JP2017126684A - Semiconductor light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting device having an emission wavelength band (spectral width) over a wide range, high color rendering properties, and a high intensity of light emission.SOLUTION: A semiconductor light-emitting device 10 comprises: a first semiconductor layer 12 having a first conductivity type; a light-emitting functional layer 13 formed on the first semiconductor layer, and including a first luminescent layer; and a second semiconductor layer 15 formed on the light-emitting functional layer, and having a conductivity type opposite to that of the first semiconductor layer. The first luminescent layer has: a base layer BL having a plurality of base segments BS having a composition subjected to stress distortion from the first semiconductor layer, and formed in a random mesh appearance; a buffer layer BU formed on the base layer so that the segment geometry of the plurality of base segments is left therein; and an active layer AC formed on the buffer layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor light emitting device such as a light emitting diode (LED).

  In a semiconductor light emitting device, a semiconductor structure layer composed of an n-type semiconductor layer, an active layer, and a p-type semiconductor layer is usually grown on a growth substrate, and a voltage is applied to the n-type semiconductor layer and the p-type semiconductor layer, respectively. It is fabricated by forming an electrode and a p-electrode.

  In Patent Document 1, at least two types of semiconductor light emitting elements are formed on one substrate material, and a plurality of types of phosphors that react to the emission wavelength of each element are applied on each semiconductor light emitting element, A light emitting device configured to simultaneously emit light from the semiconductor light emitting elements is disclosed. Patent Document 2 discloses a light emitting diode in which a red light emitting diode, a green light emitting diode, and a blue light emitting diode are stacked so that light emitted from each light emitting diode is in the same direction.

JP 2008-071805 JP JP 2011-249460 JP

  The semiconductor light emitting device emits light by recombination of electrons and holes injected from the electrode into the device in the active layer. The wavelength of light emitted from the active layer (that is, the emission color) is determined by the band gap of the semiconductor material constituting the active layer. For example, in the case of a light emitting element using a nitride-based semiconductor, blue light is emitted from the active layer.

  On the other hand, color rendering properties may be required for the light source, for example, for lighting purposes. A light source having a high color rendering property is a light source that emits light close to natural light. In order to obtain high color rendering properties, it is preferable that light having a wavelength in almost the entire visible range is extracted from the light source. For example, light extracted from a light source having high color rendering properties is observed as white light.

  On the other hand, as described in the above patent document, various methods for obtaining white light using a semiconductor light emitting element have been proposed. For example, a method has been proposed in which a plurality of active layers having different compositions are stacked to achieve a broad emission wavelength band without using a phosphor.

  However, when a light-emitting device is manufactured by these methods, there are problems in terms of uniform emission colors, complicated manufacturing processes, and emission intensity. Examples thereof include addition of a semiconductor layer forming step and a bonding step, deterioration of crystallinity of the semiconductor layer, and the like.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor light emitting device having a high color rendering property and a high light emission intensity having a light emission wavelength band (spectrum width) over a wide range.

  A semiconductor light emitting device according to the present invention is formed on a light emitting functional layer including a first semiconductor layer having a first conductivity type, a light emitting functional layer formed on the first semiconductor layer and including the first light emitting layer. And a second semiconductor layer having a conductivity type opposite to that of the first semiconductor layer, wherein the first light emitting layer has a composition that receives stress strain from the first semiconductor layer. A base layer having a plurality of base segments partitioned into a random network, a buffer layer formed on the base layer while retaining the segment shape of the plurality of base segments, and formed on the buffer layer And an active layer.

(A) is sectional drawing which shows the structure of the semiconductor light-emitting device which concerns on Example 1, (b) is a top view which shows typically the base layer of the light emitting layer in the semiconductor light-emitting device which concerns on Example 1. FIG. (A) is sectional drawing which shows the structure of the semiconductor structure layer in the semiconductor light-emitting device which concerns on Example 1, (b) is sectional drawing which shows the example of a composition of the semiconductor structure layer in the semiconductor light-emitting device which concerns on an Example. (A) is sectional drawing which shows the structure of the semiconductor light-emitting device concerning the modification of Example 1, (b) shows typically the buffer layer of the light emitting layer in the semiconductor light-emitting device concerning the modification of Example 1. It is a top view. 6 is a cross-sectional view showing a structure of a semiconductor light emitting device according to Example 2. FIG. 6 is a cross-sectional view illustrating a structure of a semiconductor light emitting element according to Example 3. FIG. It is a figure which shows the emission spectrum of the semiconductor light-emitting device which concerns on Example 3, and the semiconductor light-emitting device which concerns on a comparative example.

