WO2014167965A1 - 窒化物半導体多層膜反射鏡とそれを用いた発光素子 - Google Patents
窒化物半導体多層膜反射鏡とそれを用いた発光素子 Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/10—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a light reflecting structure, e.g. semiconductor Bragg reflector
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
- H01L33/0062—Processes for devices with an active region comprising only III-V compounds
- H01L33/0075—Processes for devices with an active region comprising only III-V compounds comprising nitride compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
- H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
-
- 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
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
- H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
- H01S5/18361—Structure of the reflectors, e.g. hybrid mirrors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/26—Materials of the light emitting region
- H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
- H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
-
- 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
- H01S5/34333—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 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
Definitions
- the present invention relates to a nitride semiconductor multilayer film reflector and a light emitting device using the same.
- An AlGaAs-based surface emitting semiconductor laser device for extracting laser light from a direction perpendicular to the substrate surface has semiconductor multilayer film reflecting mirrors in the vertical direction of the active layer in order to constitute an optical resonator.
- the semiconductor multilayer reflector is configured by alternately laminating first semiconductor layers and second semiconductor layers having a band gap energy larger than the energy corresponding to the oscillation wavelength of the laser light.
- the first semiconductor layer and the second semiconductor layer having a large difference in refractive index that is, the difference in band gap energy
- the first semiconductor layer and the second semiconductor layer having a large difference in refractive index are selected to achieve high reflectance, but they occur at their junctions. Hetero-barriers become high. This makes it difficult for the current due to electrons or holes to flow, and has a problem of showing a high resistance value.
- the first semiconductor layer is formed by interposing a non-doped third semiconductor layer having the same composition as the second semiconductor layer and having a small layer thickness between the first semiconductor layer and the second semiconductor layer.
- a third semiconductor layer are disclosed, for example, to reduce the resistance of the semiconductor multilayer reflector by lowering the hetero barrier in the hetero junction and promoting the tunneling of electrons or holes.
- the resistivity is unlikely to be lowered because the nitride semiconductor itself is a wide gap semiconductor material. Furthermore, there is a problem that the hetero barrier formed at the hetero junction interface between the semiconductor layers also becomes high.
- the inventors of the present invention earnestly examining the factor that the nitride semiconductor multilayer film reflector exhibits high resistance, the first semiconductor layer and the second semiconductor layer having different refractive indexes due to the polarization effect unique to the nitride semiconductor material. It was found that a very large polarization was formed at the junction interface of Then, it was found that the energy barrier due to this polarization effect is the main factor that the nitride semiconductor multilayer mirror exhibits high resistance.
- the present invention has been made in view of the factors newly found by the present inventors in addition to the above-described conventional circumstances, and reduces the energy barrier generated at the nitride semiconductor heterojunction interface by the polarization effect,
- An object of the present invention is to realize a low resistance nitride semiconductor multilayer reflector capable of current injection.
- the nitride semiconductor multilayer film reflector of the first invention is The semiconductor device includes a first semiconductor layer made of a group III nitride semiconductor, a second semiconductor layer, a first composition graded layer, and a second composition graded layer, and a plurality of the first semiconductor layer and the second semiconductor layer.
- a nitride semiconductor multilayer film reflector manufactured by alternately stacking pairs The Al composition of the first semiconductor layer is higher than the Al composition of the second semiconductor layer, A first, which is adjusted between the first semiconductor layer and the second semiconductor layer, on the side of the group III element surface of the first semiconductor layer, such that the Al composition becomes lower toward the second semiconductor layer.
- Composition graded layer intervenes, A second compositional gradient adjusted between the first semiconductor layer and the second semiconductor layer, on the nitrogen surface side of the first semiconductor layer, such that the Al composition becomes lower as the second semiconductor layer is approached. Layers intervene, The energy levels for the electrons at the lower end of the conduction band of the first semiconductor layer, the second semiconductor layer, the first composition graded layer, and the second composition graded layer are continuous without offset.
- the n-type impurity concentration in the first composition graded layer is 5 ⁇ 10 19 cm ⁇ 3 or more.
- the nitride semiconductor multilayer reflector has a lower Al composition as it approaches the second semiconductor layer than the first semiconductor layer, between the first semiconductor layer and the second semiconductor layer having an Al composition lower than that of the first semiconductor layer.
- a first compositionally graded layer or a second compositionally graded layer is provided.
- the light emitting device of the second invention is A nitride semiconductor multilayer film reflector according to the first aspect of the present invention is characterized.
- This light emitting device can shorten the resonator length by providing the nitride semiconductor multilayer film reflector of the first invention, so that internal loss and threshold current can be significantly reduced, and high performance with high differential quantum efficiency It is possible to provide a nitride semiconductor light emitting device.
- FIG. 2 is a cross-sectional view of the nitride semiconductor multilayer film reflector of Example 1.
- 7 is a graph showing energy levels of electrons at the lower end of the conduction band of three pairs of the nitride semiconductor multilayer reflector in Example 1; It is a graph which shows Si doping concentration dependence with respect to the 1st composition gradient AlGaN layer of the energy level of FIG. In Example 1, it is a graph which shows the energy level with respect to the electron of the conduction band lower end for three pairs of nitride semiconductor multilayer film reflecting mirrors when not considering a polarization effect.
- Example 1 it is a graph which shows the relationship of light standing wave intensity distribution and electron concentration distribution at the time of making light inject into the nitride multilayer film reflective mirror for 3 pairs.
- FIG. 1 is a side sectional view of a nitride semiconductor surface emitting laser according to Example 1;
- FIG. 7 is a cross-sectional view of a nitride semiconductor multilayer film reflector of Example 2.
- 15 is a graph showing energy levels of electrons at the lower end of the conduction band of three pairs of the nitride semiconductor multilayer reflector in Example 2;
- FIG. 7 is a cross-sectional view of a nitride semiconductor multilayer film reflector of Example 3.
