WO2005122350A1 - 面発光レーザダイオードおよびその製造方法 - Google Patents
面発光レーザダイオードおよびその製造方法 Download PDFInfo
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- WO2005122350A1 WO2005122350A1 PCT/JP2005/010520 JP2005010520W WO2005122350A1 WO 2005122350 A1 WO2005122350 A1 WO 2005122350A1 JP 2005010520 W JP2005010520 W JP 2005010520W WO 2005122350 A1 WO2005122350 A1 WO 2005122350A1
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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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- 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]
- H01S5/18308—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
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- 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
- H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
- H01S5/42—Arrays of surface emitting lasers
- H01S5/423—Arrays of surface emitting lasers having a vertical cavity
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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
- H01S5/02—Structural details or components not essential to laser action
- H01S5/022—Mountings; Housings
- H01S5/0225—Out-coupling of light
- H01S5/02251—Out-coupling of light using optical fibres
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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
- H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
- H01S5/042—Electrical excitation ; Circuits therefor
- H01S5/0425—Electrodes, e.g. characterised by the structure
- H01S5/04256—Electrodes, e.g. characterised by the structure characterised by the configuration
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- 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]
- H01S5/18344—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] characterized by the mesa, e.g. dimensions or shape of the mesa
- H01S5/18347—Mesa comprising active layer
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- 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]
- H01S5/18383—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] with periodic active regions at nodes or maxima of light intensity
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/2205—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers
Definitions
- the present invention relates to a surface emitting laser diode and a method for manufacturing the same.
- a surface-emitting laser diode (a surface-emitting laser diode) is a semiconductor laser that emits light in a direction perpendicular to a substrate, and has higher performance at a lower cost than an edge-emitting laser diode. It is used in consumer applications such as light sources for optical communication such as interconnection, light sources for optical pickups, and light sources for image forming apparatuses.
- Patent Document 1 JP 2002-164621
- Patent Document 2 JP-A-9107153
- Patent Document 3 JP 2001-60739
- Patent Document 4 JP 2001-168461
- Non-Patent Document 1 IEEE Photonics Technology Letters, Vol. 10, No. 12, pp. 1676-1678, 1998 (Tokyo Tech)
- Non-Patent Document 2 IEEE Photonics Technology Letters, Vol. 12, No. 6, pp. 603-605, 2000 (Wisconsin Univ.)
- the surface emitting laser diode has a small active layer volume, it is often required to increase the output so that the optical output is small compared to the edge emitting laser diode.
- One method of increasing the light output is to take measures to suppress the temperature rise of the light emitting section.
- FIG. 1 is a diagram showing a configuration example of a general surface emitting laser diode.
- FIG. 1 shows an example of a surface emitting laser diode having an active layer of InGaAs / GaAs and selectively oxidizing an AlAs layer to form a current confinement structure.
- the general surface-emitting laser diode shown in FIG. 1 is manufactured as follows.
- an n_AlGa AsZn-AlGaAs lower semiconductor multilayer film reflector (DBR: distributed Bragg reflector) 12 a lower GaAs spacer layer 13, An AlGaAs / AlGaAs_MQW active layer 14, an upper AlGaAs spacer layer 15, an AlAs selective oxidation layer 16, and a p_AlGaAs / p_AlGaAs upper semiconductor multilayer reflector (DBR) are sequentially stacked to form a stacked film.
- DBR distributed Bragg reflector
- the laminated film is processed into a mesa shape by a dry etching method. At this time, it is general that the etching surface reaches the lower semiconductor DBR12.
- the AlAs selectively oxidized layer 16 whose side surface is exposed by the dry etching is heat-treated in water vapor to oxidize the periphery to change to an Al 2 O insulator layer, and to pass an element driving current.
- the periphery of the mesa structure is buried with an insulating film 18, and a p-side electrode 19 and an n-side electrode 20 are formed at predetermined locations, whereby the surface emitting laser diode of FIG. 1 can be manufactured.
- Patent Document 1 discloses a configuration for further reducing the thermal resistance.
- AlAs having much higher thermal conductivity than AlGaAs is used for the low refractive index layers of most of the lower DBRs in the lower semiconductor DBR.
- the low refractive index layer above the lower semiconductor DBR uses conventional AlGaAs. The reason for this is that if the etched surface reaches the lower AlAs-DBR, the end of the AlAs layer of the lower AlAs_DBR exposed on the mesa sidewalls during the oxidation process of the AlAs selective oxidation layer in the subsequent process. This is because oxidation proceeds simultaneously from the surface, and the active portion in the device is insulated or the resistance of the device increases. This occurs because the oxidation rate of AlGaAs greatly depends on the A1 composition, and the higher the A1 composition, the higher the oxidation rate, and AlAs has the highest oxidation rate.
- Patent Document 1 an upper AlGaAs-DBR using AlGaAs having a low oxidation rate is provided, and the etching bottom surface is controlled so as to be located in the upper AlGaAs-DBR. — Avoids exposing the AlAs end face of the DBR.
- the number of pairs of such upper AlGaAs-DBR is preferably 4/7 or less as a whole, as shown in Patent Document 1, and is particularly preferably within 10 pairs.
- the change in the Ga composition or the GaZAl composition ratio is small and the wavelength varies depending on the wavelength.
- the film thickness of the DBR and resonator becomes smaller, In optical spectroscopy, the amplitude of the above-mentioned vibration waveform becomes small and monitoring becomes easy.
- the sample to be etched is large, there is a problem that monitoring becomes difficult due to the influence of the etching rate distribution in the sample.
- the 850 nm band and 980 nm band surface emitting laser diodes can obtain good carrier confinement in the active layer.
- a surface-emitting laser diode in the 850 nm band GaAs is used for the quantum well active layer, and AlGaAs is used for the barrier layer and the spacer layer (cladding layer).
- a 850-nm surface emitting laser diode can use a high-performance AlGaAs-based reflector (DBR) and a current confinement structure using an A1 oxide film, realizing practical-level performance. ing.
- DBR high-performance AlGaAs-based reflector
- Non-Patent Document 1 discloses that by using a (311) B substrate, that is, a so-called off-substrate inclined from (100) by 25 ° in the direction of the (ll) B plane, the optical gain in the inclined direction is increased. It has been shown that polarization control can be realized by such optical gain anisotropy. It is also shown that the (311) A substrate has the same effect.
- Non-Patent Document 1 crystal growth on a (311) B substrate, which is greatly inclined, is more difficult than crystal growth on a (100) substrate. 311) Crystal growth on the A-substrate has the disadvantage that it is even more difficult.
- a surface emitting laser diode having a wavelength band shorter than 850 nm is realized by adding A1 to a quantum well active layer and increasing its band gap.
- Patent Document 2 discloses an A1-free active region (a quantum well active layer and a layer adjacent thereto) for the purpose of suppressing formation of a non-radiative recombination center in a surface emitting laser diode having a wavelength band shorter than 850 nm.
- a surface-emitting laser diode (780 nm band) using a laser has been proposed.
- GaAsP having tensile strain is used for the quantum well active layer
- GalnP having compressive strain is used for the barrier layer
- the spacer layer (cladding) is used.