  Examples of the present invention will be described in detail below. In this specification, the same reference numerals are assigned to the same components.

  FIG. 1A is a cross-sectional view showing a structure of a semiconductor light emitting device 10 of the first embodiment (hereinafter sometimes simply referred to as a light emitting device or an element). The semiconductor light emitting device 10 has a structure in which a semiconductor structure layer SS is formed on a mounting substrate (hereinafter sometimes simply referred to as a substrate) 11. The semiconductor structure layer SS is formed on the n-type semiconductor layer (first semiconductor layer) 12 formed on the mounting substrate 11, the light emitting functional layer 13 formed on the n type semiconductor layer 12, and the light emitting functional layer 13. The electron block layer 14 and the p-type semiconductor layer (second semiconductor layer, semiconductor layer having a conductivity type opposite to that of the first semiconductor layer 12) 15 formed on the electron block layer 14 are included.

  In this embodiment, the mounting substrate 11 is a growth substrate used for growing the semiconductor structure layer SS, for example, and is made of sapphire, for example. The semiconductor structure layer SS is made of a nitride semiconductor. For example, the semiconductor light emitting device 10 uses the C plane of a sapphire substrate as a crystal growth surface, and grows a semiconductor structure layer SS on the sapphire substrate by using a metal organic chemical vapor deposition (MOCVD) method. Can be produced. Although not shown, the semiconductor light emitting element 10 has an n electrode and a p electrode for applying a voltage to the n type semiconductor layer 12 and the p type semiconductor layer 15, respectively.

  In the present embodiment, the case where the light emitting element 10 has a structure in which the semiconductor structure layer SS is formed on the growth substrate as the mounting substrate 11 will be described. However, when the mounting substrate 11 is a growth substrate. It is not limited. For example, the semiconductor light emitting device 10 has a structure in which a semiconductor structure layer SS is grown on a growth substrate, the semiconductor structure layer SS is bonded to another substrate (support substrate), and the growth substrate is removed. Also good. In this case, the other bonded substrate is provided on the p-type semiconductor layer 15. As the bonding substrate, for example, a material with high heat dissipation such as Si, AlN, Mo, W, or CuW can be used.

  The n-type semiconductor layer 12 is made of, for example, a GaN layer containing an n-type dopant (for example, Si). The electron block layer 14 is made of, for example, an AlGaN layer. The p-type semiconductor layer 15 is made of, for example, a GaN layer containing a p-type dopant (for example, Mg). The electron block layer 14 may contain a p-type dopant. In addition, the p-type semiconductor layer 15 may have a contact layer on the main surface opposite to the interface with the electron block layer 14.

  Although the light emitting functional layer 13 may have a plurality of light emitting layers, in this embodiment, the case where the light emitting functional layer 13 is composed of one light emitting layer will be described. In this embodiment, the light emitting layer 13 has a base layer BL formed on the n-type semiconductor layer 12 and having a composition different from that of the n-type semiconductor layer 12. The base layer BL has a groove (first groove) GR <b> 1 formed in a random mesh shape under stress from the n-type semiconductor layer 12.

  Here, the base layer BL will be described with reference to FIG. FIG. 1B is a diagram schematically showing the upper surface of the base layer BL. Further, the base layer BL has a large number of fine base segments BS defined by the grooves GR1 and formed at random sizes. Each of the base segments BS is partitioned in a random mesh pattern in the base layer BL when the base layer BL receives stress strain from the n-type semiconductor layer 12.

  The groove GR1 is composed of groove portions having different lengths and shapes at random from each other. The groove GR1 is formed in a mesh shape so as to partition the base segment BS. The groove GR1 is formed to be stretched in a mesh shape (mesh shape) on the surface of the base layer BL. Each of the base segments BS is a portion (segment) that is randomly partitioned in the base layer BL by the groove GR1. Each base segment BS has various top shapes such as a substantially circular shape, a substantially elliptical shape, and a polygonal shape.

  Referring to FIG. 1A again, the groove GR1 has, for example, a V shape and has a line-shaped bottom portion BP. In the present embodiment, each base segment BS has the bottom BP in the groove GR1 as its end. Each base segment BS is adjacent to another base segment BS at the bottom BP.

