JP2007110049A - Semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element with a small threshold current by preventing holes from spreading horizontally, in order to overcome such problems that, in the semiconductor layer of super lattice structure, the electrical resisivity of perpendicular direction is known as larger than that of horizontal direction, then the holes diffuse in the easily movable horizontal direction; and that, in the semiconductor light emitting element which makes a part of the cladding layer of the super lattice structure be a ridge structure, since the holes passed the ridge structure diffuse horizontally, hence the current density to an active layer falls off, and the threshold current of the semiconductor light emitting diode becomes large. <P>SOLUTION: To achieve the purpose, the semiconductor light emitting element adjoins the semiconductor layer of a bulk structure to the active layer side of the cladding layer of the super lattice structure, and in the perpendicular direction, forms it as the ridge structure from the cladding layer of the super lattice structure or cladding layer of the super lattice structure to a part of the semiconductor layer of the bulk structure. <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 basic structure of the semiconductor light emitting device is 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 clad layer that sandwiches the active layer from both sides and supplies carriers to the active layer. It is said.

  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 cladding 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 that controls the polarity of the carrier is added.

  Further, in the case of a semiconductor laser, a semiconductor layer having a light confinement function that promotes stimulated emission by reflecting light generated in the active layer is disposed between the cladding layer and the active layer. A structure of a semiconductor light emitting device including the cladding layer and the semiconductor layer having the optical confinement function may be referred to as a separate confinement hetero (SCH).

A group III nitride compound represented by a composition formula Al _m Ga _n In _1-mn N (0 ≦ m ≦ 1, 0 ≦ n ≦ 1, 0 ≦ m + n ≦ 1) (hereinafter, “composition formula Al _m “Group III nitride-based compound represented by Ga _n In _1-mn N (0 ≦ m ≦ 1, 0 ≦ n ≦ 1, 0 ≦ m + n ≦ 1)” is referred to as “Al _m Ga _n In _1-m-”. abbreviated as _{n n} compound ".) can adjust the band gap by changing the composition, it is possible to emit light of the desired wavelength, semiconductor light Al _{m Ga} n in _{1-m -n} N is often compound by laminating a SCH structure.

In recent years, in order to reduce the electrical resistance of a semiconductor light emitting device and lower the driving voltage, the cladding layer is made of a group III nitride compound represented by a composition formula Al _x Ga _1-x N (0 ≦ x ≦ 1). It has been reported that a superlattice structure of a thin film and a thin film of a group III nitride compound represented by GaN is effective (see, for example, Patent Document 1).

In order for the semiconductor light emitting device to emit light, a current density of about several kA / cm ² may be required for the active layer. In order to obtain the current density, the semiconductor light emitting device often squeezes the current with the positive electrode side of the active layer as a ridge structure.

Note that a description will be given assuming that the stacking direction of the semiconductor layers in the semiconductor light emitting element is a vertical direction and the direction perpendicular to the stacking direction of the semiconductor layers is a horizontal direction.
JP 2003-086898 A

  However, it is known that the electrical resistivity in the vertical direction is larger than the electrical resistivity in the horizontal direction in the semiconductor layer having the superlattice structure, and holes are diffused in the horizontal direction, which is easy to move. Therefore, in the semiconductor light emitting device having a ridge structure as a part of the superlattice structure, even if the current is narrowed by the ridge structure, the holes that have passed through the ridge structure are diffused in the horizontal direction, and the active layer As a result, there is a problem that the current density of the semiconductor light-emitting element decreases and the threshold current of the semiconductor light-emitting element increases.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a semiconductor light emitting device having a small threshold current by preventing holes from diffusing in the horizontal direction.

  In order to achieve the above object, a semiconductor light emitting device according to the present invention includes a superlattice structure cladding layer in a vertical direction, with a bulk structure semiconductor layer adjacent to the active layer side of the superlattice structure cladding layer. Alternatively, a ridge structure is formed from the cladding layer having the superlattice structure to a part of the semiconductor layer having the bulk structure.

Specifically, according to the present invention, an active layer in which electrons and holes are recombined to generate light, and a layer having a polarity of p-type with respect to the active layer are stacked, and the composition formula is Al _x Ga _{1. A} first semiconductor layer of a group III nitride compound represented by _−xN (0 ≦ x ≦ 1) and a layer adjacent to the side of the first semiconductor layer opposite to the side of the active layer. A group III nitride compound thin film whose composition formula is expressed as GaN in the direction and a group III nitride compound thin film whose composition formula is expressed as Al _y Ga _1-y N (0 <y ≦ 1). And a second semiconductor layer having a superlattice structure alternately arranged, wherein the second semiconductor layer or the second semiconductor layer to a part of the first semiconductor layer in a stacking direction is a ridge structure. It is a semiconductor light emitting element characterized by being.