- Lattice-matched GalnP is used for the layer (the layer between the layer and the first and third quantum well active layers)
- AlGalnP is used for the cladding layer.
- the active region is A1-free, so that the reliability of the surface emitting laser diode is improved.
- Non-Patent Document 2 discloses that, in addition to the effect of the A1-free active region, GalnPAs having a compressive strain in the quantum well active layer is used to increase the gain of the active layer.
- GalnP with lattice matching or tensile strain in the barrier layer, and using AlGalnP in the spacer layer (layer between the cladding layer and the first and third quantum well active layers) A 780 nm surface emitting laser diode using AlGalnP (A1 composition larger than the spacer layer) for the gate layer has been proposed.
- the barrier layer has a lattice matching composition and a band gap larger than the compressive strain composition as compared with the structure of Patent Document 2 described above. , The carrier confinement efficiency is improved.
- Patent Document 3 discloses that the plane orientation of the substrate is in the range of 15 ° to 40 ° (inclination angle) from (100) to (111) A-plane direction or (ll) B-plane direction.
- a tilted substrate utilizing optical gain anisotropy, and employing a multiple quantum well active layer composed of InAlGaAs and InGaAsP with compressive strain, the optical gain in the tilted direction is increased, and polarization is increased.
- a technique for performing control is shown.
- Patent Document 4 discloses that the mesa shape is circular, elliptical, or oblong, and the direction of the long axis is
- a method of changing the direction from (100) to (111) A plane direction or (111) B plane direction is shown. This place In this case, use a substrate with a plane orientation of 2 ° off (including -5 ° to + 5 °) from (100) to [110]. It should be noted that this is not a substrate inclined in the A-plane and B-plane directions.
- the surface of the active layer has a large and low threshold value, has a high output, is excellent in reliability, and has a shorter wavelength than 850 nm in which the polarization direction is controlled.
- the laser diode has been realized.
- Patent Document 2 improves the reliability because the active region is A1 free, but does not disclose a polarization control method.
- Non-Patent Document 2 has a structure with good carrier confinement, but does not show a polarization control method.
- the polarization direction can be controlled, but no consideration is given to the reliability and the configuration suitable for the characteristics of the material.
- Patent Document 4 no consideration is given to a high gain and a long life in a surface emitting laser diode having a wavelength capable of controlling the polarization direction having a wavelength shorter than 850 nm.
- Non-Patent Document 2 when an (Al) GalnP-based material is used as a material for forming a resonator region sandwiched between upper and lower reflecting mirrors, At the interface with the upper reflector made of AlGaAs-based material, In segregation occurs, such as carryover of In to the AlGaAs layer, causing the inconvenience of a large increase in threshold current. It is known that
- AlGalnP which is a quaternary mixed crystal, has a large thermal resistance, and the (Al) GalnP-based material has a problem that Zn (zinc) used as a p-type dopant is easily diffused.
- the active layer has a low threshold value with a large gain, has a high output, is excellent in reliability, and has a surface emission having a wavelength shorter than 850 nm whose polarization direction is controlled.
- the laser diode has been realized.
- the present invention provides a surface emitting laser diode in which the change in Ga composition and Ga / Al ratio in a semiconductor distributed Bragg reflector (DBR) is small and the heat dissipation is improved. It is an object of the present invention to provide a structure capable of improving the controllability of etching when forming a mesa structure by using the structure, and to provide a surface emitting laser diode capable of high-power operation by the structure. [0041] In addition, the present invention particularly relates to a surface emitting laser diode having a wavelength shorter than 850 nm, a surface emitting laser diode excellent in reliability, and a high threshold having a low threshold value in which the gain of the active layer is large. It is an object to provide an output surface emitting laser diode.
- DBR distributed Bragg reflector
- the present invention also provides a surface-emitting laser diode having a wavelength shorter than 850 nm, which is excellent in reliability, has a large threshold of a large gain of an active layer, has a high output, and further has a polarization direction. It is an object of the present invention to provide a surface emitting laser diode in which is controlled.
- the present invention provides a surface emitting laser diode lay, an image forming apparatus, an optical pickup system, an optical transmitting module, an optical transmitting / receiving module, and an optical communication system in which the above-described surface emitting laser diode is integrated.
- the present invention provides:
- An active layer structure including at least one quantum well active layer and a barrier layer that generate laser light; and a spacer layer provided near the active layer structure and made of at least one material, A resonator region formed on the semiconductor substrate;
- An upper reflector and a lower reflector provided above and below the resonator region on the semiconductor substrate;
- a surface emitting laser diode comprising:
- the resonator region, the upper reflecting mirror and the lower reflecting mirror form a mesa structure on the semiconductor substrate;
- the upper reflector and the lower reflector constitute a semiconductor distributed Bragg reflector in which the refractive index changes periodically and the incident light is reflected by light wave interference
- At least a part of the semiconductor distributed Bragg reflector has a low refractive index layer made of AlGaAs (0 ⁇ x ⁇ 1) and a refractive index made of AlGaAs (0 ⁇ y ⁇ x ⁇ l). From the great layers
- the lower reflector includes a first lower reflector whose low refractive index layer is made of AlAs, and a second lower reflector formed on the first lower reflector and whose low refractive index layer is made of AlGaAs,
- One of the layers constituting the resonator region is a surface emitting laser diode containing In. Provide code.
- the present invention provides, in a second aspect,
- a (100) GaAs substrate having a plane orientation inclined at an angle in the range of 5 ° to 20 ° with respect to the (111) A plane direction;
- An active layer structure part comprising at least one quantum well layer activity and a barrier layer for generating laser light; and a spacer layer provided near the active layer structure part and made of at least one kind of material.
- An upper reflector and a lower reflector provided at the upper and lower portions of the resonator region
- the resonator region and the upper and lower reflectors form a mesa structure on the GaAs substrate;
- the upper reflector and the lower reflector are semiconductor distributed Bragg reflectors whose refractive index changes periodically and reflects incident light by light wave interference
- At least a part of the semiconductor distributed Bragg reflector has a low refractive index layer composed of Al Ga As (0 x x ⁇ 1) and a refractive index composed of Al Ga As (0 ⁇ y ⁇ x ⁇ l). Greater layers and more structures
- Part of the spacer layer is composed of (AlGa) InP (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1),
- the quantum well active layer is made of Ga In P As (0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1),
- the barrier layer is made of Ga In P As (0 ⁇ e ⁇ l, O ⁇ f ⁇ l),
- the quantum well active layer has a compressive strain
- the active layer structure provides a surface emitting laser diode having a long shape anisotropy in the (111) A plane direction when viewed from the light emitting direction.
- the present invention provides, in a third aspect,
- An active layer structure including at least one quantum well active layer for generating laser light and a barrier layer on a semiconductor substrate, and a spacer made of at least one material provided near the active layer structure.
- a method for manufacturing a surface emitting laser diode comprising: a resonator region comprising a layer; and an upper reflecting mirror and a lower reflecting mirror provided above and below said resonator region. Forming a laminated structure including the lower reflector, the resonator region, and the upper reflector on the semiconductor substrate;
- the step of forming the laminated structure includes a step of including In in any of the layers constituting the resonator region,
- the step of forming the mesa structure by dry etching includes a step of controlling the height of the mesa structure by monitoring the emission of In, and provides a method of manufacturing a surface emitting laser diode.