  Further, the base layer BL has a flat portion (first flat portion) FL1 corresponding to each of the base segments BS. The surface of the base layer BL is constituted by the flat portion FL1 and the inner wall surface of the groove GR1. Each of the flat portions FL1 is partitioned for each base segment BS by the groove GR1. Base segment BS has an upper surface formed of flat portion FL1 and a side surface formed of an inner wall surface of groove GR1.

  That is, the flat portion FL1 constitutes the upper surface of each base segment BS, and the inner wall surface of the groove GR1 constitutes the side surface of the base segment BS. Accordingly, each base segment BS has an inclined side surface, and has, for example, a substantially trapezoidal shape in its cross section.

  Note that FIG. 1B only schematically illustrates the base layer BL and the base segment BS. For example, as shown in FIG. 1B, the base layer BL does not need to be partitioned by the straight groove GR1 when viewed from the upper surface (direction perpendicular to the base layer BL), and is a curved groove. It may be partitioned by. In the following, the case where the base layer BL is composed of the flat portion FL1 and the groove GR1 will be described, but the surface shape of the base layer BL is not limited to this case. For example, the upper surface of the base segment BS may have a curved surface shape.

  Furthermore, it is not necessary that the base segment BS is completely defined on the surface of the base layer BL. For example, the groove GR1 does not need to have a complete mesh shape and may be partially interrupted. The base layer BL having the base segment BS partitioned in a random network means that the base layer BL has the groove shape, the partition shape, or the top surface shape as described above.

  The light emitting layer 13 includes a buffer layer BU formed on the base layer BL. As shown in FIG. 1A, the buffer layer BU is formed on the base layer BL while retaining the segment shape of the base layer BL. More specifically, the buffer layer BU has a groove (second groove) GR2 corresponding to the groove GR1 of the base layer BL. Further, the buffer layer BU has a flat portion (second flat portion) FL2 corresponding to each of the flat portions FL1 of the base layer BL. That is, the buffer layer BU has an upper surface shape that maintains the segment shape of the base layer BL.

  The light emitting layer 13 has an active layer AC formed of the quantum well layer WA and the barrier layer BA formed on the buffer layer BU. The quantum well layer WA is formed on the buffer layer BU, and the barrier layer BA is formed on the quantum well layer WA. The buffer layer BU functions as a barrier layer with respect to the quantum well layer WA.

  In the present embodiment, the quantum well layer WA is formed on the buffer layer BU while leaving the trench GR2. More specifically, the quantum well layer WA has a groove (third groove) GR3 corresponding to the groove GR2 of the buffer layer BU. The quantum well layer WA has a flat portion (third flat portion) FL3 corresponding to each of the flat portions FL2 of the buffer layer WA. The quantum well layer WA is formed so that the upper surface shape of the buffer layer BU, that is, the segment shape of the base segment BS remains. The quantum well layer WA is formed as a strained quantum well layer.

  In the present embodiment, the barrier layer BA is formed on the quantum well layer WA by filling the groove GR3 of the quantum well layer WA. Specifically, the barrier layer BA has an uneven shape corresponding to the groove GR3 at the interface (lower surface) with the quantum well layer WA, and has a flat shape at the upper surface. Therefore, as shown in FIG. 1A, the barrier layer BA has a flat surface FS that is flattened by embedding the quantum well layer WA.

  FIG. 2A is a cross-sectional view showing the structure of the semiconductor structure layer SS. FIG. 2B is a cross-sectional view showing a composition example of the base layer BL and the buffer layer BU in the semiconductor structure layer SS. 2 (a) and 2 (b) are partial enlarged cross-sectional views showing an enlarged portion surrounded by a broken line in FIG. 1 (a). First, the light emitting layer 13 will be described in more detail with reference to FIG.

As shown in FIG. 2A, the base layer BL has a composition of Al _x1 In _y1 Ga _{1 -x2-y1} N (0 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 1, 0 ≦ x1 + y1 ≦ 1). The buffer layer BU has a composition of _{Al x2 In y2 Ga 1-x2} -y2 N (0 ≦ x2 ≦ 1,0 ≦ y2 ≦ 1,0 ≦ x2 + y2 ≦ 1). The compositions x1 and x2 satisfy the relationship of 0 ≦ x2 <x1 ≦ 1.

