WO2012086150A1 - Substrat semiconducteur, procédé de fabrication du substrat semiconducteur et laser à émission par la surface et à cavité verticale - Google Patents

Substrat semiconducteur, procédé de fabrication du substrat semiconducteur et laser à émission par la surface et à cavité verticale Download PDF

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WO2012086150A1
WO2012086150A1 PCT/JP2011/006956 JP2011006956W WO2012086150A1 WO 2012086150 A1 WO2012086150 A1 WO 2012086150A1 JP 2011006956 W JP2011006956 W JP 2011006956W WO 2012086150 A1 WO2012086150 A1 WO 2012086150A1
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layer
type
crystal layer
group
semiconductor substrate
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孝行 井上
強 中野
磨 市川
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住友化学株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H—ELECTRICITY
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02436—Intermediate layers between substrates and deposited layers
    • H01L21/02439—Materials
    • H01L21/02455—Group 13/15 materials
    • H01L21/02463—Arsenides
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02436—Intermediate layers between substrates and deposited layers
    • H01L21/02494—Structure
    • H01L21/02496—Layer structure
    • H01L21/02505—Layer structure consisting of more than two layers
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    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/0257—Doping during depositing
    • H01L21/02573—Conductivity type
    • H—ELECTRICITY
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/0262—Reduction or decomposition of gaseous compounds, e.g. CVD
    • 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
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/0206—Substrates, e.g. growth, shape, material, removal or bonding
    • 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
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0421—Electrical excitation ; Circuits therefor characterised by the semiconducting contacting layers
    • H—ELECTRICITY
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    • 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]
    • H01S5/18308—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] having a special structure for lateral current or light confinement
    • H01S5/18311—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] having a special structure for lateral current or light confinement using selective oxidation
    • 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
    • H01S5/305—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure
    • H01S5/3054—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure p-doping
    • 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
    • H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
    • H01S5/3211—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures characterised by special cladding layers, e.g. details on band-discontinuities
    • H01S5/3216—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures characterised by special cladding layers, e.g. details on band-discontinuities quantum well or superlattice cladding layers

Definitions

  • the present invention relates to a semiconductor substrate, a semiconductor substrate manufacturing method, and a vertical cavity surface emitting laser.
  • Patent Document 1 discloses a GaAs substrate, an n-type lower DBR (Distributed Bragg Reflector), an active region, a p-type current confinement layer formed on the active region, and a p formed on the current confinement layer.
  • a VCSEL Very-Cavity Surface-Emitting Laser
  • Patent Document 1 describes that the n-type lower DBR, the p-type high concentration DBR, and the p-type DBR each include a pair of a high refractive index layer and a low refractive index layer made of an AlGaAs layer. .
  • a GaAs substrate in which GaAs layers are stacked in this order is described.
  • the Al x Ga 1-x As diffusion suppression layer is grown by using the MOCVD method with a source gas arsine / trimethylgallium pressure ratio of 10 or less.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2009-194103
  • Patent Document 2 Japanese Patent Application Laid-Open No. 5-234907
  • MOCVD Metal-Organic-Chemical-Vapor-Deposition
  • VCSEL vertical cavity surface emitting laser
  • MOCVD Metal-Organic-Chemical-Vapor-Deposition
  • a Group 3-5 compound semiconductor crystal layer such as a GaAs layer, an AlGaAs layer, an InGaAs layer, or an InGaAsP layer
  • MOCVD an organic compound containing a Group 3 atom such as Al, Ga, or In is used as a Group 3 source gas.
  • a hydrogen compound containing a group 5 atom such as As or P is used as the group 5 source gas.
  • the carbon atoms contained in the Group 3 source gas are taken into the epitaxial crystal layer, and the incorporated carbon atoms are converted to p. Since it functions as a type impurity, it is convenient in forming a p-type crystal layer such as a p-type mirror layer or a p-type contact layer of a VCSEL.
  • An object of the present invention is to form a p-type crystal layer in a semiconductor substrate for a vertical cavity surface emitting laser under epitaxial conditions with a low V / III ratio and reduce the electrical resistance of the p-type crystal layer.