- 18 is a graph showing energy levels of electrons at the lower end of the conduction band of three pairs of the nitride semiconductor multilayer reflector in Example 3;
- the film thickness of each of the first composition graded layer and the second composition graded layer may be 20 nm or less. In this case, it is possible to prevent the decrease in the reflectance of the multilayer mirror.
- the first semiconductor layer and the second semiconductor layer are respectively an AlGaN layer and a GaN layer, and the Al composition value of the AlGaN layer is 0.4 to 0.6.
- the first composition graded layer and the second composition graded layer may be AlGaN layers, and the Al composition thereof may be compositionally graded from 0 to the Al composition value.
- a multilayer film having relatively high quality and high reflectance can be obtained at high speed. It is possible to form a film on The multilayer film reflector is manufactured by stacking 40 to 60 pairs of the first semiconductor layer and the second semiconductor layer, so that high speed film formation can significantly reduce the manufacturing process and the manufacturing cost.
- the first semiconductor layer and the second semiconductor layer are respectively an AlInN layer and a GaN layer, and the Al composition value of the AlInN layer is 0.82
- the first composition graded layer and the second composition graded layer are AlInN layers, and the Al composition thereof may be compositionally graded from 0.6 to the Al composition value.
- the first semiconductor layer and the second semiconductor layer are approximately the same. Since lattice matching is performed, crystal defects such as dislocations are less likely to be mixed during deposition of stacked layers, and a high-quality semiconductor layer can be obtained.
- Example 1 As shown in FIG. 1, a second composition gradient AlGaN layer (second composition gradient layer) 103 / Al 0.5 Ga 0.5 N layer (first semiconductor layer) 104 / a first composition gradient AlGaN layer (first composition gradient layer) 105
- a nitride semiconductor multilayer reflector having a laminated structure in which a / GaN layer (second semiconductor layer) 106 is laminated in order is used as one pair.
- the first semiconductor layer 104 was selected from Al 0.5 Ga 0.5 N.
- the second semiconductor layer 106 was selected from GaN.
- the Al composition value of the first semiconductor layer 104 is desirably 0.4 to 0.6. In the first embodiment, the first semiconductor layer 104 has an Al composition value of 0.5.
- the second composition graded AlGaN layer 103 uses AlGaN in which the Al composition value gradually increases monotonously from GaN to Al 0.5 Ga 0.5 N.
- the first composition graded AlGaN layer 105 uses AlGaN in which the Al composition value gradually decreases monotonously from Al 0.5 Ga 0.5 N to GaN.
- the central reflection wavelength of the multilayer film reflector is 400 nm, based on which the film thickness of the second composition gradient AlGaN layer 103 is 10 nm, the film thickness of the Al 0.5 Ga 0.5 N layer 104 is 34 nm, and the first composition gradient AlGaN layer
- the film thickness of 105 was set to 10 nm, and the film thickness of the GaN layer 106 was set to 30 nm.
- the nitride semiconductor multilayer film reflector having the structure shown in FIG. 1 was produced by the MOCVD method (metal organic chemical vapor deposition method) according to the following procedure.
- MOCVD method metal organic chemical vapor deposition method
- the GaN free-standing substrate 101 whose surface is a group III element surface was set in the reactor of the MOCVD apparatus. Thereafter, the surface of the GaN free-standing substrate 101 was thermally cleaned by raising the temperature while flowing hydrogen into the reaction furnace. Next, the substrate temperature is raised to 1050 ° C., hydrogen as a carrier gas, TMGa (trimethylgallium) as a raw material, ammonia, and SiH 4 (silane) as an n-type impurity raw material gas are put in a reaction furnace.
- TMGa trimethylgallium
- SiH 4 silane
- the n-type GaN underlayer 102 was grown to 300 nm on the GaN free-standing substrate 101.
- Si which is an n-type impurity, is doped at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- the second composition graded AlGaN layer 103 is grown.
- the substrate temperature is set to 1050 ° C. as in the film formation of the n-type GaN underlayer 102, and hydrogen as a carrier gas, TMGa, TMAl (trimethylaluminum) and ammonia as raw materials, and SiH 4 as an n-type impurity raw material gas
- the second composition-graded AlGaN layer 103 was grown to 10 nm on the n-type GaN underlayer 102 by flowing the reaction mixture into the reaction furnace.
- the gas supply amount of TMAl which is an Al raw material
- the gas supply amount of TMGa which is a Ga source
- the second composition-graded AlGaN layer 103 in which the Al composition value monotonously increases from 0 to 0.5 in the film thickness direction is formed on the n-type GaN underlayer 102.
- the second composition graded AlGaN layer 103 is doped with Si, which is an n-type impurity, at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- the doping concentration of Si is unified to 2 ⁇ 10 18 cm ⁇ 3 , but may be changed as needed within a range not exceeding 1 ⁇ 10 19 cm ⁇ 3 . That is, if a lower resistance multilayer mirror is required, high concentration doping may be performed, and if higher reflectance is required, low concentration doping may be performed.
- an Al 0.5 Ga 0.5 N layer 104 having an Al composition value of 0.5 was grown to 34 nm on the second composition graded AlGaN layer 103.
- the substrate temperature at this time, and the carrier gas, source gas, and impurity source gas flowing into the reaction furnace are all the same as those at the time of film formation of the second composition inclination AlGaN layer 103, and detailed description will be omitted.
- the gas supply amount of TMGa and TMAl was fixed to an amount capable of forming the Al 0.5 Ga 0.5 N layer 104.
- the Al 0.5 Ga 0.5 N layer 104 is doped with Si, which is an n-type impurity, at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- a first composition gradient AlGaN layer 105 was grown to 10 nm.
