WO2023163230A1 - Diode laser - Google Patents

Diode laser Download PDF

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Publication number
WO2023163230A1
WO2023163230A1 PCT/JP2023/007424 JP2023007424W WO2023163230A1 WO 2023163230 A1 WO2023163230 A1 WO 2023163230A1 JP 2023007424 W JP2023007424 W JP 2023007424W WO 2023163230 A1 WO2023163230 A1 WO 2023163230A1
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layer
laser diode
conductivity
conductivity type
film thickness
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PCT/JP2023/007424
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English (en)
Japanese (ja)
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陽 吉川
梓懿 張
真希 久志本
千秋 笹岡
浩 天野
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旭化成株式会社
国立大学法人東海国立大学機構
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Publication of WO2023163230A1 publication Critical patent/WO2023163230A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser

Definitions

  • This disclosure relates to laser diodes.
  • nitride semiconductors have been used as materials for forming light emitting diodes (LEDs) and laser diodes (LDs). Since nitride semiconductors have a recombination mode of direct transition, they are suitable as materials for LEDs and LDs in that high recombination efficiency and high optical gain can be obtained.
  • a technique for oscillating a current injection type laser diode in the ultraviolet region has been disclosed (for example, Non-Patent Document 1).
  • An object of the present disclosure is to provide a laser diode with reduced lasing threshold current.
  • a laser diode includes a nitride semiconductor substrate containing Al, and a semiconductor lamination portion arranged on the nitride semiconductor substrate, wherein the semiconductor lamination portion is a first conductivity type clad layer disposed on a nitride semiconductor substrate and including a first conductivity type nitride semiconductor layer; a first waveguide layer disposed on the first conductivity type clad layer; a light-emitting layer disposed on the waveguide layer and formed of a nitride semiconductor including one or more quantum wells; a second waveguide layer disposed on the light-emitting layer; a second waveguide layer disposed on the second waveguide layer; a second-conductivity-type clad layer including a second-conductivity-type nitride semiconductor layer, wherein the first-conductivity-type clad layer is Al a Ga (1-a) N (0.7 ⁇ a ⁇ 0.8 ), the first wave
  • FIG. 1 is a schematic cross-sectional view showing one configuration example of a laser diode according to an embodiment of the present disclosure
  • FIG. 1 is a plan view showing a configuration example of a laser diode according to an embodiment of the present disclosure
  • FIG. 1 is a schematic cross-sectional view showing one configuration example of a laser diode according to an embodiment of the present disclosure
  • FIG. 1 is a plan view showing a configuration example of a laser diode according to an embodiment of the present disclosure
  • a laser diode according to an embodiment of the present disclosure will be described.
  • (1.1) Configuration of Laser Diode A laser diode according to the present embodiment includes a nitride semiconductor substrate containing Al and a semiconductor lamination portion arranged on the nitride semiconductor substrate.
  • the semiconductor lamination portion is arranged on the nitride semiconductor substrate and includes a first conductivity type clad layer including a first conductivity type nitride semiconductor layer, and a first waveguide layer arranged on the first conductivity type clad layer.
  • a light-emitting layer disposed on the first waveguide layer and formed of a nitride semiconductor including one or more quantum wells; a second waveguide layer disposed on the light-emitting layer; and a second conductivity type clad layer disposed and including a second conductivity type nitride semiconductor layer.
  • the first conductivity type clad layer is Al a Ga (1 ⁇ a) N (0.7 ⁇ a ⁇ 0.8), and the first waveguide layer is Al c1 Ga (1 ⁇ c1) N (0.8).
  • the second waveguide layer is Al c2 Ga (1 ⁇ c2) N (0.6 ⁇ c2 ⁇ 0.7)
  • the thickness of the first waveguide layer is T1 and the film thickness T2 of the second waveguide layer, the film thickness ratio T1/T2 is 0.3 or more and 0.7 or less.
  • a nitride semiconductor substrate (hereinafter sometimes referred to as a substrate) contains a nitride semiconductor containing Al.
  • a nitride semiconductor containing Al is, for example, AlN. That is, the substrate is preferably an AlN single crystal substrate.
  • the nitride semiconductor containing Al is not limited to AlN, and may be AlGaN, for example.
  • the substrate is a nitride semiconductor single crystal substrate such as AlN or AlGaN, the difference in lattice constant from the nitride semiconductor layer formed on the substrate becomes small, and the nitride semiconductor layer is grown in a lattice matching system. This can reduce threading dislocations.
  • the threading dislocation density of the substrate is preferably 5 ⁇ 10 4 cm ⁇ 2 or less.
  • the threading dislocation density is more preferably 1 ⁇ 10 3 or more and 1 ⁇ 10 4 cm ⁇ 2 or less.
  • the expression “including” in the expression “including a nitride semiconductor” means that the nitride semiconductor is mainly included in the layer, but the expression also includes cases where other elements are included. Specifically, a small amount of an element other than a nitride semiconductor (for example, Ga (when Ga is not the main element), In, As, P, or Sb, etc. is added in a few percent or less) to the composition of this layer. This expression also includes cases where minor changes are made. The term “includes” also has the same meaning in expressing the compositions of other layers. Also, the minor elements contained are not limited to those described above.
  • the substrate preferably has a layer thickness of 100 ⁇ m or more and 600 ⁇ m or less.
  • the plane orientation includes c-plane (0001), a-plane (11-20), m-plane (10-10), etc., but the c-plane (0001) substrate is more preferable.
  • it can be formed on a plane inclined at some angle (for example, -4° to 4°, preferably -0.4° to 0.4°) from the c-plane (0001) normal direction, but this is not limited to
  • the buffer layer is formed between the substrate and the clad layer of the first conductivity type, and is preferably formed over the entire surface of the substrate.
  • a nitride semiconductor layer having a small difference in lattice constant and thermal expansion coefficient and few defects is formed on the buffer layer.
  • the buffer layer is preferably a nitride semiconductor layer containing Al. For example, AlN.
  • the buffer layer has a thickness of several ⁇ m, for example.
  • the thickness of the buffer layer is preferably thicker than 10 nm and thinner than 10 ⁇ m.
  • the thickness of the buffer layer is thicker than 10 nm, the crystallinity of the nitride semiconductor such as AlN is increased.
  • the thickness of the buffer layer is less than 10 ⁇ m, cracks are less likely to occur in the buffer layer formed by crystal growth over the entire surface of the wafer.
  • a first conductivity type clad layer is formed on the substrate.
  • the term “on” in the expression "a clad layer of the first conductivity type is formed on the substrate” means that the clad layer of the first conductivity type is formed on one side of the substrate. do.
  • the above expression also includes the case where another layer further exists between the substrate and the first-conductivity-type clad layer.
  • the word “upper” has the same meaning also in relation between other layers. For example, even when a second conductivity type clad layer is formed on a first waveguide layer, which will be described later, through an electron blocking layer, the phrase “the second conductivity type clad layer is formed on the first waveguide layer” is used. included in the expression. Further, in the description of the present embodiment, “first conductivity type” and “second conductivity type” mean semiconductors exhibiting different conductivity types. , the other becomes p-type conductive.