- the present invention provides, in a fourth aspect,
- An upper reflector and a lower reflector provided on the GaAs substrate at upper and lower portions of the resonator region, respectively.
- the upper reflector and / or the lower reflector include a semiconductor distributed Bragg reflector, and at least a part of the semiconductor distributed Bragg reflector is formed of a semiconductor layer containing Al, Ga and As as main components,
- the present invention provides, in a fifth aspect,
- the upper reflector and / or the lower reflector includes a semiconductor distributed Bragg reflector, and at least a part of the semiconductor distributed Bragg reflector is composed of a semiconductor layer containing Al, Ga, As as a main component,
- the present invention provides a surface emitting laser diode in which C (carbon) is added as a p-type dopant to a semiconductor layer containing Al, Ga, As as a main component.
- the present invention provides:
- An upper reflector and a lower reflector provided on the GaAs substrate and above and below the resonator region,
- the upper reflector and / or the lower reflector includes a semiconductor distributed Bragg reflector, and at least a part of the semiconductor distributed Bragg reflector is composed of a semiconductor layer containing Al, Ga, As as a main component,
- (Al Ga) In P (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1) layer is a short-period superclass composed of AllnP and GalnP a 1- a b 1-b
- a surface-emitting laser diode which is a semiconductor layer having a semiconductor structure.
- the present invention provides, in a seventh aspect, A GaAs substrate,
- An upper reflector and a lower reflector provided on the GaAs substrate and above and below the resonator region, respectively.
- the upper reflector and the Z or lower reflector include a semiconductor distributed Bragg reflector, and at least a part of the semiconductor distributed Bragg reflector is formed by Al Ga As (0 ⁇ x ⁇ 1).
- It consists of a low refractive index layer and a high refractive index layer made of Al Ga As (0 ⁇ y ⁇ x ⁇ l).
- At least the low-refractive-index layer closest to the active layer is (Al Ga) In P (0 ⁇ a ⁇ l, 0 ⁇ ba 1-ab 1-b
- a surface emitting laser diode in which an antinode of an electric field intensity distribution coincides with an interface between the resonator region and a low refractive index layer closest to an active layer of the upper reflecting mirror and the Z or lower reflecting mirror.
- the mesa of the laser laminated structure including the resonator and the upper and lower semiconductor DRRs is formed.
- the accuracy and reproducibility of the mesa etching are improved, and the lower semiconductor DBR contains AlAs / (Al) GaAs_DBR having excellent heat dissipation.
- AlAs / (Al) GaAs-DBR is provided up to the vicinity of the resonator can be realized.
- the mesa structure can be more reproducibly formed.
- it can be formed with higher accuracy, and as a result, a surface emitting laser diode with better temperature characteristics, higher output, and more uniform laser characteristics can be formed with high processing reproducibility and high yield. Can be achieved.
- the semiconductor DBR constituting the second lower reflector is formed to have a thickness of 10 pairs or less. Is set to be larger and smaller than the accuracy of the mesa etching. As a result, a rise in temperature during driving is further suppressed, and a surface-emitting laser diode with good temperature characteristics and high output can be obtained.
- a part of the spacer layer is made of (AlGa) InP (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1).
- the door active layer is composed of Ga in P As (0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1), and the barrier layer is Ga In
- the band gap difference between the spacer layer and the quantum well active layer can be increased as compared with the case of using an aAs system, the carrier confinement efficiency is improved, and the excellent heat dissipation inherent to a strong structure is achieved. Together with the effect, a high-power laser having a lower threshold can be realized.
- a GalnPAs material is used for the barrier layer and the quantum well active layer, that is, the quantum well active layer is formed of Ga in P As (0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1), and the barrier layer is Ga
- the active layer structure portion including the quantum well active layer and the layer adjacent thereto does not include A1. Therefore, the incorporation of oxygen by A1 into the active layer structure and the formation of a non-radiative recombination center due to this are suppressed, and a long-life surface emitting laser diode can be realized.
- the quantum well active layer is formed with a compressive strain composition so that a compressive strain is accumulated in the quantum well active layer.
- the effect of distortion is added, and the optical gain of the active layer structure further increases. This is combined with the improvement of the heat radiation effect, so that the threshold value is further lowered.
- the reflectivity of the light extraction side DBR (upper semiconductor DBR) is reduced in accordance with the improvement of the carrier confinement efficiency and the decrease in the threshold obtained by the gain increasing effect due to the use of the strained quantum well active layer. It is also possible to further increase the light output as a result of such a reduction in the reflectance of the DBR on the light extraction side.
- the semiconductor substrate may have a plane orientation (lOO) GaA s inclined at an angle in a range of 5 ° to 20 ° with respect to the (lll) A plane direction. Since it is a substrate (ie, by taking into account the plane orientation of the substrate, using a (100) GaAs substrate whose plane orientation is inclined at an angle in the range of 5 ° to 20 ° with respect to the (111) A plane direction, It is possible to reduce adverse effects on device characteristics such as semiconductor lasers, such as reduction of band gap due to formation of superlattices, deterioration of surface properties due to generation of hillocks (hill-shaped defects), and generation of non-radiative recombination centers. .
- a (100) GaAs substrate whose plane orientation is inclined at an angle in the range of 5 ° to 20 ° with respect to the (111) A plane direction.
- a (100) GaAs substrate whose plane orientation is inclined at an angle in the range of 5 ° to 20 ° in the direction of the (lll) A plane for polarization control
- the decrease in the optical gain anisotropy can be compensated by applying a compressive strain to the quantum well active layer, thereby inducing an increase in the optical gain anisotropy.
- the polarization direction can be effectively controlled. That is, according to the present invention, the synergistic effect of the improvement of the heat dissipation efficiency and the gain of the active layer structure portion has a low threshold value, is excellent in reliability, and is controlled in the polarization direction, and is shorter than 850 nm.
- a high-power surface-emitting laser diode that oscillates at a wavelength can be realized.
- an AlGalnP material that is, (AlGa) InP (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1) is formed on a part of the spacer layer.
- GaAs AlGa
- the threshold value of laser oscillation can be reduced and the output can be increased.
- the active layer composed of the quantum well layer and the layer adjacent thereto is formed.
- the structure does not include A1.
- A1 incorporation of oxygen by A1 into the active layer structure is reduced, and the formation of non-radiative recombination centers is suppressed. Thereby, a long-life surface emitting laser diode is realized.
- the quantum well active layer has a compressive strain composition, so that the threshold of laser oscillation is further reduced by the effect of the compressive strain, the efficiency of the laser is improved, and a large output is obtained. It becomes possible to take out.
- the laser oscillation is improved by improving the carrier confinement efficiency in the active layer structure and the gain by employing the strained quantum well active layer.
- the threshold is further reduced, and the reflectance of the DBR on the light extraction side can be reduced. This makes it possible to obtain a higher output.
- the plane orientation in consideration of the plane orientation of the substrate, is in the range of 5 ° to 20 ° in the (ll) A plane direction.