  • a semiconductor substrate for a vertical cavity surface emitting laser having a p-type crystal layer functioning as a contact layer
  • the crystal layer is made of a Group 3-5 compound semiconductor and contains hydrogen atoms at a concentration of 2 ⁇ 10 18 cm ⁇ 3 or more and 1 ⁇ 10 19 cm ⁇ 3 or less.
  • the p-type crystal layer is a p-type GaAs layer.
  • the p-type crystal layer may contain carbon atoms as p-type impurity atoms.
  • the group 3 source gas may contain an alkylated group 3 atom in which at least one alkyl group is bonded to the group 3 atom, or the group 5 source gas may contain a hydride of the group 5 atom.
  • the ratio of the molar supply amount of the Group 5 source gas to the molar supply amount of the Group 3 source gas (V / III ratio) can be controlled to 0.01 or more and 15.0 or less.
  • the semiconductor device has a p-type crystal layer functioning as a contact layer, and the p-type crystal layer is made of a group 3-5 compound semiconductor and is 2 ⁇ 10 18 cm ⁇ 3 or more, 1 ⁇ 10
  • a vertical cavity surface emitting laser comprising hydrogen atoms at a concentration of 19 cm ⁇ 3 or less is provided.
  • An example of a cross section of a semiconductor substrate 100 is shown.
  • the cross-sectional example of the vertical cavity surface emitting laser 200 is shown.
  • FIG. 1 shows an example of a cross section of the semiconductor substrate 100.
  • the semiconductor substrate 100 includes a base substrate 102, a buffer layer 104, an n-type stacked crystal layer 106, an i-type stacked crystal layer 108, a p-type AlGaAs layer 110, a p-type stacked crystal layer 112, and a p-type GaAs layer 114.
  • the base substrate 102 is a support substrate that supports an epitaxial growth layer formed thereon.
  • An example of the base substrate 102 is an n-type GaAs substrate.
  • an epitaxial growth layer is formed on the (100) plane of the n-type GaAs substrate or a plane having an appropriate off angle with the (100) plane.
  • the off angle is, for example, in the range of 2 ° to 10 °, preferably 4 to 6 °.
  • Examples of impurity atoms doped into the n-type GaAs substrate include Si, Se, and S.
  • the carrier concentration of the n-type GaAs substrate is in the range of 1 ⁇ 10 17 cm ⁇ 3 to 1 ⁇ 10 19 cm ⁇ 3 , preferably in the range of 1 ⁇ 10 18 cm ⁇ 3 to 4 ⁇ 10 18 cm ⁇ 3 .
  • the base substrate 102 may be a sapphire substrate, a silicon carbide substrate, a zinc oxide substrate, or a substrate whose surface is silicon.
  • the surface is silicon means that at least a part of the surface of the substrate is made of silicon.
  • the entire substrate may be made of silicon such as a Si wafer, or a structure having a silicon layer on an insulating layer such as an SOI (silicon-on-insulator) substrate.
  • SOI silicon-on-insulator
  • a silicon layer may be formed on a substrate made of a material other than silicon, such as a sapphire substrate, a glass substrate, a silicon carbide substrate, a zinc oxide substrate, or a GaAs substrate.
  • the semiconductor material of the base substrate 102 in contact with the epitaxial growth layer is a semiconductor
  • the semiconductor material is preferably doped with an n-type impurity.
  • an electrode can be connected to the base substrate 102.
  • the cathode electrode of the laser can be connected to the base substrate 102.
  • the buffer layer 104 is an n-type group 3-5 compound semiconductor crystal layer formed on the base substrate 102 by epitaxial growth.
  • the buffer layer 104 suppresses the formation of defects in the n-type stacked crystal layer 106, the i-type stacked crystal layer 108, and the like in accordance with the defects in the base substrate 102.
  • An example of the buffer layer 104 is an n-type GaAs layer.
  • the thickness of the n-type GaAs layer is preferably in the range of 10 nm to 1000 nm.
  • Examples of impurity atoms doped in the n-type GaAs layer include Si, Se, and S.