  Next, the base layer BL and the quantum well layer WA (active layer AC) will be described. First, as shown in FIG. 2B, the base layer BL has a composition of, for example, AlGaN or AlN (x1> 0, y1 = 0). The base segment BS in the base layer BL can be formed by growing an AlGaN layer or an AlN layer as the base layer BL on a GaN layer as the n-type semiconductor layer 12 at a relatively low temperature.

  First, when a base layer BL having a different crystal composition is grown on the n-type semiconductor layer 12, stress (strain) is generated in the base layer BL. For example, the base layer BL has a lattice constant smaller than that of the n-type semiconductor layer 12. For example, when an AlGaN layer is grown as the base layer BL on the GaN layer as the n-type semiconductor layer 12, tensile strain is generated in the AlGaN layer by the GaN layer. Therefore, tensile stress is generated in the AlGaN layer during its growth. Accordingly, a groove is formed in the AlGaN layer at the beginning or during the growth of the AlGaN layer, and thereafter, the AlGaN layer grows three-dimensionally. That is, the AlGaN layer grows three-dimensionally and a plurality of fine irregularities are formed. The formation start point of this groove is the bottom BP of the groove GR1.

  Furthermore, when an AlGaN layer is grown on the GaN layer at a low temperature, three-dimensional growth in the AlGaN layer is promoted. Therefore, innumerable grooves are formed on the surface of the AlGaN layer while being coupled to each other (groove GR1), and thereby the surface of the AlGaN layer is partitioned into a plurality of granular segments. In this way, the base layer BL having the base segment BS can be formed. In this example, an AlGaN layer as the base layer BL was formed at a growth temperature of 1000 ° C.

  When an InGaN layer as the quantum well layer WA is formed on the base layer BL, the quantum well layer WA is formed as a strained quantum well layer. Further, a distribution occurs in the In content in the quantum well layer WA. That is, in the quantum well layer WA, for example, the region on the flat part FL1 and the region on the trench GR1 are formed so as to have different In compositions. The layer thickness of the quantum well layer WA differs between the upper surface and the side surface of the base segment BS. Therefore, the band gap is not constant in the quantum well layer WA. In this way, light of various colors is emitted from the light emitting layer 13 having fine island-shaped irregularities.

  Further, when the InGaN layer that is the quantum well layer WA is formed on the AlGaN layer that is the base layer BL, the InGaN layer is subjected to compressive strain by the AlGaN layer. When the InGaN layer is subjected to compressive strain, In is easily taken into the well layer WA. Thereby, the band gap in the InGaN layer, that is, the energy between the quantum levels is reduced. From the quantum well layer WA, light having a longer emission wavelength is emitted.

  Next, the buffer layer BU will be described. As shown in FIG. 2B, the buffer layer BU has a composition of GaN, for example (x2 = y2 = 0). The buffer layer BU has a lattice constant between the base layer BL and the quantum well layer WA (active layer AC). The buffer layer BU is formed on the base layer BL while the segment shape of the base segment BS in the base layer BL remains.

  By interposing the buffer layer BU between the base layer BL and the quantum well layer WA, it is possible to achieve both broadening the emission spectrum from the light emitting layer 13 and improving the light emission intensity. Therefore, it is possible to provide the semiconductor light emitting device 10 having high color rendering properties and high luminance.

  More specifically, as described above, emission light having a wide spectral band can be obtained from the active layer AC by including the base layer BL. However, on the other hand, there is a concern that the crystallinity of the active layer AC (especially the quantum well layer WA) deteriorates and the emission intensity decreases. Therefore, there is a possibility that the required luminance cannot be obtained. In contrast, in this embodiment, the buffer layer BU having an intermediate lattice constant is provided between the base layer BL and the active layer AC so as not to completely embed the base segment BS.

  Therefore, first, the emission light from the active layer AC can be broadened by the base layer BL (base segment BS). Further, by providing the buffer layer BU, deterioration of the crystallinity of the active layer AC due to the base layer BL is suppressed, and the light emission intensity is improved. Therefore, for example, the semiconductor light emitting device 10 having high color rendering and high luminance can be obtained with a simple configuration without requiring an additional member such as a phosphor.