- the substrate temperature at this time, and the carrier gas, source gas, and impurity source gas flowing into the reaction furnace are all the same as those at the time of forming the second composition gradient AlGaN layer 103, and the detailed description will be omitted.
- the gas supply amount of TMAl which is an Al raw material, was monotonically decreased from 0 to a value at which the Al 0.5 Ga 0.5 N layer 104 is grown.
- the gas supply amount of TMGa which is a Ga source
- TMGa which is a Ga source
- the first composition gradient AlGaN layer 105 in which the Al composition value monotonically decreases from 0.5 to 0 was formed on the Al 0.5 Ga 0.5 N layer 104.
- the supply amount of SiH 4 as the impurity source gas is increased.
- the first composition graded AlGaN layer 105 is doped with Si, which is an n-type impurity, at a high concentration of 5 ⁇ 10 19 cm ⁇ 3 .
- the GaN layer 106 was grown to 30 nm on the first composition graded AlGaN layer 105.
- the substrate temperature at this time, and the carrier gas, the source gas, and the impurity source gas to be flowed into the reaction furnace are all the same as in the film formation of the n-type GaN underlayer 102, and detailed description will be omitted.
- the GaN layer 106 is doped with Si, which is an n-type impurity, at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- the second composition gradient AlGaN layer 103 and the Al 0.5 Ga 0.5 N layer 104 were further deposited to prepare a total of 49.5 pairs of nitride semiconductor multilayer reflectors as shown in FIG.
- FIG. 2 shows energy levels for electrons at the lower end of the conduction band of three pairs of nitride semiconductor multilayer reflectors.
- the energy level for electrons at the lower end of the conduction band of GaN is normalized to 0 eV.
- the lower end of the conduction band of the second composition gradient AlGaN layer 103 / Al 0.5 Ga 0.5 N layer 104 / the first composition gradient AlGaN layer 105 / GaN layer 106 is substantially flat with almost no offset.
- the doping concentration of Si in the first composition gradient AlGaN layer 105 is 2 ⁇ 10 15 cm ⁇ 3 , 2 ⁇ 10 18 cm ⁇ 3 , 2 ⁇ 10 19 cm ⁇ 3 , and 5 ⁇ 10 19 cm 3 in FIG. 3.
- the energy level with respect to the electron of the conduction band lower end for three pairs of nitride semiconductor multilayer film reflective mirrors at the time of changing to -3 is shown.
- the energy barrier due to the difference in the band gap energy between the Al 0.5 Ga 0.5 N layer 104 and the GaN layer 106 is smoothed by the first composition graded AlGaN layer 103 and the second composition graded AlGaN layer 105, the Al 0.5 Ga 0.5 N It is suggested that a high energy barrier due to negative fixed charge due to polarization is present at the interface between the layer 104 and the GaN layer 106 (first composition gradient AlGaN layer 105). Furthermore, when the doping concentration of Si in the first composition graded AlGaN layer 105 is 2 ⁇ 10 18 cm ⁇ 3 or less, it can be seen that the height of the energy barrier shows a very high value of about 4 eV.
- FIG. 4 shows energy levels for electrons at the lower end of the conduction band of three pairs of nitride semiconductor multilayer reflectors in the case where polarization is not taken into consideration.
- the solid line shows the energy level when the doping concentration of Si is 2 ⁇ 10 15 cm ⁇ 3 .
- the two dotted lines respectively show the energy levels when doping Si at a concentration of 2 ⁇ 10 18 cm ⁇ 3 and 7 ⁇ 10 18 cm ⁇ 3 .
- an energy barrier of about 0.8 eV is formed because the Al 0.5 Ga 0.5 N layer has a band gap energy larger than that of the GaN layer.
- the energy barrier is sufficiently lowered and the energy level becomes almost flat.
- the reason why the nitride multilayer reflector exhibits high resistance can not be explained.
- the high energy barrier associated with the polarization effect is considered to be the main factor that can not reduce the resistance of the nitride semiconductor multilayer reflector.
- the energy barrier due to the polarization effect is relaxed, and when the doping concentration of Si is 5 ⁇ 10 19 cm ⁇ 3 , the energy barrier is almost lost and flat It turns out that it becomes.
- FIG. 5 is a graph showing the relationship between the light standing wave intensity distribution and the electron concentration distribution in three pairs of nitride semiconductor multilayer film reflectors.
- the solid line indicates the profile of the electron concentration in the film thickness direction
- the dotted line indicates the profile of the light standing wave intensity in the film thickness direction.
- solid arrows indicate the interface (first inclined AlGaN layer 105) on the group III element surface side of the Al 0.5 Ga 0.5 N layer 104
- dotted arrows indicate the interface on the N surface (nitrogen) side (second inclination The AlGaN layer 103) is shown.
- a resonator structure is formed on the group III element surface side of the nitride semiconductor multilayer film reflector (see FIG. 6). Therefore, as shown in FIG. 5, antinodes of light standing waves are formed at the interface on the group III element surface side of the Al 0.5 Ga 0.5 N layer 104 indicated by the solid arrows, and at the interface on the N surface shown by the dotted arrows. , Nodes of light standing waves are formed.
- the electron concentration increases.
- the electron concentration decreases at the interface on the group III element side of the Al 0.5 Ga 0.5 N layer 104 where the energy level for electrons at the lower end of the conduction band is higher than 0 eV.
- the interface (first composition gradient AlGaN layer 105) on the side of the group III element surface of the Al 0.5 Ga 0.5 N layer 104 was subjected to Si doping at a very high concentration of 5 ⁇ 10 19 cm ⁇ 3 .
- the electron concentration remains as low as about 3 ⁇ 10 18 cm -3 as shown by the solid arrow in FIG. I understand. Therefore, the absorption coefficient is also expected to be a low value of 10 cm -1 or less.
- a method of doping a film with a high concentration of impurities for the purpose of reducing the resistance of a semiconductor multilayer film reflector is known in the prior art.