  • the first conductivity type cladding layer is a nitride semiconductor layer containing Al and Ga.
  • the first conductivity type cladding layer is made of Al a Ga (1-a) N (0 ⁇ a ⁇ 1), for example. This makes it possible to improve the crystallinity of the light-emitting layer and improve the light-emitting efficiency when the light-emitting layer is formed of a material corresponding to the bandgap energy of the deep ultraviolet region.
  • the nitride semiconductor forming the first conductivity type clad layer is preferably a mixed crystal of AlN and GaN.
  • the first conductivity type clad layer is more preferably made of Al a Ga (1-a) N (0.6 ⁇ a ⁇ 0.9). . From the viewpoint of improving the optical confinement coefficient, it is more preferably made of Al a Ga (1-a) N (0.7 ⁇ a ⁇ 0.8).
  • the Al composition of the first-conductivity-type cladding layer is preferably uniform in the film thickness direction, but is not limited to this. The average Al composition in the first-conductivity-type cladding layer is obtained by integrating the Al composition at a certain position over the film thickness range and then dividing it by the film thickness.
  • the average composition a' is 85%. Further, when 2/3 of the film thickness is 100% and 1/3 of the film thickness is 70%, the average composition a' is 90%.
  • the first conductivity type clad layer may be a graded layer in which the Al composition increases with distance from the substrate.
  • the Al composition described above can be limited to the Al composition obtained by averaging the Al composition at positions in the first conductivity type clad layer in the film thickness direction with respect to the thickness of the first conductivity type clad layer.
  • the first-conductivity-type cladding layer is an n-type conductive semiconductor layer, it may contain group V elements other than N such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si. Good, but the type of impurity element is not limited to this.
  • the impurity contained in the first-conductivity-type cladding layer is preferably Si, and the impurity concentration is 5 ⁇ 10 18 cm ⁇ 3 or more and 5 ⁇ 10 19 cm. -3 is preferred.
  • the first conductivity type clad layer preferably has a layer thickness of 250 nm or more and 600 nm or less, and has a layer thickness of 300 nm or more and 450 nm or less, from the viewpoint of lattice relaxation in the first conductivity type clad layer and the film resistance. is more preferable.
  • the light emitting layer is a nitride semiconductor layer containing Al and Ga.
  • the nitride semiconductor included in the light-emitting layer is preferably a mixed crystal of AlN and GaN, for example, from the viewpoint of achieving high light- emitting efficiency. be.
  • the quantum well layer of the light emitting layer is preferably Al b Ga (1-b) N (0.35 ⁇ b ⁇ 0.6).
  • the light-emitting layer may have either a multi-quantum well structure or a single-layer quantum well structure, but the number of quantum well structures is preferably two to four.
  • the film thickness of the quantum well layer is preferably 3 nm or more and 6 nm or less.
  • the light-emitting layer may contain group V elements other than N such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si. do not have.
  • the laser diode of this embodiment is formed above and below the light-emitting layer so as to sandwich the light-emitting layer, and has the effect of confining the light emitted from the light-emitting layer within the light-emitting layer. It may have layers.
  • the waveguide layer is composed of a first waveguide layer arranged on the first conductivity type clad layer side with respect to the light emitting layer and a second waveguide layer arranged on the second conductivity type clad layer side with respect to the light emitting layer. It is preferably composed of two layers.
  • the laser diode of this embodiment includes, for example, a first waveguide layer disposed between a first conductivity type clad layer and a light emitting layer to confine light in the light emitting layer, a second conductivity type clad layer, and a light emitting layer. a second waveguide layer disposed between the layers to confine light to the light emitting layer.
  • the waveguide layer is preferably a nitride semiconductor containing Al and Ga having a bandgap with higher energy than the light emitting layer.
  • the waveguide layer preferably has an Al composition and thickness that increase the field intensity distribution of the light residing within the device and the overlap of the light emitting layer.
  • the first waveguide layer is Al c1 Ga (1 ⁇ c1) N (0.6 ⁇ c1 ⁇ 0.7)
  • the second waveguide layer is Al c2 Ga (1 -c2) N (0.6 ⁇ c2 ⁇ 0.7) is preferred.
  • the film thickness T1 of the first waveguide layer is 20 nm or more and 50 nm or less
  • the film thickness T2 of the second waveguide layer is 50 nm or more and 90 nm or less. More preferably, the film thickness T1 of the first waveguide layer is 30 nm or more and 50 nm or less
  • the film thickness T2 of the second waveguide layer is 60 nm or more and 80 nm or less.
  • the film thickness ratio T1/T2 between the film thickness T1 of the first waveguide layer and the film thickness T2 of the second waveguide layer is preferably 0.3 or more and 0.7 or less. It is preferably 0.5 or more and 0.6 or less.
  • the waveguide layer may contain group V elements other than N, such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si. isn't it.
  • the Al composition of each of the first waveguide layer and the second waveguide layer is preferably uniform in the film thickness direction, but is not limited to this.
  • the Al composition of the second waveguide layer is higher than the Al composition of the first waveguide layer in order to avoid light absorption by the metal (for example, the second electrode) existing above the second conductivity type cladding layer, which will be described later. may be
  • the second-conductivity-type cladding layer is a nitride semiconductor layer formed on the light-emitting layer and containing Al and Ga having second-conductivity-type conductivity.
  • the second-conductivity-type cladding layer is made of Al d Ga (1-d) N (0 ⁇ d ⁇ 1), for example.
  • the second conductivity type cladding layer is formed on the waveguide layer (second waveguide layer).
  • the second-conductivity-type cladding layer has conductivity sufficient to inject carriers (electrons or holes) into the light-emitting layer, and increases the electric field intensity distribution of the optical mode existing in the device and the overlap of the light-emitting layer.
  • the conductivity type is not particularly limited as long as it is possible to increase the confinement of light (that is, to increase the optical confinement).
  • the average Al composition d' of the second-conductivity-type clad layer is preferably larger than the average Al composition a' of the first-conductivity-type clad layer. More preferably, the average Al composition d' of the second-conductivity-type clad layer is 0.8 or more and 0.9 or less.
  • the average Al composition is obtained by integrating the Al composition at a certain position in the film thickness range and then dividing it by the film thickness. For example, when the Al composition is linearly graded from 100% to 70% from the start position to the end position of the second-conductivity-type clad layer, the average composition d' is 85%. Further, when 2/3 of the film thickness is 100% and 1/3 of the film thickness is 70%, the average composition d' is 90%. From the viewpoint of relaxation, the film thickness of the second clad layer is preferably 300 nm or more and 400 nm or less.
  • the second-conductivity-type cladding layer is inclined such that the Al composition e decreases with increasing distance from the substrate, that is, the Al composition e decreases in the direction away from the upper surface of the substrate.
