WO2024257516A1 - Élément électroluminescent à semi-conducteur au nitrure et procédé de production d'élément électroluminescent à semi-conducteur au nitrure - Google Patents

Élément électroluminescent à semi-conducteur au nitrure et procédé de production d'élément électroluminescent à semi-conducteur au nitrure Download PDF

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WO2024257516A1
WO2024257516A1 PCT/JP2024/017346 JP2024017346W WO2024257516A1 WO 2024257516 A1 WO2024257516 A1 WO 2024257516A1 JP 2024017346 W JP2024017346 W JP 2024017346W WO 2024257516 A1 WO2024257516 A1 WO 2024257516A1
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type
layer
cladding layer
concentration
nitride semiconductor
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Japanese (ja)
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明彦 石橋
啓 大野
章雄 上田
隆司 狩野
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Panasonic Holdings Corp
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Panasonic Holdings Corp
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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
    • H01S5/30—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

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  • This disclosure relates to a nitride semiconductor light-emitting device and a method for manufacturing a nitride semiconductor light-emitting device.
  • semiconductor laser devices have been used in a wide range of technical fields due to their excellent features such as being small, inexpensive, and having high output.
  • high-output semiconductor laser devices are used for processing a variety of materials such as metals, resins, and composite carbon materials (CFRP: Carbon Fiber Reinforced Plastics).
  • GaN-based semiconductor light-emitting devices that emit light in the blue wavelength range of 405 nm to 540 nm, which has a high absorption rate (low reflectance) in copper materials, have been attracting attention as light sources for processing copper materials, which are often used in EV motors, etc.
  • GaN-based semiconductor light-emitting elements require high power-to-light conversion efficiency.
  • Power-to-light conversion efficiency indicates the proportion of input power that is converted into laser light. By converting input power into light with high efficiency, it is possible to increase the optical output and prevent excess energy from being converted into heat, thereby reducing the decrease in optical output caused by heat generation and the adverse effects on long-term reliability characteristics.
  • a GaN-based semiconductor light-emitting element comprises an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer, all made of GaN-based semiconductors.
  • the p-type semiconductor layer has, in order from the light-emitting layer side, a p-type cladding layer and a p-type contact layer.
  • the p-type cladding layer is made of, for example, an AlGaN semiconductor, and Mg is added as an impurity.
  • Patent document 1 describes a manufacturing method for controlling the Mg concentration in the thickness direction of the p-type cladding layer to a constant value.
  • the technology described in patent document 1 makes the carrier distribution in the thickness direction of the p-type cladding layer uniform, reducing the effect on hole injection into the light-emitting layer.
  • Patent Document 2 and Non-Patent Document 1 also propose a technique in which a p-type electron blocking layer with a higher Mg concentration than the p-type cladding layer is provided at the junction between the p-type cladding layer and the light-emitting layer, and an undoped AlGaN layer is interposed between the p-type electron blocking layer and the light-emitting layer to suppress diffusion of Mg added to the p-type electron blocking layer into the light-emitting layer.
  • the undoped AlGaN layer prevents deterioration of the light-emitting layer due to Mg diffusion, so that optical absorption loss is reduced and power-to-light conversion efficiency is improved compared to when no undoped AlGaN layer is provided.
  • a nitride semiconductor light emitting device includes: A nitride semiconductor light emitting device comprising an n-type semiconductor layer, a p-type semiconductor layer, and a light emitting layer between the n-type semiconductor layer and the p-type semiconductor layer, the p-type semiconductor layer has a p-type contact layer and a p-type cladding layer made of an Mg-doped nitride semiconductor; the p-type cladding layer includes a p-type first cladding layer disposed on the light emitting layer side, and a p-type second cladding layer disposed between the p-type first cladding layer and the p-type contact layer, the average Mg concentration of the second p-type cladding layer is higher than the average Mg concentration of the first p-type cladding layer; The overall average Mg concentration of the p-type cladding layer is lower than that of the other layers of the p-type semiconductor layer.
  • a method for manufacturing a nitride semiconductor light emitting device includes the steps of: A method for manufacturing a nitride semiconductor light-emitting device comprising an n-type semiconductor layer, a p-type semiconductor layer, and a light-emitting layer between the n-type semiconductor layer and the p-type semiconductor layer, the method comprising the steps of: the p-type semiconductor layer has a p-type contact layer and a p-type cladding layer made of an Mg-doped nitride semiconductor; the step of forming the p-type cladding layer includes a step of forming a p-type first cladding layer under first growth conditions on the light emitting layer side, and a step of forming a p-type second cladding layer between the p-type first cladding layer and the p-type contact layer under second growth conditions; The Mg supply amount under the second growth conditions is greater than the Mg supply amount under the first growth conditions.