  The difference between the electrical resistivity in the vertical direction and the horizontal direction of the semiconductor layer having the bulk structure is smaller than the difference between the electrical resistivity in the vertical direction and the horizontal direction of the semiconductor layer having the superlattice structure. The first semiconductor layer adjacent to the second semiconductor layer of the semiconductor light emitting device has a bulk structure, and holes that have passed through the ridge structure can easily move in the vertical direction also in the first semiconductor layer. It reaches the active layer without diffusing in the direction, and the current density to the active layer increases.

  Therefore, the present invention can prevent the holes after passing through the ridge structure from diffusing in the horizontal direction and provide a semiconductor light emitting device having a small threshold current.

  The semiconductor light emitting device according to the present invention is stacked between the active layer and the first semiconductor layer and adjacent to the p-type side of the active layer, and electrons from the active layer are transferred to the first semiconductor layer. An electron barrier layer for preventing diffusion; and between the electron barrier layer and the first semiconductor layer, on the first semiconductor layer side of the electron barrier layer and on the electron barrier layer side of the first semiconductor layer And a third semiconductor layer that is laminated adjacently and that guides light generated in the active layer.

  The third semiconductor layer guides light generated in the active layer and promotes stimulated emission in the active layer. The electron barrier layer prevents electrons that have obtained thermal energy from light emission of the active layer from moving to the p-type semiconductor layer and recombining with holes in the p-type semiconductor layer to lower the light emission efficiency. .

  Therefore, the present invention can prevent a hole from diffusing in the horizontal direction, and can provide a semiconductor light emitting device having a small threshold current and a high luminous efficiency.

In the semiconductor light emitting device according to the present invention, the Al content of the first semiconductor layer is increased from the active layer side of the first semiconductor layer toward the second semiconductor layer side. Of the group III nitride compound represented by the composition formula Al _y Ga _1-y N (0 <y ≦ 1) in the second semiconductor layer from a value equal to or higher than the Al content of the semiconductor layer adjacent to the layer side It is preferable to monotonously increase to a value below the Al content of the thin film.

  The third semiconductor layer adjacent to the active layer side of the first semiconductor layer by monotonically increasing the Al content of the first semiconductor layer from the active layer side to the second semiconductor layer side by a value in the range. A crystal formed at the interface between the semiconductor layer such as the third semiconductor layer and the first semiconductor layer in order to approximate the crystal lattice of the semiconductor layer such as the semiconductor layer and the crystal lattice on the active layer side of the first semiconductor layer. Defects can be reduced. Furthermore, the generation of a piezo electric field due to the lattice constant difference at the interface can also be suppressed.

  Similarly, crystal defects can be reduced at the interface between the second semiconductor layer and the first semiconductor layer, and generation of a piezoelectric field can be suppressed.

  Therefore, according to the present invention, since the reduction of crystal defects and the suppression of the piezo electric field can reduce the electric resistance, the driving voltage can be reduced, the holes are prevented from diffusing in the horizontal direction, and the semiconductor having a small threshold current is obtained. A light-emitting element can be provided.

  In the semiconductor light emitting device according to the present invention, it is preferable that the average content of Al in the first semiconductor layer and the average content of Al in the second semiconductor layer are substantially equal.

  By setting the average Al content of the first semiconductor layer and the average Al content of the second semiconductor layer to the same value, the average band gap of the first semiconductor layer and the second semiconductor layer Since the average band gap is comparable, holes can easily move from the second semiconductor layer to the first semiconductor layer.

  Therefore, since the electrical resistance can be reduced, the present invention can reduce the driving voltage, prevent the holes from diffusing in the horizontal direction, and provide a semiconductor light emitting device having a small threshold current.

  In the semiconductor light emitting device according to the present invention, the thickness of the second semiconductor layer in the stacking direction is preferably larger than the thickness of the first semiconductor layer in the stacking direction.

  The thickness of the second semiconductor layer in the superlattice structure in the stacking direction (hereinafter, “thickness in the stacking direction of the semiconductor layer” is abbreviated as “film thickness of the semiconductor layer”). By making it thicker, the electrical resistance of the semiconductor light emitting element can be reduced.

  Therefore, the present invention can reduce the driving voltage, prevent holes from diffusing in the horizontal direction, and provide a semiconductor light emitting device having a small threshold current.

  According to the present invention, it is possible to provide a semiconductor light emitting device having a small threshold current by preventing holes from diffusing in the horizontal direction.

