JP2006324280A - Semiconductor light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element capable of moving a carrier smoothly between two semiconductor layers whose composition is different each other without increasing impurity concentration, namely without deteriorating optical characteristics and reliability. <P>SOLUTION: A band gap change layer of which the composition changes is arranged between the two semiconductor layers that are laminated and have different composition mutually in a lamination direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device formed by stacking a plurality of semiconductor layers.

  The semiconductor light emitting device basically has a double heterojunction structure composed of a semiconductor layer called an active layer that generates light by recombination of carriers and a semiconductor layer called a carrier supply layer that sandwiches the active layer from both sides and supplies carriers to the active layer. It has a structure. Since the wavelength of light to be emitted is determined by the band gap of the active layer, a material and a configuration that can obtain light having a desired wavelength are selected for the active layer. The carrier supply layer is designed to have a wider band gap than the active layer in order to make it easier to supply carriers to the active layer, and an impurity for controlling the polarity of the carrier is added.

  In semiconductor light emitting devices, especially laser diodes, in order to improve the unimodality of the light intensity distribution (transverse mode) and improve the coupling efficiency between the semiconductor light emitting devices and external devices such as optical pickups, it is also possible to efficiently emit semiconductor light. In order to cause the device to emit light, it is required to concentrate and supply carriers to a part of the active layer. Therefore, a stripe structure in which electrodes and carrier supply layers are formed in a strip shape in a direction perpendicular to the stacking direction is often used (see, for example, Patent Document 1).

A conceptual view of a cross section of a conventional semiconductor light emitting device 140 is shown in FIG. The semiconductor light emitting device 140 employs stripe-shaped electrodes to concentrate and supply carriers to a part of the active layer. A stripe-shaped electrode is an electrode in which the shape of an electrode made of metal or the like laminated adjacent to a semiconductor layer is formed like a strip like a microstrip line. For example, the semiconductor light emitting device 140 includes the electrode 11, the n-type substrate 12, the n-side first semiconductor layer 25, the n-type second semiconductor layer 27, the active layer 14 as a carrier supply layer for supplying electrons, and a carrier supply for supplying holes. A p-side first semiconductor layer 15, a p-type second semiconductor layer 17, and a stripe-shaped electrode 19 are stacked as layers. In the semiconductor light emitting device 140, one or more semiconductor layers are provided between at least one of the n-type second semiconductor layer 27 and the n-type substrate 12 and between the p-type second semiconductor layer 17 and the stripe-shaped electrode 19. May be arranged. Further, the active layer 14 may have an electron barrier layer for preventing electron carrier overflow on the p-side first semiconductor layer 15 side of the active layer 14.
Japanese Patent Laid-Open No. 05-055696.

  The semiconductor light emitting device emits light in the active layer 14 for the purpose of improving electrical characteristics between the p-type second semiconductor layer 17 and the active layer 14 on the p-type side with respect to the active layer 14 as shown in FIG. The p-side first semiconductor layer 15 is often disposed for the purpose of confining light. However, when the composition of the elements of the group III nitride compound in the p-side first semiconductor layer 15 and the p-type second semiconductor layer 17 is different from each other, the polarization characteristics and the lattice constant between the two semiconductor layers are different. Due to the difference, between the p-side first semiconductor layer 15 and the p-type second semiconductor layer 17, spontaneous polarization or piezo polarization caused by lattice strain (hereinafter referred to as “spontaneous polarization or lattice strain-induced piezo polarization”) is referred to as “polarization”. Polarization charge resulting from (abbreviated) is generated. Therefore, when positive polarization charges are generated between the p-side first semiconductor layer 15 and the p-type second semiconductor layer 17, holes partially injected into the p-type second semiconductor layer 17 by the stripe-shaped electrode 19. Receives repulsion from the electric field of the polarization charge. Therefore, the transport of holes from the p-type second semiconductor layer 17 to the p-side first semiconductor layer 15 is hindered, and the holes diffuse in the p-side first semiconductor layer 15 like the hole flow 91. End up. On the other hand, on the n-type side of the active layer 14 as well as the p-type side, the purpose is to improve electrical characteristics between the n-type second semiconductor layer 27 and the active layer 14 and to confine light emitted from the active layer 14. In many cases, the n-side first semiconductor layer 25 is disposed, and when negative polarization charges are generated due to the polarization as in the description on the p-type side, electron transport is hindered.

  In particular, the polarization charge appears prominently at the heterointerface of the heterostructure of group III nitride compounds stacked in the C-axis direction, and carrier transport was facilitated by increasing the impurity concentration. However, increasing the impurity concentration of the p-side first semiconductor layer 15 and the n-side first semiconductor layer 25 in the vicinity of the active layer 14 is a semiconductor light emitting device such as light absorption by impurities and impurity diffusion into the active layer 14. In relation to the optical characteristics and reliability of 140, there is a problem that it is difficult to achieve both smooth carrier transport and the optical characteristics and reliability of the semiconductor light emitting device 140.

  The present invention has been made to solve the above-mentioned problems, and carriers can smoothly flow between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. An object is to provide a movable semiconductor light emitting device.

  In order to achieve the above object, according to the present invention, a band gap changing layer whose composition changes in the stacking direction is arranged between two stacked semiconductor layers having different compositions.

Specifically, the first invention of the present application includes an active layer that generates light by recombination of electrons and holes, and a layer on the p-type side with respect to the active layer. a first semiconductor layer of _{x Ga y in 1-x-} y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and the group III nitride compound represented by the first semiconductor The layer is laminated adjacent to the side opposite to the active layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) And a band gap changing layer of a group III nitride compound whose composition continuously changes monotonously in the stacking direction, and a layer adjacent to the side of the band gap changing layer opposite to the first semiconductor layer side. is expressed by a composition formula _{Al x Ga y In 1-x} -y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and represented by I A semiconductor light emitting device comprising a second semiconductor layer of a group I nitride compound, wherein the band gap changing layer is stacked in a stacking direction from an end of the active layer on the p-type side with respect to the active layer. The distance in the stacking direction to reach the center of the width is 30 (nm) or more and 200 (nm) or less, and the band gap of the band gap change layer is the first semiconductor layer on the side adjacent to the first semiconductor layer The semiconductor light emitting device is characterized by continuously changing monotonously from a band gap substantially equal to the band gap of the second semiconductor layer to a band gap substantially equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer.

The group III nitride compound represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is changed by changing the composition of the band. It is a semiconductor whose gap can be adjusted. Therefore, the band gap of the band gap changing layer can be monotonously changed by monotonically changing the composition designated by x and y in the group III nitride compound.

  In the first invention of the present application, the composition of the second semiconductor layer on the p-type side (hereinafter, “p-type side” is abbreviated as “p-type side”) with respect to the active layer. The band gap changing layer continuously monotonically changing from the first semiconductor layer to the composition of the first semiconductor layer is adjacent to the second semiconductor layer on the side equal to the composition of the second semiconductor layer, and the composition of the first semiconductor layer By adjoining the first semiconductor layer on the same side, a steep composition change from the second semiconductor layer to the first semiconductor layer is avoided, and a band gap is continuously formed from the second semiconductor layer to the first semiconductor layer. Can be monotonously changed. Accordingly, the polarization charge can be dispersed between the second semiconductor layer and the first semiconductor layer by the band gap change layer, and the repulsive force from the electric field of the polarization charge is reduced. The holes can smoothly move from the second semiconductor layer to the first semiconductor layer.

  Furthermore, the width of the bandgap change layer in the stacking direction (hereinafter referred to as the width in the stacking direction of the active layer within the range of 30 nm to 200 nm in the stacking direction on the p-type side from the end on the p-type side) , “Width in the stacking direction” is abbreviated as “film thickness.”), The carrier smoothly moves through the second semiconductor layer, the band gap changing layer, and the first semiconductor layer, Since the active layer can be reached, impurities added to the first semiconductor layer close to the active layer can be reduced.

  Therefore, the first invention of the present application provides a semiconductor light-emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability. Can be provided.

In the second invention of the present application, an active layer that generates light by recombination of electrons and holes, and a layer on the p-type side with respect to the active layer are laminated, and the composition formula Al _x Ga _y In _{1 A} first semiconductor layer of a group III nitride compound represented by −xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and the active layer of the first semiconductor layer And is laminated adjacent to the side opposite to the other side, and is represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A band gap changing layer of a group III nitride compound whose composition monotonously changes in a direction in a direction and a layer adjacent to the side opposite to the first semiconductor layer side of the band gap changing layer, _{x Ga y In 1-x-} y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and the group III nitride represented by A semiconductor light emitting device comprising a compound second semiconductor layer, wherein an end of the active layer having a p-type polarity with respect to the active layer reaches a center of a width of the band gap change layer in a stacking direction. The band gap of the band gap change layer is substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. The semiconductor light emitting device is characterized in that it monotonously changes stepwise from an equal band gap to a band gap substantially equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer.

The group III nitride compound represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is changed by changing the composition of the band. It is a semiconductor whose gap can be adjusted. Accordingly, the band gap changing layer is formed by stacking a plurality of group III nitride compound thin films having compositions specified by different values of x and y in the composition formula, thereby forming a band gap of the band gap changing layer. Can be monotonously changed stepwise.

  In the second invention of the present application, the band gap changing layer that monotonously changes stepwise from the composition of the second semiconductor layer to the composition of the first semiconductor layer on the p-type side with respect to the active layer is the second semiconductor layer. A side equal to the composition of the first semiconductor layer adjacent to the second semiconductor layer and a side equal to the composition of the first semiconductor layer adjacent to the first semiconductor layer, so that the second semiconductor layer to the first semiconductor layer The band gap can be monotonously changed stepwise from the second semiconductor layer to the first semiconductor layer while avoiding a steep composition change. Accordingly, the polarization charge can be dispersed between the second semiconductor layer and the first semiconductor layer by the band gap change layer, and the repulsive force from the electric field of the polarization charge is reduced. The holes can smoothly move from the second semiconductor layer to the first semiconductor layer.

  Furthermore, the center of the film thickness of the band gap change layer is arranged in the range of 30 (nm) to 200 (nm) in the stacking direction on the p-type side from the end on the stacking direction of the active layer. By doing so, carriers can smoothly move through the second semiconductor layer, the band gap change layer, and the first semiconductor layer to reach the active layer. Therefore, the carriers are added to the first semiconductor layer close to the active layer. Impurities to be reduced can be reduced.

  Therefore, the second invention of the present application provides a semiconductor light-emitting device that can smoothly move carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. Can be provided.

  The semiconductor light emitting device according to the first invention of the present application or the second invention of the present application further includes an electrode for applying a voltage from the outside to the side of the second semiconductor layer opposite to the side of the bandgap changing layer, A mesa shape may be used from the electrode to the second semiconductor layer or the first semiconductor layer.

  A part of the semiconductor light emitting element is formed in a mesa shape so that carriers are concentrated and supplied to a part of the active layer (hereinafter, a “part in which a part of the semiconductor light emitting element is formed in a mesa shape” is referred to as a “mesa portion”. It may be abbreviated) to narrow the carrier movement path and squeeze the current.

  When a group III nitride compound having a different composition in the mesa portion is laminated, the holes receive the repulsive force of the polarization charge and move in a concentrated manner near the side wall of the mesa portion having poor crystallinity. Hole transport is hindered. In the present invention, when the first semiconductor layer is formed in a mesa shape, the band gap changing layer is included in the mesa portion, and the polarization charge can be reduced, so that the hole is near the center of the mesa portion. And the hole transport from the second semiconductor layer to the first semiconductor layer can be made smooth.

  On the other hand, when a group III nitride compound having a different composition is laminated between the mesa portion and the active layer, the positive holes are subjected to the repulsive force of the polarization charge, and are positively injected by the mesa portion. The holes diffuse in the group III nitride compound. In the present invention, when the second semiconductor layer is formed in a mesa shape, the holes that have passed through the mesa portion are not diffused in the second semiconductor layer due to the reduction of the polarization charge by the band gap change layer, and the first semiconductor layer is not diffused. It can move smoothly from the two semiconductor layers to the first semiconductor layer.

  Therefore, in the first invention of the present application or the second invention of the present application, carriers are smoothly transferred between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability. A movable semiconductor light emitting element can be provided. Compared with electrons, holes having a large effective mass are easily affected by the vicinity of the side wall of the mesa portion having poor crystallinity, and the effect of the band gap changing layer is large.

The third invention of the present application includes an active layer that generates light by recombination of electrons and holes, and a layer that is laminated on the n-type side with respect to the active layer, and has a composition formula of Al _x Ga _y In _{1. A} first semiconductor layer of a group III nitride compound represented by −xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and the active layer of the first semiconductor layer And is laminated adjacent to the side opposite to the other side, and is represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A band gap changing layer of a group III nitride compound whose composition continuously changes monotonically in the direction, and is laminated adjacent to the side of the band gap changing layer opposite to the first semiconductor layer side, the composition formula Al _{x Ga y In 1-x-} y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and the group III nitride represented by A semiconductor light emitting device comprising a compound second semiconductor layer, wherein the end of the active layer on the n-type side of the active layer reaches the center of the width of the band gap change layer in the stacking direction. The band gap of the band gap change layer is substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. A semiconductor light emitting device characterized by continuously changing monotonously from an equal band gap to a band gap substantially equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer.