  • FIG. 1 is a cross-sectional view of a semiconductor light emitting device according to an embodiment.
  • FIG. 2 is a diagram showing an example of a concentration profile in the semiconductor light emitting device according to the embodiment.
  • FIG. 3 is a diagram showing another example of a concentration profile in the semiconductor light emitting device according to the embodiment.
  • FIG. 4 is a diagram showing another example of a concentration profile in the semiconductor light emitting device according to the embodiment.
  • FIG. 5 is a diagram showing another example of a concentration profile in the semiconductor light emitting device according to the embodiment.
  • an undoped AlGaN layer is inserted between the p-type semiconductor layer and the light emitting layer, so the element resistance increases compared to when the undoped AlGaN layer is not provided. Therefore, if the thickness of the undoped AlGaN layer is increased to reduce the light absorption loss, the operating voltage increases, and there is a risk that the total power-to-light conversion efficiency will decrease.
  • the objective of this disclosure is to provide a nitride semiconductor light-emitting device with high power-to-light conversion efficiency and a method for manufacturing the nitride semiconductor light-emitting device.
  • a GaN-based semiconductor light-emitting element capable of emitting blue light with a wavelength of 445 nm will be described as an example of a nitride semiconductor light-emitting element.
  • a nitride semiconductor light-emitting element is typically a semiconductor light-emitting element in which each layer is composed of a general formula In x Al y Ga 1-x-y N (0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ x+y ⁇ 1).
  • the active layer contains Ga
  • the active layer is composed of In x Al y Ga 1-x-y N (0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ x+y ⁇ 1)
  • it is called a GaN-based semiconductor light-emitting element.
  • FIG. 1 is a cross-sectional view of a GaN-based semiconductor light-emitting element 1 according to an embodiment.
  • FIGS. 2 to 5 are diagrams showing examples of concentration profiles in the GaN-based semiconductor light-emitting element 1. The concentration profiles shown in FIGS. 2 to 5 were analyzed by secondary ion mass spectrometry (SIMS).
  • SIMS secondary ion mass spectrometry
  • the n-type impurity is silicon (Si) and the p-type impurity is magnesium (Mg).
  • the group III raw material for example, trimethylgallium (TMG), trimethylindium (TMI), and trimethylaluminum (TMA) are used as the group III raw material.
  • ammonia (NH 3 ) is used as the group V raw material.
  • silane (SiH 4 ) is used as the Si raw material.
  • cyclopentadienylmagnesium (Cp 2 Mg) is used as the Mg raw material.
  • the configuration of the GaN-based semiconductor light-emitting element 1 described in this embodiment is an example, and the stacked structure of the n-type semiconductor layer 20, the light-emitting layer 30, and the p-type semiconductor layer 40, the film thickness of each layer, the composition ratio of the group III elements forming each layer, etc. can be changed as appropriate.
  • the substrate 10 is, for example, an n-type hexagonal GaN substrate having a (0001) surface.
  • the n-type semiconductor layer 20 is a cladding layer for confining light in the light emitting layer 30.
  • the n-type semiconductor layer 20 is composed of, for example, Si-doped Al y Ga 1-y N (0 ⁇ y ⁇ 1).
  • the Al composition ratio y of the n-type semiconductor layer 20 is, for example, 0.03.
  • the film thickness of the n-type semiconductor layer 20 is, for example, 3 ⁇ m.
  • the Si concentration of the n-type semiconductor layer 20 is, for example, about 1 ⁇ 10 18 cm ⁇ 3 .
  • the light-emitting layer 30 is a layer that emits blue light when a current is passed through it.
  • the light-emitting layer 30 has, in order from the substrate 10 side, an n-side light guide layer 31, an active layer 32, and a p-side light guide layer 33.
  • the n-side optical guiding layer 31 is made of Si-doped In x Ga 1-x N (0 ⁇ x ⁇ 1).
  • the n-side optical guiding layer 31 has, for example, a first optical guiding layer made of Si-doped GaN with an In composition ratio x of 0, and a second optical guiding layer made of Si-doped InGaN containing In (not shown).
  • the first optical guiding layer is formed on the n-type semiconductor layer 20.
  • the first optical guiding layer has a thickness of, for example, 250 nm.
  • the first optical guiding layer has a Si concentration of, for example, about 1 ⁇ 10 18 cm ⁇ 3 .
  • the second optical guide layer is formed while gradually increasing the In composition ratio x from the first optical guide layer side.
  • the thickness of the second optical guide layer is, for example, 150 nm.
  • the second optical guide layer is not intentionally doped with Si.