- impurity doping is performed at a high concentration, free carriers at the interface of the multilayer film are increased, and there is a problem in that the reflectance is reduced due to the absorption loss of light.
- the nitride semiconductor multilayer reflector is a high concentration n-type impurity (Si) with respect to the interface (first composition gradient AlGaN layer 105) on the group III element surface side of the Al 0.5 Ga 0.5 N layer 104. Even if doping is performed, the absorption loss does not increase because the polarization fixed charges keep electrons away. Therefore, the resistance of the nitride semiconductor multilayer reflector can be reduced while suppressing the decrease in reflectance.
- the interface on the N surface side of the Al 0.5 Ga 0.5 N layer 104 was subjected to Si doping at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- the electron concentration has a high value of about 3 ⁇ 10 19 cm -3 as indicated by the dotted arrow in FIG. Therefore, the absorption coefficient is also expected to be as large as 100 cm -1 .
- the interface on the N surface side of the Al 0.5 Ga 0.5 N layer 104 corresponds to a node of the light standing wave as shown by the dotted arrow in FIG. There is no.
- the nitride multilayer film reflector of the first embodiment is It meets the required specifications.
- an n-type GaN layer 201 of 70 nm was grown on the multilayer film reflection mirror (Al 0.5 Ga 0.5 N layer 104).
- Si which is an n-type impurity, is doped at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- 2.5 pairs of 3 nm of GaInN quantum well layer 302 and 6 nm of GaN barrier layer 301 are formed on n-type GaN layer 201 to form GaInN triple quantum well active layer 304 as a stacked layer.
- a 60 nm p-type GaN layer 202 was grown on the GaInN triple quantum well active layer 304 (GaN barrier layer 304).
- CP 2 Mg cyclopentadienyl magnesium
- the p-type GaN layer 202 is doped with Mg, which is a p-type impurity, at a concentration of 2 ⁇ 10 19 cm ⁇ 3 .
- the p-type GaN contact layer 204 was grown to 10 nm on the p-type GaN layer 202.
- the p-type GaN contact layer 204 is doped with Mg, which is a p-type impurity, at a concentration of 2 ⁇ 10 20 cm ⁇ 3 .
- Mg which is a p-type impurity
- p-side and n-side electrodes nC for current injection are formed.
- a SiO 2 film 401 is deposited to 20 nm on the one-wavelength resonator 203 (p-type GaN contact layer 204).
- an opening with a diameter of 10 um is formed in the center of the SiO 2 film 401 by photolithography and dry etching, and the p-type GaN contact layer 204 is exposed.
- an ITO transparent electrode tC is grown to 20 nm as a p-side contact electrode which also serves as current constriction.
- the p-side electrode is formed by forming a Ti / Au electrode having an outer peripheral part in contact with the outer peripheral part of the ITO transparent electrode tC and a pad part for wire bonding.
- photolithography is performed to partially dry-etch the multilayer mirror and the one-wavelength resonator 203 to expose the n-type GaN underlayer 102.
- a Ti / Al / Ti / Au electrode is laminated on the surface thereof to form an n-side electrode nC as shown in FIG.
- the Al 0.5 Ga 0.5 N layer 104 is a first semiconductor layer, between the GaN layer 106 is a second semiconductor layer, closer to the GaN layer 106 from Al 0.5 Ga 0.5 N layer 104
- a nitride multilayer reflector is manufactured by laminating a plurality of layers.
- the barrier can be significantly reduced, the resistance of the nitride semiconductor multilayer reflector can be lowered to allow current injection.
- each of the first AlGaN composition graded layer 105 and the second AlGaN composition graded layer 103 is reduced to 10 nm, it is possible to prevent a decrease in reflectance of the nitride semiconductor multilayer mirror.
- the Al composition value of the first semiconductor layer 104 is set to 0.5, it is possible to achieve both good crystallinity and high reflectance.
- AlGaN and GaN can be grown relatively fast among nitride semiconductors, the manufacturing process and manufacturing cost of the nitride semiconductor multilayer film reflector can be significantly reduced.
- the nitride semiconductor surface emitting laser provided with the above-mentioned nitride semiconductor multilayer film reflector can perform the laser oscillation operation by current injection. Therefore, it is not necessary to form the conventional intra-cavity structure for performing current injection from the side of the resonator, and the resonator length can be made into the one-wavelength resonator 203. Along with this, since the resonator length can be shortened, the internal loss and the threshold current necessary for laser oscillation can be greatly reduced, and the differential quantum efficiency is also improved.
- Example 2 As shown in FIG. 7, a second compositionally graded AlInN layer (second composition graded layer) 501 / Al 0.85 In 0.15 N layer (first semiconductor layer) 502 / a first composition graded AlInN layer (first composition graded layer) 503 A nitride semiconductor multilayer reflector having a laminated structure of the / GaN layer (second semiconductor layer) 106 as one pair is manufactured.
- the second embodiment is different from the first embodiment in that AlInN is used instead of AlGaN of the first semiconductor layer 502, the first composition graded layer 503, and the second composition graded layer 501.
- Al 0.85 In 0.15 N was selected as the first semiconductor layer 502.
- GaN was selected as the second semiconductor layer 106 as in the first embodiment.
- the Al composition value of the first semiconductor layer 502 may be 0.83 in order to achieve lattice matching with GaN, but compressive strain is inherent in the first composition graded AlInN layer 503 and the second composition graded AlInN layer 501. Therefore, tensile strain is included by setting the Al composition value of the first semiconductor layer 502 to 0.85, and cumulative strain in the entire multilayer film is reduced as much as possible.
- the second compositionally graded AlInN layer 501 gradually increases from Al composition value 0.6 of AlInN to Al composition value 0.85 of the first semiconductor layer 502, which substantially matches the energy level for electrons at the lower end of the conduction band of GaN. AlInN in which the composition monotonously increases was used.
