure showing the mounting state of the light emitting element of an Example or a comparative example The figure showing the laminated structure of the light emitting element of a comparative example The figure showing a mode that the emitted light beam from a light emitting layer part is taken out of an element. The figure which shows the 3rd modification of the light emitting element of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light emitting layer part 3 Current diffusion layer 35 First layer of current diffusion layer 36 Second layer of current diffusion layer 3 37 Highly doped layer 4 First electrode 5 Current blocking layer PF Light extraction surface

Claims (7)

A light emitting layer portion made of a compound semiconductor, a current diffusion layer, and an electrode for applying a light emission driving voltage to the light emitting layer portion are laminated in this order, and the electrode is formed on the main surface of the current diffusion layer. The unexposed area becomes the light extraction surface,
In the current diffusion layer, a current blocking layer that bypasses a current-carrying path between the electrode and the light-emitting layer portion is embedded immediately below the electrode, and a light flux from the light-emitting layer portion is diffused in the current diffusion layer. A layer is extracted from the light extraction surface through a region located outside the current blocking layer;
In addition, the current blocking layer is made of a material that has a larger absorption capacity for the luminous flux from the light emitting layer portion than the current diffusion layer, and is directly or reflected from the light emitting layer portion on the side surface of the current diffusion layer. A light emitting element characterized in that a part of the emitted luminous flux is directed to be absorbed by the current blocking layer.   The light emitting device according to claim 1, wherein the current blocking layer is formed so as to be included in a region immediately below the electrode.   The said current blocking layer is comprised with the compound semiconductor whose band gap energy is smaller than the light energy corresponding to the peak light emission wavelength of the emitted light beam from the said light emitting layer part, The Claim 1 or 2 characterized by the above-mentioned. Light emitting element. The current spreading layer is composed of a compound semiconductor having a band gap energy larger than the light energy corresponding to the peak emission wavelength of the luminous flux from the light emitting layer portion,
4. The light emitting device according to claim 3, wherein the current blocking layer is made of a compound semiconductor having a conductivity type different from that of the current diffusion layer.   The light emitting layer portion has a double hetero structure in which a p-type cladding layer composed of AlGaInP mixed crystal, an active layer, and an n-type cladding layer are laminated in this order, and the current blocking layer is composed of GaAs. The light emitting device according to claim 3, wherein the light emitting device is a light emitting device.   The current spreading layer has the same conductivity type as that of the p-type cladding layer and the n-type cladding layer located on the electrode side, and corresponds to the peak emission wavelength of the luminous flux from the light emitting layer portion. The light emitting device according to claim 5, wherein the light emitting device is configured by at least one of GaP, AlGaAs, and AlInP having a band gap energy larger than the light energy.   Compound semiconductor layers having different refractive indexes are alternately stacked on the main surface opposite to the light extraction surface side of the light emitting layer portion, and the light extraction light beam from the light emitting layer portion is extracted by Bragg reflection. The light emitting device according to claim 1, further comprising a reflective layer that reflects the light with directivity in the surface direction.

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