  • the Si concentration is, for example, about 5 ⁇ 10 15 cm ⁇ 3 or less.
  • the In composition ratio x can be increased by gradually increasing the supply amount of the In raw material (TMI).
  • the supply amount of the Ga raw material (TMG) may be gradually decreased while keeping the supply amount of the TMI constant, thereby increasing the In composition ratio x of the second optical guide layer.
  • TMI may be supplied in a pulsed manner and the duty may be gradually increased, thereby substantially continuously increasing the In composition ratio x of the second optical guide layer.
  • the In composition ratio x of the second optical guide layer may be increased by gradually lowering the growth temperature while keeping the TMI supply amount and the TMG supply amount constant. Note that it is preferable that the composition ratio x of the second optical guide layer does not exceed the composition ratio x of the n-side optical guide layer to be stacked next, i.e., it increases monotonically.
  • the active layer 32 is composed of an In x Ga 1-x N layer (0 ⁇ x ⁇ 1).
  • the active layer 32 has, for example, a quantum well layer and a barrier layer (not shown).
  • the active layer 32 has, for example, a two-period multiple quantum well structure in which quantum well layers and barrier layers are alternately stacked. Specifically, a first barrier layer, a first quantum well layer, a second barrier layer, a second quantum well layer, and a third barrier layer (all not shown) are formed in this order on the n-side light guide layer 31.
  • the first barrier layer has, for example, an In composition ratio x of 0.03 and a thickness of 20 nm.
  • the first quantum well layer has, for example, an In composition ratio x of 0.18 and a thickness of 3.0 nm.
  • the second barrier layer has, for example, an In composition ratio x of 0.08 and a thickness of 10 nm.
  • the second quantum well layer has, for example, an In composition ratio x of 0.18 and a thickness of approximately 3.0 nm.
  • the third barrier layer has, for example, an In composition ratio x of 0.03 and a thickness of 10 nm.
  • each barrier layer may be set appropriately taking into account the uniformity of carrier injection, etc., and may be the same or different.
  • the p-side light guiding layer 33 is made of undoped In x Al y Ga 1-x-y N (0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ x+y ⁇ 1).
  • the p-side light guiding layer 33 is, for example, a layer made of undoped InGaN, undoped GaN, undoped AlGaN, or a combination thereof.
  • the thickness of the p-side light guiding layer 33 is, for example, 0.2 ⁇ m.
  • the p-side light guide layer 33 is configured so that the refractive index decreases from the active layer 32 side toward the p-type semiconductor layer 40 (p-type cladding layer 42) side.
  • the light confinement effect can be improved by forming the p-side light guide layer 33 by depositing InGaN, GaN, and AlGaN in this order from the active layer 32 side.
  • the p-type semiconductor layer 40 has a p-type electron blocking layer 41, a p-type cladding layer 42, and a p-type contact layer 43.
  • the p-type electron blocking layer 41 is composed of Mg-doped Al y Ga 1-y N (0 ⁇ y ⁇ 1). By providing the p-type electron blocking layer 41, it is possible to improve the efficiency of hole injection into the active layer 32.
  • the Al composition ratio y of the p-type electron blocking layer 41 is preferably 0.35 or more, for example, 0.35.
  • the film thickness of the p-type electron blocking layer 41 is, for example, 5 nm.
  • the Mg concentration of the p-type electron blocking layer 41 is preferably 1 ⁇ 10 19 cm ⁇ 3 or more in order to efficiently inject holes into the active layer 32.
  • the p-type cladding layer 42 is composed of Mg-doped Al y Ga 1-y N (0 ⁇ y ⁇ 1).
  • the p-type cladding layer 42 may include an Mg-doped AlGaN layer, and may have a superlattice structure in which Mg-doped AlGaN layers and Mg-doped GaN layers are periodically stacked.
  • the Al composition ratio y of the p-type cladding layer 42 is preferably 0.02 to 0.05, for example, 0.03.
  • the Al composition ratio means an average Al composition ratio.
  • the total thickness of the p-type cladding layer 42 is preferably 500 to 800 nm, for example, 650 nm.
  • the overall average Mg concentration of the p-type cladding layer 42 is, for example, 3 ⁇ 10 18 cm ⁇ 3 to 1 ⁇ 10 19 cm ⁇ 3 .
  • the overall average Mg concentration of the p-type cladding layer 42 is lower than the average Mg concentration of the other layers of the p-type semiconductor layer 40, i.e., the p-type contact layer 43 and the p-type electron blocking layer 41.
  • the p-type cladding layer 42 has a p-type first cladding layer 421 arranged on the light-emitting layer 30 side, and a p-type second cladding layer 422 arranged between the p-type first cladding layer 421 and the p-type contact layer 43.