- the first composition graded AlGaN layer 503 uses AlInN in which the Al composition value gradually decreases monotonously from 0.85 to 0.6. As a result, the change in the energy level for electrons at the lower end of the conduction band of the first semiconductor layer 502, the second semiconductor layer 106, the first composition graded layer 503, and the second composition graded layer 501 becomes smooth, and the energy barrier for electrons Can be reduced.
- the central reflection wavelength of the multilayer film reflector is 400 nm, based on which the film thickness of the second composition-graded AlInN layer 501 is 10 nm, the film thickness of the Al 0.85 In 0.15 N layer 502 is 32 nm, and the first composition-graded AlInN layer 503
- the film thickness of the GaN layer 106 was set to 10 nm, and the film thickness of the GaN layer 106 to 30 nm.
- the nitride semiconductor multilayer film reflector having the structure shown in FIG. 7 was produced by the MOCVD method (metal organic chemical vapor deposition method) according to the following procedure.
- MOCVD method metal organic chemical vapor deposition method
- the fabrication procedure up to the n-type GaN underlayer 102 is the same as that of the first embodiment, and thus the detailed description is omitted.
- a second compositionally graded AlInN layer 501 is grown on the n-type GaN underlayer 102.
- the substrate temperature is set to 750 ° C.
- n-type GaN is produced by flowing carrier gas nitrogen, TMAl, TMIn (trimethyl indium) and ammonia as raw materials, and SiH 4 as n-type impurity raw material gas into the reaction furnace.
- a second composition-graded AlInN layer 501 was grown to 10 nm on the underlayer 102.
- the gas supply amount of TMAl which is an Al raw material, depends on the supply amount for growing Al 0.6 In 0.3 N having an Al composition value of 0.6.
- the gas supply amount of TMIn which is an In raw material is Al 0.85 In 0.15 N layer 502 with an In composition value of 0.15 from the supply amount for growing Al 0.6 In 0.3 N with an In composition value of 0.3.
- the second composition-graded AlInN layer 501 in which the Al composition value monotonously increases from 0.6 to 0.85 was formed on the n-type GaN underlayer 102.
- the second composition graded AlInN layer 501 is doped with Si, which is an n-type impurity, at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- an Al 0.85 In 0.15 N layer 502 having an Al composition value of 0.85 was grown to a thickness of 32 nm.
- the substrate temperature at this time, and the carrier gas, the source gas, and the impurity source gas to be flowed into the reaction furnace are all the same as in the film formation of the second composition gradient AlInN layer 501, and the detailed description is omitted.
- the gas supply amounts of TMAl and TMIn were fixed to the growth conditions of the Al 0.85 In 0.15 N layer 502.
- the Al 0.85 In 0.15 N layer 502 is doped with Si, which is an n-type impurity, at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- a first composition graded AlInN layer 503 was grown to 10 nm on the Al 0.85 In 0.15 N layer 502.
- the substrate temperature at this time, and the carrier gas, the source gas, and the impurity source gas to be flowed into the reaction furnace are all the same as in the film formation of the second composition graded AlInN layer 501, and thus the detailed description is omitted.
- the gas supply amount of TMAl which is an Al raw material is monotonically decreased from the supply amount for growing the Al 0.85 In 0.15 N layer 502 to the supply amount for growing Al 0.6 In 0.3 N
- the gas supply amount of TMIn, which is an In raw material was monotonously changed from the supply amount for growing the Al 0.85 In 0.15 N layer 502 to the supply amount for growing Al 0.6 In 0.3 N.
- the first composition gradient AlInN layer 503 in which the Al composition value monotonously decreases from 0.85 to 0.6 was formed on the Al 0.85 In 0.15 N layer 502.
- the first composition graded AlInN layer 503 corresponds to the group III element surface side of the Al 0.85 In 0.15 N layer 502, the supply amount of SiH 4 as the impurity source gas was increased.
- the first composition graded AlInN layer 503 is doped with Si, which is an n-type impurity, at a high concentration of 5 ⁇ 10 19 cm ⁇ 3 .
- a GaN layer 106 was grown to 30 nm on the first composition graded AlInN layer 503.
- the substrate temperature at this time, and the carrier gas, the source gas, and the impurity source gas to be flowed into the reaction furnace are all the same as at the time of forming the n-type GaN underlayer 102, and the detailed description will be omitted.
- the GaN layer 106 is doped with Si, which is an n-type impurity, at a concentration of 2 ⁇ 10 18 cm ⁇ 3 .
- FIG. 8 shows the energy levels of electrons at the lower end of the conduction band of three pairs of nitride semiconductor multilayer reflectors.
- the energy level for electrons at the lower end of the conduction band of GaN is normalized to 0 eV.
- electrons which are carriers can move without being affected by the energy barrier. That is, as in the first embodiment, the reduction in resistance of the nitride semiconductor multilayer reflector can be realized.
- the first semiconductor layer 502 is substantially lattice matched with the GaN layer 106 which is the second semiconductor layer 106. Therefore, crystal defects such as dislocations are less likely to be mixed in during film formation, and the crystallinity and reflectance of the multilayer film can be improved.
- the Al composition value of the first semiconductor layer 502 is set to 0.85 instead of the Al composition value of 0.83 which is completely lattice-matched with the GaN layer which is the second semiconductor layer 106.
- tensile strain is generated in the first semiconductor layer 502 and accumulated strain in the entire multilayer film is alleviated, so that the crystallinity of the multilayer film is further improved.
- the nitride semiconductor surface emitting laser provided with the nitride semiconductor multilayer film reflector of the second embodiment can perform a laser oscillation operation by current injection, and the same effect as that of the first embodiment can be exhibited.