  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 in which electrons and holes are recombined to generate light, and the active layer is stacked on the p-type side, and the composition formula is Al _x Ga _1-x N ( The first semiconductor layer of a group III nitride compound represented by 0 ≦ x ≦ 1) is laminated adjacent to the side of the first semiconductor layer opposite to the active layer side, and the composition formula is Group III nitride-based compound thin film represented by GaN and Group III nitride-based compound thin film represented by the compositional formula Al _y Ga _1-y N (0 <y ≦ 1) are alternately arranged. A second semiconductor layer having a superlattice structure, wherein the second semiconductor layer or the second semiconductor layer to a part of the first semiconductor layer in the stacking direction has a ridge structure. The semiconductor light emitting device is characterized.

  FIG. 1 shows a conceptual diagram of a cross section of a semiconductor light emitting device 101 according to an embodiment of the present invention. The semiconductor light emitting device 101 includes an electrode 11, a substrate 12, an n-type underlayer 13, an n-type fourth semiconductor layer 27, an active layer 14, a p-type first semiconductor layer 15, a p-type second semiconductor layer 17, and a p-type contact layer 18. The electrode 19 and the insulating film 20 are provided.

  In the semiconductor light emitting device 101, each semiconductor layer is stacked on the substrate 12, and the semiconductor layer on the electrode 19 side with respect to the active layer 14, that is, the p-type first semiconductor layer 15, the p-type second semiconductor layer 17 and the p-type semiconductor layer. The type contact layer 18 is p-type.

  On the other hand, the semiconductor layer on the substrate 12 side with respect to the active layer 14, that is, the n-type fourth semiconductor layer 27 and the n-type underlayer 13 are n-type. The semiconductor light emitting device 101 is a surface electrode type semiconductor light emitting device in which a positive electrode and a negative electrode are in the same direction with respect to a substrate.

  The electrode 11 and the electrode 19 are arranged for applying a voltage to the semiconductor light emitting device 101. Since the efficiency as a semiconductor light-emitting element is impaired if rectification occurs when the electrode and the semiconductor are in contact with each other, it is desirable that the electrode 11 and the electrode 19 are materials 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 electrode 19 in contact with the p-type semiconductor include Ni / Au, Pd / Au, Pt / Au, and Pd / Pt / Au.

The 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, sapphire is exemplified when an Al _m Ga _n In _1-mn N compound is laminated.

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. For example, by using an Al _m Ga _n In _1-mn N compound, a wide band gap can be created by changing the composition, and a semiconductor light emitting device having a desired wavelength can be manufactured.

  Further, the active layer 14 is formed by alternately arranging at least two kinds 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 smaller 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.

  MQW is a group III nitride compound of m = 0 and n = d (0.95 ≦ d ≦ 1, preferably 0.97 ≦ d ≦ 1) in the composition formula as a barrier layer and the composition formula as a quantum well. And a group III nitride compound of m = 0, n = e (e <d and 0.80 ≦ e ≦ 0.95, preferably e <d and 0.85 ≦ e ≦ 0.9) Illustrated. Further, the MQW barrier layer is exemplified by a thickness of 5 nm to 20 nm, and the MQW well layer is exemplified by a thickness of 1 nm to 10 nm. It is exemplified that the number of pairs of the barrier layer and the well layer constituting the MQW is 2 or more and 3 or less.

The n-type fourth semiconductor layer 27 is a semiconductor layer made of an Al _m Ga _n In _1-mn N compound. The n-type fourth semiconductor layer 27 is a group III nitride system in which m = a (0.01 ≦ a ≦ 0.15, preferably 0.05 ≦ a ≦ 0.1) and m + n = 1 in the composition formula. Examples are compounds. The film thickness of the n-type fourth semiconductor layer 27 is 300 nm or more and 2000 nm or less, preferably 400 nm or more and 1200 nm or less.

The n-type fourth semiconductor layer 27 is added with an n-type impurity such as Si or O in order to increase the carrier density. The impurity concentration is 5 × 10 ¹⁷ cm ⁻³ or more and 1 × 10 ¹⁹ cm ⁻³ or less, preferably 3 × 10 ¹⁸ cm ⁻³ .

The p-type second semiconductor layer 17 is represented by a group III nitride compound thin film whose composition formula is GaN in the stacking direction and a composition formula of Al _y Ga _1-y N (0 <y ≦ 1). It has a superlattice structure in which Group III nitride compound thin films are alternately arranged. The film thickness of the p-type second semiconductor layer 17 is from 100 nm to 2000 nm, preferably from 200 nm to 500 nm, from the viewpoint of electrical resistance and hole supply. Further, the average content of Al in the p-type second semiconductor layer 17 is 4% or more and 10% or less, preferably 6% or more and 8% or less.