- the use of a (100) GaAs substrate that is inclined to the lower side reduces the band gap due to the formation of a natural superlattice, deteriorates the surface properties due to the occurrence of hillocks (hill-shaped defects), and generates non-radiative recombination centers.
- adverse effects on device characteristics of a semiconductor laser or the like can be reduced.
- the effect of using the (311) B substrate which is currently regarded as the most promising, is considered.
- the optical gain anisotropy due to the use of a tilted substrate cannot be used, the optical gain anisotropy is increased by applying compressive strain to the quantum well active layer.
- the outer peripheral shape of the active layer as viewed from the light emitting direction of the surface emitting laser diode is made anisotropic, and in particular, the substrate tilt direction ((11 1) A surface Direction) is compensated by the effect of increasing the optical gain.
- the polarization direction can be controlled extremely easily.
- the optical gain of the active layer structure is large, the threshold value of laser oscillation is small, and the reliability is excellent.
- High-power surface-emitting laser that has a polarization plane and oscillates at a wavelength shorter than 850 nm A diode can be realized.
- the band discontinuity with the quantum well active layer can be further increased, and the gain can be increased. It becomes possible. As a result, the threshold value of the laser oscillation is reduced, and the surface emitting laser diode can operate at a high output.
- the semiconductor material constituting the barrier layer can increase the band gap by reducing the lattice constant.
- the oscillation wavelength is approximately
- a surface emitting laser diode having a wavelength longer than 680 nm can be realized.
- the active layer including the quantum well layer and the barrier layer is formed of a material that does not include A1. Even in this case, it is possible to achieve carrier confinement equal to or greater than that of a 780 nm surface emitting laser diode using an AlGaAs-based active layer. Further, the effect of the strained quantum well active layer is added to this, so that it is possible to realize characteristics equal to or higher than those of the surface emitting laser diode in the 78 Onm band having the AlGaAs-based active layer.
- an active layer structure including at least one quantum well active layer for generating laser light and a barrier layer on a semiconductor substrate;
- a resonator region provided near the layer structure and comprising a spacer layer made of at least one kind of material, and an upper reflector and a lower reflector provided above and below the resonator region.
- a stacked structure including the lower reflecting mirror, the resonator region, and the upper reflecting mirror is formed on the semiconductor substrate, and the stacked film is patterned by dry etching.
- the emission of In is monitored to monitor the mesa structure. height More controlling, the can reliably detect the cavity portion in the dry etching process, thereby, it is possible to form the reproducibility Yogu also good accuracy instrument mesa structure. According to the present invention, it becomes possible to manufacture such a surface emitting laser diode with good reproducibility and high yield.
- a semiconductor layer containing A1, In, P as a main component and a semiconductor layer containing Al, Ga, As as a main component are different from each other.
- the interface By setting the interface to the position of the node of the electric field intensity distribution, the crystal growth of the semiconductor layer containing Al, Ga, As as the main component on the semiconductor layer containing Al, In, P as the main component, Even if the separation occurs to some extent, the influence of optical absorption at the interface can be greatly reduced, and the adverse effect on the threshold increase due to the In separation can be effectively suppressed.
- Mg magnesium
- C carbon
- dopant and memory effect can be reduced, and doping can be performed with good controllability. This makes it possible to obtain a doping profile close to the design, suppress the decrease in the crystallinity of the active layer, and easily realize a surface emitting laser diode that operates at a high output with a low threshold.
- heat dissipation is improved by quasi-constituting the AlGalnP mixed crystal with AllnP and GalnP having low thermal resistance. High output operation can be easily realized.
- the spacer layer is changed to AlGa l -a b 1 -b
- the band gap difference between the spacer layer and the quantum well active layer can be increased, the threshold of laser oscillation is reduced, the efficiency of laser oscillation is improved, and the Operation can be realized.
- Ga In P As (0 ⁇ c ⁇ l c 1 -c d 1 -d
- the active layer is composed of a material that does not contain Al, the active region consisting of the quantum well active layer and the layer adjacent thereto becomes A1 free, the incorporation of oxygen can be reduced, and the formation of a non-radiative recombination center can be achieved. It is possible to realize a surface-emitting laser diode that is suppressed and has a long life. That is, a high output surface emitting laser diode having a wavelength shorter than 850 nm is realized, which is excellent in reliability in which the gain of the active layer is large and the laser oscillation threshold is low.
- the laser oscillation threshold can be reduced by the effect of strain, the laser oscillation efficiency can be improved, and the efficiency of carrier confinement is improved and the strained quantum well active layer is used. Due to the effect of increasing the gain, the laser oscillation threshold is further reduced, and the reflectivity of the DBR on the light extraction side can be reduced. Thereby, the laser output can be further increased.
- a quantum well active layer having a larger strain in the surface emitting laser diode, by compensating for the strain in the quantum well active layer, a quantum well active layer having a larger strain can be employed. This increases the degree of freedom in design. Furthermore, in the GalnPAs-based material, the semiconductor material used as the barrier layer has a larger band gap when the material has a smaller lattice constant, so that the band discontinuity with the quantum well active layer can be increased, and the gain increases. This enables low threshold operation and high output operation.
- the lower reflective mirror is configured so that the low refractive index layer contains AlAs having a small thermal resistance, so that it is generated in the active layer.
- the heat radiation characteristics are improved, the temperature rise during driving is suppressed, and a surface-emitting laser diode with good temperature characteristics and high output can be obtained.
- an intermediate layer having a small A1 composition is inserted between the low refractive index layer and the high refractive index layer of the semiconductor distributed Bragg reflector. This facilitates bonding between the AlGalnP-based material and the AlGaAs-based material.
- Al Ga In P (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1) Al Ga As (0 ⁇ y ⁇ x ⁇ l) a 1— a b 1— b y l-y
- the growth of the high refractive index layer can be performed in a wide range of conditions by reducing the A1 composition at the interface. Furthermore, a strong configuration can reduce band discontinuity in the valence band, and can reduce resistance to a current flowing in the stacking direction.
- the composition wavelength is longer than 680 nm, A1
- a free active layer quantum well active layer and barrier layer
- carrier confinement equal to or more than that of a 780 nm surface emitting laser diode using an AlGaAs-based active layer can be achieved. Since the effect is added, it is possible to obtain the same or better characteristics.
- the surface emitting laser diode Considering the plane orientation of the plate, by using a (100) GaAs substrate whose plane orientation is inclined at 5 ° in the direction of the (111) A plane and within 20 ° in the direction of the plane, it is possible to reduce the band gap due to the formation of a natural superlattice, In addition, it is possible to reduce adverse effects on device characteristics such as semiconductor lasers due to deterioration of surface properties due to generation of hillocks (hill-shaped defects) and generation of non-radiative recombination centers. Polarization control.
- the effect of using the (311) B substrate, which is currently regarded as the most promising, cannot be used, and the optical gain anisotropy due to the use of the inclined substrate is small. Although it is inevitable, this decrease in optical gain anisotropy is compensated for by increasing the optical gain anisotropy by applying compressive strain to the quantum well active layer. In any case, the controllability of the polarization plane can be improved.