  Similarly to the description of the first invention of the present application, the band gap is also on the n-type side with respect to the active layer (hereinafter, “the n-type side” is abbreviated as “n-type side”). Since the polarization charge can be dispersed between the second semiconductor layer and the first semiconductor layer by the change layer, and the repulsive force received from the electric field of the polarization charge is reduced, electrons serving as carriers are the second semiconductor. It can move smoothly from the layer to the first semiconductor layer.

  Further, the center of the film thickness of the band gap change layer is arranged in the range of 30 (nm) or more and 200 (nm) or less in the stacking direction on the n-type side from the end of the stacking direction of the active layer. By doing so, carriers can smoothly move through the second semiconductor layer, the band gap change layer, and the first semiconductor layer to reach the active layer. Therefore, the carriers are added to the first semiconductor layer close to the active layer. Impurities to be reduced can be reduced.

  Accordingly, the third invention of the present application provides a semiconductor light-emitting device that can smoothly move carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. Can be provided.

According to a fourth aspect of the present invention, an active layer that generates light by recombination of electrons and holes, and a layer on the n-type side of the active layer are stacked, and the composition formula Al _x Ga _y In _{1 A} first semiconductor layer of a group III nitride compound represented by −xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and the active layer of the first semiconductor layer And is laminated adjacent to the side opposite to the other side, and is represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A band gap changing layer of a group III nitride compound whose composition monotonously changes in a direction in a direction and a layer adjacent to the side opposite to the first semiconductor layer side of the band gap changing layer, _{x Ga y In 1-x-} y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and the group III nitride represented by A semiconductor light emitting device comprising a compound second semiconductor layer, wherein the end of the active layer on the n-type side of the active layer reaches the center of the width of the band gap change layer in the stacking direction. The band gap of the band gap change layer is substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. The semiconductor light emitting device is characterized in that it monotonously changes stepwise from an equal band gap to a band gap substantially equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer.

  Also on the n-type side with respect to the active layer, the polarization charge is dispersed between the second semiconductor layer and the first semiconductor layer by the band gap changing layer, as in the description of the second invention of the present application. Since the repulsive force received from the electric field of the polarization charge is reduced, electrons as carriers can smoothly move from the second semiconductor layer to the first semiconductor layer.

  Further, the center of the film thickness of the band gap change layer is arranged in the range of 30 (nm) or more and 200 (nm) or less in the stacking direction on the n-type side from the end of the stacking direction of the active layer. By doing so, carriers can smoothly move through the second semiconductor layer, the band gap change layer, and the first semiconductor layer to reach the active layer. Therefore, the carriers are added to the first semiconductor layer close to the active layer. Impurities to be reduced can be reduced.

  Therefore, the fourth invention of the present application provides a semiconductor light-emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability. Can be provided.

  The width of the band gap changing layer in the stacking direction of the semiconductor light emitting device according to the present invention is preferably 3 (nm) or more and less than 100 (nm).

  The film thickness of the band gap changing layer inserted for the purpose of relaxing the steep composition change between the first semiconductor layer and the second semiconductor layer is 3 (nm) or more for achieving the object. Is required. On the other hand, the band gap change layer is proportional to the film thickness, and the electric resistance increases. Therefore, the film thickness of the band gap change layer is preferably less than 100 (nm).

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability. Can do.

  In the semiconductor light emitting device according to the present invention, the band gap of the second semiconductor layer is preferably wider than the band gap of the first semiconductor layer.

  By making the band gap of the group III nitride compound of the second semiconductor layer wider than the band gap of the group III nitride compound of the first semiconductor layer, the first semiconductor layer for carriers is more than the second semiconductor layer. Is more stable in terms of energy. Accordingly, carriers can smoothly move from the second semiconductor layer through the band gap changing layer to the first semiconductor layer.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability. Can do.

  The semiconductor light emitting device according to the present invention includes a stacking direction of the first semiconductor layer, the band gap change layer, and the second semiconductor layer, a crystal of a group III nitride compound of the first semiconductor layer, and the band gap change layer. It is preferable that the group III nitride compound crystal and the group III nitride compound crystal of the second semiconductor layer are parallel to the C-axis direction.

  Even when the crystal of the group III nitride compound in which the polarization charge appears remarkably is laminated in the C-axis direction, the first semiconductor layer, the band gap change layer, and the second semiconductor layer are sequentially formed. By laminating, the polarization charge is reduced, and carrier transport from the first semiconductor layer to the second semiconductor layer can be facilitated.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability. Can do.

  In the semiconductor light emitting device according to the present invention, the first semiconductor layer has x = 0 and 0.95 ≦ y ≦ 1 in the composition formula, and functions as a light guide layer for guiding light generated in the active layer. The second semiconductor layer has a relationship of x = m (0.05 ≦ m ≦ 0.1) and x + y = 1 in the composition formula, functions as a clad layer for supplying carriers to the active layer, and The band gap changing layer has a relationship of 0 ≦ x ≦ m and x + y = 1 in the composition formula, and preferably has a function as a semiconductor laser as a whole structure.

The composition of the group III nitride compound of the second semiconductor layer is x = m (0.05 ≦ m ≦ 0.1) and x + y = 1 in the composition formula, that is, Al _m Ga _1-m N. By setting the composition of the group III nitride compound of the first semiconductor layer to x = 0 and y = 1 in the composition formula, that is, GaN, the band gap of the second semiconductor layer is the first semiconductor layer. It becomes larger than the band gap of the semiconductor layer. Accordingly, carriers can smoothly move from the second semiconductor layer through the band gap changing layer to the first semiconductor layer, and the second semiconductor layer functions as a cladding layer for supplying carriers.

  Moreover, the refractive index is reduced by setting the composition of the group III nitride compound of the first semiconductor layer to x = 0 and 0.95 ≦ y ≦ 1 in the composition formula, that is, GaN or InGaN compound. Light generated in the active layer is reflected by the first semiconductor layer. By disposing the first semiconductor layer on the p-type side and / or the n-type side with respect to the active layer, the light generated in the active layer guides the first semiconductor layer and stimulates emission, One semiconductor layer functions as a light guide layer.

  Accordingly, the present invention provides a semiconductor that can smoothly move carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability, and functions as a semiconductor laser. A light-emitting element can be provided.

In the semiconductor light emitting device according to the present invention, the charge density of polarization generated at the adjacent interface between the group III nitride compound of the first semiconductor layer and the group III nitride compound of the second semiconductor layer is ρ (cm ^{− 2} ) When the width of the band gap change layer in the stacking direction is expressed as d (cm), the impurity concentration n (cm ⁻³ ) of the impurity added to the band gap change layer is 0.5ρ / d ≦ It is preferable that n ≦ 3ρ / d.

  In order to lower the electrical resistance of the semiconductor light emitting device, it is preferable to add an impurity to the band gap changing layer. On the other hand, when the impurity concentration is high, crystal defects increase, so that the electrical resistance of the semiconductor light emitting device increases, the amount of light absorbed by the crystal defects increases, and the light emission efficiency of the semiconductor light emitting device decreases. . Further, when Mg is added as an impurity, the semiconductor light emitting element is deteriorated due to Mg diffusion, and the reliability is lowered. Therefore, the impurity concentration of the band gap changing layer is preferably within the above range.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability. Can do.

  According to the present invention, it is possible to provide a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below.

(Embodiment 1)
In the present embodiment, an active layer that generates light by recombination of electrons and holes is stacked on the p-type side of the active layer, and the composition formula Al _x Ga _y In _{1-x A} first semiconductor layer of a group III nitride compound represented by _−yN (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and the active layer side of the first semiconductor layer Is laminated adjacent to the opposite side, and is represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), A band gap changing layer of a group III nitride compound whose composition continuously changes monotonously and a layer adjacent to the side opposite to the first semiconductor layer side of the band gap changing layer are laminated, and the composition formula Al _x Ga _{y In 1-x-y N} (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and the group III nitride reduction represented A semiconductor light emitting device comprising: a second semiconductor layer comprising: a second semiconductor layer, the end of the active layer having a p-type polarity with respect to the active layer, and a center of a width of the band gap change layer in a stacking direction. The band gap of the band gap change layer is substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. A semiconductor light emitting device characterized by continuously changing monotonously from an equal band gap to a band gap substantially equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer.

  The conceptual diagram of the cross section of the semiconductor light emitting element 101 which is one embodiment which concerns on 1st invention of this application is shown in FIG. The semiconductor light emitting device 101 includes an electrode 11, an n-type substrate 12, an n-type underlayer 13, an n-side first semiconductor layer 25, an n-type second semiconductor layer 27, an active layer 14, a p-side first semiconductor layer 15, and a p-side band. A gap change layer 16, a p-type second semiconductor layer 17, a p-type contact layer 18, and a stripe-shaped electrode 19 are provided. In the semiconductor light emitting device 101, each semiconductor layer is stacked on an n-type substrate 12, and at least a p-type semiconductor layer on the stripe-shaped electrode 19 side with respect to the active layer 14, that is, on the p-type side with respect to the active layer 14. The second semiconductor layer 17 and the p-type contact layer 18 are p-type. On the other hand, the semiconductor layer on the electrode 11 side with respect to the active layer 14, that is, at least the n-type second semiconductor layer 27, the n-type base layer 13, and the n-type substrate 12 on the n-type side with respect to the active layer 14 Yes. The semiconductor light emitting device 101 is a back electrode type semiconductor light emitting device in which a semiconductor layer including the n-type substrate 12 is sandwiched between the electrode 11 and the stripe-shaped electrode 19.

  The electrode 11 and the stripe-shaped electrode 19 are arranged for applying a voltage to the semiconductor light emitting device 101. Since the efficiency as a semiconductor light emitting device is impaired if rectification occurs when the electrode and the semiconductor are in contact with each other, the electrode 11 and the stripe-shaped electrode 19 are desirably made of a material that can make ohmic contact with the semiconductor. Furthermore, it is desirable that the material has a small contact resistance with a wiring with an external power supply or other device. Therefore, a structure in which a material serving as a buffer is sandwiched between a material in contact with a semiconductor and a material connected to a wiring is preferable. For example, Ti / Al / Ti / Au and Al / Au are exemplified as the material of the electrode 11 in contact with the n-type semiconductor. Examples of the material of the stripe-shaped electrode 19 that contacts the p-type semiconductor include Ni / Au, Pd / Au, and Pt / Au.

  In order to reduce the contact resistance with the n-type substrate 12, the electrode 11 is opposite to the side of the n-type substrate 12 where the n-type underlayer 13 is laminated (hereinafter referred to as “the n-type underlayer 13 of the n-type substrate 12 is laminated). The side opposite to the side ”is abbreviated as“ back surface of the n-type substrate 12 ”. On the other hand, the stripe-shaped electrode 19 is disposed in a strip shape on the p-type contact layer 18 in order to concentrate and supply carriers to a part of the active layer 14.

The n-type substrate 12 is disposed to physically support the semiconductor light emitting device 101 composed of a semiconductor thin film. A material on which a semiconductor thin film is favorably grown is selected as the substrate of the semiconductor light emitting device 101. For example, a group III nitride compound represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) (hereinafter “composition formula”) “Group III nitride compound represented by Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1”) is referred to as “Al _x Ga _y In _{1− When} abbreviated as “ _xy N compound”), gallium nitride (GaN) or silicon carbide (SiC) is exemplified.

The active layer 14 is a layer that emits light by recombination of electrons and holes. The wavelength of the emitted light is determined by the band gap of the material used for the active layer 14. The material employed for the active layer 14 is preferably a direct transition type semiconductor with high luminous efficiency. By using the Al _x Ga _y In _1-xy N compound thin film, a wide band gap can be created by changing the composition, and a semiconductor light emitting device having a desired wavelength can be manufactured. In addition, the active layer 14 is formed by alternately arranging at least two types of semiconductor thin films having different band gaps, so that the semiconductor thin film having the wider band gap is used as the barrier layer, and the semiconductor thin film having the narrow band gap is used as the well layer. A multiple quantum well structure (MQW) can also be used. By setting the active layer 14 to the MQW, it is possible to realize that light is efficiently emitted even with a small current because electrons are concentrated in a specific energy state. When MQW is used, the wavelength of light emitted by the band gap of the well layer is determined. Note that both ends of the MQW may be barrier layers or well layers. For example, as the barrier layer, x = 0, y = q (0.95 ≦ q ≦ 1, preferably 0.97 ≦ q ≦ 1) in the composition formula, that is, the composition formula is expressed as Ga _q In _1-q N. In the composition formula, the group III nitride compound thin film and the well layer are formed with x = 0, y = p (p <q and 0.80 ≦ p ≦ 0.95, preferably 0.85 ≦ p ≦ 0. 9), that the composition formula is a combination of an III nitride compound film represented as _{Ga p In 1-p} N MQW are illustrated. In the following description, “Group III nitride compound whose composition formula is represented as GaN” is abbreviated as “GaN compound”, and “Group III nitride whose composition formula is represented as Ga _q In _1-q N”. system compound "and abbreviated as" _{Ga q In 1-q} N compound ", a" group III nitride based compound composition formula is expressed as _{Ga p In 1-p} N "," _{Ga p In 1-p} N compound ".