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 average p-type impurity concentration of the p-type second semiconductor layer 17 is 5 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ²⁰ cm ⁻³ or less, preferably 3 × 10 ¹⁹ cm ⁻³ .

The p-type first semiconductor layer 15 is a group III nitride compound semiconductor layer whose composition formula is expressed as Al _x Ga _1-x N (0 ≦ x ≦ 1). Since the p-type first semiconductor layer 15 has higher electrical resistance than the p-type second semiconductor layer 17, the thickness of the p-type first semiconductor layer 15 is preferably smaller than the thickness of the p-type second semiconductor layer 17. For example, the thickness of the p-type first semiconductor layer 15 is exemplified by a value that is ¼ of the thickness of the p-type second semiconductor layer 17. In order to reduce the electrical resistance, the thickness of the p-type first semiconductor layer 15 is preferably 50 nm or more and 100 nm or less.

  Moreover, the average content of Al in the p-type first semiconductor layer 15 is 4% or more and 10% or less, preferably 6% or more and 8% or less. The average Al content of the p-type first semiconductor layer 15 is preferably substantially equal to the average Al content of the p-type second semiconductor layer 17.

  The p-type contact layer 18 is a semiconductor layer for making ohmic contact with the 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 insulating film 20 electrically separates the electrode and each semiconductor layer. For example, ZrO ₂ or SiO ₂ can be exemplified.

  The semiconductor light emitting device 101 is formed as described below.

(Semiconductor layer lamination process)
On the substrate 12, an n-type underlayer 13, an n-type fourth semiconductor layer 27, an active layer 14, a p-type first semiconductor layer 15, a p-type second semiconductor layer 17, and a p-type contact layer 18 are sequentially stacked.

  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.

The n-type underlayer 13, the n-type fourth semiconductor layer 27, the active layer 14, the p-type first semiconductor layer 15, the p-type second semiconductor layer 17, and the p-type contact layer 18 are made of Al _m Ga _n In _1-mn. In the case of an N compound, the MOCVD method uses Ga (CH ₃ ) ₃ (trimethylgallium, hereinafter abbreviated as “TMG”), In (C ₂ H ₅ ) ₃ (triethylindium, hereinafter abbreviated as “TMI”) as a group III element. And a vapor obtained by bubbling Al (CH ₃ ) ₃ (trimethylaluminum, hereinafter abbreviated as “TMA”) with hydrogen or nitrogen as a carrier gas as a source gas and ammonia to form a nitride. Use gas. The source gas is introduced into the chamber by hydrogen or nitrogen carrier gas.

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 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 manufacturing parameter of a substrate temperature and an Al _m Ga _n In _{1- mn} having a desired composition. N compounds can be grown, and the film thickness can be controlled by reaction time. Therefore, the n-type underlayer 13, the n-type fourth semiconductor layer 27, the active layer 14, the p-type first semiconductor layer 15, the p-type second semiconductor layer 17 and the p-type contact layer 18 are formed on the substrate 12 by MOCVD. It can be laminated continuously.

(Ridge structure etching process)
Next, a semiconductor layer having a ridge structure is formed as follows. First, an etching mask layer is stacked on the upper surface of the p-type contact layer 18. The etching mask layer is SiO ₂ layer is formed by heating and solidified or UV cured after the SiO ₂ layer and spin coating formed by sputtering can be exemplified. After the etching mask layer is formed, a resist pattern is formed on the upper surface of the etching mask layer by a lithography technique on a portion where a ridge structure is to be formed. After the resist pattern is formed, the etching mask layer is etched using the formed resist pattern as a mask. Thereafter, the resist pattern on the etching mask layer that has not been etched is removed to form an etching mask pattern.

  Next, the p-type contact layer 18, the p-type second semiconductor layer 17, and a part of the p-type first semiconductor layer 15 are etched using the etching mask pattern as a mask. Examples of the etching include dry etching using Cl-based plasma. In this step, as shown in FIG. 1, a part of the p-type contact layer 18, the p-type second semiconductor layer 17, and the p-type first semiconductor layer 15 has a ridge structure. The p-type first semiconductor layer 15 may not be etched, and the p-type contact layer 18 and the p-type second semiconductor layer 17 may have a ridge structure.

(Insulating film formation process)
An insulating film 20 is formed to cover the etching mask pattern, the p-type first semiconductor layer 15 exposed in the ridge structure etching process, and the side surface of the ridge structure. Examples of the means for forming the insulating film 20 include sputtering.