  • the carrier concentration of the n-type GaAs layer is preferably in the range of 1 ⁇ 10 18 cm ⁇ 3 to 5 ⁇ 10 18 cm ⁇ 3 .
  • the n-type stacked crystal layer 106 is a stacked crystal layer made of a plurality of n-type group 3-5 compound semiconductor crystal layers formed on the buffer layer 104 by epitaxial growth.
  • the n-type stacked crystal layer 106 functions as an n-type mirror layer that is one mirror of the resonator when the semiconductor substrate 100 is used in a vertical cavity surface emitting laser.
  • the n-type stacked crystal layer 106 is, for example, a distributed Bragg reflector (DBR).
  • DBR distributed Bragg reflector
  • the n-type stacked crystal layer 106 may include a plurality of stacked structures in which high refractive index layers and low refractive index layers are alternately stacked. By repeatedly disposing a plurality of high refractive index layers and low refractive index layers, the reflectance of light having a predetermined wavelength can be increased.
  • Examples of the low refractive index layer included in the n-type stacked crystal layer 106 include an n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer.
  • the thickness of the n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer used for the low refractive index layer is required for the laser. It is designed according to the emission wavelength band.
  • n-type Al q Ga 1-q As ( 0 ⁇ q ⁇ 1) layer of the Al composition (q) is suitably in the range of 0.8-1.0.
  • Examples of impurity atoms doped in the n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer include Si, Se, and S.
  • the carrier concentration of the n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer is preferably in the range of 1 ⁇ 10 18 cm ⁇ 3 to 3 ⁇ 10 18 cm ⁇ 3 .
  • Examples of the high refractive index layer included in the n-type stacked crystal layer 106 include an n-type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) layer.
  • the Al composition (r) of the n - type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) layer is changed to the Al composition of the n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer (q ),
  • the refractive index of the n - type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) layer is changed to that of the n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer. It can be larger than the refractive index.
  • the thickness of the n-type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) layer used for the high refractive index layer is: It is designed according to the emission wavelength band required for the laser.
  • the Al composition (r) of the n-type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) layer is in the range of 0.0 to 0.2 (however, the n-type Al q Ga 1-q As It is appropriate that it is smaller than the Al composition (q) of the layer (0 ⁇ q ⁇ 1).
  • Examples of impurity atoms doped in the n-type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) layer include Si, Se, and S.
  • the carrier concentration of the n-type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) layer is preferably in the range of 1 ⁇ 10 18 cm ⁇ 3 to 3 ⁇ 10 18 m ⁇ 3 .
  • the Al s Ga 1-s An n-type Al s Ga 1-s As (0 ⁇ s ⁇ 1) layer in which the Al composition (s) of As is continuously changed in the thickness direction of the layer may be disposed.
  • Al composition (s) may be substantially equal to the Al composition (q).
  • the Al composition (s) may be substantially equal to the Al composition (r).
  • the n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer and the n-type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) By continuously changing the Al composition (s), the n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer and the n-type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) ) The electrical resistance between the layers can be reduced.
  • the number of repetitions of the n-type Al q Ga 1-q As (0 ⁇ q ⁇ 1) layer and the n-type Al r Ga 1-r As (0 ⁇ r ⁇ 1, q> r) layer is preferably 30 to 60.
  • the i-type stacked crystal layer 108 is a stacked crystal layer made of a plurality of i-type Group 3-5 compound semiconductor crystal layers formed on the n-type stacked crystal layer 106 by epitaxial growth.
  • the i-type stacked crystal layer 108 functions as an active layer when the semiconductor substrate 100 is used in a vertical cavity surface emitting laser.
  • the i-type stacked crystal layer 108 includes a stacked crystal layer in which two i-type AlGaAs layers 120 are formed with an i-type GaAs / AlGaAs layer 122 interposed therebetween.
  • the i-type AlGaAs layer 120 functions as a cladding layer when the semiconductor substrate 100 is used in a vertical cavity surface emitting laser.
  • the thickness of the i-type AlGaAs layer 120 is designed according to the emission wavelength band required for the laser.
  • the Al composition of the i-type AlGaAs layer 120 is suitably in the range of 0.1 to 0.9. By continuously changing the Al composition in the thickness direction, the band gap energy of the i-type AlGaAs layer 120 continuously changes in the thickness direction.