  The thickness of the barrier layer is preferably 5 (nm) or more and 20 (nm) or less, and more preferably 7 (nm) or more and 15 (nm) or less.

  The thickness of the well layer is preferably 1 (nm) to 10 (nm), and more preferably 3 (nm) to 5 (nm).

  Of the film thickness of the active layer 14, the MQW film thickness (the total film thickness of the barrier layer and the well layer) is preferably 380 nm or more and 480 nm or less.

Further, Al _x Ga _y In ₁₋ prevents the phenomenon of carrier overflow, in which electrons receiving heat energy due to heat generated by light emission of the semiconductor light emitting element move to the p-type semiconductor layer beyond the barrier of the quantum well. an electron barrier layer of _{x-y N} compound may be placed on the edge of the MQW p-side with respect to the MQW. Since the electron barrier layer has a wide band gap and the bottom level of the transmission band is high, even electrons having obtained the thermal energy can pass through the electron barrier layer and move to the p-type semiconductor layer. Can not. For example, x = s and x + y = 1 (0.1 ≦ s ≦ 0.3, preferably 0.15 ≦ s ≦ 0.25) in the composition formula as the electron barrier layer, that is, the composition formula is Al _s Ga _1. group III represented as _-s N nitride compound (hereinafter, the "group III nitride based compound composition formula is represented as _{Al s Ga 1-s} N", _{"Al s Ga 1-s} N compound" Abbreviated.) A thin film is illustrated. The film thickness of the electron barrier layer is 10 (nm) or more and 30 (nm) or less, preferably 15 (nm) or more and 25 (nm) or less. In the p-type semiconductor layer, carrier overflowed electrons become ineffective carriers that do not participate in light emission and reduce the light emission efficiency of the semiconductor light emitting device. Therefore, the active layer 14 has the electron barrier layer to reduce ineffective carriers. Thus, the light emission efficiency of the semiconductor light emitting element can be increased.

The n-type second semiconductor layer 27 is a semiconductor layer of an Al _x Ga _y In _1-xy N compound. The n-type second semiconductor layer 27 has a relationship of x = m (0.01 ≦ m ≦ 0.15, preferably 0.05 ≦ m ≦ 0.1) and x + y = 1 in the composition formula, that is, the composition formula is Al. Group III nitride compound represented by _m Ga _1-m N (hereinafter, “Group III nitride compound represented by a composition formula of Al _m Ga _1-m N” is referred to as “Al _m Ga _1-m N”. Abbreviated as "compound"). The n-type second semiconductor layer 27 is added with an n-type impurity such as Si in order to increase the carrier density. The impurity concentration is exemplified to be 5 × 10 ¹⁷ (cm ⁻³ ) or more and 1 × 10 ¹⁹ (cm ⁻³ ) or less. The film thickness of the n-type second semiconductor layer 27 is preferably 300 (nm) or more and 2000 (nm) or less, and more preferably 400 (nm) or more and 1200 (nm) or less.

The n-side first semiconductor layer 25 is a semiconductor layer of Al _x Ga _y In _1-xy N compound. An impurity is not added to the n-side first semiconductor layer 25 so that the impurity does not diffuse into the active layer 14, or a concentration lower than the concentration of the impurity added to the n-type second semiconductor layer 27 is designed. The band gap of the n-side first semiconductor layer 25 is designed to be wider than the band gap of the active layer 14 and narrower than the band gap of the n-type second semiconductor layer 27. When the active layer 14 is the MQW, the band gap of the n-side first semiconductor layer 25 is wider than the band gap of the barrier layer constituting the MQW and narrower than the band gap of the n-type second semiconductor layer 27. Specifically, the composition of the n-side first semiconductor layer 25 is exemplified by x = 0 and y = 1 in the composition formula, that is, a GaN compound. The composition of the n-side first semiconductor layer 25 may be x = 0 and 0.95 ≦ y ≦ 1 in the composition formula, that is, a GaInN compound. The film thickness of the n-side first semiconductor layer 25 is preferably 20 (nm) or more and 200 (nm) or less, and more preferably 50 (nm) or more and 150 (nm) or less.

The p-type second semiconductor layer 17 is a semiconductor layer of an Al _x Ga _y In _1-xy N compound. The p-type second semiconductor layer 17 has a relationship of x = m (0.01 ≦ m ≦ 0.15, preferably 0.05 ≦ m ≦ 0.1) and x + y = 1 in the composition formula, that is, Al _m Ga _{1. -MN} compounds are exemplified. The p-type second semiconductor layer 17 is added with a p-type impurity such as Mg in order to increase the carrier density. The impurity concentration is exemplified to be 5 × 10 ¹⁸ (cm ⁻³ ) or more and 1 × 10 ²⁰ (cm ⁻³ ) or less. The film thickness of the p-type second semiconductor layer 17 is preferably 100 (nm) or more and 2000 (nm) or less, and more preferably 200 (nm) or more and 500 (nm) or less.

The p-side first semiconductor layer 15 is a semiconductor layer of an Al _x Ga _y In _1-xy N compound. To prevent the impurities from diffusing into the active layer 14, no impurities are added to the p-side first semiconductor layer 15, or the concentration is lower than the concentration of impurities added to the p-type second semiconductor layer 17. Further, the band gap of the p-type first semiconductor layer 15 is designed to be wider than the band gap of the active layer 14. When the active layer 14 is the MQW, the band gap of the p-side first semiconductor layer 15 is wider than the band gap of the barrier layer constituting the MQW and narrower than the band gap of the p-type second semiconductor layer 17. Specifically, the composition of the p-side first semiconductor layer 15 is exemplified by x = 0 and y = 1 in the composition formula, that is, a GaN compound. The composition of the p-side first semiconductor layer 15 may be x = 0 and 0.95 ≦ y ≦ 1 in the composition formula, that is, a GaInN compound. The thickness of the p-side first semiconductor layer 15 is preferably 20 (nm) or more and 200 (nm) or less, and more preferably 50 (nm) or more and 150 (nm) or less.

The p-side band gap change layer 16 is a layer of an Al _x Ga _y In _1-xy N compound whose composition continuously changes monotonously in the stacking direction. That is, the p-side band gap change layer 16 has a composition in which the values of x and y in the composition formula continuously and monotonously change from one side to the other side in the stacking direction. For example, the p-side band gap changing layer 16 is a GaN compound in which one side of the p-side band gap changing layer 16 with respect to the stacking direction is x = 0 and y = 1 in the composition formula, and the other side is in the composition formula. an Al _0.08 Ga _0.92 N compound in which x = 0.08 and y = 0.92, and the value of x in the composition formula is 0 to 0. 0 from the one side toward the other side. The composition has a monotonous change continuously to 08 and the value of y continuously monotonously changes from 1 to 0.92 while maintaining the relationship of x + y = 1.

  Since the composition of the p-side band gap changing layer 16 continuously monotonously changes, lattice distortion due to a sharp composition change in the p-side band gap changing layer 16 can be reduced.

  The film thickness of the p-side band gap changing layer 16 is preferably 3 (nm) or more and less than 100 (nm), and more preferably 3 (nm) or more and 50 (nm) or less.

A p-type impurity may be added to the p-side band gap changing layer 16 in order to make it p-type. Specifically, Mg is exemplified as the p-type impurity. For example, the impurity concentration can be 1 × 10 ¹⁸ (cm ⁻³ ) or more and 1 × 10 ¹⁹ (cm ⁻³ ) or less.

The charge density of polarization generated at the adjacent interface between the group III nitride compound of the first semiconductor layer and the group III nitride compound of the second semiconductor layer is ρ (cm ⁻² ), and the band gap change When the width in the stacking direction of the layer is expressed as d (cm), the impurity concentration n (cm ⁻³ ) of the impurity added to the band gap changing layer is in the range of Formula 1, that is, the charge density ρ is changed in the band gap. It is preferably in the range of 50% to 300% of the quotient divided by the layer thickness d.

Furthermore, it is preferable that it is the range of several 2 for smooth carrier transport, and it is more preferable that it is the range of several 3.

The impurity concentration of the band gap change layer disposed between the GaN compound and the Al _0.08 Ga _0.92 N compound is exemplified below. The polarization charge density generated at the interface between the GaN compound and the Al _0.08 Ga _0.92 N compound is ρ = 3 × 10 ¹² (cm ⁻² ). When the film thickness of the band gap changing layer is 10 (nm), the impurity concentration n of the impurity added to the band gap changing layer is 1.5 × 10 ¹⁸ (cm ⁻³ ) or more and 9 × 10 ¹⁸ (cm ^{− 3} ) The following range is preferable.

  The p-type contact layer 18 is a semiconductor layer for making ohmic contact with the stripe-shaped electrode 19. For example, a GaN compound having a film thickness of 10 (nm) to 100 (nm) can be exemplified. When the p-type contact layer 18 is a GaN compound, Mg is exemplified as an impurity to be added.

The n-type underlayer 13 can improve the crystallinity of the semiconductor stacked on the n-type underlayer 13. For example, a GaN compound having n-type Si with a film thickness of 1 μm or more and 5 μm or less can be exemplified. The impurity concentration is exemplified to be 5 × 10 ¹⁷ (cm ⁻³ ) or more and 1 × 10 ¹⁹ (cm ⁻³ ) or less.

  The semiconductor light emitting device 101 includes an n-type underlayer 13, an n-type second semiconductor layer 27, an n-side first semiconductor layer 25, an active layer 14, a p-side first semiconductor layer 15, and a p-side band gap change on the n-type substrate 12. The layer 16, the p-type second semiconductor layer 17, and the p-type contact layer 18 are stacked in this order. Means for laminating each semiconductor layer will be described later.

When the composition of the one side of the p-side band gap changing layer 16 is equal to the composition of the p-side first semiconductor layer 15 and the composition of the other side is equal to the composition of the p-type second semiconductor layer 17, p The p-side bandgap changing layer 16 is arranged so that the one side of the side bandgap changing layer 16 and the p-side first semiconductor layer 15 are adjacent to each other, and the other side and the p-type second semiconductor layer 17 are adjacent to each other. Are laminated. Since the composition continuously and monotonously changes from the p-side first semiconductor layer 15 to the p-type second semiconductor layer 17, the band gap also continues from the p-side first semiconductor layer 15 to the p-type second semiconductor layer 17. Changes monotonically. For example, when the p-side first semiconductor layer 15 is a GaN compound and the p-type second semiconductor layer 17 is a composition formula Al _0.08 Ga _0.92 N compound, the one of the p-side band gap changing layer 16 is By setting the composition on the side to GaN and the composition on the other side to Al _0.08 Ga _0.92 N, the p-side band and the p-side first semiconductor layer 15 and the p-side bandgap changing layer 16 are separated. The steep composition change disappears between the gap change layer 16 and the p-type second semiconductor layer 17, and the composition continuously and monotonously changes from the p-side first semiconductor layer 15 to the p-type second semiconductor layer 17. .

  Accordingly, since there is no steep composition change between the p-side first semiconductor layer 15 and the p-side band gap change layer 16 and between the p-side band gap change layer 16 and the p-type second semiconductor layer 17, the carrier Polarized charges that have hindered transport can be dispersed, and holes can move smoothly from the p-type second semiconductor layer 17 to the p-side first semiconductor layer 15.

  Each semiconductor layer of the semiconductor light emitting device 101 is laminated using a metal organic vapor phase epitaxy method (hereinafter, “metal organic vapor phase epitaxy” is abbreviated as “MOCVD method”). The MOCVD method is a method in which a raw material gas is introduced into a reaction furnace (chamber) and fixed in the chamber, and the raw material gas is thermally decomposed and reacted on a substrate maintained at 600 to 1100 degrees Celsius to epitaxially grow a thin film. is there. By controlling manufacturing parameters such as the flow rate and concentration of the source gas, the reaction temperature and time, and the type of dilution gas, it is possible to easily stack and manufacture semiconductor layers having different compositions and film thicknesses.

n-type underlayer 13, n-type second semiconductor layer 27, n-side first semiconductor layer 25, active layer 14, p-side first semiconductor layer 15, p-side band gap changing layer 16, p-type second semiconductor layer 17, and When the p-type contact layer 18 is an Al _x Ga _y In _1-xy N compound thin film, the MOCVD method uses Ga (CH ₃ ) ₃ (trimethylgallium, hereinafter abbreviated as “TMG”), In as the group III element. (C ₂ H ₅ ) ₃ (triethylindium, hereinafter abbreviated as “TMI”) and Al (CH ₃ ) ₃ (trimethylaluminum, hereinafter abbreviated as “TMA”) were bubbled with hydrogen or nitrogen as a carrier gas. The vapor thus used is used as a raw material gas, and ammonia vapor is used to form a nitride. Further, as impurities, CP ₂ Mg (cyclopentadienyl magnesium) as a p-type dopant and SiH ₄ (silane) as an n-type dopant can be introduced into the chamber as vapor as well. The MOCVD method uses a desired Al _x Ga _y In _1-xy N compound with a flow rate of a mixed gas in which CP ₂ Mg or SiH ₄ , TMG, TMI, TMA and ammonia are mixed at a predetermined mixing ratio and a substrate temperature manufacturing parameter. Can grow. The MOCVD method can control the film thickness of the Al _x Ga _y In _1-xy N compound by the reaction time.