(Etching mask pattern removal process)
After the insulating film forming step, the etching mask pattern on the p-type contact layer 18 is removed. As a means for removing the etching mask pattern, it is possible to exemplify wet etching by immersing in buffered hydrofluoric acid which is a 1-hydrogen 2-ammonium fluoride solution for a predetermined time. By removing the etching mask pattern, the insulating film 20 laminated on the etching mask pattern is also lifted off, and the p-type contact layer 18 is exposed.

(Electrode 19 formation process)
After the etching mask pattern removing step, an electrode 19 is formed to cover the entire surface of the exposed p-type contact layer 18 and the insulating film 20 that has not been lifted off. Examples of means for forming the electrode 19 include sputtering and vacuum deposition.

(Electrode 11 formation process)
After forming the electrode 19, a resist pattern is formed again to cover the upper layer of the positive electrode part P using lithography technology to form the negative electrode part M where the electrode 11 is to be formed, and the electrode of the negative electrode part M is formed by dry etching. 19. The semiconductor layer from the insulating film 20 and the p-type semiconductor layer 15 to a part of the n-type underlayer 13 is removed. An electrode 11 is formed on the upper surface of the n-type underlayer 13 exposed by the dry etching. Examples of means for forming the electrode 11 include sputtering and vacuum deposition.

  The semiconductor light emitting device 101 is obtained through the semiconductor layer stacking step to the electrode 11 forming step.

FIG. 2 shows an example of the transition of the Al content 201 in each semiconductor layer from the active layer 14 to the p-type contact layer 18 of the semiconductor light emitting device 101. In FIG. 2, the vertical axis indicates the Al content. In FIG. 2, 14a on the horizontal axis is a region of the active layer 14, 15a is a region of the p-type first semiconductor layer 15, 17a is a region of the p-type second semiconductor layer 17, 18a is a region of the p-type contact layer 18, and 17c is In the p-type second semiconductor layer 17, the Al _y Ga _1-y N compound layer region and 17 b indicate the GaN compound region in the p-type second semiconductor layer 17. In the example of FIG. 2, the Al content of the p-type first semiconductor layer 15 is 6%, and the Al content of the Al _y Ga _1-y N compound in the p-type second semiconductor layer 17 is 10%. . The Al content of the p-type contact layer 18 is 0%.

  It is exemplified that the average Al content of the p-type first semiconductor layer 15 and the average Al content of the p-type second semiconductor layer 17 are substantially equal. For example, when the Al content of the p-type first semiconductor layer 15 is 6%, the average Al content of the p-type second semiconductor layer is in the range of 5% to 7%. Means.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 101 is shown in FIG. 3, the same reference numerals as those used in FIG. 2 denote the same semiconductor layer region. In FIG. 3, 11 a indicates a region of the electrode 11, 13 a indicates a region of the n-type underlayer 13, 27 a indicates a region of the n-type fourth semiconductor layer 27, and 19 a indicates a region of the electrode 19. 301 is the top level of the valence band, and 302 is the bottom level of the conduction band. The active layer 14 of the semiconductor light emitting device 101 has an MQW structure. In the region 14a of the active layer 14, 14b represents a well layer region, and 14c represents a barrier layer region. In FIG. 3, a part of the band gap from the electrode 11 to the n-type underlayer 13 and from the p-type contact layer 18 to the electrode 19 is omitted.

  By applying a voltage with the 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 electrode 19 into the semiconductor light emitting device 101. The injected electrons sequentially move through the n-type underlayer 13 and the n-type fourth semiconductor layer 27 and enter the active layer 14, and the injected holes are the p-type contact layer 18, the p-type second semiconductor layer 17, and the p-type. The first semiconductor layer 15 is sequentially moved and implanted into the active layer 14.

  Although the p-type second semiconductor layer 17 has a superlattice structure, holes do not diffuse because of the ridge structure. Furthermore, since the p-type first semiconductor layer 15 has a bulk structure, the holes are difficult to diffuse in the horizontal direction and are concentrated in the active layer 14 under the ridge structure.

  The active layer 14 is expressed between the top level 301 of the valence band of the quantum well and the bottom level 302 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.

  Therefore, the present invention adopts a superlattice structure, prevents the holes after passing through the ridge structure from diffusing in the horizontal direction, increases the current density to the active layer, and has a low resistance and a small threshold current. A semiconductor light emitting device can be provided.

(Embodiment 2)
The semiconductor light emitting device according to this embodiment is stacked between the active layer and the first semiconductor layer and adjacent to the p-type side of the active layer, and electrons from the active layer are accumulated in the first semiconductor layer. An electron barrier layer that prevents diffusion to the surface, and between the electron barrier layer and the first semiconductor layer, the electron barrier layer side of the electron barrier layer and the electron barrier layer side of the first semiconductor layer And a third semiconductor layer that is laminated adjacent to and guides light generated in the active layer.