  • a composition gradient layer (second conductivity type vertical conduction layer) made of Al e Ga (1 ⁇ e) N (0.1 ⁇ e ⁇ 1) and Al f Ga (1 ⁇ f) N (0 ⁇ f ⁇ 1) 1) and a lateral conductive layer of the second conductivity type including 1).
  • the second conductivity type cladding layer may be, for example, p-type AlGaN doped with Mg.
  • the second conductivity type cladding layer may contain, for example, group V elements other than N, such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si. is not limited to this.
  • group V elements other than N such as P, As, and Sb
  • impurities such as C, H, F, O, Mg, and Si. is not limited to this.
  • the second-conductivity-type vertical conduction layer and the second-conductivity-type horizontal conduction layer will be described below.
  • the second-conductivity-type vertical conduction layer is a layer forming a region of the second-conductivity-type clad layer on the light-emitting layer side.
  • the second-conductivity-type vertical conduction layer is a layer containing AleGa (1-e) N.
  • the profile (slope) of the Al composition e in the second-conductivity-type vertical conduction layer may decrease continuously or may decrease intermittently.
  • "intermittently decreasing" means that a portion of the film of the second-conductivity-type vertical conduction layer includes a portion in which the Al composition e is the same (constant in the film thickness direction). . That is, the second-conductivity-type vertical conduction layer may include a portion where the Al composition e does not decrease in the direction away from the substrate, but does not include a portion where the Al composition e increases.
  • the film thickness of the second-conductivity-type vertical conduction layer is preferably 500 nm or less, more preferably 20 nm or more and 400 nm or less, and even more preferably 30 nm or more and 350 nm or less.
  • the second-conductivity-type lateral conduction layer is a layer forming a region of the second-conductivity-type cladding layer opposite to the light-emitting layer, and is formed on the second-conductivity-type vertical conduction layer.
  • the second conductivity type lateral conduction layer is a layer containing Al f Ga (1 ⁇ f) N (0 ⁇ f ⁇ 1).
  • the Al composition f of the surface of the second-conductivity-type horizontal conduction layer facing the second-conductivity-type vertical conduction layer is larger than the minimum value of the Al composition e of the second-conductivity-type vertical conduction layer.
  • the thickness of the second-conductivity-type lateral conducting layer is preferably 20 nm or less, more preferably 10 nm or less, and 5 nm. More preferably:
  • the Al composition at the interface between the second-conductivity-type lateral-conducting layer and the second-conductivity-type contact layer is It is preferably less than the Al composition in the layer and fully strained relative to the substrate.
  • the net internal electric field accumulated on the surface and near the surface of the second-conductivity-type lateral conductive layer becomes negative, and carriers are induced at the interface, thereby laterally Conductivity can be improved.
  • the second-conductivity-type vertical conduction layer generates carriers (for example, holes when the second-conductivity-type vertical conduction layer is formed of a p-type semiconductor) by the polarization doping effect, and the carriers are efficiently generated. It has a good effect of injecting into the active layer in the light emitting layer. Therefore, the carrier injection efficiency of the laser diode can be increased by providing the vertical conduction layer of the second conductivity type on the light emitting layer.
  • the lateral conductive layer of the second conductivity type has the effect of widening the carrier distribution, which is narrowed by the electric field concentrated under the electrode, in the lateral direction (within the plane of the lateral conductive layer of the second conductivity type). Due to this effect, the second-conductivity-type horizontal conduction layer can increase the efficiency of carrier injection into the light-emitting layer in the same manner as the second-conductivity-type vertical conduction layer.
  • the semiconductor lamination portion of the laser diode of this embodiment may further include a second conductivity type contact layer disposed on the second conductivity type clad layer.
  • the nitride semiconductor constituting the second-conductivity-type contact layer is preferably made of, for example, GaN, AlN, or InN, or a mixed crystal containing them, and more preferably a nitride semiconductor containing GaN.
  • the second conductivity type contact layer may contain V group elements other than N, such as P, As, and Sb, and impurities such as C, H, F, O, Mg, Si, and Be. Due to the versatility of the raw material gas, the impurity contained in the second conductivity type contact layer is preferably Mg. From the viewpoint of reducing the contact resistance, the Mg concentration is preferably 8 ⁇ 10 19 cm ⁇ 3 or more and 5 ⁇ 10 21 cm ⁇ 3 or less, and more preferably 5 ⁇ 10 20 cm ⁇ 3 or more and 5 ⁇ 10 21 cm ⁇ 3 or less. It is more preferable to have
  • the layer thickness of the second-conductivity-type contact layer is preferably 1 nm or more and 20 nm or less.
  • the carrier injection efficiency of the light-emitting layer improves as the layer thickness of the second-conductivity-type contact layer decreases, and the carrier injection efficiency decreases as the layer thickness increases.
  • the semiconductor lamination portion of the light emitting layer of the present embodiment may further have an electron blocking layer above the light emitting layer and having a bandgap larger than that of the light emitting layer.
  • the electron blocking layer may be provided, for example, on the light-emitting layer, inside the second waveguide layer, between the second waveguide layer and the light-emitting layer, or between the second waveguide layer and the second conductivity type vertical conduction layer. It can also be set between The layer thickness of the electron blocking layer is preferably 30 nm or less, more preferably 20 nm or less so that carriers (holes) can easily quantum penetrate the electron blocking layer.
  • a laser diode can emit light or oscillate by injecting a current through a second electrode arranged on a second-conductivity-type clad layer and a first electrode arranged on a first-conductivity-type clad layer.
  • the first electrode is formed so as to be in electrical contact with the clad layer of the first conductivity type
  • the second electrode is formed so as to be in electrical contact with the clad layer of the second conductivity type.
  • the first electrode can be arranged, for example, on the back side of the substrate.
  • the first electrode is arranged on the first conductivity type cladding layer exposed by removing the layer above the first conductivity type cladding layer of the semiconductor lamination portion by chemical etching or dry etching, for example. That is, the first electrode is arranged on a region in which the mesa structure is not formed in the first-conductivity-type cladding layer.
  • the first electrode is Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Rh, Ir, Ni, Pd, Pt. , Cu, Ag, Au, Zr, etc., a mixed crystal thereof, or a conductive oxide such as ITO or Ga 2 O 3 .
  • the first electrode is Ni, Au, Pt, Ag, Rh, Pd, Pt, Cu, Al, Ti, Zr, Hf, V, Nb, Ta, Cr , Mo, W, Co, Ir, and Zr, or mixed crystals thereof, or conductive oxides such as ITO or Ga 2 O 3 .
  • the second electrode is Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Rh, Ir, Ni, Pd, Pt. , Cu, Ag, Au, Zr, etc., a mixed crystal thereof, or a conductive oxide such as ITO or Ga 2 O 3 .
  • the second electrode is Ni, Au, Pt, Ag, Rh, Pd, Pt, Cu, Al, Ti, Zr, Hf, V, Nb, Ta, Cr , Mo, W, Co, Ir, and Zr, or mixed crystals thereof, or conductive oxides such as ITO or Ga 2 O 3 .