  • the p-type first cladding layer 421 and the p-type second cladding layer 422 can be distinguished, for example, by their respective Mg concentrations.
  • the first p-type cladding layer 421 has a constant Mg concentration C1 in the thickness direction (see FIGS. 2 to 5).
  • Constant Mg concentration means that the variation (deviation) of the Mg concentration in the thickness direction is small and falls within a predetermined concentration range, and typically, the deviation (difference between the maximum and minimum values) is 1 ⁇ 10 18 cm -3 or less.
  • the Mg concentration of the first p-type cladding layer 421, i.e., the first Mg concentration C1, is controlled to be in the range of at least 0.5 to 5 ⁇ 10 18 cm -3 . It is preferable that the Mg concentration changes sharply at the boundary between the p-type electron blocking layer 41 and the first p-type cladding layer 421 (see FIG. 2). For example, by setting the Mg supply amount in the deposition process of the first p-type cladding layer 421 to 1% or less of the Mg supply amount in the deposition process of the p-type electron blocking layer 41, the Mg concentration can be sharply reduced and a desired Mg concentration profile can be realized.
  • the first Mg concentration C1 is higher than 2 ⁇ 10 18 cm -3 , the blue light emitted from the active layer 32 may be absorbed in the p-type first cladding layer 421, increasing the optical absorption loss and possibly decreasing the power-light conversion efficiency. If the first Mg concentration C1 is lower than 1 ⁇ 10 18 cm -3 , the element resistance may increase and possibly decreasing the power-light conversion efficiency. For this reason, it is preferable that the first Mg concentration C1 is 1 to 2 ⁇ 10 18 cm -3 .
  • the Mg concentration in the p-type cladding layer 42 is constant at about 1 to 2 ⁇ 10 19 cm ⁇ 3 throughout the entire p-type cladding layer 42.
  • the element resistance is low, but since a high Mg level exists near the light emitting layer 30, the light absorption loss is large compared to the case where a p-type first cladding layer 421 with a low Mg concentration is provided as in this embodiment.
  • the p-type second cladding layer 422 has a constant Mg concentration in the thickness direction, which is a second Mg concentration C2 (see Figures 2 to 5). As shown in Figures 2 to 5, the second Mg concentration C2 is greater than the first Mg concentration C1. Naturally, the average Mg concentration of the p-type second cladding layer 422 is greater than the average Mg concentration of the p-type first cladding layer 421.
  • the Mg concentration of the p-type second cladding layer 422, i.e., the second Mg concentration C2, is controlled to be at least 0.5 ⁇ 10 19 cm -3 or more from the viewpoint of reducing resistance.
  • the second Mg concentration C2 is higher than 2 ⁇ 10 19 cm -3 , the blue light emitted from the active layer 32 may be absorbed by the p-type second cladding layer 422, increasing the light absorption loss and decreasing the power light conversion efficiency.
  • the second Mg concentration C2 is preferably 0.5 to 2 ⁇ 10 19 cm -3 .
  • the first p-type cladding layer 421 and the second p-type cladding layer 422 can also be distinguished by the inflection point of the Mg concentration profile.
  • An inflection point is a boundary where the rate of change in Mg concentration with respect to depth (the slope of the Mg concentration profile) is greater than the rate of change in Mg concentration in the regions before and after it.
  • the p-type first cladding layer 421 and the p-type second cladding layer 422 can be distinguished by their respective growth conditions. That is, when forming the p-type cladding layer 42, the region formed with a first Mg supply amount can be defined as the p-type first cladding layer 421, and the region formed with a second Mg supply amount greater than the first Mg supply amount can be defined as the p-type second cladding layer 422.
  • the thickness of the p-type first cladding layer 421 is 0.3 ⁇ m or less, the distribution of laser light intensity is substantially broadened. Furthermore, when the thickness of the p-type first cladding layer 421 is less than 0.2 ⁇ m (see FIG. 5), the p-type second cladding layer 422 approaches the light-emitting layer 30, and absorption loss of blue light due to the Mg level in the p-type second cladding layer 422 is likely to occur. For this reason, the thickness of the p-type first cladding layer 421 is preferably 0.2 to 0.4 ⁇ m, for example, 0.35 ⁇ m.
  • the thickness of the p-type second cladding layer 422 is preferably 100 to 600 nm, for example, 300 nm.
  • the total thickness of the p-type cladding layer 42 is preferably 500 to 800 nm, because when the thickness of the p-type first cladding layer 421 is 0.2 to 0.4 ⁇ m, the thickness of the p-type second cladding layer 422 is in the range of 100 to 600 nm.