  FIG. 4 shows a conceptual diagram of a cross section of a semiconductor light emitting device 102 according to another embodiment of the present invention. 4, the same reference numerals as those used in FIG. 1 are the same semiconductor layers and have the same functions. The difference between the semiconductor light emitting device 102 and the semiconductor light emitting device 101 of FIG. 1 is that the semiconductor light emitting device 102 includes a p type third semiconductor layer 23 between the p type first semiconductor layer 15 and the active layer 14 of the semiconductor light emitting device 101. And an n-side fifth semiconductor layer 25 between the electron barrier layer 24 and the active layer 14 and the n-type fourth semiconductor layer 27.

In a semiconductor light emitting device, electrons receiving thermal energy due to heat generated by light emission move to the p-type semiconductor layer beyond the barrier of the quantum well and become ineffective carriers that do not participate in light emission. This causes a phenomenon of carrier overflow that lowers. The electron barrier layer 24 is an Al _m Ga _n In _1-mn N compound that prevents carrier overflow. Since the electron barrier layer 24 has a wide band gap and a high bottom level of the conduction band, even electrons having obtained the thermal energy can pass through the electron barrier layer 24 and move to the p-type semiconductor layer. Can not.

For example, the electron barrier layer 24 may be a p-type group III nitride compound whose composition formula is expressed as Al _1-s Ga _s N (0 ≦ s ≦ 1). The Al content of the electronic barrier 24 is 10% or more and 30% or less, preferably 15% or more and 25% or less.

  The film thickness of the electron barrier layer 24 is 10 nm or more and 30 nm or less, preferably 15 nm or more and 25 nm or less.

The p-side third semiconductor layer 23 is a semiconductor layer made of an Al _m Ga _n In _1-mn N compound. Impurities are designed to be lower in the p-side third semiconductor layer 23 than in the p-type second semiconductor layer 17 and the p-type first semiconductor layer 15 so that the impurities do not diffuse into the active layer 14. . Further, the band gap of the p-side third semiconductor layer 23 is designed wider than that of the active layer 14. When the active layer 14 is the MQW, the band gap of the p-side third semiconductor layer 23 is wider than the band gap of the barrier layer constituting the MQW and narrower than the band gap of the p-type first semiconductor layer 15.

  Specifically, the composition of the p-side third semiconductor layer 23 is exemplified by m = 0 and n = 1 in the composition formula, that is, a GaN compound. In the composition formula, m = 0 and 0.95 ≦ n ≦ 1, that is, a GaInN compound may be used.

  Further, the film thickness of the p-side third semiconductor layer 23 is 20 nm to 200 nm, preferably 50 nm to 150 nm.

The n-side fifth semiconductor layer 25 is a semiconductor layer of an Al _m Ga _n In _1-mn N compound. The impurity of the n-side fifth semiconductor layer 25 is designed to be lower than the concentration of the impurity added to the n-type fourth semiconductor layer 27 so that the impurity does not diffuse into the active layer 14. The band gap of the n-side fifth semiconductor layer 25 is designed in the range described for the p-side third semiconductor layer 23.

  The range of the composition and film thickness of the n-side fifth semiconductor layer 25 is the same as the range of the composition and film thickness of the p-side third semiconductor layer 23.

  The semiconductor light emitting device 102 includes an n-type underlayer 13, an n-type fourth semiconductor layer 27, an n-side fifth semiconductor layer 25, an active layer 14, an electron barrier layer 24, a p-side third semiconductor layer 23, and a p-type on the substrate 12. The first semiconductor layer 15, the p-type second semiconductor layer 17, and the p-type contact layer 18 are stacked in this order.

  The semiconductor light emitting device 102 can be manufactured as described in the semiconductor light emitting device 101 of FIG.

  FIG. 5 shows an example of the transition of the Al content 201 in each semiconductor layer from the active layer 14 to the p-type contact layer 18 of the semiconductor light emitting device 102. In FIG. 5, the vertical axis and the horizontal axis indicate the same as those in FIG. 2, and the same reference numerals as those used in FIG. 2 indicate the same semiconductor layer region. In FIG. 5, reference numeral 23 a denotes a region of the p-side third semiconductor layer 23, and 24 a denotes a region of the electron barrier layer 24. In the example of FIG. 5, the Al content of the p-side third semiconductor layer 23 is 0%, and the Al content of the electron barrier layer 24 is 20%.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 102 is shown in FIG. 6, the same reference numerals as those used in FIGS. 2, 3, and 5 indicate the same semiconductor layer region.