  • the i-type GaAs / AlGaAs layer 122 functions as a light emitting layer when the semiconductor substrate 100 is used in a vertical cavity surface emitting laser.
  • the i-type GaAs / AlGaAs layer 122 includes a quantum well structure (MQW) in which a plurality of GaAs layers and AlGaAs layers are alternately arranged.
  • the quantum well structure (MQW) may be an InGaAs / GaAs structure, an InGaAs / AlGaAs structure, a GaAs / GaAsP structure, an InGaAs / GaAsP structure, or a GaInNAs / GaAs structure instead of a GaAs / AlGaAs structure.
  • the thickness of the GaAs layer included in the quantum well structure (MQW) is designed according to the emission wavelength band required for the laser.
  • the thickness of the AlGaAs layer included in the quantum well structure (MQW) is preferably in the range of 5 nm to 12 nm.
  • the Al composition of the AlGaAs layer is suitably in the range of 0.1 to 0.4.
  • the number of repetitions of the laminated structure of the GaAs layer and the AlGaAs layer is suitably in the range of 2-6.
  • the p-type AlGaAs layer 110 is formed on the i-type stacked crystal layer 108 by epitaxial growth.
  • the p-type AlGaAs layer 110 is partially oxidized when the semiconductor substrate 100 is used in a vertical cavity surface emitting laser, and functions as an oxidized constriction layer.
  • the thickness of the p-type AlGaAs layer 110 is preferably in the range of 20 nm to 40 nm.
  • the Al composition of the p-type AlGaAs layer 110 is suitably in the range of 0.95 to 1.0. Examples of impurity atoms doped in the p-type AlGaAs layer 110 include C (carbon) and Zn.
  • the carrier concentration of the p-type AlGaAs layer 110 is preferably in the range of 1 ⁇ 10 18 cm ⁇ 3 to 3 ⁇ 10 18 cm ⁇ 3 .
  • the p-type stacked crystal layer 112 is a stacked crystal layer made of a plurality of p-type Group 3-5 compound semiconductor crystal layers formed on the p-type AlGaAs layer 110 by epitaxial growth.
  • the p-type stacked crystal layer 112 functions as a p-type mirror layer that is the other mirror of the resonator when the semiconductor substrate 100 is used in a vertical cavity surface emitting laser.
  • the p-type stacked crystal layer 112 is, for example, a distributed Bragg reflector (DBR).
  • the p-type stacked crystal layer 112 includes a stacked crystal layer in which a first crystal layer 130 that is a low refractive index layer and a second crystal layer 132 that is a high refractive index layer are stacked.
  • the first crystal layer 130 or the second crystal layer 132 constitutes a part of the p-type stacked crystal layer 112 that functions as a p-type mirror layer.
  • the first crystal layer 130 is a p-type Al m Ga 1-m As (0 ⁇ m ⁇ 1) layer.
  • the thickness of the p-type Al m Ga 1-m As (0 ⁇ m ⁇ 1) layer used for the first crystal layer 130 is required for the laser. It is designed according to the emission wavelength band.
  • the Al composition (m) of the p-type Al m Ga 1-m As (0 ⁇ m ⁇ 1) layer is suitably in the range of 0.5 to 1.0, particularly 0.8 to 1. A range of 0 is preferable.
  • Examples of impurity atoms doped in the p-type Al m Ga 1-m As (0 ⁇ m ⁇ 1) layer include C and Zn.
  • the carrier concentration of the p-type Al m Ga 1-m As (0 ⁇ m ⁇ 1) layer is preferably in the range of 1 ⁇ 10 18 cm ⁇ 3 to 4 ⁇ 10 18 cm ⁇ 3 .
  • the Al composition (n) of the p-type Al n Ga 1-n As (0 ⁇ n ⁇ 1, m> n) layer as the second crystal layer 132 is changed to p-type Al m Ga 1-m As (0 ⁇ m ⁇ 1).
  • the refractive index of the p - type Al n Ga 1-n As (0 ⁇ n ⁇ 1, m> n) layer is reduced to p-type Al m Ga 1-m As (0).