  • the p-type contact layer 43 is composed of an Mg-doped GaN layer.
  • the thickness of the p-type contact layer 43 is, for example, 10 nm.
  • the average Mg concentration of the p-type contact layer 43 is preferably 1 ⁇ 10 20 cm ⁇ 3 or more in order to reduce the contact resistance with the p-side electrode 51.
  • the n-type semiconductor layer 20, the light-emitting layer 30, and the p-type semiconductor layer 40 are successively formed using, for example, a metal organic chemical vapor deposition (MOCVD) method.
  • MOCVD metal organic chemical vapor deposition
  • the process of forming the p-type cladding layer 42 includes a first process of forming the p-type first cladding layer 421 and a second process of forming the p-type second cladding layer 422.
  • the first and second processes have different growth conditions, in particular, different Mg supply amounts.
  • Mg source material (TMG) is supplied so that the Mg concentration in the thickness direction of the p-type first cladding layer 421 is constant at a first Mg concentration C1 (first growth condition).
  • Mg source material (TMG) is supplied so that the Mg concentration in the thickness direction of the p-type second cladding layer 422 is constant at a second Mg concentration C2 (second growth condition).
  • the Mg supply amount in the second growth condition is set to be larger than the Mg supply amount in the first growth condition.
  • each electrode is formed as follows.
  • a SiO 2 insulating film is formed on the p-type semiconductor layer 40 (p-type contact layer 43) by, for example, a thermal CVD method.
  • the thickness of the SiO 2 insulating film is, for example, 0.3 ⁇ m.
  • the SiO 2 insulating film is left in a stripe shape with a width of 16 ⁇ m, and other regions are etched.
  • the direction of the stripe is parallel to the m-axis direction of the hexagonal GaN-based semiconductor.
  • the stacked structure on which the SiO 2 insulating film is formed is etched to a depth of, for example, 1.0 ⁇ m by an inductively coupled plasma (ICP) etching method.
  • ICP inductively coupled plasma
  • a ridge stripe portion constituting the optical waveguide WG is formed in the p-type contact layer 43 and the p-type cladding layer 42.
  • the SiO 2 insulating film is removed using hydrofluoric acid to expose the p-type contact layer 43 and the p-type cladding layer 42.
  • a SiO 2 insulating film is again formed by thermal CVD over the entire surface including the ridge stripe portion on the exposed p-type contact layer 43 and p-type cladding layer 42.
  • the thickness of the SiO 2 insulating film is, for example, 0.2 ⁇ m.
  • This SiO 2 insulating film constitutes the insulating layer 55.
  • a resist pattern having an opening corresponding to the ridge stripe portion is formed on the upper surface of the SiO 2 insulating film by lithography.
  • the SiO 2 insulating film is etched using the resist pattern as a mask by reactive ion etching (RIE) using, for example, methane trifluoride (CHF 3 ) gas, so that the p-type contact layer 43 is exposed from the upper surface of the ridge stripe portion.
  • RIE reactive ion etching
  • a metal laminate film made of, for example, palladium (Pd) and platinum (Pt) is formed by electron beam (EB) deposition on at least the p-type contact layer 43 exposed from the upper surface of the ridge stripe portion.
  • Pd palladium
  • Pt platinum
  • the metal laminate film in the area other than the ridge stripe portion is removed by lift-off.
  • a p-side electrode 51 is formed on the upper surface of the p-type contact layer 43 in the ridge stripe portion.
  • the p-side electrode 51 may be made of a transparent oxide such as indium tin oxide or indium oxide.
  • the wiring electrode 52 is selectively formed by lithography and lift-off so as to cover the SiO 2 insulating film and the p-side electrode 51.
  • the wiring electrode 52 has, for example, a planar dimension of 750 ⁇ m in a direction parallel to the ridge stripe portion and a planar dimension of 150 ⁇ m in a direction perpendicular to the ridge stripe portion.
  • the wiring electrode 52 is formed of, for example, a metal laminate film made of titanium (Ti), platinum (Pt), and gold (Au).
  • Ti titanium
  • Pt platinum
  • Au gold
  • the thickness of Ti is 50 nm
  • the thickness of Pt is 200 nm
  • the thickness of Au is 100 nm.
  • a pad electrode 53 made of an Au layer is formed on the upper surface of the wiring electrode 52 by electrolytic plating.
  • the thickness of the pad electrode 53 is, for example, 10 ⁇ m. This makes it possible to mount the laser chip by wire bonding, and also makes it possible to effectively dissipate heat generated in the active layer 32, thereby improving the reliability of the GaN-based semiconductor light-emitting element 1.