  By applying a voltage with the 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 electrode 19 into the semiconductor light emitting device 102. The injected electrons move sequentially through the n-type underlayer 13, the n-type fourth semiconductor layer 27, and the n-side fifth semiconductor layer 25 to enter the active layer 14, and the injected holes are the p-type contact layer 18, p-type. The second semiconductor layer 17, the p-type first semiconductor layer 15, the p-side third semiconductor layer 23, and the electron barrier layer 24 are sequentially moved and injected into the active layer 14.

  Since the p-type first semiconductor layer 15 is also present in the semiconductor light emitting device 102, the holes are concentrated in the active layer 14 under the ridge structure as in the semiconductor light emitting device 101 described with reference to FIGS.

  The semiconductor light emitting device 102 emits light having a wavelength corresponding to the band gap of each quantum well of the active layer 14 in the same manner as the semiconductor light emitting device 101 described with reference to FIGS.

  Furthermore, the p-side third semiconductor layer 23 and the n-side fifth semiconductor layer 25 of the semiconductor light emitting device 102 guide the light generated in the active layer 14 and promote stimulated emission in the active layer 14. It functions as a semiconductor laser as a whole. In addition, since the semiconductor light emitting element 102 includes the electron barrier layer 24, it is possible to prevent electron carrier overflow and to increase the light emission efficiency.

  Therefore, the present invention adopts a superlattice structure, prevents the holes after passing through the ridge structure from diffusing in the horizontal direction, increases the current density to the active layer, and has a low resistance and a small threshold current. A semiconductor light emitting device can be provided.

(Embodiment 3)
In the semiconductor light emitting device according to the present embodiment, the Al content of the first semiconductor layer is increased from the active layer side of the first semiconductor layer toward the second semiconductor layer side. Group III nitride compound represented by the composition formula Al _y Ga _1-y N (0 <y ≦ 1) in the second semiconductor layer from a value equal to or higher than the Al content of the semiconductor layer adjacent to the active layer side It is preferable to monotonously increase to a value equal to or less than the Al content of the thin film.

  FIG. 7 shows a conceptual diagram of a cross section of a semiconductor light emitting device 103 according to another embodiment of the present invention. 7, the same reference numerals as those used in FIGS. 1 and 4 are the same semiconductor layers and have the same functions. The difference between the semiconductor light emitting device 103 and the semiconductor light emitting device 102 of FIG. 4 is that the semiconductor light emitting device 103 does not include the p-type first semiconductor layer 15 of the semiconductor light emitting device 102 of FIG. It is that.

The p-type first semiconductor layer 75 is a group III nitride compound similar to the p-type first semiconductor layer 15 of FIG. 1, but the Al content is p-type second from the p-side third semiconductor layer 23 side. Towards the semiconductor layer 17 side, monotonically from a value greater than or equal to the Al content of the p-side third semiconductor layer 23 to a value less than or equal to the Al content of the Al _y Ga _1-y N compound in the p-type second semiconductor layer 17 It has increased.

  FIG. 8 shows an example of the transition of the Al content from the active layer 14 to the p-type contact layer 18 of the semiconductor light emitting device 103. In FIG. 8, the same reference numerals as those used in FIGS. 2 and 5 indicate the same semiconductor layer region. Reference numeral 75 a denotes a region of the p-type first semiconductor layer 75. In FIG. 8, the Al content of the p-type first semiconductor layer 75 monotonously increases from 2% to 8% from the p-side third semiconductor layer 23 side to the p-type second semiconductor layer 17 side.

  A conceptual diagram of a band diagram of the semiconductor light emitting device 103 is shown in FIG. 9, the same reference numerals as those used in FIGS. 2, 3, 5, 6, and 8 indicate the same semiconductor layer region. The difference between the band diagram of the semiconductor light emitting device 103 in FIG. 9 and the band diagram of the semiconductor light emitting device 102 in FIG. 6 is that a region 75a is provided as an alternative to the region 15a in FIG. Since the Al content of the p-type first semiconductor layer 75 changes, the band gap also changes in accordance with the Al content in the region 75a.

  In the semiconductor light emitting device 103, the carriers move to the active layer 14 and emit light as in the semiconductor light emitting device 102 described with reference to FIGS. The semiconductor light emitting device 103 functions as a semiconductor laser as a whole in the same manner as the semiconductor light emitting device 102 described with reference to FIGS.

  Therefore, the present invention adopts a superlattice structure, prevents the holes after passing through the ridge structure from diffusing in the horizontal direction, increases the current density to the active layer, and has a low resistance and a small threshold current. A semiconductor light emitting device can be provided.