  Specifically, the semiconductor light emitting device 101 is created as follows. The n-type substrate 12 is introduced into the chamber, the inside of the chamber is replaced with a carrier gas, and the temperature of the n-type substrate 12 is raised to about 600 to 1100 ° C.

  Hereinafter, the source gas is introduced into the chamber by a hydrogen or nitrogen carrier gas.

Next, a mixed gas (mixed gas A) in which source gases of TMG, ammonia and SiH ₄ are mixed at a predetermined ratio so that the GaN compound grows is introduced and reacted on the n-type substrate 12 for a predetermined time. The shape base layer 13 is laminated.

Next, a mixed gas (mixed gas B) in which source gases of TMG, TMI, TMA, ammonia and SiH ₄ are mixed at a growth rate of the n-type second semiconductor layer 27 is introduced, and the n-type underlayer 13 is supplied for a predetermined time. The n-type second semiconductor layer 27 is stacked by reacting above. For example, when the n-type second semiconductor layer 27 is an Al _0.08 Ga _0.92 N compound, a mixed gas B of TMG, TMA, ammonia and SiH ₄ is used.

Similarly, a mixed gas (mixed gas C) in which source gases of TMG, TMI, TMA, ammonia, and SiH ₄ are mixed at a growth rate of the n-side first semiconductor layer 25 is introduced for a predetermined time for the n-type second semiconductor layer 25. The n-side first semiconductor layer 25 is stacked by reacting on the semiconductor layer 27. In the case of adding no impurity is reacted stop the SiH _4. For example, when the n-side first semiconductor layer 25 is a non-doped GaN compound, a mixed gas C of TMG and ammonia is used.

  Similarly, the active layer 14 is stacked on the n-side first semiconductor layer 25. When the active layer 14 is MQW, the barrier layers and the well layers can be alternately stacked by switching manufacturing parameters at predetermined time intervals. Further, when the active layer 14 has an electron barrier layer, the electron barrier layer can be stacked on the end of the MQW on the p-type side by switching manufacturing parameters at a predetermined time.

For example, the barrier layer is a Ga _0.97 In _0.03 N compound thin film, the well layer is a Ga _0.9 In _0.1 N compound thin film, and the electron barrier layer is an active layer made of an Al _0.2 Ga _0.8 N compound. 14 is first grown, a Ga _0.9 In _0.1 N compound thin film is grown with a mixed gas of TMG, TMI and ammonia (mixed gas D) in order to stack a well layer on the n-side first semiconductor layer 25. Let Next, a Ga _0.97 In _0.03 N compound thin film is grown using a mixed gas of TMG, TMI, and ammonia (mixed gas E) to form a barrier layer on the well layer. Subsequently, the mixed gas D is switched again, and a well layer is stacked. Furthermore, it switches to the mixed gas E and a barrier layer is laminated | stacked. Similarly, a predetermined number of well layers can be formed by switching the mixed gas D and the mixed gas E a predetermined number of times. After forming a predetermined number of well layers, an Al _0.2 Ga _0.8 N compound thin film is grown with a mixed gas (mixed gas F) of TMG, TMA, CP ₂ Mg and ammonia in order to stack an electron barrier layer. .

After laminating the active layer 14, a mixed gas (mixed gas G) with a mixed ratio of TMG, TMI, TMA, ammonia and CP ₂ Mg on which the p-side first semiconductor layer 15 is grown is introduced for a predetermined time. Then, the p-side first semiconductor layer 15 is stacked by reacting on the substrate 14. For example, when the p-side first semiconductor layer 15 is a non-doped GaN compound, a mixed gas G of TMG and ammonia is used.

  Next, the p-side band gap changing layer 16 is stacked on the p-side first semiconductor layer 15. The reaction gas for laminating the p-side band gap changing layer 16 will be described later.

Next, a mixed gas (mixed gas H) having a mixed ratio of TMG, TMI, TMA, ammonia, and CP ₂ Mg on which the p-type second semiconductor layer 17 is grown is introduced and reacted on the p-side band gap 16 for a predetermined time. Then, the p-type second semiconductor layer 17 is laminated. For example, when the p-type second semiconductor layer 17 is an Al _0.08 Ga _0.92 N compound, a mixed gas H containing TMG, TMA, ammonia, and CP ₂ Mg in a predetermined ratio is used.

In the growth of the p-side bandgap changing layer 16, the p-side first semiconductor layer is continuously and monotonously changed from the mixed gas G to the mixed gas H according to the reaction time, from the mixed gas TMG, TMI, TMA and ammonia. It is possible to obtain a semiconductor layer in which the composition monotonously changes in the stacking direction from 15 to the p-type second semiconductor layer 17 and there is no steep change in the band gap. Further, by adding CP ₂ Mg to the reaction gas, the p-side band gap changing layer 16 can be made p-type.

After the p-type second semiconductor layer 17 is stacked, a mixed gas (mixed gas I) having a mixed ratio of TMG, ammonia, and CP ₂ Mg in which the p-type contact layer 18 is grown is introduced for a predetermined time. The p-type contact layer 18 is stacked by reacting on the semiconductor layer 17.

  Note that the distance in the stacking direction from the interface between the active layer 14 and the p-side first semiconductor layer 15 to the center of the thickness of the p-side band gap changing layer 16 is 30 (nm) or more and 200 (nm) or less, more preferably. The p-side first semiconductor layer 15 and the p-side band gap changing layer 16 are controlled to be stacked so as to be 30 (nm) or more and 100 (nm) or less. That is, the time from the time when the mixed gas F is switched to the mixed gas G to the time that is half the stacking time of the p-side band gap changing layer 16 is controlled. Accordingly, the film thickness of the p-side first semiconductor layer 15 is limited so that the distance in the stacking direction between the active layer 14 and the p-side band gap changing layer 16 is in the above range.

  As a method for growing the group III nitride compound on the n-type substrate 12, a molecular beam epitaxial growth method (MBE method) may be used.

  After the p-type contact layer 18 is stacked, the material for the stripe-shaped electrode 19 and the material for the electrode 11 are stacked on the back surface of the n-type substrate 12 on the p-type contact layer 18. As a method for laminating the electrode material, a sputtering method or a vacuum deposition method can be used.

  After the electrode materials are stacked, the stripe-shaped electrode 19 is formed. As a method of forming the stripe-shaped electrode 19, lithography technology and dry etching can be used. A stripe-shaped resist pattern is formed by a lithography technique, and the material of the stripe-shaped electrode 19 is etched into a stripe shape. By using an etching gas having a high selection ratio between the material of the stripe-shaped electrode 19 and the p-type contact layer 18, for example, a GaN compound, the stripe-shaped electrode 19 that is not covered with the resist pattern using the p-type contact layer 18 as an etching stop layer. This material can be etched well. Subsequently, the striped electrode 19 can be formed by removing the resist.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 101 is shown in FIG. In FIG. 2, 11a is a region of the electrode 11, 12a is a region of the n-type substrate 12, 13a is a region of the n-type underlayer 13, 25a is a region of the n-side first semiconductor layer 25, and 27a is an n-type second semiconductor layer 27. 14a is a region of the active layer 14, 15a is a region of the p-side first semiconductor layer 15, 16a is a region of the p-side band gap changing layer 16, 17a is a region of the p-type second semiconductor layer 17, and 18a is p The region 19a of the mold contact layer 18 and the band gap of the region of the stripe-shaped electrode 19 are shown. 21 is the top level of the valence band, and 22 is the bottom level of the conduction band. In the band diagram of FIG. 2, the active layer 14 of the semiconductor light emitting device 101 has an MQW structure, and has an electron barrier layer at the end of the MQW on the p-type side with respect to the MQW. In the region 14 a of the active layer 14, 14 b indicates a well layer region, 14 c indicates a barrier layer region, and 14 d indicates an electron barrier layer region. In FIG. 2, a part of the band gap from the electrode 11 to the n-type substrate 12 and from the p-type contact layer 18 to the stripe-shaped electrode 19 is omitted.

  By applying a voltage using the stripe-shaped electrode 19 as an anode and the electrode 11 as a cathode, electrons are injected from the electrode 11 and holes are injected from the stripe-shaped electrode 19 into the semiconductor light emitting device 101.

  Electrons injected from the electrode 11 can smoothly move in the direction of the active layer 14 through the n-type n-type substrate 12, the n-type underlayer 13, and the n-type second semiconductor layer 27 in which majority carriers are electrons. Since the band gap of the n-side first semiconductor layer 25 is narrower than the band gap of the n-type second semiconductor layer 27, the electrons go to the n-side first semiconductor layer 25 that is energetically stable along the bottom level 22 of the conduction band. I can move. The electrons are concentrated in each well layer of the active layer 14 having a narrower band gap than the n-side first semiconductor layer 25.

  On the other hand, holes injected from the stripe-shaped electrode 19 can smoothly move in the direction of the active layer 14 in the p-type p-type contact layer 18 and the p-type second semiconductor layer 17 in which majority carriers are holes. . The band gap of the p-side first semiconductor layer 15 is narrower than the band gap of the p-type second semiconductor layer 17, and the p-side band gap changing layer 16 causes the top level 21 and p of the valence band of the p-side first semiconductor layer 15. The valence band top level 21 of the second semiconductor layer 17 is gently connected, and holes move to the p-side first semiconductor layer 15 that is energetically stable along the valence band top level 21. it can. The holes that have moved to the p-side first semiconductor layer 15 are concentrated in each well layer of the active layer 14 that is narrower than the band gap of the p-side first semiconductor layer 15. Although the p-type electron barrier layer of the active layer 14 has a wide band gap, the electron barrier layer has little influence on the movement of holes because the top level 21 of the valence band is high.

  The active layer 14 is expressed between the top level 21 of the valence band of the quantum well and the bottom level 22 of the conduction band by recombination of the electrons and holes concentrated in each well layer of the active layer 14. The light of the wavelength according to the band gap to be emitted is emitted.

  In addition, since the distance in the stacking direction between the active layer 14 and the p-side band gap changing layer 16 is in a certain range, the holes that are narrowed and injected by the stripe-shaped electrode 19 are transferred to the p-type second semiconductor layer 17, p Diffusion in the side band gap changing layer 16 and the p-side first semiconductor layer 15 is reduced and concentrated in a portion immediately below the stripe-shaped electrode 19 of the active layer 14 as shown by a hole flow 91 shown in FIG. To reach.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. Can do. In particular, when Mg is conventionally added as a p-type impurity, it has been necessary to increase the impurity concentration in order to smoothly transport holes, but even in a state where the impurity concentration is reduced by the p-side band gap change layer 16, Therefore, the effect of the present invention is great.

  In addition, since the repulsive force received by the holes due to the dispersion of the polarization charge is reduced, the electrical resistance and built-in voltage of the semiconductor light emitting device 101 are lowered, and the operating voltage of the semiconductor light emitting device 101 can be lowered. Therefore, when the semiconductor light emitting device 101 is a semiconductor laser, the threshold current can be reduced and the slope efficiency of the current versus light quantity can be improved, and when the semiconductor light emitting device 101 is an LED, the brightness can be improved. it can.

  In addition, when the crystals of two Group III nitride compounds having different compositions are stacked in the C-axis direction, the lattice distortion is most intense and the polarization charge appears remarkably. Therefore, the stacking direction of the p-side first semiconductor layer 15, the p-side band gap changing layer 16 and the p-type second semiconductor layer 17, the crystal of the group III nitride compound of the p-side first semiconductor layer 15, the p-side band gap The effect of the p-side band gap changing layer 16 when the group III nitride compound crystal of the change layer 16 and the C-axis direction of the group III nitride compound crystal of the p-type second semiconductor layer 17 are parallel, that is, The effect of dispersion of the polarization charge is maximized. Therefore, the p-side band gap changing layer 16 does not increase the impurity concentration of the p-side first semiconductor layer 15, that is, does not cause deterioration in optical characteristics and reliability, and thus carriers between two semiconductor layers having different compositions from each other. Transport can be made smooth.

(Embodiment 2)
FIG. 3 shows a conceptual diagram of a cross section of a semiconductor light emitting device 103 which is another embodiment according to the first invention of the present application. 3, the same reference numerals as those used in FIG. 1 are semiconductor layers and have the same functions. The difference between the semiconductor light emitting device 103 and the semiconductor light emitting device 101 of FIG. 1 is that the semiconductor light emitting device 101 has a negative electrode on the back surface of the substrate, whereas the semiconductor light emitting device 103 has a positive electrode and a negative electrode on the substrate. The mold is in the same direction. Specifically, the semiconductor light emitting device 103 does not include the electrode 11 and the n-type substrate 12 of the semiconductor light emitting device 101 but includes the n-type substrate 32 and the electrode 31.

The n-type substrate 32 is disposed to physically support the semiconductor light emitting device 103 composed of a semiconductor thin film. A material on which a semiconductor thin film is favorably grown is selected as the substrate of the semiconductor light emitting device 103. For example, sapphire is exemplified when an Al _x Ga _y In _1-xy N compound is laminated.