  • the rear surface of the semiconductor wafer on which the p-side electrode 51, wiring electrode 52, and pad electrode 53 are formed is polished with diamond slurry to thin the substrate 10 to a thickness of approximately 100 ⁇ m.
  • the n-side electrode 54 is formed on the rear surface of the substrate 10, for example, by EB deposition.
  • the n-side electrode 54 is formed, for example, from a metal laminate film made of Ti, Pt, and Au.
  • the thickness of Ti is 5 nm
  • the thickness of Pt is 10 nm
  • the thickness of Au is 1000 nm.
  • the wafer-state laminate structure thus produced is cleaved (primary cleavage) along the m-plane.
  • the length in the m-axis direction is, for example, 1200 ⁇ m.
  • a frontcoat film (not shown) capable of emitting laser light is disposed on one cleavage surface in the resonator length direction of the optical waveguide WG.
  • a rearcoat film for reflecting the laser light is disposed on the other cleavage surface in the resonator length direction of the optical waveguide WG.
  • the one end surface on which the frontcoat film is disposed becomes the emission end surface from which the laser light is emitted, and the other end surface on which the rearcoat film is formed becomes the reflection end surface that reflects the laser light.
  • the front coat film and the rear coat film are formed by, for example, an electron cyclotron resonance (ECR) sputtering method.
  • the front coat film is made of a dielectric film such as a single layer of SiO2 .
  • the rear coat film is made of a dielectric film such as a stacked layer of ZrO2 / SiO2 .
  • the reflectance of the emission end surface where the front coat film is disposed is, for example, 6%, and the reflectance of the emission end surface where the rear coat film is disposed is, for example, 95%. This makes it possible to realize a highly efficient GaN-based semiconductor light-emitting element 1.
  • the laminated structure with the front coat film and rear coat film formed is cleaved (secondary cleavage) along the a-plane between the optical waveguides WG formed at a pitch of, for example, 200 ⁇ m. In this way, the GaN-based semiconductor light-emitting element 1 for a semiconductor laser device is produced.
  • the Mg concentration changes sharply at the boundary between the p-type electron blocking layer 41 and the first p-type cladding layer 421.
  • the Mg raw material Cp 2 Mg may be incorporated into the first p-type cladding layer 421 in a larger amount than set due to the memory effect, or Mg may diffuse from the p-type electron blocking layer 41 into the first p-type cladding layer 421 in a solid phase.
  • the p-type third cladding layer 423 is interposed between the p-type first cladding layer 421 and the p-type electron blocking layer 41.
  • the p-type third cladding layer 423 is not an intentionally formed layer, but a transition layer that is formed as a result when the p-type first cladding layer 421 is formed on the p-type electron blocking layer 41.
  • the growth conditions of the p-type third cladding layer 423 are typically the same as those of the p-type first cladding layer 421. Note that the growth conditions of the p-type third cladding layer 423 may be set to be different from those of the p-type first cladding layer 421.
  • p-type third cladding layer 423 can be defined as a layer in which the Mg concentration increases monotonically from p-type first cladding layer 421 toward p-type electron blocking layer 41.
  • the Mg concentration C3 of p-type third cladding layer 423 is higher than the Mg concentration C1 of p-type first cladding layer 421, and exceeds 2 ⁇ 10 18 cm -3 , for example.
  • the thickness of the p-type third cladding layer 423 is 0.2 ⁇ m or less, the effect of providing the p-type first cladding layer 421, that is, the effect of suppressing light absorption loss due to the Mg level in the p-type second cladding layer 422, can be obtained.
  • the thickness of the p-type third cladding layer 423 exceeds 0.2 ⁇ m, the absorption loss of blue light becomes significant due to the Mg level in the p-type third cladding layer 423, and the deterioration of the element characteristics cannot be ignored.
  • the thickness of the p-type third cladding layer 423 must be 0.2 ⁇ m or less, and is preferably 0.1 ⁇ m or less.
  • the thickness of the p-type third cladding layer 423 can be controlled by appropriately adjusting the growth conditions of the p-type electron blocking layer 41 and the growth conditions in the initial stage of growth of the p-type first cladding layer 421.
  • the growth temperature of the p-type electron blocking layer 41 and the p-type cladding layer 42 at an initial stage to a low temperature (e.g., 850°C) similar to that of the active layer 32 and the p-side light guide layer 33, and adjusting the growth rate appropriately, it is possible to suppress the diffusion of Mg from the p-type electron blocking layer 41 into the p-type cladding layer 42 (the third p-type cladding layer 423).
  • a low temperature e.g., 850°C
  • C carbon
  • C atoms are incorporated into both C lattice sites and Ga lattice sites in the GaN crystal lattice, and have the property of compensating for impurities.