  As shown in FIG. 2A, when the active layer AC having the quantum well structure is formed, the active layer AC has a structure in which the quantum well layer WA and the barrier layer BA are stacked on the buffer layer BU. Here, considering that the segment shape of the base layer BL remains, the buffer layer BU is formed with a relatively small layer thickness T1. On the other hand, a certain layer thickness is required for the buffer layer BL to function as a barrier layer for the quantum well layer WA.

  On the other hand, in this embodiment, not only the buffer layer BU but also the base layer BL functions as a barrier layer for the quantum well layer WA. Therefore, for example, even when the buffer layer BU is formed with a layer thickness T1 smaller than the layer thickness T2 of the normal barrier layer BA, the buffer layer BU and the base layer BL can function as a barrier layer for the quantum well layer WA. Therefore, as shown in FIG. 2A, the buffer layer BU has a smaller layer thickness T1 than the barrier layer BA of the active layer AC. The layer thickness T1 of the buffer layer BU is smaller than the layer thickness T2 of the barrier layer BA.

  Further, as shown in FIG. 2A, the buffer layer BU is formed so as to fill the groove GR1 formed in the surface of the base layer BL to some extent. Accordingly, the flat portion FL2 of the buffer layer BU has a larger area than the flat portion FL1 of the base layer BL1. Further, the groove GR2 of the buffer layer BU is shallower than the groove GR1 of the base layer BL.

  FIG. 3A is a cross-sectional view illustrating a structure of a semiconductor light emitting element 10A according to a modification of the first embodiment. The semiconductor light emitting device 10A has the same configuration as the semiconductor light emitting device 10 except for the structure of the buffer layer BU1 and the quantum well layer WA1 (light emitting layer 13A). In the present modification, the buffer layer BU1 is formed by embedding some of the base segments BS among the plurality of base segments BS provided in the base layer BL. The quantum well layer WA1 is flattened by embedding the buffer layer BU.

  More specifically, the buffer layer BU1 is formed by embedding a part of the groove GR1 provided in the base layer BL. In other words, the buffer layer BU1 has a flat surface FL2 in which the segment shape of the base segment BS is partially embedded. FIG. 3B is a diagram schematically showing the upper surface of the buffer layer BU1. As shown in FIG. 3B, the upper surface of the buffer layer BU1 has a portion in which the groove GR1 constituting the base segment BS is embedded.

  The buffer layer BU1 can be formed, for example, by forming a GaN layer with a relatively large thickness on the base layer BL. Therefore, the segment shape of the base segment BS in the base layer BL remains on the surface of the buffer layer BU1, but a part of the base segment BS is buried and disappears.

  Thus, the buffer layer BU1 may be formed so as to partially embed the base segment BS. Further, the groove GR2 provided on the surface of the buffer layer BU1 may be partially broken. That is, the groove GR2 does not have to be formed in a complete mesh shape. The buffer layers BU and BU1 only need to be formed on the base layer BL while retaining the segment shape of the base segment BS. As shown in the present embodiment and the present modification, the degree of maintenance of the segment shape of the base segment BS in the buffer layers BU and BU1 can be appropriately adjusted according to the required color rendering properties and luminance. The more the base segment BS is embedded, the more the spectrum peak shifts to the short wavelength side.

  In this embodiment, the case where the active layer AC has a quantum well structure including the quantum well layer WA and the barrier layer BA has been described. However, the active layer AC is not limited to the case where the active layer AC has a quantum well structure. The active layer AC may be a single active layer.

  In the present embodiment, the case where the electron blocking layer 14 is formed between the light emitting functional layer (light emitting layer) 13 and the p-type semiconductor layer 15 has been described. However, the electron block layer 14 is not necessarily provided. For example, the p-type semiconductor layer 15 may be formed on the light emitting functional layer 13. The electron block layer 14 has a larger band gap than the n-type semiconductor layer 12, the light emitting functional layer 13, and the p-type semiconductor layer 15. Therefore, it is possible to suppress the electrons from overflowing to the p-type semiconductor layer 15 side beyond the light emitting functional layer 13. Therefore, it is preferable to provide the electronic block layer 14 at the time of driving with a large current and at the time of high temperature operation.

  FIG. 4 is a cross-sectional view illustrating the structure of the semiconductor light emitting device 30 according to the second embodiment. The semiconductor light emitting element 30 has the same configuration as the semiconductor light emitting element 10 except for the structure of the light emitting functional layer (light emitting layer) 33. As shown in FIG. 4, in the present embodiment, the light emitting functional layer 33 includes a base layer BL1 having a two-layer structure and an active layer AC1 having a multiple quantum well structure.