  The electrode 31 is disposed to apply a voltage to the semiconductor light emitting device 103. The electrode 31 has the function described with reference to the electrode 11 in FIG. 1, and examples of the material include Ti / Al / Ti / Au and Al / Au.

  The semiconductor light emitting device 103 is formed as described below. Using the MOCVD method, the n-type underlayer 13, the n-type second semiconductor layer 27, the n-side first semiconductor layer 25, the active layer 14, the p-side first semiconductor layer 15, and the p-side band gap change are formed on the n-type substrate 32. The layer 16, the p-type second semiconductor layer 17, and the p-type contact layer 18 are stacked in this order. Subsequently, the stripe-shaped electrode 19 is formed as described in the semiconductor light emitting device 101 of FIG.

  Subsequently, in order to remove the semiconductor layer of the negative electrode portion M where the electrode 31 is to be formed, a resist pattern that covers the upper layer of the positive electrode portion P is formed again by using a lithography technique, and p of the negative electrode portion M is formed by dry etching. The semiconductor layer from the type contact layer 18 to a part of the thickness of the n-type underlayer 13 is removed. Since the etching is performed up to a part of the film thickness of the n-type underlayer 13, the end point, that is, the film thickness of the n-type underlayer 13 left in the negative electrode portion M is controlled by the etching time.

  After forming the negative electrode portion M, the electrode 31 is formed in the same manner as the formation of the stripe-shaped electrode 19.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 103 is shown in FIG. In FIG. 4, the same reference numerals as those used in FIG. 2 are the same laminated film regions and have the same functions. In the band diagram of the semiconductor light emitting device 103 of FIG. 4, the portions different from the band diagram of the semiconductor light emitting device 101 of FIG. 2 are the region 12 a of the n type substrate 12 and the region of the electrode 11 on the n type side with respect to the region 14 a of the active layer 14. 11a is not displayed and the region 31a of the electrode 31 is displayed. In FIG. 4, a part of the band gap from the p-type contact layer 18 to the stripe-shaped electrode 19 and from the n-type underlayer 13 to the electrode 31 is omitted.

  By applying a voltage using the stripe-shaped electrode 19 as an anode and the electrode 31 as a cathode, electrons are injected from the electrode 31 and holes are injected from the stripe-shaped electrode 19 into the semiconductor light emitting device 103.

  Electrons injected from the electrode 31 are concentrated in each well layer of the active layer 14 of the semiconductor light emitting device 103 as described in the band diagram of the semiconductor light emitting device 101 of FIG.

  On the other hand, the holes injected from the stripe-shaped electrode 19 are concentrated in each well layer of the active layer 14 of the semiconductor light emitting device 103 as described in the band diagram of the semiconductor light emitting device 101 of FIG. Therefore, the semiconductor light emitting device 103 emits light having a wavelength corresponding to the band gap expressed between the top level 21 of the valence band of the quantum well and the bottom level 22 of the conduction band.

  Further, the semiconductor light emitting element 103 is squeezed by the stripe-shaped electrode 19 because the distance in the stacking direction between the active layer 14 and the p-side band gap changing layer 16 is in a certain range, similar to the semiconductor light emitting element 101 of FIG. The injected holes are concentrated and reach the portion immediately below the stripe-shaped electrode 19 of the active layer 14 as shown by a hole flow 91 shown in FIG.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. Can do.

  That is, the semiconductor light emitting device 103 can obtain effects such as a reduction in threshold current, improvement in the slope efficiency of the current versus light amount, and an improvement in luminance as in the semiconductor light emitting device 101.

  Similarly to the semiconductor light emitting device 101, the semiconductor light emitting device 103 has the crystal C axis of the group III nitride compound crystal in the p-side first semiconductor layer 15, the p-side band gap changing layer 16, and the p-type second semiconductor layer 17. When the layers are stacked together, the effect of the p-side band gap changing layer 16, that is, the effect of dispersion of the polarization charge is maximized. Therefore, the p-side band gap changing layer 16 does not increase the impurity concentration of the p-side first semiconductor layer 15, that is, does not cause deterioration in optical characteristics and reliability, and thus carriers between two semiconductor layers having different compositions from each other. Transport can be made smooth.

(Embodiment 3)
In the present embodiment, an active layer that generates light by recombination of electrons and holes is stacked on the p-type side of the active layer, and the composition formula Al _x Ga _y In _{1-x A} first semiconductor layer of a group III nitride compound represented by _−yN (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and the active layer side of the first semiconductor layer Is laminated adjacent to the opposite side, and is represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), A band gap changing layer of a group III nitride compound whose composition monotonously changes in a stepwise manner and a layer adjacent to the side of the band gap changing layer opposite to the first semiconductor layer side are stacked, and the composition formula Al _x Ga _{y In 1-x-y N} (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and the group III nitride reduction represented A semiconductor light emitting device comprising: a second semiconductor layer comprising: a second semiconductor layer, the end of the active layer having a p-type polarity with respect to the active layer, and a center of a width of the band gap change layer in a stacking direction. The band gap of the band gap change layer is substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. The semiconductor light emitting device is characterized in that it monotonously changes stepwise from an equal band gap to a band gap substantially equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer.

  FIG. 5 shows a conceptual diagram of a cross section of the semiconductor light emitting device 105 according to one embodiment of the second invention of the present application. In FIG. 5, the same reference numerals as those used in FIGS. 1 and 3 are the same semiconductor layers and have the same functions. The difference between the semiconductor light emitting device 105 and the semiconductor light emitting device 103 of FIG. 3 is that the semiconductor light emitting device 105 does not include the p-side band gap changing layer 16 of the semiconductor light emitting device 103 but includes the p-side band gap changing layer 56. It is.

The p-side band gap changing layer 56 is a layer of an Al _x Ga _y In _1-xy N compound whose composition monotonously changes stepwise in the stacking direction. That is, the p-side band gap changing layer 56 has a composition in which the values of x and y in the composition formula monotonously change in a stepwise manner from one side to the other side in the stacking direction. Specifically, the p-side band gap changing layer 56 is formed by laminating a plurality of Al _x Ga _y In _1-xy N compound thin films having different band gaps in order of increasing or decreasing band gap width. For example, the p-side band gap change layer 56 is a GaN compound thin film or an Al _0.02 Ga _0.98 N compound having a thickness of 10 nm from one side in the stacking direction to the other side in the stacking direction. A thin film, an Al _0.04 Ga _0.96 N compound thin film, an Al _0.06 Ga _0.94 N compound thin film, and an Al _0.08 Ga _0.92 N compound thin film are sequentially stacked. The band gap of the p-side band gap change layer 56 is from the narrowest band gap of the GaN compound thin film to the widest band gap of the Al _0.08 Ga _0.92 N compound thin film from the one side to the other side. It changes monotonously in a staircase pattern. The composition of the compound thin film may be changed unevenly, and the film thickness of the compound thin film may also be uneven.

  Since the composition of the p-side band gap changing layer 56 changes monotonically in a stepped manner, lattice distortion due to a sharp composition change in the p-side band gap changing layer 56 can be reduced.

  The film thickness of the p-side band gap changing layer 56 is preferably 3 (nm) or more and less than 100 (nm), more preferably 3 (nm) or more and 50 (nm) or less.

A p-type impurity may be added to the p-side band gap changing layer 56 in order to make it p-type. Specifically, Mg is exemplified as the p-type impurity, and the impurity concentration n is exemplified by a range of 1 × 10 ¹⁸ (cm ⁻³ ) to 1 × 10 ¹⁹ (cm ⁻³ ). The impurity concentration range of the p-side bandgap changing layer 56 is the interface between the p-side first semiconductor layer 15 and the p-type second semiconductor layer 17 as described in the p-side bandgap changing layer 16 of FIG. It is preferable to calculate from the charge density of the polarization generated in FIG.

  The semiconductor light emitting element 105 is produced as described below. Using the MOCVD method, the n-type underlayer 13, the n-type second semiconductor layer 27, the n-side first semiconductor layer 25, the active layer 14, the p-side first semiconductor layer 15, and the p-side band gap change are formed on the n-type substrate 32. The layer 56, the p-type second semiconductor layer 17, and the p-type contact layer 18 are stacked in this order. The p-side band gap changing layer 56 is formed by changing the manufacturing parameters in a stepped manner every predetermined time. Note that the distance in the stacking direction from the interface between the active layer 14 and the p-side first semiconductor layer 15 to the center of the thickness of the p-side band gap change layer 56 is 30 (nm) or more and 200 (nm) or less, more preferably. The p-side first semiconductor layer 15 and the p-side band gap change layer 56 are stacked so as to be 30 (nm) or more and 100 (nm) or less.

  Subsequently, a stripe-shaped electrode 91 is formed as described in the semiconductor light emitting device 101 of FIG. Subsequently, as described in the semiconductor light emitting device 103 in FIG. 3, the negative electrode portion M is formed to form the electrode 31.

  By making the composition on one side of the p-side band gap changing layer 56 equal to the composition of the p-side first semiconductor layer 15 and making the composition on the other side equal to the composition of the p-type second semiconductor layer 17, FIG. The same effect as that of the p-side band gap changing layer 16 can be obtained. That is, the p-side band gap is formed such that the one side of the p-side band gap changing layer 56 and the p-side first semiconductor layer 15 are adjacent to each other, and the other side and the p-type second semiconductor layer 17 are adjacent to each other. By stacking the change layer 56, a steep composition is formed between the p-side first semiconductor layer 15 and the p-side band gap change layer 56 and between the p-side band gap change layer 56 and the p-type second semiconductor layer 17. Therefore, the polarization charge that hinders carrier transport can be dispersed, and the holes can be smoothly moved from the p-type second semiconductor layer 17 to the p-side first semiconductor layer 15.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 105 is shown in FIG. In FIG. 6, the same reference numerals as those used in FIG. 2 or 4 are the same laminated film regions and have the same functions. In the band diagram of the semiconductor light emitting device 105 in FIG. 6, the portion different from the band diagram of the semiconductor light emitting device 103 in FIG. 4 has no region 16 a of the p-side band gap changing layer 16 on the p-type side with respect to the region 14 a of the active layer 14. , The region 56a of the p-side band gap changing layer 56 is displayed. In FIG. 6, a part of the band gap from the p-type contact layer 18 to the stripe-shaped electrode 19 and from the n-type base layer 13 to the electrode 31 is omitted.

  By applying a voltage using the stripe-shaped electrode 19 as an anode and the electrode 31 as a cathode, electrons are injected from the electrode 11 and holes are injected from the stripe-shaped electrode 19 into the semiconductor light emitting device 105.

  Electrons injected from the electrode 31 are concentrated in each well layer of the active layer 14 of the semiconductor light emitting device 105 as described in the band gap of the semiconductor light emitting device 101 in FIG.

  On the other hand, on the p-type side with respect to the active layer 14, the top level 21 of the valence band of the p-side first semiconductor layer 15 and the valence band of the p-type second semiconductor layer 17 by the p-side band gap change layer 56. The top level 21 is connected in a stepped manner, and holes injected from the stripe-shaped electrode 19 move to the p-side first semiconductor layer 15 that is energetically stable along the top level 21 of the valence band. it can. The holes that have moved to the p-side first semiconductor layer 15 are concentrated in each well layer of the active layer 14 of the semiconductor light emitting device 105 as described in the band gap of the semiconductor light emitting device 101 of FIG.

  Accordingly, the semiconductor light emitting device 105 emits light having a wavelength corresponding to the band gap expressed between the top level 21 of the valence band of the quantum well and the bottom level 22 of the conduction band.

  Further, the semiconductor light emitting element 105 is squeezed by the stripe-shaped electrode 19 because the distance in the stacking direction between the active layer 14 and the p-side band gap changing layer 16 is in a certain range, similar to the semiconductor light emitting element 101 of FIG. The injected holes are concentrated and reach the portion immediately below the stripe-shaped electrode 19 of the active layer 14 as shown by a hole flow 91 shown in FIG.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. Can do.

  That is, the semiconductor light emitting element 105 can obtain effects such as a reduction in threshold current, an improvement in slope efficiency of current versus light intensity, and an improvement in luminance, as in the semiconductor light emitting element 101.

  Similarly to the semiconductor light emitting device 101, the semiconductor light emitting device 105 has the crystal C axis of the group III nitride compound crystal in the p-side first semiconductor layer 15, the p-side band gap changing layer 56, and the p-type second semiconductor layer 17. When the layers are stacked together, the effect of the p-side band gap changing layer 56, that is, the effect of dispersion of the polarization charge is maximized. Therefore, the p-side band gap change layer 56 does not increase the impurity concentration of the p-side first semiconductor layer 15, that is, does not cause deterioration in optical characteristics and reliability, and thus carriers between two semiconductor layers having different compositions from each other. Transport can be made smooth.

  The semiconductor light emitting element 105 can be formed as a back electrode type semiconductor light emitting element like the semiconductor light emitting element 101 by stacking a semiconductor layer on the n-type substrate 12 described in the semiconductor light emitting element 101 of FIG.