  • Mg is known to supply holes at about 1/10 of the atomic concentration.
  • the hole concentration is about 1 ⁇ 10 18 cm -3 .
  • the C concentration that may compensate for the holes is preferably 10% or less of the Mg concentration. If the C concentration is too low, the effect of suppressing the diffusion of Mg atoms decreases. For this reason, the C concentration in the p-type electron blocking layer 41 is preferably 5 ⁇ 10 16 to 1 ⁇ 10 17 cm -3 .
  • the GaN-based semiconductor light-emitting device 1 has the following characteristics, either alone or in appropriate combination:
  • the GaN-based semiconductor light-emitting element 1 is a GaN-based semiconductor element including an n-type semiconductor layer 20, a p-type semiconductor layer 40, and a light-emitting layer 30 between the n-type semiconductor layer 20 and the p-type semiconductor layer 40.
  • the p-type semiconductor layer 40 has a p-type contact layer 43 and a p-type cladding layer 42 made of Mg-doped nitride semiconductor, and the p-type cladding layer 42 has a p-type first cladding layer 421 arranged on the light-emitting layer 30 side, and a p-type second cladding layer 422 arranged between the p-type first cladding layer 421 and the p-type contact layer 43.
  • the average Mg concentration of the p-type second cladding layer 422 is higher than the average Mg concentration of the p-type first cladding layer 421, and the overall average Mg concentration of the p-type cladding layer 42 is lower than other layers of the p-type semiconductor layer 40 (for example, the p-type contact layer 43).
  • the method for manufacturing a GaN-based semiconductor light-emitting element 1 includes an n-type semiconductor layer 20, a p-type semiconductor layer, and a light-emitting layer 30 between the n-type semiconductor layer and the p-type semiconductor layer, the p-type semiconductor layer 40 includes a p-type contact layer 43 and a p-type cladding layer 42 made of an Mg-doped nitride semiconductor, and the process for forming the p-type cladding layer 42 includes a process for forming a p-type first cladding layer 421 on the light-emitting layer 30 side under first growth conditions, and a process for forming a p-type second cladding layer 422 between the p-type first cladding layer 421 and the p-type contact layer 43 under second growth conditions, and the Mg supply amount under the second growth conditions is greater than the Mg supply amount under the first growth conditions.
  • the GaN-based semiconductor light-emitting device 1 and its manufacturing method according to the embodiment ensure low element resistance by using the p-type second cladding layer 422 with a high Mg concentration, while the p-type first cladding layer 421 with a low Mg concentration reduces the optical absorption loss of blue light due to the Mg level of the p-type second cladding layer 422, thereby increasing the total power-to-light conversion efficiency (the product of current and voltage).
  • the p-type semiconductor layer 40 preferably has a p-type electron blocking layer 41 made of an Mg-doped nitride semiconductor at the portion where it joins with the light-emitting layer 30.
  • a p-type electron blocking layer 41 made of an Mg-doped nitride semiconductor at the portion where it joins with the light-emitting layer 30.
  • the p-type first cladding layer 421 has a constant Mg concentration in the thickness direction at a first Mg concentration C1
  • the p-type second cladding layer 422 has a constant Mg concentration in the thickness direction at a second Mg concentration C2 that is higher than the first Mg concentration C1.
  • the first Mg concentration C1 is preferably 1 to 2 ⁇ 10 18 cm ⁇ 3 . This makes it possible to reduce the element resistance while suppressing the optical absorption loss of blue light due to the Mg level of the p-type first cladding layer 421, and effectively improve the power-to-light conversion efficiency of the GaN-based semiconductor element 1.
  • the second Mg concentration is preferably 5 ⁇ 10 18 cm ⁇ 3 or more, which makes it possible to effectively reduce the element resistance and improve the power-to-light conversion efficiency of the GaN-based semiconductor element 1.
  • the thickness of the p-type first cladding layer 421 is preferably 0.2 to 0.3 ⁇ m. This provides the effect of suppressing the optical absorption loss of blue light due to the Mg level in the p-type second cladding layer 422, and also effectively widens the distribution of the laser light intensity.
  • the p-type cladding layer 42 may have a p-type third cladding layer 423 between the p-type first cladding layer 421 and the p-type electron blocking layer 41, in which the Mg concentration increases monotonically from the p-type first cladding layer 421 toward the p-type electron blocking layer 41. This allows some diffusion of Mg from the p-type electron blocking layer 41 to the p-type cladding layer 42, making it easy to control the Mg concentration in the p-type cladding layer 42.
  • the thickness of the p-type third cladding layer 423 is preferably 0.2 ⁇ m or less. This makes it possible to suppress light absorption loss due to Mg levels in the p-type third cladding layer 423.