  First, the base layer BL1 has a structure in which first and second sub-base layers BLA and BLB are stacked. The base layer BL1 includes a first sub base layer BLA formed on the n-type semiconductor layer 12 and a second sub base layer BLB formed on the first sub base layer BLA. In this embodiment, the buffer layer BU is formed on the second sub-base layer BLB. For example, the first sub base layer BLA has an AlGaN composition, and the second sub base layer BLB has an AlN composition.

  As in this embodiment, by forming the base layer BL1 with a two-layer structure, the size of the base segment BS in the base layer BL1 can be stably adjusted. For example, the first sub base layer BLA has a lattice constant smaller than that of the n-type semiconductor layer 12, and the second sub base layer BLB has a lattice constant smaller than that of the first sub base layer BLA. By providing the first sub base layer BLA having an intermediate lattice constant between the n-type semiconductor layer 12 and the second sub base layer BLB, deterioration of crystallinity is suppressed, and the base segment in the base layer BL1 is suppressed. The size of the BS increases.

  As in this embodiment, not only the buffer layer BU but also the base layer BL1 can adjust the shape of the base segment BS, that is, the degree of stress strain applied to the active layer AC1 (that is, the emission spectrum).

  In this embodiment, the active layer AC1 includes two quantum well layers WA and a barrier layer BA. The active layer AC1 has a structure in which two quantum well layers WA and barrier layers BA are alternately stacked on the buffer layer BU.

  In the first embodiment, the case where the active layer AC has a single quantum well structure has been described. On the other hand, in this embodiment, the active layer AC1 has a multiple quantum well structure. In other words, as shown in the first and second embodiments, when the active layer AC (AC1) has a quantum well structure, at least one quantum well layer WA and a barrier layer formed on the buffer layer BU (BU1). What is necessary is just to have BA.

  In addition, the light emitting layers 13 and 33 may have a structure laminated | stacked several times. For example, the light emitting functional layer may have a structure in which a plurality of light emitting layers 13 or 33 are stacked. In this case, the uppermost layer (for example, the barrier layer BA) of each light emitting layer 13 or 33 only needs to have a composition that gives stress strain to the base layer BL (or BL1) laminated thereon.

  FIG. 5 is a cross-sectional view illustrating the structure of the semiconductor light emitting device 50 according to the third embodiment. The semiconductor light emitting device 50 has the same configuration as that of the semiconductor light emitting device 10 except for the structure of the light emitting functional layer 53. In this example, the light emitting functional layer 53 is a light emitting layer having a quantum well structure (a quantum well layer WB and a barrier layer BB) between the n-type semiconductor layer 12 and the light emitting layer (first light emitting layer) 13. (Second light emitting layer) 53A.

  In the present embodiment, a light emitting layer 53A is provided as a second light emitting layer on the n-type semiconductor layer 12 side of the light emitting layer 13 in the first embodiment. As shown in FIG. 5, the light emitting layer 53A has a structure in which two quantum well layers WB and three barrier layers BB are alternately stacked. The quantum well layer WB has a composition of InGaN, for example. Further, the barrier layer BB has, for example, a GaN composition. Each of the quantum well layer WA and the barrier layer BB has a uniformly flat layer structure. The base layer BL of the light emitting layer 13 is formed on the barrier layer BB of the light emitting layer 53A.

  The light emitting layer 53 </ b> A has an emission spectrum peak on the shorter wavelength side than the light emitting layer 13. The semiconductor light emitting device 50 exhibits a spectral characteristic in which the emission spectrum on the short wavelength side from the light emitting layer 53 </ b> A is added to the emission spectrum on the long wavelength side from the light emitting layer 13. This example is an effective configuration when it is desired to obtain the emission intensity on the short wavelength side.

  FIG. 6 is a diagram showing an emission spectrum from the semiconductor light emitting device 50 and the light emitting device according to the comparative example. In order to evaluate the emission spectrum from the semiconductor light emitting device 50, a semiconductor light emitting device having the same configuration as that of the semiconductor light emitting device 50 was prepared except that the buffer layer BU was not provided, and the emission spectrum was measured. As shown in FIG. 6, in Example 3 and the comparative example, it can be seen that there are two emission spectrum peaks. The peak on the short wavelength side (around 450 nm) is due to the light emitted from the light emitting layer 53A.