- Example 3 As shown in FIG. 9, a second composition gradient AlGaN layer (second composition gradient layer) 601 / Al 0.82 In 0.18 N layer (first semiconductor layer) 602 / a first composition gradient AlGaN layer (first composition gradient layer) 603 A nitride semiconductor multilayer film reflection mirror of 49.5 pairs of laminations in which the laminated structure of the / GaN layer (second semiconductor layer) 106 is one pair is manufactured.
- the second embodiment is different from the second embodiment in that AlGaN is used instead of AlInN for the first composition graded layer 603 and the second composition graded layer 601. Al 0.82 In 0.18 N was selected as the first semiconductor layer 602. Then, GaN was selected as the second semiconductor layer 106 as in the first and second embodiments.
- the Al composition value of the first semiconductor layer 602 may be 0.83 in order to achieve lattice matching with GaN, but tensile strain is inherent in the first composition graded AlGaN layer 603 and the second composition graded AlGaN layer 601. Therefore, compressive strain is included by setting the Al composition value of the first semiconductor layer 602 to 0.82, and cumulative strain in the entire multilayer film is reduced as much as possible.
- the second composition gradient AlGaN layer 601 gradually changes the Al composition value from 0 to 0.5 corresponding to the energy level for electrons of the lower end of the conduction band of Al 0.82 In 0.18 N which is the first semiconductor layer 602. The monotonically increasing AlGaN was used.
- the first composition graded AlGaN layer 603 uses AlGaN in which the Al composition value gradually decreases monotonously from 0.5. As a result, the change in the energy level for electrons in the lower end of the conduction band of the first semiconductor layer 602, the second semiconductor layer 106, the first composition graded layer 603, and the second composition graded layer 601 becomes smooth and an energy barrier for electrons Can be reduced.
- the central reflection wavelength of the multilayer mirror is 400 nm, based on which the film thickness of the second composition gradient AlGaN layer 601 is 10 nm, the film thickness of the Al 0.82 In 0.18 N layer 602 is 32 nm, and the first composition gradient AlGaN layer
- the film thickness of 603 was set to 10 nm
- the film thickness of the GaN layer 106 was set to 30 nm.
- the manufacturing procedure of the nitride semiconductor reflecting mirror is the same as in the first and second embodiments, and the detailed description will be omitted.
- FIG. 10 shows the energy levels for electrons at the lower end of the conduction band of three pairs of nitride semiconductor multilayer reflectors.
- the energy level for electrons at the lower end of the conduction band of GaN is normalized to 0 eV.
- the energy level for electrons at the lower end of the conduction band of the second composition gradient AlGaN layer 601 / Al 0.82 In 0.18 N layer 602 / the first composition gradient AlGaN layer 603 / GaN layer 106 is almost offset. It is almost flat.
- the resistance reduction in the nitride semiconductor multilayer film reflector can be realized. Then, if a nitride semiconductor surface emitting laser provided with the nitride semiconductor multilayer film reflector of the third embodiment is manufactured, the laser oscillation operation can be performed by current injection. As described above, according to the third embodiment, the same effect as the first and second embodiments can be obtained.
- the first semiconductor may be interposed between the first semiconductor layers 104, 502, 602 and the second semiconductor layer 106 having an Al composition lower than that of the first semiconductor layers 104, 502, 602.
- the first and second composition graded layers 105, 503, 603, 103, 501, 601 are provided such that the Al composition is lowered as approaching the second semiconductor layer 106 than the layers 104, 502, 602.
- the energy level for electrons at the lower end of the conduction band of each layer is almost offset and has a continuous shape, thereby reducing the energy barrier for electrons as carriers.
- the first semiconductors 104, 502, 602 and the second semiconductor 106 by doping the first composition graded layers 105, 503, 603 with an n-type impurity at a concentration of 5 ⁇ 10 19 cm -3 or more. Since the energy barrier generated due to the polarization effect can also be significantly reduced, the resistance of the nitride semiconductor multilayer reflector can be lowered to allow current injection.
- the resonator length can be shortened by providing a nitride semiconductor multilayer film reflector capable of current injection, internal loss and threshold current can be significantly reduced, and a high performance nitride with high differential quantum efficiency can be obtained. It becomes possible to provide a semiconductor light emitting device.
- the present invention is not limited to the first to third embodiments described above with reference to the drawings.
- the following embodiments are also included in the technical scope of the present invention.
- the GaN free-standing substrate is used as the substrate.
- the present invention is not limited to this.
- a sapphire substrate or ZnO (zinc oxide) substrate having high transparency to the oscillation wavelength is used.
- the nitride semiconductor multilayer film is formed by MOCVD (organic metal vapor phase epitaxy).
- MOCVD organic metal vapor phase epitaxy
- HVPE hydrogen vapor phase epitaxy
- MBE Molecular beam epitaxy
- sputtering or laser ablation may be used for film formation.
- TMGa trimethylgallium
- TMAl trimethylaluminum
- TMIn trimethylindium
- TEGa triethylindium
- TEAl triethylaluminum
- Si and Mg were used as the n-type and p-type impurities, respectively.
- the present invention is not limited thereto, and Ge, Zn, Be or the like may be used.
- the raw material supply amount was changed in order to control the Al composition of the first composition graded layer and the second composition graded layer, but the invention is not limited thereto, and the substrate temperature etc. is changed.
- You may (7) In Examples 1 to 3, GaN, AlGaN and AlInN were used for the first semiconductor layer, the second semiconductor layer, the first composition graded layer, and the second composition graded layer, but the invention is not limited thereto. AlGaInN may be used.
- the number of pairs of the first semiconductor layer and the second semiconductor layer constituting the nitride multilayer reflector is 49.5, but the number of pairs is not limited.
- the single-wavelength resonator structure is adopted as the light emitting element.
- the present invention is not limited to this.
- a resonator structure having two or more wavelengths may be used.
- the n-side electrode of the light emitting element is formed on the front side of the substrate, but may be formed on the back side as long as it is a conductive substrate.