  • the carbon concentration in p-type electron blocking layer 41 and p-type third cladding layer 423 is 0.5 to 1 ⁇ 10 17 cm ⁇ 3 . This makes it possible to suppress diffusion of Mg from p-type electron blocking layer 41 to p-type cladding layer 42, and to suppress light absorption loss due to Mg levels in p-type third cladding layer 423.
  • the GaN-based semiconductor light-emitting element 1 described in the embodiment has a p-type electron blocking layer 41 at the junction between the p-type semiconductor layer 40 and the light-emitting layer 30, but the p-type electron blocking layer 41 may be omitted.
  • a GaN-based semiconductor light-emitting device having a single optical waveguide WG has been described, but the same effect can be obtained by applying this disclosure to a GaN-based semiconductor light-emitting device (so-called bar laser) in which multiple optical waveguides are formed in an array.
  • the nitride semiconductor light-emitting element and manufacturing method disclosed herein are useful as a blue laser light source suitable for laser processing machines for cutting and welding copper materials, which are often used in EV motors, etc.
  • GaN-based semiconductor light-emitting element (nitride semiconductor light-emitting element) REFERENCE SIGNS LIST 10: Substrate 20: n-type semiconductor layer 30: Light emitting layer 32: Active layer 40: P-type semiconductor layer 41: P-type electron blocking layer 42: P-type cladding layer 43: P-type contact layer 421: P-type first cladding layer 422: P-type second cladding layer 423: P-type third cladding layer

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Semiconductor Lasers (AREA)

Abstract

Un élément électroluminescent à semi-conducteur au nitrure comprend une couche semi-conductrice de type n, une couche semi-conductrice de type p et une couche luminescente entre la couche semi-conductrice de type n et la couche semi-conductrice de type p, la couche semi-conductrice de type p comprenant une couche de contact de type p et une couche de revêtement de type p qui sont constituées d'un semi-conducteur au nitrure dopé au Mg, la couche de revêtement de type p comprenant une première couche de revêtement de type p, qui est disposée sur le côté de la couche luminescente, et une deuxième couche de revêtement de type p, qui est interposée entre la première couche de revêtement de type p et la couche de contact de type p. La seconde couche de revêtement de type p présente une concentration moyenne en Mg supérieure à la concentration moyenne en Mg de la première couche de revêtement de type p. La couche de revêtement de type p dans son ensemble présente une concentration moyenne en Mg inférieure à celle de n'importe quelle autre couche de la couche semi-conductrice de type p.
PCT/JP2024/017346 2023-06-12 2024-05-10 Élément électroluminescent à semi-conducteur au nitrure et procédé de production d'élément électroluminescent à semi-conducteur au nitrure Pending WO2024257516A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011013621A1 (fr) * 2009-07-31 2011-02-03 日亜化学工業株式会社 Diode laser à semi-conducteur nitruré
JP2012227492A (ja) * 2011-04-22 2012-11-15 Sumitomo Electric Ind Ltd 窒化物半導体レーザ、及びエピタキシャル基板
JP2013033930A (ja) * 2011-06-29 2013-02-14 Sumitomo Electric Ind Ltd Ｉｉｉ族窒化物半導体素子、及び、ｉｉｉ族窒化物半導体素子の製造方法
US20150060908A1 (en) * 2013-09-03 2015-03-05 Sensor Electronic Technology, Inc. Optoelectronic Device with Modulation Doping
WO2021090849A1 (fr) * 2019-11-08 2021-05-14 ヌヴォトンテクノロジージャパン株式会社 Élément électroluminescent à semi-conducteurs et procédé de fabrication d'élément électroluminescent à semi-conducteurs

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011013621A1 (fr) * 2009-07-31 2011-02-03 日亜化学工業株式会社 Diode laser à semi-conducteur nitruré
JP2012227492A (ja) * 2011-04-22 2012-11-15 Sumitomo Electric Ind Ltd 窒化物半導体レーザ、及びエピタキシャル基板
JP2013033930A (ja) * 2011-06-29 2013-02-14 Sumitomo Electric Ind Ltd Ｉｉｉ族窒化物半導体素子、及び、ｉｉｉ族窒化物半導体素子の製造方法
US20150060908A1 (en) * 2013-09-03 2015-03-05 Sensor Electronic Technology, Inc. Optoelectronic Device with Modulation Doping
WO2021090849A1 (fr) * 2019-11-08 2021-05-14 ヌヴォトンテクノロジージャパン株式会社 Élément électroluminescent à semi-conducteurs et procédé de fabrication d'élément électroluminescent à semi-conducteurs

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