  • ⁇ M ⁇ 1) Can be larger than the refractive index of the layer.
  • the layer thickness is designed according to the emission wavelength band required for the laser.
  • the Al composition (n) of the p-type Al n Ga 1-n As (0 ⁇ n ⁇ 1, m> n) layer is within the range of 0.0 to 0.2 (however, p-type Al m Ga 1-m As It is appropriate that it is smaller than the Al composition (m) of the layer (0 ⁇ m ⁇ 1).
  • Examples of impurity atoms doped in the p-type Al n Ga 1-n As (0 ⁇ n ⁇ 1, m> n) layer include C and Zn.
  • the carrier concentration of the p-type Al n Ga 1-n As (0 ⁇ n ⁇ 1, m> n) layer is preferably in the range of 1 ⁇ 10 18 cm ⁇ 3 to 4 ⁇ 10 18 cm ⁇ 3 .
  • the electrical resistance between the first crystal layer 130 and the second crystal layer 132 can be reduced.
  • the number of repetitions of the first crystal layer 130 and the second crystal layer 132 is preferably 10-30.
  • the p-type GaAs layer 114 is a p-type group 3-5 compound semiconductor crystal layer epitaxially grown on the p-type stacked crystal layer 112.
  • the p-type GaAs layer 114 may include other p-type semiconductor layers.
  • the p-type GaAs layer 114 functions as a contact layer when the semiconductor substrate 100 is used for a vertical cavity surface emitting laser.
  • the thickness of the p-type GaAs layer 114 is preferably in the range of 10 nm to 40 nm. Examples of impurity atoms doped in the p-type GaAs layer 114 include C and Zn.
  • the carrier concentration of the p-type GaAs layer 114 is preferably in the range of 4 ⁇ 10 19 cm ⁇ 3 to 1 ⁇ 10 20 cm ⁇ 3 .
  • the p-type GaAs layer 114 corresponds to the p-type crystal layer in the present invention. That is, the p-type GaAs layer 114 is made of a Group 3-5 compound semiconductor and contains hydrogen atoms at a concentration of 2 ⁇ 10 18 cm ⁇ 3 or more and 1 ⁇ 10 19 cm ⁇ 3 or less. The p-type GaAs layer 114 contains carbon atoms as p-type impurity atoms. In FIG. 1, the p-type GaAs layer 114 is not provided, and the carrier concentration of the second crystal layer 132 may be increased and used as a contact layer. In this case, the second crystal layer 132 corresponds to the p-type crystal layer in the present invention.
  • the p-type GaAs layer 114 When the p-type GaAs layer 114 is epitaxially grown, a condition is selected in which the molar ratio (V / III ratio) of the Group 5 source gas supply amount to the Group 3 source gas supply amount is relatively large in order to improve the flatness of the crystal layer surface. .
  • the V / III ratio when the V / III ratio is reduced, the carbon atoms contained in the group 3 source gas are taken into the crystal layer, and the carbon atoms taken into the crystal layer function as p-type impurities.
  • a p-type crystal layer such as the p-type GaAs layer 114
  • an epitaxial growth condition with a small V / III ratio is selected, carbon atoms that are p-type impurities are taken into the crystal layer, and the resistivity of the p-type crystal layer is reduced.
  • the resistivity of the p-type crystal layer can be easily controlled.
  • the concentration range of hydrogen atoms contained in the p-type GaAs layer 114 which is a p-type crystal layer is 2 ⁇ 10 18 cm ⁇ 3 or more and 1 ⁇ 10 19 cm ⁇ 3 or less. If the concentration of hydrogen atoms is 1 ⁇ 10 19 cm ⁇ 3 or less, the rate of activation of carbon atoms contained in the p-type GaAs layer 114 is increased, and the hole concentration can be further increased. As a result, the electrical resistance can be further reduced. In addition, since the number of carbon atoms to be deactivated is relatively small, there are few factors that lower the hole mobility, and as a result, the electrical resistance can be further reduced.
  • the concentration of hydrogen atoms is 2 ⁇ 10 18 cm ⁇ 3 or more, the crystallinity of the p-type GaAs layer 114 is further improved, and an increase in electrical resistance can be suppressed.