  • the arrangement regions and shapes of the first electrode and the second electrode are the same as those of the first-conductivity-type clad layer and the second-conductivity-type clad layer (the second-conductivity-type contact layer when the second-conductivity-type contact layer is provided). There is no limitation as long as electrical contact is obtained.
  • the laser diode of the present embodiment is manufactured through steps of forming layers on a substrate.
  • the substrate is formed by a general substrate growth method such as a vapor phase growth method such as a sublimation method, a hydride vapor phase epitaxy (HVPE) method, or a liquid phase growth method.
  • a general substrate growth method such as a vapor phase growth method such as a sublimation method, a hydride vapor phase epitaxy (HVPE) method, or a liquid phase growth method.
  • Each layer of the semiconductor laminate formed on the substrate is formed by, for example, a molecular beam epitaxy (MBE) method, a hydride vapor phase epitaxy (HVPE) method, or a metal organic chemical vapor deposition (MOCVD) method. It can be formed by a method or the like.
  • the nitride semiconductor layer is, for example, an Al raw material containing trimethylaluminum (TMAl), a Ga raw material containing trimethylgallium (TMGa) or triethylgallium (TEGa), or ammonia ( NH 3 ) can be used as the N source material.
  • a first conductivity type clad layer containing a first conductivity type nitride semiconductor is formed on a buffer layer formed on a substrate.
  • a light-emitting layer is formed on the first-conductivity-type clad layer using a nitride semiconductor (such as AlGaN) including one or more quantum wells, and a second-conductivity-type clad layer is formed on the light-emitting layer.
  • a nitride semiconductor such as AlGaN
  • waveguide layers made of a nitride semiconductor such as AlGaN may be formed above and below the light emitting layer.
  • an intermediate layer made of a nitride semiconductor such as AlGaN may be formed between the second-conductivity-type clad layer and the waveguide, or a second-conductivity-type nitride semiconductor containing GaN or the like may be formed on the second-conductivity-type clad layer.
  • a contact layer may be provided, and an electron blocking layer may be formed above the light emitting layer.
  • a laser diode is manufactured through a process (mesa structure forming process) of removing unnecessary portions of each layer of a semiconductor laminate formed on a substrate by etching.
  • the removal of unnecessary portions of each layer of the semiconductor laminate can be performed by, for example, inductively coupled plasma (ICP) etching or the like.
  • ICP inductively coupled plasma
  • unnecessary portions of each layer of the conductor laminate are removed by etching, thereby partially exposing the first conductivity type clad layer.
  • the laser diode can be manufactured through a process of forming electrodes. Electrodes such as the first electrode and the second electrode are formed by various methods of evaporating metal by electron beam evaporation (EB), such as resistance heating evaporation, electron gun evaporation, or sputtering. is not limited. Each electrode may be formed as a single layer, or may be formed by laminating a plurality of layers. Further, each electrode may be subjected to heat treatment in an atmosphere of oxygen, nitrogen, air, or the like after the layer is formed. Finally, the substrate on which each layer is formed through the above steps is divided into individual pieces by dicing to manufacture laser diodes.
  • EB electron beam evaporation
  • a first electrode is formed on the surface of the first-conductivity-type clad layer.
  • the second electrode is formed on the uppermost layer (for example, the second-conductivity-type clad layer) of the mesa structure formed in part of the semiconductor laminate.
  • the layer thickness of each layer constituting the laser diode is measured by cutting out a predetermined cross section perpendicular to the substrate, observing this cross section with a transmission electron microscope (TEM), and using the length measurement function of the TEM.
  • TEM transmission electron microscope
  • a measuring method first, a TEM is used to observe a cross section perpendicular to the main surface of the substrate of the laser diode.
  • the observation width is defined as a range of 2 ⁇ m or more in a direction parallel to the main surface of the substrate in a TEM image showing a cross section perpendicular to the main surface of the substrate of the laser diode.
  • the layer thickness of each layer can be obtained by calculating the average value of the thickness of each layer included in the observation area of 200 nm width from five points arbitrarily extracted from the observation width of 2 ⁇ m or more.
  • the concentration of dopants and impurities contained in each layer constituting the laser diode can be measured by secondary ion mass spectrometry (SIMS).
  • SIMS secondary ion mass spectrometry
  • the concentrations of dopants and impurities contained in each layer can be measured by SIMS after processing into a device, it can be performed in a state where electrodes are removed by chemical etching or physical polishing.
  • the concentration of dopants and impurities contained in each layer can be measured by sputtering from the side of the substrate where no electrodes are formed.
  • SIMS measurement is performed under measurement conditions provided by Evans Analytical Group (EAG).
  • a cesium (Cs) ion beam having an energy of 14.5 keV is used for sputtering the sample during measurement.
  • Methods for measuring the atomic concentration contained in each layer constituting a laser diode include reciprocal space mapping (RSM) by X-ray diffraction (XRD). Specifically, by analyzing the reciprocal lattice mapping data in the vicinity of the diffraction peak obtained with the asymmetric plane as the diffraction plane, the lattice relaxation rate and Al composition for the underlayer can be obtained. Examples of diffraction planes include the (10-15) plane and the (20-24) plane.
  • XPS X-ray photoelectron spectroscopy
  • EDX Energy Dispersive X-ray spectroscopy
  • EELS electron energy-loss spectroscopy
  • EELS analyzes the composition of a sample by measuring the energy lost by an electron beam as it passes through the sample. Specifically, for example, in a sliced sample used for TEM observation, etc., an energy loss spectrum of the intensity of a transmitted electron beam is measured and analyzed. Using the fact that the peak position appearing near the energy loss of 20 eV changes according to the composition of each layer, the composition can be obtained from the peak position. In the same manner as the layer thickness calculation method by TEM observation described above, the average value of the Al composition at an observation width of 200 nm is calculated from 5 points arbitrarily extracted from the observation area of 2 ⁇ m or more to obtain the Al composition of each layer.
  • the EDX measures and analyzes the characteristic X-rays generated by the electron beam in the thinned sample used for the above-mentioned TEM observation.
  • the average value of the Al composition at an observation width of 200 nm is calculated from 5 points arbitrarily extracted from the observation area of 2 ⁇ m or more to obtain the Al composition of each layer.
  • XPS X-ray photoelectron spectroscopy
  • Ar + is generally used for the ion beam, but other ion species such as Ar cluster ions may be used as long as the ions can be irradiated by an etching ion gun mounted on the XPS apparatus.
  • the XPS peak intensities of Al, Ga, and N are measured and analyzed to obtain the depth direction distribution of the Al composition of each layer.
  • the laser diode may be obliquely polished so that the cross section perpendicular to the main surface of the substrate is enlarged and exposed, and the exposed cross section may be measured by XPS.
  • the composition of each layer can be measured not only by XPS but also by using Auger Electron Spectroscopy (AES). In this case, the composition can be measured by measurement by Auger electron spectroscopy on a section exposed by sputter etching or oblique polishing. The composition of each layer can also be measured by SEM-EDX measurement of a section exposed by oblique polishing.