- the surface emitting laser is exemplified as the light emitting element, but it may be another light emitting element having a multilayer mirror.
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Abstract
Description
III族窒化物半導体より成る第1半導体層と、第2半導体層と、第1組成傾斜層と、第2組成傾斜層とを備えており、前記第1半導体層と第2半導体層とを複数組交互に積層して作製した窒化物半導体多層膜反射鏡であって、
前記第1半導体層のAl組成は前記第2半導体層のAl組成よりも高く、
前記第1半導体層と第2半導体層との間であって、前記第1半導体層のIII族元素面側に、前記第2半導体層に近づくにつれてAl組成が低くなるように調整された第1組成傾斜層が介在しており、
前記第1半導体層と第2半導体層との間であって、前記第1半導体層の窒素面側に、前記第2半導体層に近づくにつれてAl組成が低くなるように調整された第2組成傾斜層が介在しており、
前記第1半導体層、第2半導体層、前記第1組成傾斜層、及び第2組成傾斜層の伝導帯下端の電子に対するエネルギー準位はオフセットがなく連続しており、
前記第1組成傾斜層におけるn型不純物濃度は5×1019cm-3以上であることを特徴とする。
第1発明の窒化物半導体多層膜反射鏡を有していることを特徴とする。
図1に示すように、第2組成傾斜AlGaN層(第2組成傾斜層)103/Al0.5Ga0.5N層(第1半導体層)104/第1組成傾斜AlGaN層(第1組成傾斜層)105/GaN層(第2半導体層)106の順に積層した積層構造を1ペアとする窒化物半導体多層膜反射鏡を作製する。第1半導体層104はAl0.5Ga0.5Nを選択した。そして、第2半導体層106はGaNを選択した。第1半導体層104のAl組成値が高すぎると、第2半導体層106であるGaNとの格子不整合が大きくなりすぎるため、結晶性が劣化し、それに伴って反射率が低下する。逆に、第1半導体層104のAl組成値が低すぎると、第1半導体層104、及び第2半導体層106の屈折率段差が小さくなるため、反射率が低下する。このため、第1半導体層104のAl組成値は0.4~0.6とすることが望ましい。本実施例1においては、第1半導体層104はAl組成値を0.5にした。第2組成傾斜AlGaN層103はGaNからAl0.5Ga0.5Nへと徐々にAl組成値が単調増加するAlGaNを用いた。また、第1組成傾斜AlGaN層105はAl0.5Ga0.5NからGaNへと徐々にAl組成値が単調減少するAlGaNを用いた。そして、多層膜反射鏡の中心反射波長は400nmとし、それに基づいて、第2組成傾斜AlGaN層103の膜厚を10nm、Al0.5Ga0.5N層104の膜厚を34nm、第1組成傾斜AlGaN層105の膜厚を10nm、及びGaN層106の膜厚を30nmと設定した。
図7に示すように、第2組成傾斜AlInN層(第2組成傾斜層)501/Al0.85In0.15N層(第1半導体層)502/第1組成傾斜AlInN層(第1組成傾斜層)503/GaN層(第2半導体層)106の積層構造を1ペアとする窒化物半導体多層膜反射鏡を作製する。第1半導体層502、第1組成傾斜層503、及び第2組成傾斜層501のAlGaNに替えて、AlInNを用いている点が実施例1と異なっている。第1半導体層502として、Al0.85In0.15Nを選択した。そして、第2半導体層106として、実施例1と同様にGaNを選択した。GaNと格子整合させるために、第1半導体層502のAl組成値を0.83としても良いが、第1組成傾斜AlInN層503、及び第2組成傾斜AlInN層501は圧縮歪が内在する。よって、第1半導体層502のAl組成値を0.85にすることで引張歪を内在させ、多層膜全体での累積歪をできるだけ低減させた。第2組成傾斜AlInN層501は、GaNの伝導帯下端の電子に対するエネルギー準位と略一致するAlInNのAl組成値0.6から第1半導体層502のAl組成値0.85へと徐々にAl組成が単調増加するAlInNを用いた。また、第1組成傾斜AlGaN層503は、0.85から0.6へと徐々にAl組成値が単調減少するAlInNを用いた。これによって、第1半導体層502、第2半導体層106、第1組成傾斜層503、及び第2組成傾斜層501の伝導帯下端の電子に対するエネルギー準位の変化はなだらかになり、電子に対するエネルギー障壁を低減することができる。また、多層膜反射鏡の中心反射波長は400nmとし、それに基づいて第2組成傾斜AlInN層501の膜厚を10nm、Al0.85In0.15N層502の膜厚を32nm、第1組成傾斜AlInN層503の膜厚を10nm、及びGaN層106の膜厚を30nmと設定した。
図9に示すように、第2組成傾斜AlGaN層(第2組成傾斜層)601/Al0.82In0.18N層(第1半導体層)602/第1組成傾斜AlGaN層(第1組成傾斜層)603/GaN層(第2半導体層)106の積層構造を1ペアとする49.5ペア積層の窒化物半導体多層膜反射鏡を作製する。第1組成傾斜層603、及び第2組成傾斜層601にAlInNに替えて、AlGaNを用いている点が実施例2と異なっている。第1半導体層602として、Al0.82In0.18Nを選択した。そして、第2半導体層106として、実施例1及び2と同様にGaNを選択した。GaNと格子整合させるために、第1半導体層602のAl組成値を0.83としても良いが、第1組成傾斜AlGaN層603、及び第2組成傾斜AlGaN層601は引張歪が内在する。