- the outer peripheral shape of the active layer viewed from the light emitting direction of the surface emitting laser diode has anisotropy. (ll) Since the shape is long in the A-plane direction, the controllability of the polarization direction can be further improved by adding the effect of increasing the optical gain in the substrate tilt direction ((ll) A-plane direction).
- a surface emitting laser diode ray can be formed.
- a surface emitting laser diode ray with improved mesa formation accuracy and reproducibility, uniform laser characteristics, and good process reproducibility is manufactured at a high yield and a low cost. It becomes possible.
- the surface emitting laser diode according to the first aspect of the present invention when used, heat radiation characteristics are improved, so that thermal interference between elements in the array is suppressed, and the surface emitting laser diode elements are further connected to each other. A closer, higher density array can be formed.
- a configuration in which a large number of surface emitting laser diodes capable of high-output operation are integrated on the same substrate is used in an image writing optical system such as an electrophotographic image forming apparatus.
- an image writing optical system such as an electrophotographic image forming apparatus.
- high speed writing is realized by multiple beams at the same time, and writing speed is remarkably improved.
- the image forming apparatus using the surface emitting laser diode has a higher density than the conventional image forming apparatus. High-speed printing becomes possible.
- the surface emitting laser diode of the present invention is applied to communication, data transmission is performed by multiple beams at the same time, and high-speed communication is realized.
- the surface emitting laser diode of the present invention operates with low power consumption, and therefore, particularly when incorporated and operated in a device, a rise in temperature in the device can be reduced.
- a conventional surface-emitting laser diode laser can be used. It is possible to improve the printing speed as compared with the image forming apparatus using the image forming apparatus.
- the number of laser arrays can be reduced, and the manufacturing yield of the surface emitting laser diode ray chip can be greatly improved, and the cost of the image forming apparatus can be reduced. it can.
- a surface emitting laser diode capable of controlling the polarization plane is used, the reliability of image formation is improved.
- a communication surface emitting laser diode such as a 850 nm band surface emitting laser diode is used. The same life can be achieved, and therefore, the optical writing optical unit itself can be reused, which can contribute to a reduction in environmental load.
- a handy type having a long battery life is provided.
- An optical pickup system can be realized.
- a compact disk drive uses a semiconductor laser with a wavelength of 780 nm for optical writing and reproduction on a recording medium, and a surface emitting laser diode consumes about one digit of power compared to an edge emitting laser diode. Note that it is small.
- a surface emitting laser diode having an oscillation wavelength of 650 nm has been conventionally considered as a light source in consideration of its absorption loss characteristics, but its high-temperature characteristics are poor. Not practical. For this reason, LEDs are currently used, but high-speed modulation is difficult with LEDs, and semiconductor lasers are required to achieve high-speed transmission exceeding 1 Gbps.
- the surface emitting laser diode of the present invention having a wavelength longer than 680 nm has a large active layer gain, has a large output, and has excellent high-temperature characteristics. Therefore, by using such a surface emitting laser diode, Although the absorption loss due to the fiber increases, short-distance optical transmission is possible, and an economical high-speed optical transmission module or optical device combining an inexpensive P ⁇ F with a surface emitting laser diode, which is an inexpensive light source. A transmission / reception module and an optical communication system using the same are realized. Such an optical communication system is extremely economical, and is particularly suitable for use in an optical communication system in a general home, office room, equipment, or the like.
- FIG. 1 is a diagram showing a configuration example of a general surface emitting laser diode.
- FIG. 2 is a diagram illustrating a basic configuration example of a surface emitting laser diode according to a first embodiment.
- FIG. 3 is a diagram showing a configuration of a surface emitting laser diode of Example 1.
- FIG. 4 is a diagram showing a time change of an In (451 nm) / Al (396 nm) emission intensity ratio in Example 1.
- FIG. 5 is a diagram illustrating a configuration of a surface emitting laser diode according to a fifth embodiment.
- FIG. 6 is a diagram showing a surface emitting laser diode of Example 6.
- FIG. 7 is a diagram showing a surface emitting laser diode of Example 6.
- FIG. 8 is a top view of a surface emitting laser diode according to a seventh embodiment.
- FIG. 9 is a diagram showing a surface emitting laser diode of Example 8.
- FIG. 10 is a diagram showing a surface emitting laser diode ray of Example 9.
- FIG. 11 is a diagram showing an optical transmission module according to Embodiment 10.
- FIG. 12 is a diagram showing an optical transceiver module according to an eleventh embodiment.
- FIG. 13 is a diagram showing a laser printer according to a twelfth embodiment.
- FIG. 14 is a diagram (top view) showing a schematic configuration of a surface emitting laser diode ray chip (16-beam VCSEL array) used in the laser printer of FIG.
- FIG. 15 is a principle sectional view showing a part of a first configuration example according to a twelfth embodiment of the present invention.
- FIG. 16 is a principle sectional view showing a part of a second configuration example according to the twelfth embodiment of the present invention.
- FIG. 17 is a principle sectional view showing a configuration example of a thirteenth embodiment of the present invention.
- FIG. 18 is a cross-sectional view showing an extracted and enlarged structure around the active layer in FIG. 17.
- FIG. 19 is a plan view of a part of FIG.
- FIG. 20 is a cross-sectional view showing an extracted and enlarged structure around an active layer according to a fourteenth embodiment of the present invention.
- FIG. 21 shows an example of a peripheral cross-sectional structure of an active layer of a surface-emitting laser diode when an AlGalnP layer is provided in a resonator region sandwiched between upper and lower reflectors in the seventeenth and eighteenth embodiments.
- FIG. 22 is a diagram showing a configuration example of a surface emitting laser diode according to a twenty-first embodiment of the present invention.
- a semiconductor substrate an active layer structure including at least one quantum well active layer and a barrier layer that generate laser light, and an active layer structure provided near the active layer structure are provided.
- a resonator layer formed of at least one kind of material, the resonator region formed on the semiconductor substrate, and an upper reflecting mirror provided on the semiconductor substrate above and below the resonator region.
- a surface emitting laser diode comprising a lower reflector, wherein the resonator region, the upper reflector and the lower reflector form a mesa structure on the semiconductor substrate, and the upper reflector and the lower reflector
- the mirror constitutes a semiconductor distributed Bragg reflecting mirror whose refractive index changes periodically and reflects incident light by light wave interference, and at least a part of the semiconductor distributed Bragg reflecting mirror includes AlGa.
- the first in which the refractive index layer is made of AlAs A lower reflecting mirror, and a second lower reflecting mirror formed on the first lower reflecting mirror and having a low refractive index layer made of AlGaAs, and one of the layers constituting the resonator region contains In A surface emitting laser diode is provided.
- any of the layers constituting the resonator region contains In, and the lower semiconductor DBR contains AlAs / (Al) GaAs_DBR excellent in heat dissipation. Therefore, the accuracy and reproducibility of mesa formation are improved, and a configuration in which A1A sZ (Al) GaAs_DBR is provided up to the vicinity of the resonator region.
- At least the lower spacer layer and the upper spacer layer of the layers constituting the resonator region may include In. .
- the spacer layer which is much thicker than the active layer structure portion, contains In, so that the reproducibility is higher.