  The peak on the long wavelength side (around 530 nm) in the light emitting device 50 of Example 3 is due to the light emitted from the light emitting layer 13, and the peak on the long wavelength side (around 540 nm) in the comparative example is the same. As shown in FIG. 6, it can be seen that the light emission layer 13 has the buffer layer BU, so that the light emission intensity is improved. On the other hand, even when the buffer layer BU is not provided, the band of the emission spectrum is not narrowed. This is because the buffer layer BU is formed with the shape of the base segment BS remaining (maintained). Therefore, the emission intensity can be improved without sacrificing the color rendering properties. In this example, the half width in the emission spectrum from the light emitting element 50 was about 45 nm.

  The first embodiment, the second embodiment, and the third embodiment can be combined with each other. For example, a light emitting functional layer including the light emitting layer 13, the light emitting layer 33, and the light emitting layer 53A can be formed.

  In this embodiment and its modification, the light emitting layer (first light emitting layer) 13 has a composition that receives stress strain from the n-type semiconductor layer 12 and has a plurality of base segments BS formed in a random network shape. , A buffer layer BU formed on the base layer BL while retaining the segment shape of the base segment BS, and an active layer AC formed on the buffer layer BU. Therefore, it is possible to provide a semiconductor light emitting device capable of emitting light having high emission intensity over a wide visible range.

  In the present embodiment, the case where the first conductivity type is the n-type conductivity type and the second conductivity type is the p-type has been described, but the first conductivity type is the p-type, The conductivity type of 2 may be n-type.

10, 10A, 30, 50 Semiconductor light emitting element 12 n-type semiconductor layer (first semiconductor layer)
13, 13A, 33, 53A Light emitting functional layer (light emitting layer)
BL base layer WA, WB quantum well layer BA, BB barrier layer 15 p-type semiconductor layer (second semiconductor layer)
BS Base segment

Claims (9)

A first semiconductor layer having a first conductivity type; a light emitting functional layer formed on the first semiconductor layer and including a first light emitting layer; formed on the light emitting functional layer; A semiconductor light emitting device having a second semiconductor layer having a conductivity type opposite to that of the semiconductor layer,
The first light-emitting layer includes a base layer having a plurality of base segments having a composition that receives stress strain from the first semiconductor layer and partitioned in a random network, and a segment shape of the plurality of base segments A semiconductor light emitting device comprising: a buffer layer formed on the base layer while remaining in the base layer; and an active layer formed on the buffer layer. The active layer includes at least one quantum well layer and a barrier layer;
The semiconductor light emitting device according to claim 1, wherein the buffer layer has a lattice constant between the base layer and the quantum well layer. The base layer has a smaller lattice constant than the first semiconductor layer;
3. The semiconductor light emitting element according to claim 1, wherein the base layer has a mesh-like groove that partitions the plurality of base segments. 4. The base layer has a composition of Al _x1 In _y1 Ga _1-x1-y1 N (0 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 1, 0 ≦ x1 + y1 ≦ 1),
The buffer layer has a composition of Al _x2 In _y2 Ga _{1 -x2-y2} N (0 ≦ x2 ≦ 1, 0 ≦ y2 ≦ 1, 0 ≦ x2 + y2 ≦ 1),
The first and second semiconductor layers have a GaN composition;
The quantum well layer has a composition of InGaN,
4. The semiconductor light emitting device according to claim 1, wherein the compositions x1 and x2 satisfy a relationship of 0 ≦ x2 <x1 ≦ 1. 5.   5. The semiconductor light emitting element according to claim 1, wherein the buffer layer is formed so as to embed a part of the plurality of base segments.   The semiconductor light emitting device according to claim 1, wherein the buffer layer has a smaller layer thickness than the barrier layer. The base layer has a composition of AlN or AlGaN,
The semiconductor light emitting device according to claim 3, wherein the buffer layer has a composition of GaN. The base layer has a structure in which first and second sub-base layers are laminated,
8. The semiconductor light emitting device according to claim 1, wherein the first sub-base layer has an AlGaN composition, and the second sub-base layer has an AlN composition.   The light emitting functional layer is formed between the first semiconductor layer and the first light emitting layer, and has a second light emitting layer composed of at least one quantum well layer and a plurality of barrier layers. The semiconductor light-emitting device according to claim 1.

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