  • AES Auger Electron Spectroscopy
  • the laser diode according to the present disclosure is applicable to devices in, for example, the medical/life science field, the environmental field, the industrial/industrial field, the life/home appliance field, the agricultural field, and other fields.
  • Laser diodes are used in equipment for synthesizing and decomposing drugs or chemical substances, sterilizing equipment for liquids, gases, and solids (containers, food, medical equipment, etc.), cleaning equipment for semiconductors, etc., equipment for surface modification of films, glass, metals, etc., semiconductors ⁇ FPD (Flat Panel Display) ⁇ PCB (Printed Wiring Board) ⁇ Exposing equipment for manufacturing other electronic products, printing/coating equipment, adhesive/sealing equipment, transfer/molding equipment for film/pattern/mock-up, banknote/scratches ⁇ Applicable to measuring and testing devices for blood, chemical substances, etc.
  • liquid sterilizers include automatic ice makers, ice trays and ice storage containers in refrigerators, water supply tanks for ice makers, freezers, ice makers, humidifiers, dehumidifiers, cold water tanks, hot water tanks, and flow paths of water servers. Piping, stationary water purifiers, portable water purifiers, water supply equipment, water heaters, waste water treatment equipment, disposers, waste water traps for toilet bowls, washing machines, dialysis water sterilization modules, peritoneal dialysis connector sterilizers, disaster water storage systems, etc. are listed, but are not limited to these.
  • gas sterilizers include air purifiers, air conditioners, ceiling fans, floor or bedding vacuum cleaners, futon dryers, shoe dryers, washing machines, clothes dryers, indoor germicidal lamps, and storage ventilation. Examples include, but are not limited to, systems, shoeboxes, chests of drawers, and the like.
  • solid sterilizers include vacuum packers, belt conveyors, hand tool sterilizers for medical, dental, barber and beauty salon use, toothbrushes, toothbrush cases, chopstick cases, cosmetic pouches, Drain lids, local washes of toilet bowls, toilet bowl lids, etc., but not limited to these.
  • FIG. 1 is a schematic cross-sectional view of a laser diode 1 according to this embodiment.
  • FIG. 2 is a plan view of the laser diode 1 according to this embodiment.
  • the laser diode 1 includes a substrate 11, a semiconductor lamination portion 10 arranged on the substrate 11, a first electrode 12, and a second electrode 13.
  • FIG. 1 is a schematic cross-sectional view of a laser diode 1 according to this embodiment.
  • FIG. 2 is a plan view of the laser diode 1 according to this embodiment.
  • the laser diode 1 includes a substrate 11, a semiconductor lamination portion 10 arranged on the substrate 11, a first electrode 12, and a second electrode 13.
  • FIG. 1 is a schematic cross-sectional view of a laser diode 1 according to this embodiment.
  • the laser diode 1 includes a substrate 11, a semiconductor lamination portion 10 arranged on the substrate 11, a first electrode 12, and a second electrode 13.
  • FIG. 1 is a schematic cross-sectional view of a laser dio
  • the semiconductor lamination portion 10 includes a first conductivity type cladding layer 101 having n-type conductivity, a first waveguide layer 102, a light emitting layer 103, a second waveguide layer 104, and a second waveguide layer 104 having p-type conductivity.
  • a conductive clad layer 105 and a contact layer 106 are provided.
  • a laser diode according to the present disclosure includes a nitride semiconductor substrate containing Al and a semiconductor lamination portion arranged on the nitride semiconductor substrate, the semiconductor lamination portion being arranged on the nitride semiconductor substrate, a first conductivity type cladding layer including a first conductivity type nitride semiconductor layer; a first waveguide layer disposed on the first conductivity type cladding layer; and one or more waveguide layers disposed on the first waveguide layer a light emitting layer formed of a nitride semiconductor including a quantum well of; a second waveguide layer disposed on the light emitting layer; and a nitride semiconductor layer of a second conductivity type disposed on the second waveguide layer and a second conductivity type clad layer comprising: the first conductivity type clad layer is Al a Ga (1 ⁇ a) N (0.7 ⁇ a ⁇ 0.8); , Al c1 Ga (1 ⁇ c1) N (0.6 ⁇ c1
  • the film thickness T1 of the first waveguide layer is 20 nm or more and 50 nm or less, and the film thickness T2 of the second waveguide layer is 50 nm or more and 90 nm or less. This makes it possible to improve the optical confinement factor and reduce the oscillation threshold current density.
  • the first conductivity type clad layer preferably has a thickness of 250 nm or more and 500 nm or less.
  • the second conductivity type clad layer is Al d Ga (1 ⁇ d) N (0 ⁇ d ⁇ 1)
  • the average composition d′ is the average of the first conductivity type clad layer It is preferably larger than the Al composition a'. This makes it possible to improve the optical confinement factor and reduce the oscillation threshold current density.
  • the film thickness of the second-conductivity-type clad layer is 300 nm or more and 400 nm or less. This makes it possible to improve the optical confinement factor and reduce the oscillation threshold current density.
  • the quantum well layer of the light-emitting layer is Al b Ga (1-b) N (0.4 ⁇ b ⁇ 0.6) and has a thickness of 3 nm or more and 6 nm or less. , preferably has a multiple quantum well structure of two to four layers.
  • the nitride semiconductor substrate is preferably an AlN single crystal substrate.
  • the lattice constant difference between the substrate and the nitride semiconductor layer formed on the upper side of the substrate is reduced, and the nitride semiconductor layer is grown in a lattice matching system, thereby reducing threading dislocations and increasing stability.
  • a high nitride semiconductor layer can be formed.
  • the laser diode of the present disclosure includes a second conductivity type contact layer disposed on the second conductivity type cladding layer and formed of a nitride semiconductor containing GaN, wherein the second conductivity type cladding layer is made of Al A first film containing e Ga (1 ⁇ e) N (0.1 ⁇ e ⁇ 1), having a composition gradient in which the Al composition e decreases with increasing distance from the nitride semiconductor substrate, and having a film thickness of less than 0.5 ⁇ m. It is preferable to have a two-conductivity-type vertical conduction layer and a second-conductivity-type horizontal conduction layer containing Al f Ga (1 ⁇ f) N (0 ⁇ f ⁇ 1). This makes it possible to inject carriers into the light-emitting layer more efficiently, improve the light-emitting efficiency, and reduce the oscillation threshold current density.
  • the laser diode of the present disclosure will be described with examples and comparative examples. Note that the laser diode of the present disclosure is not limited to these examples.
  • Example 1 A (0001) plane AlN single crystal substrate having a thickness of 550 ⁇ m was used as the substrate. Next, an AlN layer as a buffer layer was formed on the substrate. The AlN layer was formed with a thickness of 500 nm under an environment of 1200°C. At this time, the ratio (V/III ratio) between the supply rate of the group III element source gas and the supply rate of the nitrogen source gas was set to 50. The growth rate of the AlN layer at this time was 0.5 ⁇ m/hr. Also, trimethylaluminum (TMAl) was used as an Al raw material. Ammonia (NH 3 ) was used as the N raw material.