(Embodiment 4)
In this embodiment, an active layer that generates light by recombination of electrons and holes, and a layer on the n-type side of the active layer are stacked, and the composition formula Al _x Ga _y In _{1-x A} first semiconductor layer of a group III nitride compound represented by _−yN (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and the active layer side of the first semiconductor layer Is laminated adjacent to the opposite side, and is represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), A band gap changing layer of a group III nitride compound whose composition continuously changes monotonously and a layer adjacent to the side opposite to the first semiconductor layer side of the band gap changing layer are laminated, and the composition formula Al _x Ga _{y In 1-x-y N} (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and the group III nitride reduction represented A semiconductor light emitting device comprising: a second semiconductor layer of an object, wherein an end of the active layer on the n-type side with respect to the active layer reaches a center of a width in a stacking direction of the band gap change layer The band gap of the band gap change layer is substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. A semiconductor light emitting device characterized by continuously changing monotonously from an equal band gap to a band gap substantially equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer.

  FIG. 7 shows a conceptual diagram of a cross section of a semiconductor light emitting device 107 according to an embodiment of the third invention of the present application. In FIG. 7, the same reference numerals as those used in FIGS. 1, 3, and 5 are the same semiconductor layers and have the same functions. The difference between the semiconductor light emitting device 107 and the semiconductor light emitting device 103 in FIG. 3 is that the semiconductor light emitting device 107 does not include the p-side band gap changing layer 16 of the semiconductor light emitting device 103 but includes the n-side band gap changing layer 76. It is.

The n-side band gap changing layer 76 is an Al _x Ga _y In _1-xy N compound layer whose composition continuously changes monotonously in the stacking direction like the p-type band gap changing layer 16 of FIG. That is, the n-side band gap change layer 76 has a composition in which the values of x and y in the composition formula continuously and monotonously change from one side of the n-side band gap change layer 76 to the other side in the stacking direction. For example, the n-side band gap change layer 76 can be exemplified by a group III nitride compound having the same composition as that of the p-side band gap change layer 16 described in FIG.

  Since the composition of the n-side band gap changing layer 76 continuously monotonously changes, lattice distortion due to a sharp composition change in the n-side band gap changing layer 76 can be reduced.

  The film thickness of the n-side band gap changing layer 76 is preferably 3 (nm) or more and less than 100 (nm), and more preferably 3 (nm) or more and 50 (nm) or less.

An n-type impurity may be added to the n-side band gap changing layer 76 in order to make it n-type. Specifically, Si is exemplified as the n-type impurity, and the impurity concentration n is exemplified by a range of 5 × 10 ¹⁷ (cm ⁻³ ) to 5 × 10 ¹⁸ (cm ⁻³ ). The range of the impurity concentration of the n-side band gap changing layer 76 is the interface between the n-side first semiconductor layer 25 and the n-type second semiconductor layer 27 adjacent to each other as described for the p-side band gap changing layer 16 in FIG. It is preferable to calculate from the charge density of the polarization generated in FIG.

  The semiconductor light emitting element 107 is produced as described below. Using the MOCVD method, the n-type underlayer 13, the n-type second semiconductor layer 27, the n-side band gap changing layer 76, the n-side first semiconductor layer 25, the active layer 14, and the p-side first semiconductor are formed on the n-type substrate 32. The layer 15, the p-type second semiconductor layer 17, and the p-type contact layer 18 are sequentially stacked. The distance in the stacking direction from the interface between the active layer 14 and the n-side first semiconductor layer 25 to the center of the film thickness of the n-side band gap change layer 76 is 30 (nm) or more and 200 (nm) or less, more preferably. The n-side first semiconductor layer 25 and the n-side band gap change layer 76 are stacked so as to be 30 (nm) or more and 100 (nm) or less.

  Therefore, the thickness of the n-side first semiconductor layer 25 is not less than 20 (nm) and not more than 200 (nm) so that the distance in the stacking direction between the active layer 14 and the n-side band gap changing layer 76 is within the above range. Is preferred.

  Subsequently, a stripe-shaped electrode 91 is formed as described in the semiconductor light emitting device 101 of FIG. Subsequently, as described in the semiconductor light emitting device 103 in FIG. 3, the negative electrode portion M is formed to form the electrode 31.

  When the composition on one side of the n-side band gap changing layer 76 is made equal to the composition of the n-side first semiconductor layer 25 and the composition on the other side is made equal to the composition of the n-type second semiconductor layer 27, FIG. The same effect as that of the p-side band gap changing layer 16 can be obtained. That is, the n-side bandgap changing layer 76 is arranged so that the one side of the n-side bandgap changing layer 76 is adjacent to the n-side first semiconductor layer 25 and the other side is adjacent to the n-type semiconductor layer 27. By stacking 76, a steep composition change between the n-side first semiconductor layer 25 and the n-side band gap change layer 76 and between the n-side band gap change layer 76 and the n-type second semiconductor layer 27 is achieved. Therefore, the polarization charge that hinders the transport of carriers can be dispersed, and electrons can move smoothly from the n-type second semiconductor layer 27 to the n-side first semiconductor layer 25.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 107 is shown in FIG. In FIG. 8, the same reference numerals as those used in FIG. 2, FIG. 4, and FIG. In the band diagram of the semiconductor light emitting device 107 of FIG. 8, the portion different from the band diagram of the semiconductor light emitting device 103 of FIG. 4 has no region 16a of the p-side band gap changing layer 16 on the p-type side with respect to the region 14a of the active layer 14. In other words, the region 76a of the n-side band gap changing layer 76 is displayed on the n-type side with respect to the region 14a of the active layer 14. In FIG. 8, a part of the band gap from the p-type contact layer 18 to the stripe-shaped electrode 19 and from the n-type underlayer 13 to the electrode 31 is omitted.

  By applying a voltage using the stripe-shaped electrode 19 as an anode and the electrode 31 as a cathode, electrons are injected from the electrode 11 and holes are injected from the stripe-shaped electrode 19 into the semiconductor light emitting device 107.

  Electrons injected from the electrode 31 can smoothly move in the direction of the active layer 14 through the n-type n-type underlayer 13 and the n-type second semiconductor layer 27 in which majority carriers are electrons. The band gap of the n-side first semiconductor layer 25 is narrower than the band gap of the n-type second semiconductor layer 27, and the bottom level 22 of the conduction band of the n-side first semiconductor layer 25 and the n-type are changed by the n-side band gap changing layer 76. The bottom level 22 of the conduction band of the second semiconductor layer 27 is gently connected, and electrons can move along the bottom level 22 of the conduction band to the n-side first semiconductor layer 25 that is energetically stable. The electrons that have moved to the n-side first semiconductor layer 25 are concentrated in each well layer of the active layer 14 that is narrower than the band gap of the n-side first semiconductor layer 25.

  On the other hand, holes injected from the stripe-shaped electrode 19 can smoothly move in the direction of the active layer 14 in the p-type p-type contact layer 18 and the p-type second semiconductor layer 27 in which majority carriers are holes. . Since the band gap of the p-side first semiconductor layer 15 is narrower than the band gap of the p-type second semiconductor layer 17, the holes are energetically stable along the top level 21 of the valence band. You can move to 15. The holes are concentrated in each well layer of the active layer 14 having a narrower band gap than the p-side first semiconductor layer 15.

  Therefore, the semiconductor light emitting device 107 emits light having a wavelength corresponding to the band gap expressed between the top level 21 of the valence band of the quantum well and the bottom level 22 of the conduction band.

  Further, the distance in the stacking direction between the active layer 14 and the n-side band gap changing layer 76 is in a certain range, and electrons can move smoothly from the n-type second semiconductor layer 27 to the n-side first semiconductor layer 25. Electrons injected by the electrode 31 do not concentrate in one place, but in the n-type second semiconductor layer 27, the n-side band gap changing layer 76, and the n-side first semiconductor layer as in the electron flow 97 shown in FIG. 25 can move uniformly, and the electrical resistance of the semiconductor light emitting element 107 can be lowered.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. Can do.

  That is, the semiconductor light emitting element 107 can obtain effects such as a reduction in threshold current, an improvement in slope efficiency of current versus light intensity, and an improvement in luminance, as in the semiconductor light emitting element 101.

  Similarly to the semiconductor light emitting device 101, the semiconductor light emitting device 107 has the crystal C axis of the group III nitride compound crystal in the n side first semiconductor layer 25, the n side band gap changing layer 76, and the n type second semiconductor layer 27. When the layers are stacked together, the effect of the n-side band gap changing layer 76, that is, the effect of dispersion of the polarization charge becomes the largest. Therefore, the n-side bandgap changing layer 76 does not increase the impurity concentration of the n-side first semiconductor layer 25, that is, does not cause deterioration of optical characteristics and reliability, and carriers between two semiconductor layers having different compositions from each other. Transport can be made smooth.

  The semiconductor light emitting element 107 can be a back electrode type semiconductor light emitting element similar to the semiconductor light emitting element 101 by stacking a semiconductor layer on the n-type substrate 12 described in the semiconductor light emitting element 101 of FIG.

(Embodiment 5)
In this embodiment, an active layer that generates light by recombination of electrons and holes, and a layer on the n-type side of the active layer are stacked, and the composition formula Al _x Ga _y In _{1-x A} first semiconductor layer of a group III nitride compound represented by _−yN (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and the active layer side of the first semiconductor layer Is laminated adjacent to the opposite side, and is represented by the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), A band gap changing layer of a group III nitride compound whose composition monotonously changes in a stepwise manner and a layer adjacent to the side of the band gap changing layer opposite to the first semiconductor layer side are stacked, and the composition formula Al _x Ga _{y In 1-x-y N} (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) and the group III nitride reduction represented A semiconductor light emitting device comprising: a second semiconductor layer of an object, wherein an end of the active layer on the n-type side with respect to the active layer reaches a center of a width in a stacking direction of the band gap change layer The band gap of the band gap change layer is substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. The semiconductor light emitting device is characterized in that it monotonously changes stepwise from an equal band gap to a band gap substantially equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer.

  FIG. 9 shows a conceptual diagram of a cross section of the semiconductor light emitting device 109 according to the fourth embodiment of the present invention. In FIG. 9, the same reference numerals as those used in FIGS. 1, 3, 5, and 7 are the same semiconductor layers and have the same functions. The difference between the semiconductor light emitting device 109 and the semiconductor light emitting device 107 of FIG. 7 is that the semiconductor light emitting device 109 does not include the n-side band gap changing layer 76 of the semiconductor light emitting device 107 but includes the n-side band gap changing layer 96. It is.

The n-side band gap changing layer 96 is an Al _x Ga _y In _1-xy N compound layer whose composition monotonously changes stepwise in the stacking direction. That is, the n-side band gap changing layer 96 has a composition in which the values of x and y in the composition formula monotonously change in a stepwise manner from one side to the other side in the stacking direction. For example, the n-side bandgap changing layer 96 is configured in the same manner as the p-side bandgap changing layer 56 described with reference to FIG. 5, and a group III nitride compound having the same composition can be exemplified.

  Since the composition of the n-side band gap change layer 96 changes monotonously in a stepped manner, lattice strain due to a steep composition change in the n-side band gap change layer 96 can be reduced.

  The film thickness of the n-side band gap changing layer 96 is preferably 3 (nm) or more and less than 100 (nm), and more preferably 3 (nm) or more and 50 (nm) or less.

In order to make the n-side band gap changing layer 96 n-type, an n-type impurity may be added in the impurity concentration range described with reference to the p-side band gap changing layer 16 in FIG. Specifically, Si is exemplified as the n-type impurity, and the impurity concentration n is exemplified by a range of 5 × 10 ¹⁷ (cm ⁻³ ) to 5 × 10 ¹⁸ (cm ⁻³ ). The impurity concentration range of the n-side band gap changing layer 96 is the interface between the n-side first semiconductor layer 25 and the n-type second semiconductor layer 27 adjacent to each other as described for the p-side band gap changing layer 16 in FIG. It is preferable to calculate from the charge density of the polarization generated in the above and the width of the n-side band gap changing layer 96 in the stacking direction.

  The semiconductor light emitting device 109 is created as described below. The n-type underlayer 13, the n-side first semiconductor layer 25, the n-side band gap changing layer 96, the n-type second semiconductor layer 27, the active layer 14, and the p-side first semiconductor are formed on the n-type substrate 32 using the MOCVD method. The layer 15, the p-type second semiconductor layer 17, and the p-type contact layer 18 are sequentially stacked. The n-side band gap changing layer 96 is formed by changing the manufacturing parameters in a stepped manner every predetermined time as described with reference to the semiconductor light emitting device 105 of FIG. The distance in the stacking direction from the interface between the active layer 14 and the n-side first semiconductor layer 25 to the center of the film thickness of the n-side band gap change layer 96 is 30 (nm) or more and 200 (nm) or less, more preferably. The n-side first semiconductor layer 25 and the n-side band gap change layer 96 are stacked so as to be 30 (nm) or more and 100 (nm) or less.

  Subsequently, a stripe-shaped electrode 91 is formed as described in the semiconductor light emitting device 101 of FIG. Subsequently, as described in the semiconductor light emitting device 103 in FIG. 3, the negative electrode portion M is formed to form the electrode 31.