  • the heat treatment in (2) forcibly desorbs hydrogen atoms present in the p-type GaAs layer 114.
  • an organic compound of a group 5 atom is used as a source gas in the stage of growing the p-type GaAs layer 114. It can be used. However, even in the case of such a measure, it is considered that the electrical resistance is increased due to impurity mixing or generation of defects. Therefore, an appropriate range exists for the hydrogen atom concentration in the p-type GaAs layer 114 that realizes good electrical resistance characteristics.
  • a method for setting the concentration of hydrogen atoms in the p-type crystal layer in the above-described range will be described in the manufacturing method.
  • the p-type GaAs layer 114 functioning as a contact layer is formed by epitaxial growth under conditions where the V / III ratio is smaller than that of the p-type AlGaAs layer 110.
  • the V / III ratio in this case include 0.01 or more and 15.0 or less.
  • the manufacturing method of the semiconductor substrate 100 is as follows.
  • a base substrate 102 is prepared, and a buffer layer 104, an n-type stacked crystal layer 106, an i-type stacked crystal layer 108, a p-type AlGaAs layer 110, a p-type stacked crystal layer 112, and a p-type GaAs layer 114 are sequentially formed on the base substrate 102.
  • the MOCVD method is used for epitaxial growth.
  • the group 3 source gas used in the MOCVD method contains an alkylated group 3 atom in which at least one alkyl group is bonded to the group 3 atom.
  • Examples of the group 3 source gas include TMG (trimethylgallium), TMA (trimethylaluminum), and TMI (trimethylindium).
  • the group 5 source gas contains a hydride of group 5 atoms.
  • Examples of the Group 5 source gas include AsH 3 (arsine) and PH 3 (phosphine).
  • An example of the n-type impurity gas is Si 2 H 6 (disilane).
  • the epitaxial growth temperature is controlled within the range of 400 ° C to 800 ° C.
  • the composition of each crystal layer can be controlled by controlling the supply amount of the Group 3 source gas and the Group 5 source gas.
  • the doping amount of the n-type impurity can be controlled by controlling the supply amount of the n-type impurity gas.
  • autodoping of carbon atoms contained in the group 3 source gas can be used. That is, when the ratio of the molar supply amount of the Group 5 source gas to the molar supply amount of the Group 3 source gas (V / III ratio) is small, carbon atoms derived from the alkyl group of the Group 3 source gas are mixed into the epitaxial growth layer. To do.
  • the doping amount of carbon atoms, that is, p-type impurities, into the epitaxial growth layer is controlled by controlling the V / III ratio by utilizing such carbon atoms derived from alkyl groups. it can. If the V / III ratio is reduced, expensive group 5 source gas can be saved, and the manufacturing cost can be reduced.
  • the V / III ratio is reduced and carbon atoms which are p-type impurities are mixed by autodoping.
  • the p-type GaAs layer 114 at the stage where the epitaxial growth is completed contains a lot of hydrogen atoms together with carbon atoms. Therefore, when the epitaxial growth of the p-type GaAs layer 114 is completed, the epitaxially grown p-type GaAs layer 114 is heated to reduce the hydrogen atom concentration in the p-type GaAs layer 114.
  • the step of forming the p-type GaAs layer 114 and the step of reducing the hydrogen atom concentration in the p-type GaAs layer 114 can be continuously performed in the same reactor. In this case, the gas supply to the reactor can be stopped and the atmosphere in the reactor can be reduced. Alternatively, the step of forming the p-type GaAs layer 114 and the step of reducing the hydrogen atom concentration in the p-type GaAs layer 114 can be performed discontinuously by changing the reaction furnace. In this case, the p-type GaAs layer 114 can be heated in a state where the atmosphere in the reaction furnace is replaced with an inert gas such as nitrogen, argon or helium and the inert gas is kept flowing.
  • an inert gas such as nitrogen, argon or helium
  • the hydrogen partial pressure in the atmosphere can be lowered, for example, the hydrogen molecule concentration can be made below the detection limit. Thereby, the hydrogen atom concentration in the p-type GaAs layer 114 can be effectively reduced. Nitrogen is preferred as the inert gas.