このため、第1半導体層602のAl組成値を0.82にすることで圧縮歪を内在させ、多層膜全体での累積歪をできるだけ低減させた。第2組成傾斜AlGaN層601は、Al組成が0から第1半導体層602であるAl0.82In0.18Nの伝導帯下端の電子に対するエネルギー準位に一致する0.5へと徐々にAl組成値が単調増加するAlGaNを用いた。また、第1組成傾斜AlGaN層603は、0.5から0へと徐々にAl組成値が単調減少するAlGaNを用いた。これによって、第1半導体層602、第2半導体層106、第1組成傾斜層603、及び第2組成傾斜層601の伝導帯下端の電子に対するエネルギー準位の変化はなだらかになり、電子に対するエネルギー障壁を低減することができる。また、多層膜反射鏡の中心反射波長は400nmにし、これに基づいて第2組成傾斜AlGaN層601の膜厚を10nm、Al0.82In0.18N層602の膜厚を32nm、第1組成傾斜AlGaN層603の膜厚を10nm、GaN層106の膜厚を30nmに設定した。窒化物半導体反射鏡の作製手順については実施例1及び2と同様であり、詳細な説明は割愛する。
(1)実施例1~3では、基板としてGaN自立基板を用いたが、これに限らず、発振波長に対して高い透過性を有しているサファイア基板やZnO(酸化亜鉛)基板等を用いてもよい。
(2)実施例1~3では、MOCVD法(有機金属気相成長法)によって、窒化物半導体多層膜を成膜したが、これに限らず、HVPE法(ハイドライド気相成長法)やMBE法(分子線エピタキシー法)、スパッタリング法やレーザアブレーション法を用いて成膜してもよい。
(3)実施例1~3では、窒化物多層膜反射鏡を作製する原料としてトリメチルガリウム(TMGa)、トリメチルアルミニウム(TMAl)、トリメチルインジウム(TMIn)を用いたが、これに限らず、トリエチルガリウム(TEGa)、トリエチルインジウム(TEIn)、トリエチルアルミニウム(TEAl)などを用いてもよい。
(4)実施例1~3では、キャリアガスに水素や窒素を用いたが、これに限らず、他の活性ガスやアルゴンなどの他の不活性ガスを用いても良く、それらを混合して用いてもよい。
(5)実施例1~3では、n型、p型不純物にそれぞれSi、Mgを用いたが、これに限らず、GeやZn、Be等であってもよい。
(6)実施例1~3では、第1組成傾斜層、及び第2組成傾斜層のAl組成を制御するために、原料供給量を変化させたが、これに限らず、基板温度等を変化させてもよい。
(7)実施例1~3では、第1半導体層、第2半導体層、第1組成傾斜層、及び第2組成傾斜層にGaN、AlGaN、AlInNを用いたが、これに限らず、AlNやAlGaInNを用いてもよい。
(8)実施例1~3では、窒化物多層膜反射鏡を構成する第1半導体層、及び第2半導体層のペア数を49.5ペアとしたが、ペア数に制限はない。
(9)実施例1~3では、発光素子に一波長共振器構造を採用したが、これに限らず、二波長以上の共振器構造を用いてもよい。
(10)実施例1~3では、発光素子のn側電極を基板の表面側に形成したが、導電性を有する基板であれば、裏面側に形成してもよい。
(11)実施例1~3では、発光素子として面発光レーザを例示したが、その他の多層膜反射鏡を有する発光素子であってもよい。
104…Al0.5Ga0.5N層(第1半導体層)
105、603…第1組成傾斜AlGaN層(第1組成傾斜層)
106…GaN層(第2半導体層)
501…第2組成傾斜AlInN層(第2組成傾斜層)
502…Al0.85In0.15N層(第1半導体層)
503…第1組成傾斜AlInN層(第1組成傾斜層)
602…Al0.82In0.18N層(第1半導体層)
Claims (5)
- III族窒化物半導体より成る第1半導体層と、第2半導体層と、第1組成傾斜層と、第2組成傾斜層とを備えており、前記第1半導体層と第2半導体層とを複数組交互に積層して作製した窒化物半導体多層膜反射鏡であって、
前記第1半導体層のAl組成は前記第2半導体層のAl組成よりも高く、
前記第1半導体層と第2半導体層との間であって、前記第1半導体層のIII族元素面側に、前記第2半導体層に近づくにつれてAl組成が低くなるように調整された第1組成傾斜層が介在しており、
前記第1半導体層と第2半導体層との間であって、前記第1半導体層の窒素面側に、前記第2半導体層に近づくにつれてAl組成が低くなるように調整された第2組成傾斜層が介在しており、
前記第1半導体層、第2半導体層、前記第1組成傾斜層、及び第2組成傾斜層の伝導帯下端の電子に対するエネルギー準位はオフセットがなく連続しており、
前記第1組成傾斜層におけるn型不純物濃度は5×1019cm-3以上であることを特徴とする窒化物半導体多層膜反射鏡。 - 前記第1組成傾斜層、及び第2組成傾斜層の膜厚は、それぞれ20nm以下であることを特徴とする請求項1記載の窒化物半導体多層膜反射鏡。
- 前記第1半導体層と第2半導体層はそれぞれ、AlGaN層とGaN層であって、前記AlGaN層のAl組成値は0.4から0.6であり、
前記第1組成傾斜層、及び第2組成傾斜層は、AlGaN層であって、そのAl組成は0から前記Al組成値まで組成傾斜していることを特徴とする請求項1又は2記載の窒化物半導体多層膜反射鏡。 - 前記第1半導体層、及び前記第2半導体層は、それぞれ、AlInN層とGaN層であって、前記AlInN層のAl組成値は0.82から0.85であり、
前記第1組成傾斜層、及び第2組成傾斜層は、AlInN層であって、そのAl組成は0.6から前記Al組成値まで組成傾斜していることを特徴とする請求項1又は2記載の窒化物半導体多層膜反射鏡。 - 請求項1乃至4のいずれか1項記載の窒化物半導体多層膜反射鏡を有していることを特徴とする窒化物半導体発光素子。
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