  • TMAl trimethylaluminum
  • the first-conductivity-type cladding layer was an n-type AlGaN layer (Al: 75%, ie, an Al 0.75 Ga 0.25 N layer) using Si as a dopant impurity.
  • the first conductivity type cladding layer was formed at a temperature of 1080° C., a degree of vacuum of 50 mbar and a V/III ratio of 4000 to a thickness of 400 nm.
  • the growth rate of the first conductivity type clad layer at this time was 0.4 ⁇ m/hr.
  • trimethylaluminum (TMAl) was used as an Al raw material.
  • triethylgallium (TEGa) was used as a Ga source. Ammonia (NH 3 ) was used as the N raw material.
  • monosilane (SiH 4 ) was used as the Si raw material.
  • an n-type waveguide layer as a first waveguide layer was formed on the first conductivity type clad layer.
  • the n-type waveguide layer was an AlGaN layer (Al: 63%, ie Al 0.63 Ga 0.37 N layer) containing no dopant.
  • the n-type waveguide layer was formed with a thickness of 40 nm under the conditions of a temperature of 1080° C., a degree of vacuum of 50 mbar, and a V/III ratio of 4000.
  • the growth rate of the n-type waveguide layer at this time was 0.35 ⁇ m/hr.
  • trimethylaluminum (TMAl) was used as an Al raw material.
  • triethylgallium (TEGa) was used as a Ga source. Ammonia (NH 3 ) was used as the N raw material.
  • the light-emitting layer was formed by forming a film so as to have a multi-quantum well structure in which two periods of quantum well layers and barrier layers were laminated.
  • the quantum well layer was an AlGaN layer (Al: 52%, ie Al 0.52 Ga 0.48 N layer) having a thickness of 4.5 nm.
  • the barrier layer having a thickness of 6.0 nm was an AlGaN layer (Al: 63%, that is, an Al 0.63 Ga 0.37 N layer).
  • the light-emitting layer was formed under the conditions that the degree of vacuum was set to 50 mbar and the V/III ratio was set to 4000.
  • the growth rate of the quantum well layer at this time was 0.18 ⁇ m/hr.
  • the growth rate of the barrier layer was 0.15 ⁇ m/hr.
  • a p-type waveguide layer as a second waveguide layer was formed on the light emitting layer.
  • the p-type waveguide layer was an AlGaN layer (Al: 63%, ie Al 0.63 Ga 0.37 N layer) containing no dopant.
  • the p-type waveguide layer was formed at a temperature of 1080° C., a degree of vacuum of 50 mbar and a V/III ratio of 4000 to a thickness of 70 nm.
  • the growth rate of the p-type waveguide layer at this time was 0.35 ⁇ m/hr.
  • trimethylaluminum (TMAl) was used as an Al raw material.
  • triethylgallium (TEGa) was used as a Ga source.
  • the second-conductivity-type cladding layer has a laminated structure including a second-conductivity-type vertical conduction layer and a second-conductivity-type horizontal conduction layer, and is a graded layer with a graded Al composition ratio.
  • the second-conductivity-type clad layer was formed at a temperature of 1,080° C.
  • the growth rate of the second conductivity type clad layer at this time was 0.3 to 0.5 ⁇ m/hr.
  • trimethylaluminum (TMAl) was used as an Al raw material.
  • triethylgallium (TEGa) was used as a Ga source.
  • the average Al composition d' in the second-conductivity-type clad layer was 0.85, which was larger than the average Al composition a' in the first-conductivity-type clad layer.
  • a p-type contact layer as a second conductivity type contact layer was formed on the second conductivity type cladding layer.
  • the p-type contact layer was formed of an AlGaN layer and a GaN layer.
  • the GaN layer was formed of GaN (that is, Al: 0%) with a thickness of 10 nm.
  • the second conductivity type contact layer was formed at a temperature of 950.degree. The growth rate of the second conductivity type contact layer at this time was 0.2 ⁇ m/hr.
  • a semiconductor lamination portion was formed on the AlN substrate.
  • the reciprocal lattice mapping measurement by XRD was performed on this semiconductor lamination portion, it was found that the semiconductor lamination portion undergoes pseudomorphic growth without relaxation up to the contact layer of the second conductivity type.
  • the semiconductor lamination portion formed as described above was annealed at 700° C. for 10 minutes or longer in an N 2 atmosphere to further reduce the resistance of the second conductivity type contact layer.
  • a mesa structure with the first conductivity type clad layer exposed was formed.
  • the formed mesa structure had a length of 700 ⁇ m in the ⁇ 1-100> direction and a length of 40 ⁇ m in the ⁇ 11-20> direction.
  • the length in the ⁇ 1-100> direction of the mesa structure is the distance between the resonator mirror end faces in plan view
  • the length in the ⁇ 11-20> direction is the distance between the side surfaces of the mesa structure. is.
  • Ni and Au were sequentially formed into films in a rectangular shape elongated in the ⁇ 1-100> direction to form a plurality of electrode metal regions to form a p-type second electrode.
  • the width of the second electrode was 5 ⁇ m and the length was 700 ⁇ m.
  • V, Al, Ni, Ti and Au are deposited in order in a rectangular shape elongated in the ⁇ 1-100> direction to form a plurality of electrode metal regions. It was used as the first electrode of the mold.
  • An RTA apparatus was used to anneal the first electrode and the second electrode at 750° C. for 60 seconds in a nitrogen atmosphere.
  • the substrate was divided into stripes by cleaving in parallel in the ⁇ 11-20> direction multiple times to form singulated laser diodes.
  • the length of the mesa structure after division in the ⁇ 1-100> direction was 600 ⁇ m.
  • the threshold voltage was 12.0 V and the oscillation threshold current density was 7.5 kA/cm 2 .
  • Example 2 The laser diode of Example 2 was produced in the same manner as in Example 1 except that the first waveguide layer and the second waveguide layer were AlGaN layers (Al: 61%, that is, Al 0.61 Ga 0.39 N layers). formed.
  • the threshold voltage was 11.5 V and the oscillation threshold current density was 8.5 kA/cm 2 .
  • Example 3 The laser diode of Example 3 was manufactured in the same manner as in Example 1 except that the first waveguide layer and the second waveguide layer were AlGaN layers (Al: 66%, that is, Al 0.66 Ga 0.34 N layers). formed.
  • the threshold voltage was 12.5 V and the oscillation threshold current density was 7.2 kA/cm 2 .
  • Example 4 The laser diode of Example 4 was produced in the same manner as in Example 1 except that the first waveguide layer and the second waveguide layer were AlGaN layers (Al: 69%, that is, Al 0.69 Ga 0.31 N layers). formed.
  • the threshold voltage was 12.9 V and the oscillation threshold current density was 7.0 kA/cm 2 .
  • Example 5 A laser diode of Example 5 was formed in the same manner as in Example 1 except that the film thickness T1 of the first waveguide layer was changed to 23 nm and the film thickness ratio T1/T2 was set to 0.33.
  • the threshold voltage was 12.0 V and the oscillation threshold current density was 8.8 kA/cm 2 .