  • the hydrogen carrier gas and the group 5 source gas may continue to flow.
  • the hydrogen partial pressure in the atmosphere in the reaction furnace cannot be lowered. Therefore, the effect is limited as compared with the case where the hydrogen partial pressure in the reactor is low.
  • the hydrogen atom concentration in the p-type GaAs layer 114 is high, the hydrogen atoms can be diffused to the outside and removed.
  • Examples of the pressure, heating temperature, and heating time for heating the p-type GaAs layer 114 in a reduced pressure atmosphere include 1 ⁇ 10 ⁇ 3 to 1 ⁇ 10 3 Pa, 300 to 600 ° C., and 1 to 30 minutes.
  • the nitrogen flow rate, pressure, heating temperature, and heating time are 1 to 200 SLM, 1 ⁇ 10 3 to 1 ⁇ 10 5 Pa, 400 to 700 ° C., and 1 to 60 minutes. Can be mentioned.
  • the H 2 flow rate is 1 to 200 SLM
  • the Group 5 source gas flow rate is 1 to 2000 SCCM. Examples include 1 ⁇ 10 3 to 1 ⁇ 10 4 Pa, 500 to 800 ° C., and 1 to 60 minutes.
  • p-type impurities can also be doped by supplying a p-type impurity gas.
  • the p-type impurity gas include CX 4-y H y (where X is a halogen atom and y is an integer of 0 or more and 3 or less), specifically, CBrCl 3 .
  • Another p-type impurity gas is diethyl zinc (DEZn).
  • the semiconductor substrate 100 can be manufactured as described above. After the p-type GaAs layer 114 is formed by epitaxial growth, the semiconductor substrate 100 is heated so that the hydrogen atom concentration in the p-type GaAs layer 114 is 2 ⁇ 10 18 cm ⁇ 3 or more and 1 ⁇ 10 19 cm ⁇ 3. The following appropriate ranges can be used. As a result, the rate at which the carbon atoms present in the p-type GaAs layer 114 are activated increases, while the crystallinity of the p-type GaAs layer 114 can be prevented from being lowered. Resistance decreases. Since the electrical resistance of the p-type GaAs layer 114 functioning as a contact layer has a great influence on the VCSEL characteristics, the VCSEL characteristics can be remarkably improved by reducing the electrical resistance.
  • FIG. 2 shows a cross-sectional example of the vertical cavity surface emitting laser 200.
  • the vertical cavity surface emitting laser 200 includes a base substrate 102, a buffer layer 104, an n-type mirror layer 206, an active layer 208, an oxide constriction layer 210, a p-type mirror layer 212, a contact layer 214, an electrode 216, and an oxide layer 218.
  • the active layer 208 has a cladding layer 220 and a light emitting layer 222.
  • the n-type mirror layer 206, the active layer 208, the oxidized constricting layer 210, the p-type mirror layer 212, and the contact layer 214 are respectively the n-type stacked crystal layer 106, the i-type stacked crystal layer 108, and the p-type AlGaAs layer of the semiconductor substrate 100. 110, p-type stacked crystal layer 112 and p-type GaAs layer 114 are each formed by mesa processing.
  • the electrode 216 is a metal layer formed in a donut shape in contact with the contact layer 214 and functions as an anode electrode of the vertical cavity surface emitting laser 200.
  • the oxide layer 218 is an oxide layer obtained by laterally oxidizing the mesa-processed p-type AlGaAs layer 110.
  • the active layer 208 includes a cladding layer 220 and a light emitting layer 222.
  • Each of the cladding layer 220 and the light emitting layer 222 is formed by mesa processing each of the i-type AlGaAs layer 120 and the i-type GaAs / AlGaAs layer 122. It is.
  • a cathode electrode is formed on the upper surface or the lower surface of the base substrate 102.
  • the mesa processing may be stopped in the middle of the n-type mirror layer 206, for example, at a depth of several layers above the n-type mirror layer 206.