- the mesa etching can be performed with higher accuracy, and as a result, a higher-output surface-emitting laser diode with better temperature characteristics and more uniform laser characteristics can be manufactured with high processing reproducibility and high processability. It can be obtained by staying.
- the second lower semiconductor DBR has 10 pairs or less.
- the thickness force of the second lower semiconductor DBR is set to a value larger than the accuracy at the time of the mesa processing and the minimum value, so that the surface emitting laser diode can be manufactured with a higher yield.
- the surface-emitting laser diode according to the first embodiment of the present invention has an active layer structure including at least one quantum well active layer for generating laser light and a barrier layer on a semiconductor substrate. And a reflector region provided around the active layer structure portion and made of at least one kind of material. An upper reflector and a lower reflector are provided above and below the resonator region. Formed as a laminated film, and dry-etched the laminated film to form a mesa It can be manufactured by processing into a shape. At this time, in the present embodiment, the height of the mesa structure obtained by including In in any of the layers constituting the resonator region and monitoring the emission of In in the dry etching step. Control.
- the height of the mesa structure is controlled by monitoring the emission of In in the step of dry-etching the laminated film to form the mesa structure. That is, since dry etching is performed while monitoring the emission of In from the resonator layer, the resonator layer can be reliably detected, and thereby, the mesa structure can be formed with high reproducibility and accuracy. As a result, according to the present embodiment, it is possible to manufacture the first surface emitting laser diode with a high level of reproducibility, reproducibility, and yield.
- FIG. 2 shows a basic configuration example of the surface emitting laser diode 40 according to the first embodiment of the present invention.
- the surface emitting laser diode 40 is formed on a single crystal semiconductor substrate 41 such as GaAs, InP, GaP, GaNAs, Si, or Ge by MOCVD or MBE, or directly.
- a single crystal semiconductor substrate 41 such as GaAs, InP, GaP, GaNAs, Si, or Ge by MOCVD or MBE, or directly.
- a resonator layer 44 composed of a spacer layer 44A, an active layer 44B, and an upper spacer layer 44C, and having any one of the lower spacer layer 44A, the active layer 44B, and the upper spacer layer 44C containing In; A1
- the layer containing In is composed of Al Ga In As ⁇ (0 ⁇ 1,
- it may contain other Group V and Group V elements such as B, N, Sb, and ⁇ 1.
- Table 1 shows a specific example of such a VCSEL laminated structure.
- a mesa mask pattern is formed with a photoresist or the like, and the laminated structure thus formed is held in a processing vessel of a dry etching apparatus. Further, in the processing container
- a halogen-based gas such as CI, BC1, SiCl, CC1, or CF is introduced, and a reactive ion beam is introduced.
- Mesa etching is performed by a dry etching method using a plasma such as an etching method (RIBE), an inductively coupled plasma (ICP) etching method, and a reactive ion etching method (RIE).
- RIBE etching method
- ICP inductively coupled plasma
- RIE reactive ion etching method
- plasma emission spectroscopy is performed through a sight window provided in a processing vessel of a dry etching apparatus, and a time change of the emission intensity of In at a wavelength of 451 nm is monitored.
- the etching can be reliably stopped in the second semiconductor DBR43.
- the Al (Ga) As selectively oxidized layer 45 is heat-treated in water vapor to form a current confinement structure made of Al 2 O 3.
- the space around the mesa structure thus formed was filled with an insulating film 47 made of polyimide ⁇ Si ⁇ except for the electrode take-out part and the light output part.
- the surface emitting laser element is planarized.
- a p-side electrode 48 and an n-side electrode 49 are formed at predetermined locations, and the manufacture of the surface emitting laser diode 40 of FIG. 2 is completed.
- the lower spacer layer 44A, the active layer 44B, and the upper spacer layer 44C constitute a resonator 44 as a whole, and thus the total thickness of the resonator is (N + 1) X ( ⁇ / ⁇ ) and
- the resonator thickness is f / ⁇ .
- ⁇ is an integer greater than or equal to 0 and ⁇
- I the oscillation wavelength
- ⁇ is the refractive index of the semiconductor constituting the resonator 44.
- the active layer 44 # usually has a thin quantum well structure
- most of the length of the resonator is the thickness of the upper and lower spacer layers 44 # and 44C.
- the semiconductor thickness of DBR43 is (1 + 2 chi New) X tut / (4 11), often; 17 (4 1 1) Dearu. Therefore, the upper and lower spacers
- Layers 44 ⁇ and 44C have a significantly greater thickness than the films in the other stacks.
- the above-mentioned VCSEL laminated structure was formed on one wafer by the monitoring method.
- the variation of the etching depth can be controlled to such an extent that the bottom surface of the mesa structure is located within the range of a few pairs of the second lower semiconductor DBR43. Therefore, even if the variation in the mesa height within the wafer and the variation between processes during etching a large number of wafers at the same time are considered, the high refractive index film and the low refractive index film pair in the second lower semiconductor DBR43 are considered. If the number of repetitions is at most 10, the necessary etching control can be achieved by the normal etching process.
- the present embodiment it is possible to provide the configuration in which the AlAs / (Al) GaAs_DBR43 having a small thermal resistance is provided up to the vicinity of the cavity of the surface emitting laser diode, the heat radiation effect can be improved, and the driving time can be improved. The temperature rise can be suppressed, and a surface-emitting laser diode with good temperature characteristics and high output can be obtained.
- the oxidation rate of the low refractive index layer of the first lower semiconductor DBR 42 is a material having a thickness higher than the oxidation rate of the selective oxidation layer 45
- the mesa etching is performed by the first lower semiconductor.
- both the selective oxidation layer 45 and the low refractive index layer of the first lower semiconductor DBR 42 are made of AlAs.
- the low-refractive-index layer of the second lower semiconductor DBR43 is a material having a lower oxidation rate than the selective oxidation layer 45, and the low-refractive-index layer of the first lower semiconductor DBR42 has a lower refractive index. If the composition or the material has a lower thermal resistance than the low refractive index layer in the second lower semiconductor DBR43, a satisfactory heat radiation effect can be obtained.
- the emission intensity of In and the emission intensities of other constituent elements must be canceled in order to cancel the effects of changes in the plasma state. It is also possible to use a method of monitoring the ratio of the emission intensity of In or the emission intensity of In to the emission intensity of a wavelength not belonging to any of them.
- the etching bottom surface directly below the resonator it is also possible to use a method in which the uppermost layer of the lower semiconductor DBR43 is made of GalnP or AlGalnP, and the upper layer including the resonator is made of GaAs or AlGaAs.
- selective etching using H 2 SO 3 / HO 2 / HO solution becomes possible. Shi In such wet etching, it is difficult to control the mesa width, and problems such as an asymmetric mesa being easily formed due to etching anisotropy occur. Under such circumstances, the mesa etching is preferably performed by dry etching.
- the AlAs selectively oxidized layer 45 is provided in the vicinity of the active layer 44B. And its position is not limited.
- a layer containing In may be provided in a region other than the resonator region 44, such as a part of the reflector 43 closest to the resonator region 44.
- the surface emitting laser diode according to the second embodiment of the present invention is different from the surface emitting laser diode 40 according to the first embodiment in that a part of the spacer layers 44A and 44C is (AlGa) In.