  • Example 6 A laser diode of Example 6 was formed in the same manner as in Example 1 except that the film thickness T1 of the first waveguide layer was changed to 33 nm and the film thickness ratio T1/T2 was set to 0.47.
  • the threshold voltage was 12.0 V and the oscillation threshold current density was 8.2 kA/cm 2 .
  • Example 7 A laser diode of Example 7 was formed in the same manner as in Example 1 except that the film thickness T1 of the first waveguide layer was changed to 47 nm and the film thickness ratio T1/T2 was set to 0.67.
  • the threshold voltage was 12.0 V and the oscillation threshold current density was 8.3 kA/cm 2 .
  • Example 8> Conducted in the same manner as in Example 1 except that the film thickness T1 of the first waveguide layer was changed to 35 nm, the film thickness T2 of the second waveguide layer was changed to 55 nm, and the film thickness ratio T1/T2 was changed to 0.64.
  • a laser diode of Example 8 was formed. When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 11.6 V and the oscillation threshold current density was 9.3 kA/cm 2 .
  • Example 9 A laser diode of Example 9 was formed in the same manner as in Example 1 except that the film thickness T2 of the second waveguide layer was changed to 85 nm and the film thickness ratio T1/T2 was set to 0.47.
  • the threshold voltage was 12.7 V and the oscillation threshold current density was 7.2 kA/cm 2 .
  • Example 10 A laser diode of Example 10 was formed in the same manner as in Example 1 except that the first conductivity type cladding layer was an AlGaN layer (Al: 72%, ie, an Al 0.72 Ga 0.28 N layer).
  • the threshold voltage was 10.0 V and the oscillation threshold current density was 9.0 kA/cm 2 .
  • Example 11 A laser diode of Example 11 was formed in the same manner as in Example 1 except that the first conductivity type cladding layer was an AlGaN layer (Al: 78%, ie, an Al 0.78 Ga 0.22 N layer).
  • the threshold voltage was 14.0 V and the oscillation threshold current density was 7.2 kA/cm 2 .
  • Example 12 A laser diode of Example 12 was formed in the same manner as in Example 1 except that the light emitting layer was an AlGaN layer (Al: 43%, that is, an Al 0.43 Ga 0.57 N layer).
  • the threshold voltage was 11.5 V and the oscillation threshold current density was 6.5 kA/cm 2 .
  • Example 13 A laser diode of Example 13 was formed in the same manner as in Example 1 except that the light emitting layer was an AlGaN layer (Al: 58%, ie, an Al 0.58 Ga 0.42 N layer).
  • the threshold voltage was 12.5 V and the oscillation threshold current density was 8.5 kA/cm 2 .
  • Example 14 A laser diode of Example 14 was formed in the same manner as in Example 1 except that the number of periods of the light emitting layer was 3, that is, the number of quantum well structures was 3.
  • the threshold voltage was 11.5 V and the oscillation threshold current density was 7.1 kA/cm 2 .
  • Example 15 A laser diode of Example 15 was formed in the same manner as in Example 1 except that the periodicity of the light emitting layer was 4, that is, the number of quantum well layers was 4.
  • the threshold voltage was 11.0 V and the oscillation threshold current density was 6.8 kA/cm 2 .
  • Example 16 A laser diode of Example 16 was formed in the same manner as in Example 1, except that the film thickness of the light emitting layer was 3.5 nm.
  • the threshold voltage was 11.3 V and the oscillation threshold current density was 8.0 kA/cm 2 .
  • Example 17 A laser diode of Example 17 was formed in the same manner as in Example 1, except that the thickness of the light emitting layer was 5.5 nm.
  • the threshold voltage was 10.4 V and the oscillation threshold current density was 7.1 kA/cm 2 .
  • Example 18 A laser diode of Example 18 was formed in the same manner as in Example 1 except that the film thickness of the second-conductivity-type cladding layer was 300 nm. Current-edge emission intensity measurement by current injection was performed on the laser diode thus obtained, and the threshold voltage was 10.5 V, and the oscillation threshold current density was 8.3 kA/cm 2 .
  • Example 19 A laser diode of Example 19 was formed in the same manner as in Example 1, except that the thickness of the second-conductivity-type cladding layer was set to 250 nm.
  • the threshold voltage was 10.2 V and the oscillation threshold current density was 9.1 kA/cm 2 .
  • Example 20 A laser diode of Example 20 was formed in the same manner as in Example 1, except that the film thickness of the second-conductivity-type clad layer was 400 nm.
  • the threshold voltage was 12.6 V and the oscillation threshold current density was 7.0 kA/cm 2 .
  • Example 21 A laser diode of Example 21 was formed in the same manner as in Example 1 except that the film thickness of the second-conductivity-type cladding layer was set to 450 nm.
  • the threshold voltage was 12.9 V and the oscillation threshold current density was 7.1 kA/cm 2 .
  • a laser diode of Example 22 was formed. When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 10.0 V and the oscillation threshold current density was 9.0 kA/cm 2 .
  • Comparative Example 1 A laser diode of Comparative Example 1 was formed in the same manner as in Example 1 except that the first waveguide layer was an AlGaN layer (Al: 55%, that is, an Al 0.55 Ga 0.45 N layer).
  • the threshold voltage was 11.8 V and the oscillation threshold current density was 11.7 kA/cm 2 .
  • Comparative Example 2 A laser diode of Comparative Example 2 was formed in the same manner as in Example 1 except that the first waveguide layer was an AlGaN layer (Al: 75%, ie, an Al 0.75 Ga 0.25 N layer).
  • the threshold voltage was 12.2 V and the oscillation threshold current density was 12.1 kA/cm 2 .
  • Comparative Example 3 A laser diode of Comparative Example 3 was formed in the same manner as in Example 1 except that the second waveguide layer was an AlGaN layer (Al: 55%, ie, an Al 0.55 Ga 0.45 N layer).
  • the threshold voltage was 11.8 V and the oscillation threshold current density was 11.9 kA/cm 2 .
  • Comparative Example 4 A laser diode of Comparative Example 4 was formed in the same manner as in Example 1 except that the second waveguide layer was an AlGaN layer (Al: 75%, ie, an Al 0.75 Ga 0.25 N layer).
  • the threshold voltage was 12.2 V and the oscillation threshold current density was 12.1 kA/cm 2 .
  • a laser diode of Comparative Example 5 was formed in the same manner as in Example 1 except that the first conductivity type cladding layer was an AlGaN layer (Al: 65%, ie, an Al 0.65 Ga 0.35 N layer).
  • the threshold voltage was 9.0 V and the oscillation threshold current density was 12.0 kA/cm 2 .
  • Comparative Example 6 A laser diode of Comparative Example 6 was formed in the same manner as in Comparative Example 1 except that the first conductivity type cladding layer was an AlGaN layer (Al: 85%, ie, an Al 0.85 Ga 0.15 N layer).
  • the threshold voltage was 17.0 V and the oscillation threshold current density was 12.0 kA/cm 2 .