  • the manufacturing method of the vertical cavity surface emitting laser 200 is as follows. After manufacturing the semiconductor substrate 100, the buffer layer 104, the n-type stacked crystal layer 106, the i-type stacked crystal layer 108, the p-type AlGaAs layer 110, the p-type stacked crystal layer 112, and the p-type GaAs layer 114 are mesa processed. Thereafter, the mesa-processed semiconductor substrate 100 is placed in an oxidizing atmosphere, and the p-type AlGaAs layer 110 is laterally oxidized to form an oxide layer 218. Further, a metal layer to be the electrode 216 is formed by an evaporation method or a sputtering method, and the electrode layer 216 is formed by patterning the metal layer by a photolithography method or a lift-off method.
  • Example 1 The crystal layers shown in Table 1 were epitaxially grown on the base substrate 102 having an off angle of 5 °.
  • TMG and TMA were used as Group 3 source gases.
  • Arsine was used as a Group 5 source gas.
  • Disilane was used as the n-type impurity gas.
  • the V / III ratio is as small as 15 or less, so C atoms derived from the methyl group of the group 3 source gas become p-type impurities, but p-type impurity gas was also used.
  • CBrCl 3 was used as the p-type impurity gas.
  • the reaction temperature for epitaxial growth was controlled in the range of 570 ° C. to 680 ° C.
  • the p-type GaAs layer of layer number 1 corresponds to the p-type GaAs layer 114.
  • the p-type AlGaAs layer with layer number 3 corresponds to the first crystal layer 130.
  • the p-type AlGaAs layer of layer number 2 corresponds to the second crystal layer 132.
  • heat treatment was performed after epitaxial growth.
  • the heat treatment step was performed continuously with the epitaxial growth step in the same reactor as the epitaxial growth. Specifically, the supply of the source gas was stopped after the epitaxial growth step, and the epitaxially grown crystal layer was heated. The heating temperature and heating time were 600 ° C. and 20 minutes.
  • Comparative example As a comparative example, the crystal layer shown in Table 2 was epitaxially grown on the base substrate 102. The formation process of each layer in the comparative example is the same as that in Example 1 except that the heat treatment was not performed on each layer from layer number 5 to layer number 1.
  • Example 1 When the semiconductor substrate formed as described above is subjected to mesa processing in the same manner as in Example 1 to form electrodes and a vertical cavity surface emitting laser is produced, the laser output decreases when the current is increased. An element was generated, and the yield decreased. Further, the oscillation threshold current was 0.80 mA, which was higher than that of Example 1, and the slope efficiency was 0.52 W / A, which was lower than that of Example 1. The defective rate was 18.9%, which was higher than Example 1.

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Abstract

<span lang=FR style='font-family:"Courier New"'>L'invention concerne un substrat semiconducteur pour un laser à émission par la surface et à cavité verticale. Le substrat semiconducteur comprend une couche de cristal de type p qui joue le rôle de couche de contact, la couche de cristal de type p étant composée d'un semiconducteur composé 3-5 et le substrat semiconducteur contenant des atomes d'hydrogène dans une concentration égale ou supérieure à 2 </span>× 1018 cm-3 mais égale ou inférieure à 1 × 1019 cm-3. Une couche de GaAs de type p peut être utilisée comme couche de cristal de type p. La couche de cristal de type p peut contenir des atomes de carbone comme atomes d'impureté de type p.
PCT/JP2011/006956 2010-12-21 2011-12-13 Substrat semiconducteur, procédé de fabrication du substrat semiconducteur et laser à émission par la surface et à cavité verticale WO2012086150A1 (fr)

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WO2015011966A1 (fr) * 2013-07-24 2015-01-29 株式会社村田製作所 Laser à cavité verticale émettant par la surface et son procédé de fabrication

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TWI781445B (zh) * 2019-09-24 2022-10-21 全新光電科技股份有限公司 高功率垂直共振腔表面放射雷射二極體（vcsel）

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JPH0832181A (ja) * 1994-07-05 1996-02-02 Motorola Inc 発光デバイスをｐ型ドーピングする方法
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WO2015011966A1 (fr) * 2013-07-24 2015-01-29 株式会社村田製作所 Laser à cavité verticale émettant par la surface et son procédé de fabrication

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