- the active layer 44B is formed by Ga In P As (0 ⁇ c ⁇
- It is characterized by being constituted by a barrier layer.
- a part of the spacer layers 44A and 44C includes (AlGa) InP (0 ⁇ a ⁇ l, 0 ⁇ b ⁇
- the band gap difference between the spacer layer and the quantum well active layer can be greatly increased as compared with the case where the spacer layer is formed of an AlGaAs system.
- Table 2 shows surface emitting laser diodes of 780 nm and 850 nm band of AlGaAs (spacer layer) / AlGaAs (quantum well active layer), and AlGalnP (spacer layer) / GalnPAs (quantum well active layer). 2) Indicates the band gap difference that occurs between the spacer layer and the quantum well layer, and between the barrier layer and the quantum well layer, in a typical material composition used in a 780-nm surface emitting laser diode of the system.
- AIGaAs / AIGaAs-based materials AIGalnP / GalnPAs-based materials
- Onm band surface emitting laser diodes are not only AlGaAs / AlGaAs 780 nm band surface emitting laser diodes, but also AlGaAs / AlGaAs. It can be seen that the above band gap difference can be made larger than the 850 nm band surface emitting laser diode of the system.
- the quantum well active layer can have a compression strain configuration.
- the band separation between the heavy hole and the light hole increases, so that the gain increases, the threshold value of laser oscillation decreases, and the efficiency of laser oscillation improves. That is, the laser output increases. It should be noted that this effect cannot be realized with an AlGaAs / AlGaAs 850 nm surface emitting laser diode.
- the threshold value is reduced and the laser output efficiency is improved compared to the 850 nm surface emitting laser diode of AlGaAs / AlGaAs system. Can be realized.
- the carrier confinement efficiency is improved, and the threshold value is reduced even by increasing the gain by using the strained quantum well active layer.
- the threshold value is reduced even by increasing the gain by using the strained quantum well active layer.
- the quantum well active layer power SGa ln P As (0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1) and the barrier layer is Ga In P As (0 c 1 -cd 1 -de 1 -ef 1 -f
- the active layer structure 44 consisting of the quantum well active layer and its adjacent layers contains A1. Therefore, the incorporation of oxygen into the quantum well active layer is reduced, and the formation of a non-radiative recombination center can be suppressed. As a result, a long-life surface emitting laser diode can be realized.
- the optical gain of the active layer is significantly low.
- a high-power surface-emitting laser diode that emits light in a band shorter than 850 nm and has a threshold value and excellent reliability can be realized.
- the plane orientation is inclined at an angle (inclination angle) in the range of 5 ° to 20 ° with respect to the (111) A plane direction. It is preferable to use a (100) GaAs substrate as the substrate 41. This is because when the plane orientation of the substrate is close to (100), the band gap decreases due to the formation of a natural superlattice, the surface shape deteriorates due to the generation of hillocks (hill-shaped defects), and the non-radiative recombination center occurs. This is because there is a risk of adversely affecting device characteristics such as a semiconductor laser formed on the substrate.
- the band gap has a tilt angle of 10 ° 15. , And then gradually approach the normal band gap (band gap value of the mixed crystal), and hillocks gradually disappear.
- AlGalnP materials used in red laser (630 nm to 680 nm) material systems have the following characteristics. Substrates tilted to angles in the range of ⁇ 20 ° (and more often in the range of 7 ° to 15 °) are commonly used. This is true not only for the AlGalnP spacer layer (cladding layer) but also for the barrier layer made of GalnP as shown in Table 2. Furthermore, even when the barrier layer and the quantum well active layer are made of GalnPAs, there is a concern that adverse effects may occur.
- the growth of these materials requires the plane orientation to be in the range of 5 ° to 20 ° in the (111) A plane direction. It is preferable to use a (100) GaAs substrate inclined at an angle (more preferably, an angle in the range of 7 ° to 15 °).
- the polarization angle using the optical gain anisotropy of the (311) B substrate which is currently considered the most prominent, (Polarization direction) control technology cannot be used. That is, in the present embodiment, by using an inclination angle (an angle in the range of 5 ° to 20 °) smaller than the (311) B substrate (the inclination angle is 25 °), the cost of the substrate can be suppressed and the cleavage can be performed. However, the optical gain anisotropy to be obtained must be reduced.
- the above-mentioned decrease in optical gain anisotropy is applied to the quantum well active layer. Compensation is performed by increasing the optical gain anisotropy induced by applying the compressive strain.
- the force limiting to a wavelength shorter than 850 nm is because the advantage difference is extremely large in this wavelength range as compared with the conventional example, and the same effect is obtained when the wavelength is shorter than 850 nm. It should be noted that even wavelengths can be obtained.
- operation is performed at a wavelength shorter than 850 nm, and in addition to the features of the first embodiment, the threshold at which the gain of the active layer is large is reduced, and high output and reliability are achieved.
- a surface emitting laser diode having excellent characteristics a surface emitting laser diode whose polarization direction is further controlled is provided.
- a (100) GaAs substrate having a plane orientation inclined at an angle in the range of 5 ° to 20 ° with respect to the (A) plane direction, and at least one layer for generating a laser beam are provided.
- An active layer structure including a quantum well layer active layer and a barrier layer, and a spacer layer provided near the active layer structure and made of at least one kind of material, are formed on the GaAs substrate.
- Resonator region, and an upper reflector and a lower reflector provided above and below the resonator region. The resonator region and the upper and lower reflectors are formed on the GaAs substrate.
- the upper reflector and the lower reflector are semiconductor distributed Bragg reflectors whose refractive index changes periodically and reflects incident light by light wave interference, and the semiconductor distributed Bragg reflector is used.
- mirror At least in part, a layer Al Ga As (0 ⁇ x ⁇ 1) than becomes a refractive index of small, Al Ga
- the quantum well active layer is made of GaIa-ab-bcnPAs (0 ⁇ c ⁇ l 0 ⁇ d ⁇ l), and the barrier layer is made of GaInPAs (0 ⁇ el -cd 1 -de 1 -ef 1 -f
- the quantum well active layer has a compressive strain
- the active layer structure has an anisotropic shape elongated in the (111) A plane direction when viewed from the light emitting direction. It has characteristics.
- the polarization angle (polarization direction) is controlled by using the optical gain anisotropy obtained by inclining the plane orientation of the substrate in the (ll) A plane direction
- 31 1) Use a tilt angle (angle within the range of 5 ° to 20 °) smaller than the B board (tilt angle is 25 °). Therefore, the effect of using the (311) B substrate, which is currently regarded as the most promising, cannot be used.
- this reduction is compensated for by increasing the optical gain anisotropy by applying compressive strain to the quantum well active layer.
- the substrate tilt direction ((111) A plane Direction) is compensated by the effect of increasing the optical gain.
- the optical gain in the direction of the tilt angle (the direction of the (ll) surface) is further increased, and the controllability of the deflection angle is improved.
- the fourth embodiment of the present invention provides the surface emitting laser diode according to the second or third embodiment, wherein the barrier layer has a tensile strain.
- the band gap of GalnP is the largest when compared with the same lattice constant.