  When the composition on one side of the n-side band gap changing layer 96 is made equal to the composition of the n-side first semiconductor layer 25 and the composition on the other side is made equal to the composition of the n-type second semiconductor layer 27, FIG. The same effect as that of the p-side band gap changing layer 16 can be obtained. That is, the n-side bandgap changing layer 96 is adjacent to the one side of the n-side bandgap changing layer 96 and the n-side first semiconductor layer 25, and adjacent to the other side and the n-type semiconductor layer 27. By stacking the layers 96, a steep composition change is made between the n-side first semiconductor layer 25 and the n-side band gap change layer 96 and between the n-side band gap change layer 96 and the n-type second semiconductor layer 27. Therefore, the polarization charge that hinders the transport of carriers can be dispersed, and electrons can move smoothly from the n-type second semiconductor layer 27 to the n-side first semiconductor layer 25.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 109 is shown in FIG. 10, the same reference numerals as those used in FIG. 2, FIG. 4, FIG. 6 and FIG. 8 are regions of the same laminated film and have the same functions. In the band diagram of the semiconductor light emitting device 109 of FIG. 10, the portion different from the band diagram of the semiconductor light emitting device 107 of FIG. 7 has no region 76 a of the n-side band gap changing layer 76 on the n-type side with respect to the region 14 a of the active layer 14. The region 96a of the n-side band gap changing layer 96 is displayed. In FIG. 10, a part of the band gap from the p-type contact layer 18 to the stripe-shaped electrode 19 and from the n-type underlayer 13 to the electrode 31 is omitted.

  By applying a voltage using the stripe-shaped electrode 19 as an anode and the electrode 31 as a cathode, electrons are injected from the electrode 11 and holes are injected from the stripe-shaped electrode 19 into the semiconductor light emitting device 109.

  On the n-type side with respect to the active layer 14, the bottom level 22 of the conduction band of the n-side first semiconductor layer 25 and the bottom level 22 of the conduction band of the n-type second semiconductor layer 27 by the n-side band gap change layer 96. Are connected stepwise, and electrons can move along the bottom level 22 of the conduction band to the n-side first semiconductor layer 25 that is energetically stable. The electrons that have moved to the n-side first semiconductor layer 25 are concentrated in each well layer of the active layer 14 of the semiconductor light emitting device 109.

  On the other hand, the holes injected from the stripe-shaped electrode 19 are concentrated in each well layer of the active layer 14 of the semiconductor light emitting device 109 as described in the band diagram of the semiconductor light emitting device 101 of FIG.

  Accordingly, the semiconductor light emitting device 105 emits light having a wavelength corresponding to the band gap expressed between the top level 21 of the valence band of the quantum well and the bottom level 22 of the conduction band.

  Further, the n-side band gap changing layer 96 of the semiconductor light emitting device 109 is the distance in the stacking direction between the active layer 14 and the n-side band gap changing layer 96 in the same manner as the n-side band gap changing layer 76 of the semiconductor light emitting device 107 of FIG. Is in a certain range, and electrons can smoothly move from the n-type second semiconductor layer 27 to the n-side first semiconductor layer 25 as in the electron flow 97, and the electrical resistance of the semiconductor light emitting device 109 can be lowered.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. Can do.

  That is, the semiconductor light emitting device 109 can obtain effects such as a reduction in threshold current, an improvement in slope efficiency of current versus light intensity, and an improvement in luminance, as in the semiconductor light emitting device 101.

  Similarly to the semiconductor light emitting device 101, the semiconductor light emitting device 109 has the crystal C axis of the group III nitride compound crystal in the n side first semiconductor layer 25, the n side band gap changing layer 96, and the n type second semiconductor layer 27. When the layers are laminated together, the effect of the n-side band gap changing layer 96, that is, the effect of dispersion of the polarization charge becomes the largest. Therefore, the n-side band gap changing layer 96 does not increase the impurity concentration of the n-side first semiconductor layer 25, that is, does not cause deterioration in optical characteristics and reliability, and thus carriers between two semiconductor layers having different compositions from each other. Transport can be made smooth.

  The semiconductor light emitting element 109 can be a back electrode type semiconductor light emitting element similar to the semiconductor light emitting element 101 by stacking a semiconductor layer on the n-type substrate 12 described in the semiconductor light emitting element 101 of FIG.

(Embodiment 6)
FIG. 11 shows a conceptual diagram of a cross section of a semiconductor light emitting device 111 according to another embodiment of the first invention of the present application. In FIG. 11, the same reference numerals as those used in FIGS. 1, 3, 5, 7, and 9 are the same semiconductor layers and have the same functions. The difference between the semiconductor light emitting device 111 and the semiconductor light emitting device 103 of FIG. 3 is that the semiconductor light emitting device 111 has an n side band between the n side first semiconductor layer 25 and the n type second semiconductor layer 27 of the semiconductor light emitting device 103. The gap change layer 76 is provided.

  The semiconductor light emitting device 111 is formed as described below. Using the MOCVD method, the n-type underlayer 13, the n-type second semiconductor layer 27, the n-side band gap changing layer 76, the n-side first semiconductor layer 25, the active layer 14, and the p-side first semiconductor are formed on the n-type substrate 32. The layer 15, the p-side band gap changing layer 16, the p-type second semiconductor layer 17, and the p-type contact layer 18 are sequentially stacked. Note that the distance in the stacking direction from the interface between the active layer 14 and the p-side first semiconductor layer 15 to the center of the film thickness of the p-side band gap change layer 16 and the interface between the active layer 14 and the n-side first semiconductor layer 25. To the center of the film thickness of the n-side band gap changing layer 76 in the stacking direction is 30 (nm) or more and 200 (nm) or less, more preferably 30 (nm) or more and 100 (nm) or less. The first semiconductor layer 15, the p-side band gap change layer 16, the n-side first semiconductor layer 25, and the n-side band gap change layer 96 are stacked.

  Subsequently, a stripe-shaped electrode 91 is formed as described in the semiconductor light emitting device 101 of FIG. Subsequently, as described in the semiconductor light emitting device 103 in FIG. 3, the negative electrode portion M is formed to form the electrode 31.

  As described in the semiconductor light emitting device 101 in FIG. 1 and the semiconductor light emitting device 107 in FIG. 7, the polarization charge that hinders carrier transport by disposing the p-side band gap change layer 16 and the n-side band gap change layer 76. The holes move smoothly from the p-type second semiconductor layer 17 to the p-side first semiconductor layer 15, and the electrons move smoothly from the n-type second semiconductor layer 27 to the n-side first semiconductor layer 25. be able to.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 111 is shown in FIG. In FIG. 12, the same reference numerals as those used in FIGS. 2, 4, 6, 8, and 10 are regions of the same laminated film and have the same functions. In the band diagram of the semiconductor light emitting device 111 of FIG. 12, the portion different from the band diagram of the semiconductor light emitting device 103 of FIG. 4 is indicated by the region 76a of the n-side band gap changing layer 76 on the n-type side with respect to the region 14a of the active layer 14. It is that. In FIG. 12, a part of the band gap from the p-type contact layer 18 to the stripe-shaped electrode 19 and from the n-type base layer 13 to the electrode 31 is omitted.

  By applying a voltage using the stripe-shaped electrode 19 as an anode and the electrode 31 as a cathode, electrons are injected from the electrode 11 and holes are injected from the stripe-shaped electrode 19 into the semiconductor light emitting device 111.

  Electrons injected from the electrode 31 are concentrated in each well layer of the active layer 14 of the semiconductor light emitting device 111 as described in the band gap of the semiconductor light emitting device 107 in FIG.

  On the other hand, the holes injected from the stripe-shaped electrode 19 are concentrated in each well layer of the active layer 14 of the semiconductor light emitting device 111 as described in the band diagram of the semiconductor light emitting device 101 of FIG.

  Therefore, the semiconductor light emitting device 111 emits light having a wavelength corresponding to the band gap expressed between the top level 21 of the valence band of the quantum well and the bottom level 22 of the conduction band.

  Further, the semiconductor light emitting device 111 is squeezed by the stripe-shaped electrode 19 because the distance in the stacking direction between the active layer 14 and the p-side band gap changing layer 16 is in a certain range, similar to the semiconductor light emitting device 101 of FIG. The injected holes are concentrated and reach the portion immediately below the stripe-shaped electrode 19 of the active layer 14 as shown by a hole flow 91 shown in FIG.

  On the other hand, the semiconductor light emitting device 111 has a constant distance in the stacking direction between the active layer 14 and the n-side band gap changing layer 76 as in the semiconductor light emitting device 107 of FIG. 7, and the electrons flow as shown in FIG. As in 97, the n-type second semiconductor layer 27 can smoothly move to the n-side first semiconductor layer 25, and the electrical resistance of the semiconductor light emitting device 111 can be lowered.

  Accordingly, the present invention provides a semiconductor light emitting device capable of smoothly moving carriers between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without deteriorating optical characteristics and reliability. Can do.

  That is, the semiconductor light emitting device 111 can obtain effects such as reduction of threshold current, improvement of slope efficiency of current versus light amount, and improvement of brightness, like the semiconductor light emitting device 101.

  Similarly to the semiconductor light emitting device 101 and the semiconductor light emitting device 107, the semiconductor light emitting device 111 has a p-side band gap when the stacking direction of each semiconductor layer is parallel to the C-axis direction of the group III nitride compound of each semiconductor layer. The effect of the change layer 16 and the n-side band gap change layer 76, that is, the effect of dispersion of the polarization charge becomes the largest.

  In the semiconductor light emitting device 111, the n-side band described in FIG. 9 as an alternative to the p-side band gap change layer 56 and / or the n-side band gap change layer 76 described in FIG. Even if the gap change layer 96 is disposed, the same effect can be obtained.

(Embodiment 7)
The embodiment further includes an electrode for applying a voltage from the outside to the side opposite to the band gap changing layer side of the second semiconductor layer, and the second semiconductor layer or the first semiconductor layer from the electrode. It may be mesa shape.

  FIG. 13 shows a conceptual diagram of a cross section of a semiconductor light emitting device 113 that is a semiconductor laser according to another embodiment of the first invention of the present application. The difference between the semiconductor light emitting device 113 and the semiconductor light emitting device 111 of FIG. 11 is that the mesa portion 8 is formed in a mesa shape from the stripe-shaped electrode 19 to a part of the thickness of the p-type first semiconductor layer 15. is there. In FIG. 13, the same reference numerals as those used in FIGS. 1, 3, 5, 7, 9, and 11 are the same semiconductor layers and have the same functions, but the semiconductor light emitting device 113 functions as a semiconductor laser. Therefore, the semiconductor layer to be stacked is more preferably a semiconductor described below.

The n-type underlayer 13 is preferably a GaN compound that is n-type with Si having a thickness of 1 μm or more as an impurity. It is exemplified that the impurity concentration is 3 × 10 ¹⁸ (cm ⁻³ ).

Since the n-type second semiconductor layer 27 functions as a cladding layer for supplying electrons to the active layer 14, m = 0.08, that is, Al _0.08 Ga _{0.92 in the} composition formula having a film thickness of 1000 (nm). It is an N compound, and the Si concentration of the impurity is desirably 3 × 10 ¹⁸ (cm ⁻³ ).

The n-side first semiconductor layer 25 reflects the light generated in the active layer 14 and functions as an optical guide layer that guides the light, and the non-doped GaN compound having a film thickness of 100 (nm) or the impurity Si concentration is 1 ×. A low-doped GaN compound of 10 ¹⁸ (cm ⁻³ ) or less is desirable.

In the n-side band gap changing layer 76, the composition adjacent to the n-side first semiconductor layer 25 is a GaN compound, and the composition adjacent to the n-type second semiconductor layer 27 is the Al _0.08 Ga _0.92 N compound. From the side adjacent to the n-side first semiconductor layer 25 toward the side adjacent to the n-type second semiconductor layer 27, the Al composition continuously changes monotonically from 0 to 0.08, and the Ga composition changes to x + y. It is desirable to continuously change monotonically from 1 to 0.92 while maintaining the relationship of = 1. The film thickness of the n-side band gap changing layer 76 is 10 (nm). Moreover, it is illustrated that Si concentration of the impurity added is in the range of 1.5 × 10 ¹⁸ (cm ⁻³ ) or more and 9 × 10 ¹⁸ (cm ⁻³ ) or less, and 3 × 10 ¹⁸ (cm ⁻³ ). It is preferable that

The active layer 14 is an MQW having a well layer disposed outside, and has an electron barrier layer at the end of the MQW on the p-type side with respect to the MQW. The well layer is p = 0.87 in the composition formula, that is, Ga _0.87 In _0.13 N compound, the barrier layer is q = 1 in the composition formula, that is, the GaN compound and the electron barrier layer are s in the composition formula. = 0.2, that is, an Al _0.2 Ga _0.8 N compound is desirable. The well layer preferably has a thickness of 3 nm, the barrier layer has a thickness of 10 nm, and the electron barrier layer has a thickness of 20 nm. Mg is added as an impurity to make the electron barrier layer p-type. The impurity concentration is, for example, in the range of 1 × 10 ¹⁹ (cm ⁻³ ) to 1 × 10 ²⁰ (cm ⁻³ ) and preferably 5 × 10 ¹⁹ (cm ⁻³ ).

The p-side first semiconductor layer 15 reflects the light generated in the active layer 14 and functions as an optical guide layer for guiding the non-doped GaN compound having a film thickness of 100 (nm) or the Mg concentration of impurities is 1 ×. A low-doped GaN compound of 10 ¹⁹ (cm ⁻³ ) or less is desirable.