  • Comparative Example 7 was carried out in the same manner as in Example 1 except that the film thickness T1 of the first waveguide layer was 25 nm, the film thickness T2 of the second waveguide layer was 100 nm, and the film thickness ratio T1/T2 was 0.25. of laser diodes were formed. When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12.0 V and the oscillation threshold current density was 10.9 kA/cm 2 .
  • Comparative Example 8 The laser of Comparative Example 8 was produced in the same manner as in Example 1 except that the film thickness T1 of the first waveguide layer was 50 nm, the film thickness T2 of the second waveguide layer was 50 nm, and the film thickness ratio T1/T2 was 1. formed a diode.
  • the threshold voltage was 12.0 V and the oscillation threshold current density was 11.8 kA/cm 2 .
  • Table 1 below shows the evaluation results of each example and each comparative example.
  • the Al composition a of the first conductivity type cladding layer satisfies 0.7 ⁇ a ⁇ 0.8
  • the Al composition c1 of the first waveguide layer satisfies 0.6 ⁇ c1 ⁇ 0.7
  • the Al composition c2 of the second waveguide layer satisfies 0.6 ⁇ c2 ⁇ 0.7
  • the film thickness ratio between the film thickness T1 of the first waveguide layer and the film thickness T2 of the second waveguide layer is T1/
  • the oscillation threshold current density was 10.9 kA/cm 2 or more.
  • the laser diodes of the examples in which each layer satisfies the above range, had an oscillation threshold current density of less than 10 kA/cm 2 , which was lower than that of the laser diodes of the comparative examples.
  • the Al composition c1 of the first waveguide layer and the Al composition c2 of the second waveguide layer are within the ranges described above, the Al composition c1 and the Al composition c2 are The higher the value, the stronger the light confinement effect in the light-emitting layer, and the lower the oscillation threshold current density, but the higher the threshold voltage.
  • the thickness ratio T1/T2 between the first waveguide layer and the second waveguide layer is 0.3 to 0.3. 7 or less, when the thickness T1 of the first waveguide layer and the thickness T2 of the second waveguide layer are large, the resistance tends to deteriorate and the threshold voltage tends to increase, but the optical confinement effect is strong and the oscillation threshold current Density decreased.
  • the average Al composition a' of the clad layer of the first conductivity type is smaller than the average Al composition d' of the clad layer of the second conductivity type, the average Al composition a' and the average Al The oscillation threshold current density was lower than in the case of the same composition d'. Therefore, it is preferable that the average Al composition a' of the clad layer of the first conductivity type is smaller than the average Al composition d' of the clad layer of the second conductivity type.
  • the oscillation threshold current density decreases as the film thickness of the second-conductivity-type clad layer increases from 300 nm, but the oscillation threshold current density decreases within the film thickness range of 400 to 450 nm. The densities were almost the same.
  • the threshold voltage tends to be higher than when the thickness is 400 nm. From the above, it is preferable that the film thickness of the second-conductivity-type clad layer is 300 nm or more and 400 nm or less.
  • the Al composition of the first conductivity type cladding layer, the first waveguide layer, and the second waveguide layer, the film thickness T1 of the first waveguide layer, and the second waveguide layer By adjusting the film thickness ratio T1/T2 of the film thickness T2, the oscillation threshold current density can be lowered to enable stable continuous oscillation by pulse driving.

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Abstract

Une diode laser est décrite, qui concerne la réduction d'un courant de seuil oscillant. La diode laser comprend un substrat semi-conducteur au nitrure contenant de l'Al, et une partie de stratification de semi-conducteur disposée sur le substrat semi-conducteur au nitrure. La partie de stratification de semi-conducteur est formée par stratification séquentielle d'une couche de gainage d'un premier type de conductivité contenant une couche semi-conductrice de nitrure d'un premier type de conductivité, une première couche de guide d'ondes, une couche électroluminescente formée par un semi-conducteur de nitrure contenant un ou plusieurs puits quantiques, une seconde couche de guide d'ondes, et une couche de gainage d'un second type de conductivité contenant une couche semi-conductrice de nitrure d'un second type de conductivité. La couche de gainage du premier type de conductivité est AlaGa(1-a)N (0.7<a<0.8), la première couche de guide d'ondes est Alc1Ga(1-c1)N (0.6<c1<0.7), la seconde couche de guide d'ondes est Alc2Ga(1-c2)N (0.6<c2<0.7), et le rapport d'épaisseur de film T1/T2 de la première épaisseur de film de couche de guide d'ondes T1 et de la seconde épaisseur de film de couche de guide d'ondes T2 est de 0,3 à 0,7 inclus.
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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11340580A (ja) * 1997-07-30 1999-12-10 Fujitsu Ltd 半導体レーザ、半導体発光素子、及び、その製造方法
JP2001057461A (ja) * 1999-06-10 2001-02-27 Nichia Chem Ind Ltd 窒化物半導体レーザ素子
JP2002299768A (ja) * 2001-03-30 2002-10-11 Matsushita Electric Ind Co Ltd 半導体発光装置
JP2004111853A (ja) * 2002-09-20 2004-04-08 Sanyo Electric Co Ltd 窒化物系半導体レーザ素子
US20110103421A1 (en) * 2009-10-29 2011-05-05 Tarun Kumar Sharma Application-oriented nitride substrates for epitaxial growth of electronic and optoelectronic device structures
WO2014123092A1 (fr) * 2013-02-05 2014-08-14 株式会社トクヤマ Élément électroluminescent semi-conducteur à base de nitrure
JP2016111353A (ja) * 2014-12-08 2016-06-20 パロ アルト リサーチ センター インコーポレイテッド ｎ−クラッド層に工学的不均一合金組成を有する窒化物レーザーダイオード
WO2021060538A1 (fr) * 2019-09-27 2021-04-01 旭化成株式会社 Diode laser

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11340580A (ja) * 1997-07-30 1999-12-10 Fujitsu Ltd 半導体レーザ、半導体発光素子、及び、その製造方法
JP2001057461A (ja) * 1999-06-10 2001-02-27 Nichia Chem Ind Ltd 窒化物半導体レーザ素子
JP2002299768A (ja) * 2001-03-30 2002-10-11 Matsushita Electric Ind Co Ltd 半導体発光装置
JP2004111853A (ja) * 2002-09-20 2004-04-08 Sanyo Electric Co Ltd 窒化物系半導体レーザ素子
US20110103421A1 (en) * 2009-10-29 2011-05-05 Tarun Kumar Sharma Application-oriented nitride substrates for epitaxial growth of electronic and optoelectronic device structures
WO2014123092A1 (fr) * 2013-02-05 2014-08-14 株式会社トクヤマ Élément électroluminescent semi-conducteur à base de nitrure
JP2016111353A (ja) * 2014-12-08 2016-06-20 パロ アルト リサーチ センター インコーポレイテッド ｎ−クラッド層に工学的不均一合金組成を有する窒化物レーザーダイオード
WO2021060538A1 (fr) * 2019-09-27 2021-04-01 旭化成株式会社 Diode laser

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