  Furthermore, since the semiconductor light emitting device 103 includes the p-type first semiconductor layer 75, the interface between the p-type first semiconductor layer 75 and the p-type second semiconductor layer 17 and the p-side third semiconductor layer 23 and the p-type first semiconductor layer 75 are provided. The generation of crystal defects and piezoelectric fields generated at the interface with the two semiconductor layers 17 can be reduced, and the drive voltage can be lowered.

  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.

1 is a conceptual diagram of a configuration of a semiconductor light emitting device 101 according to an embodiment of the present invention. 5 is a diagram showing an example of the transition of the Al content in each semiconductor layer of the semiconductor light emitting device 101. FIG. 2 is a conceptual diagram of a band diagram of a semiconductor light emitting device 101. FIG. It is a composition conceptual diagram of semiconductor light emitting element 102 which is other embodiments concerning the present invention. 6 is a diagram showing an example of the transition of the Al content in each semiconductor layer of the semiconductor light emitting device 102. FIG. 3 is a conceptual diagram of a band diagram of a semiconductor light emitting device 102. FIG. It is a composition conceptual diagram of semiconductor light emitting element 103 which is other embodiments concerning the present invention. 6 is a diagram showing an example of the transition of the Al content in each semiconductor layer of the semiconductor light emitting device 103. FIG. 3 is a conceptual diagram of a band diagram of a semiconductor light emitting device 103. FIG.

Explanation of symbols

101, 102, 103 Semiconductor light emitting element 11, 19 Electrode 12 Substrate
13 n-type underlayer 14 active layer 15, 75 p-type first semiconductor layer 17 p-type second semiconductor layer 18 p-type contact layer 20 insulating film 23 p-side third semiconductor layer 24 electronic barrier layer 25 n-side fifth semiconductor layer 27 n-type fourth semiconductor layer 11a electrode 13 region 13a n-type underlayer 13 region 14a active layer 14 region 14b active layer 14 well layer region 14c active layer 14 barrier layer region 15a p-type first semiconductor Region 17a of layer 15 Region 17b of p-type second semiconductor layer 17 Region of GaN compound 17c of p-type second semiconductor layer 17 Layer of Al _y Ga _1-y N compound of p-type second semiconductor layer 17 Region 18a region 19a of p-type contact layer 18 region 23a of electrode 19 region 24a of p-side third semiconductor layer 23 region 25a of electron barrier layer 27a region of n-side fifth semiconductor layer 27a n-type fourth semiconductor layer Bottom level M cathode portion P anode portion of the top level 302 the conduction band of the content rate transition 301 valence band region 75a p-type region 201 of the first semiconductor layer 75 Al

Claims (5)

An active layer in which electrons and holes recombine to generate light;
A first semiconductor layer of a group III nitride-based compound that is laminated on the p-type side with respect to the active layer and whose composition formula is represented by Al _x Ga _1-x N (0 ≦ x ≦ 1);
A thin film of a group III nitride compound having a composition formula of GaN in the stacking direction and a composition formula of Al _y Ga ₁₋ is laminated adjacent to the opposite side of the first semiconductor layer to the active layer side. _a second semiconductor layer having a superlattice structure in which thin films of a group III nitride compound represented by _y N (0 <y ≦ 1) are alternately arranged;
A semiconductor light emitting device comprising:
A semiconductor light emitting element characterized in that the second semiconductor layer or the second semiconductor layer to a part of the first semiconductor layer in the stacking direction has a ridge structure. An electron barrier layer between the active layer and the first semiconductor layer, stacked adjacent to the p-type side of the active layer, and preventing diffusion of electrons from the active layer into the first semiconductor layer When,
Between the electron barrier layer and the first semiconductor layer, stacked adjacent to the first semiconductor layer side of the electron barrier layer and the electron barrier layer side of the first semiconductor layer, and generated in the active layer A third semiconductor layer for guiding the transmitted light;
The semiconductor light emitting device according to claim 1, further comprising: The Al content of the first semiconductor layer is such that the Al of the semiconductor layer adjacent to the active layer side of the first semiconductor layer from the active layer side of the first semiconductor layer toward the second semiconductor layer side. A value equal to or lower than the Al content of the Group III nitride compound thin film represented by the composition formula Al _y Ga _1-y N (0 <y ≦ 1) in the second semiconductor layer The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device monotonously increases.   4. The semiconductor light emitting element according to claim 1, wherein an average Al content of the first semiconductor layer and an average Al content of the second semiconductor layer are substantially equal. 5. 5. The semiconductor light emitting element according to claim 1, wherein a thickness of the second semiconductor layer in the stacking direction is larger than a thickness of the first semiconductor layer in the stacking direction.

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