Since the p-type second semiconductor layer 17 functions as a cladding layer that supplies holes to the active layer 14, m = 0.08, that is, Al _0.08 Ga _{0. It is a 92} N compound, and the Mg concentration of the impurity is desirably 3 × 10 ¹⁹ (cm ⁻³ ).

The p-side band gap changing layer 16 has a composition adjacent to the p-side first semiconductor layer 15 as a GaN compound, and a composition adjacent to the p-type second semiconductor layer 17 as an Al _0.08 Ga _0.92 N compound. From the side adjacent to the p-side first semiconductor layer 15 toward the side adjacent to the p-type second semiconductor layer 17, the Al composition continuously changes monotonically from 0 to 0.08 and the Ga composition x + y It is desirable to continuously change monotonically from 1 to 0.92 while maintaining the relationship of = 1. The film thickness of the p-side band gap changing layer 16 is 10 (nm). Moreover, it is illustrated that Mg concentration of the impurity to be added is in the range of 1.5 × 10 ¹⁸ (cm ⁻³ ) to 9 × 10 ¹⁸ (cm ⁻³ ), and 3 × 10 ¹⁸ (cm ⁻³ ). It is preferable that

  The p-type contact layer 18 is preferably a GaN compound having a thickness of 50 (nm) and using p-type Mg as an impurity.

  The semiconductor light emitting device 113 forms the mesa portion 8 after forming the semiconductor light emitting device 111 of FIG.

  By applying a voltage using the stripe-shaped electrode 19 as an anode and the electrode 31 as a cathode, electrons are injected from the electrode 11 and holes are injected from the stripe-shaped electrode 19 into the semiconductor light emitting device 113.

  As described in the semiconductor light emitting device 101 of FIG. 1, the p-side bandgap changing layer 16 facilitates hole transport between the p-type second semiconductor layer 17 and the p-type first semiconductor layer 15. The holes of the element 113 can move around the center of the mesa portion 8 having good crystallinity.

  Further, since the distance in the stacking direction between the active layer 14 and the p-side band gap changing layer 16 is in a certain range, the holes injected by being narrowed by the stripe-shaped electrode 19 and the mesa portion 8 are p-type second semiconductor. Diffusion in the layer 17, the p-side band gap changing layer 16 and the p-side first semiconductor layer 15 is reduced, and a hole flow 91 shown in FIG. 1 directly below the stripe-shaped electrode 19 of the active layer 14. Reach concentrated on the part.

  On the other hand, in the semiconductor light emitting device 113, the distance in the stacking direction between the active layer 14 and the n-side band gap changing layer 76 is in a certain range, as in the semiconductor light emitting device 107 in FIG. 7, and electrons flow as shown in FIG. As shown in 97, the n-type second semiconductor layer 27 can smoothly move to the n-side first semiconductor layer 25, and the electrical resistance of the semiconductor light emitting device 113 can be lowered.

  The holes and electrons concentrated in the active layer 14 are recombined to generate light having a wavelength represented by the band gap of the MQW well layer. The p-side first semiconductor layer 15 and the n-side first semiconductor layer 25 guide the light as a guide layer and promote stimulated emission.

  Therefore, according to the present invention, a semiconductor that can smoothly move between two semiconductor layers having different compositions without increasing the impurity concentration, that is, without causing deterioration of optical characteristics and reliability, and functions as a semiconductor laser. A light-emitting element can be provided.

  In the semiconductor light emitting device 113, the n-side described in FIG. 9 as an alternative to the p-side band gap changing layer 56 and / or the n-side band gap changing layer 76 described in FIG. Even if the band gap changing layer 96 is provided, the same effect can be obtained.

  Similar to the semiconductor light emitting device 113, the p-side first semiconductor layer 15 and the n-side first semiconductor layer 25 are designed to have a refractive index smaller than that of the active layer 14 in order to reflect light generated in the active layer 14. The p-type second semiconductor layer 17 and the n-type second semiconductor layer 27 serve as cladding layers for supplying carriers to the active layer 14. By having the function, the semiconductor light emitting element 101, the semiconductor light emitting element 103, the semiconductor light emitting element 105, the semiconductor light emitting element 107, the semiconductor light emitting element 109, and the semiconductor light emitting element 111 function as a semiconductor laser as a whole structure.

  The configuration of the semiconductor light emitting device of the present invention can be used as a light receiving device. Moreover, it can utilize also for electronic devices, such as a transistor and a diode, and a compound high frequency electronic device represented by HEMT.

It is a conceptual diagram of the section of semiconductor light emitting element 101 which is one embodiment concerning the 1st invention of this application. It is a conceptual diagram of the band diagram of the semiconductor light emitting element 101 which is one embodiment according to the first invention of the present application. It is a conceptual diagram of the cross section of the semiconductor light-emitting device 103 which is other embodiment which concerns on 1st invention of this application. It is a conceptual diagram of the band diagram of the semiconductor light emitting element 103 which is other embodiment which concerns on 1st invention of this application. It is a conceptual diagram of the cross section of the semiconductor light-emitting device 105 which is one embodiment which concerns on 2nd invention of this application. It is a conceptual diagram of the band diagram of the semiconductor light emitting element 105 which is one embodiment according to the second invention of the present application. It is a conceptual diagram of the cross section of the semiconductor light-emitting device 107 which is one embodiment which concerns on 3rd invention of this application. It is a conceptual diagram of the band diagram of the semiconductor light emitting element 107 which is one embodiment according to the third invention of the present application. It is a conceptual diagram of the cross section of the semiconductor light-emitting device 109 which is one embodiment which concerns on 4th invention of this application. It is a conceptual diagram of the band diagram of the semiconductor light emitting element 109 which is one embodiment according to the fourth invention of the present application. It is a conceptual diagram of the cross section of the semiconductor light-emitting device 111 which is other embodiment which concerns on 1st invention of this application. It is a conceptual diagram of the band diagram of the semiconductor light emitting element 111 which is other embodiment which concerns on 1st invention of this application. It is a conceptual diagram of the cross section of the semiconductor light-emitting device 113 which is other embodiment which concerns on 1st invention of this application. FIG. 6 is a conceptual diagram of a cross section of a conventional semiconductor light emitting device 140.

Explanation of symbols

101, 103, 105, 107, 109, 111, 113, 140 Semiconductor light emitting device 8 Mesa portion 11, 31 Electrode 12, 32 n-type substrate 13 n-type underlayer 14 active layer 15 p-side first semiconductor layer 16, 56 p Side band gap changing layer 76, 96 n side band gap changing layer 17 p-type second semiconductor layer 18 p-type contact layer 19 striped electrode 21 top level of valence band 22 bottom level of conduction band 25 n-side first Semiconductor layer 27 n-type second semiconductor layer 91 hole flow 97 electron flow 11a region of electrode 11 12a region of n-type substrate 12 13a region of n-type underlayer 13 14a region of active layer 14b region of well layer 14c Barrier layer region 14d electron barrier layer region 15a p-side first semiconductor layer 15 region 16a p-side band gap changing layer 16 region 17 p-type second semiconductor layer 17 region 18a p-type contact layer 18 region 19a stripe-shaped electrode 19 region 25a n-side first semiconductor layer 25 region 27a n-type second semiconductor layer 27 region 31a electrode 31 region 56a Region of the p-side band gap change layer 56a 76a Region of the n-side band gap change layer 76a Region of the n-side band gap change layer 96

Claims (10)

An active layer that generates light by recombination of electrons and holes;
Stacked on the p-type side with respect to the active layer, the composition formula is Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A first semiconductor layer of a Group III nitride compound,
The first semiconductor layer is laminated adjacent to the side opposite to the active layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and a band gap changing layer of a group III nitride compound whose composition continuously changes monotonously in the stacking direction;
The band gap change layer is stacked adjacent to the side opposite to the first semiconductor layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, A second semiconductor layer of a group III nitride compound represented by 0 ≦ x + y ≦ 1),
A semiconductor light emitting device comprising:
The distance in the stacking direction from the end of the active layer on the side of the p-type polarity to the active layer to the center of the width in the stacking direction of the band gap change layer is 30 (nm) or more and 200 (nm) or less. And
The band gap of the band gap changing layer is equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer from a band gap substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. A semiconductor light emitting element characterized by continuously monotonously changing to a band gap substantially equal to the band gap. An active layer that generates light by recombination of electrons and holes;
Stacked on the p-type side with respect to the active layer, the composition formula is Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A first semiconductor layer of a Group III nitride compound,
The first semiconductor layer is laminated adjacent to the side opposite to the active layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), a band gap changing layer of a group III nitride compound whose composition monotonously changes stepwise in the stacking direction;
The band gap change layer is stacked adjacent to the side opposite to the first semiconductor layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, A second semiconductor layer of a group III nitride compound represented by 0 ≦ x + y ≦ 1),
A semiconductor light emitting device comprising:
The distance in the stacking direction from the end of the active layer on the side of the p-type polarity to the active layer to the center of the width in the stacking direction of the band gap change layer is 30 (nm) or more and 200 (nm) or less. And
The band gap of the band gap changing layer is equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer from a band gap substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. A semiconductor light-emitting element that monotonously changes in a stepwise manner to a band gap substantially equal to the band gap. An electrode for applying a voltage from the outside to the side opposite to the band gap changing layer side of the second semiconductor layer;
The semiconductor light emitting element according to claim 1, wherein the semiconductor light emitting element has a mesa shape from the electrode to the second semiconductor layer or the first semiconductor layer. An active layer that generates light by recombination of electrons and holes;
Stacked on the n-type side with respect to the active layer, the composition formula is Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A first semiconductor layer of a Group III nitride compound,
The first semiconductor layer is laminated adjacent to the side opposite to the active layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and a band gap changing layer of a group III nitride compound whose composition continuously changes monotonously in the stacking direction;
The band gap change layer is stacked adjacent to the side opposite to the first semiconductor layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, A second semiconductor layer of a group III nitride compound represented by 0 ≦ x + y ≦ 1),
A semiconductor light emitting device comprising:
The distance in the stacking direction from the end of the active layer on the n-type side with respect to the active layer to the center of the width in the stacking direction of the band gap changing layer is 30 (nm) or more and 200 (nm) or less. And
The band gap of the band gap changing layer is equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer from a band gap substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. A semiconductor light emitting element characterized by continuously monotonously changing to a band gap substantially equal to the band gap. An active layer that generates light by recombination of electrons and holes;
Stacked on the n-type side with respect to the active layer, the composition formula is Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A first semiconductor layer of a Group III nitride compound,
The first semiconductor layer is laminated adjacent to the side opposite to the active layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), a band gap changing layer of a group III nitride compound whose composition monotonously changes stepwise in the stacking direction;
The band gap change layer is stacked adjacent to the side opposite to the first semiconductor layer side, and the composition formula Al _x Ga _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, A second semiconductor layer of a group III nitride compound represented by 0 ≦ x + y ≦ 1),
A semiconductor light emitting device comprising:
The distance in the stacking direction from the end of the active layer on the n-type side with respect to the active layer to the center of the width in the stacking direction of the band gap changing layer is 30 (nm) or more and 200 (nm) or less. And
The band gap of the band gap changing layer is equal to the band gap of the second semiconductor layer adjacent to the second semiconductor layer from a band gap substantially equal to the band gap of the first semiconductor layer adjacent to the first semiconductor layer. A semiconductor light-emitting element that monotonously changes in a stepwise manner to a band gap substantially equal to the band gap.   6. The semiconductor light emitting element according to claim 1, wherein a width of the band gap change layer in a stacking direction is 3 (nm) or more and less than 100 (nm).   7. The semiconductor light emitting element according to claim 1, wherein a band gap of the second semiconductor layer is wider than a band gap of the first semiconductor layer.   Stacking direction of the first semiconductor layer, the band gap changing layer, and the second semiconductor layer and a crystal of a group III nitride compound of the first semiconductor layer, a crystal of a group III nitride compound of the band gap changing layer 8. The semiconductor light emitting device according to claim 1, wherein the group III nitride compound crystal of the second semiconductor layer is parallel to the C-axis direction. 9. The first semiconductor layer has x = 0 and 0.95 ≦ y ≦ 1 in the composition formula, and functions as a light guide layer for guiding light generated in the active layer,
The second semiconductor layer has a relationship of x = m (0.05 ≦ m ≦ 0.1) and x + y = 1 in the composition formula, and functions as a clad layer for supplying carriers to the active layer,
And the band gap change layer is in the range of the relationship of 0 ≦ x ≦ m and x + y = 1 in the composition formula,
9. The semiconductor light emitting element according to claim 1, wherein the entire structure functions as a semiconductor laser. The charge density of polarization generated at an adjacent interface between the group III nitride compound of the first semiconductor layer and the group III nitride compound of the second semiconductor layer is ρ (cm ⁻² ), and the band gap change layer When the width in the stacking direction is expressed as d (cm), the impurity concentration n (cm ⁻³ ) of the impurity added to the band gap change layer is in the range of 0.5ρ / d ≦ n ≦ 3ρ / d. The semiconductor light-emitting device according to claim 1, wherein

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