- a material having a smaller lattice constant can ensure a larger band gap.
- a large band discontinuity can be realized between the barrier layer and the quantum well active layer, and the gain of the surface emitting laser diode can be increased. .
- the band gap of the Ga In P tensile strain layer is 2 ⁇ 02
- the band gap of the GaInP lattice matching layer is 1.87 eV.
- the fifth embodiment of the present invention provides a surface emitting laser diode having an oscillation wavelength longer than about 680 nm in the surface emitting laser diode of the second to fourth embodiments.
- the band gap is the largest in the typical composition range of the spacer layer. (Al Ga) In a 1 -a b 1
- the band gap difference with the active layer is about 200 meV, which is almost the same as that of a 780 nm surface emitting laser diode using an AlGaAsZAlGaAs-based active layer.
- the sixth embodiment of the present invention provides a surface emitting laser diode ray in which a plurality of the surface emitting laser diodes according to any of the first to fifth embodiments are formed on the same substrate.
- a surface-emitting laser diode has a surface-emitting configuration, so that a laser array can be easily formed.
- each surface-emitting laser diode element is formed by a normal semiconductor process, each surface-emitting laser diode is individually formed.
- the element can be formed with high positional accuracy.
- the etching controllability at the time of mesa formation is improved, and as a result, the yield is improved, and the manufacturing cost can be reduced.
- the heat dissipation of the lower DBR is improved, and as a result, the thermal interference between elements in the array is reduced, the output of each element is increased, and the formation density of the elements is increased. S power.
- a high-power surface-emitting laser diode of the present invention in which the polarization direction is controlled to a predetermined direction.
- a laser array in which a large number of lasers are integrated on the same substrate, writing using a plurality of beams at the same time is easily realized in a writing optical system such as an image forming apparatus, and the writing speed is remarkably improved.
- printing can be performed without lowering the printing speed even when the writing dot density increases. In the case of the same writing dot density, the printing speed can be increased.
- a powerful laser array is applied to communication, data can be transmitted by multiple beams at the same time, and high-speed communication can be realized.
- the surface emitting laser diode operates with low power consumption, it is possible to suppress the rise in temperature inside the device, especially when it is installed in the device.
- the surface emitting laser diode according to any one of the first to fifth aspects or the surface emitting laser diode ray according to the sixth aspect is used as a writing light source.
- An image forming apparatus is provided.
- the image forming apparatus of the present embodiment using them has a conventional surface emitting laser. High-speed printing is possible compared to an image forming apparatus using a laser diode ray. Also, if the image forming apparatus is designed to have the same printing speed as the conventional one, the number of laser arrays to be used can be reduced, and the manufacturing yield of the surface emitting laser diode chip can be greatly improved. The manufacturing cost of the device can be reduced.
- the active layer of the surface emitting laser diode is an A1-free active layer, the lifetime is the same as that of a surface emitting laser diode for communication such as the 850 nm band surface emitting laser diode (the estimated room temperature is 1 million hours). Is reported), and the optical writing optical unit can be reused. Thereby, the environmental load can be reduced.
- An eighth embodiment of the present invention is a laser using the surface emitting laser diode of any of the first to fifth embodiments or the surface emitting laser diode ray of the sixth embodiment as a light source. To provide an optical pickup system.
- a compact disk device has been used as a light source for optical writing and reproduction on optical media. Uses a wavelength of 780 nm. Since surface-emitting laser diodes consume about one order of magnitude less power than edge-emitting laser diodes, using the 780 nm band surface-emitting laser diode of the present invention as a light source for reproduction allows hand-held light with a long buttery life to be used. It becomes possible to realize a pickup system.
- a ninth embodiment of the present invention is directed to an optical transmitter using the surface emitting laser diode according to any one of the first to fifth embodiments or the surface emitting laser diode ray according to the sixth embodiment as a light source.
- the surface emitting laser diode of the present invention having the shortest wavelength of 680 nm has a large active layer gain, and therefore has high output and excellent high-temperature characteristics. Although the absorption loss of the optical fiber increases, optical transmission is sufficiently possible over short distances, realizing an economical and high-speed optical transmission module using an inexpensive surface-emitting laser diode and an inexpensive POF. can do.
- a tenth embodiment of the present invention is directed to an optical transceiver using the surface emitting laser diode of any one of the first to fifth embodiments or the surface emitting laser diode ray of the sixth embodiment as a light source.
- the surface emitting laser diode of the present invention having the shortest wavelength of 680 nm has a large active layer gain. Because of its high power and excellent high-temperature characteristics, the use of such a surface emitting laser diode as a light source increases the absorption loss of the optical fiber, but allows for sufficient optical transmission over short distances. Therefore, an economical and high-speed optical transceiver module using an inexpensive surface emitting laser diode and an inexpensive POF can be realized.
- An eleventh embodiment of the present invention is directed to an optical communication system using the surface emitting laser diode of any one of the first to fifth embodiments or the surface emitting laser diode ray of the sixth embodiment as a light source. provide.
- the surface-emitting laser diode of the present invention having the shortest wavelength of 680 nm has a large active layer gain, and therefore has high output and excellent high-temperature characteristics. Although optical fiber absorption loss is large, optical transmission is sufficiently possible over short distances, realizing an economical and high-speed optical transceiver module using an inexpensive surface-emitting laser diode and an inexpensive POF. can do.
- FIG. 3 is a diagram showing a configuration of the surface emitting laser diode 60 according to the first embodiment of the present invention.
- the surface emitting laser diodes of Examples 2, 3, and 4 described later have the same configuration as that of FIG.
- Example 1 a first lower semiconductor in which an n—AlAs / Al Ga As pair was repeatedly stacked 42.5 times on an n—GaAs single crystal (100) substrate 61 by MOCVD.
- DB n—AlAs / Al Ga As pair
- TQW active layer 64B Ga In P upper spacer layer 64C, p-AlAs selected
- the upper semiconductor DBR 66 and the p_GaAs contact layer 67 are sequentially laminated to form a VCSEL laminated structure.
- the lower spacer layer 64A, the active layer 64B, and the upper spacer layer 64C form a resonator structure 64.
- a circular mesa mask was patterned with a photoresist on the VCSEL laminated structure thus formed, C1 gas was introduced, and the mask was formed by reactive ion beam etching (RIBE).
- RIBE reactive ion beam etching
- the emission intensity of In (451 nm) and the emission intensity of A1 (396 nm) were obtained using a plasma emission spectrometer, and the ratio (In / Al ratio) was determined. Monitor the time change.
- FIG. 4 shows the time change of the In (451 nm) / Al (396 nm) emission intensity ratio obtained in Example 1.
- the AlAs selectively oxidized layer 65 is subjected to a heat treatment at 400 ° C. in water vapor so that the non-oxidized AlAs region becomes 25 / im 2.
- a current confinement structure is formed in the selected oxide layer 65, and the periphery of the mesa structure is filled with a polyimide protective film 68 except for the electrode extraction portion and the light output portion.
- a p-side electrode film 69 is deposited on the upper surface of the mesa structure M by vapor deposition so as to be in contact with the p-type contact layer 67, and an opening for light output is formed by a lift-off method. Further, by forming an n-side electrode 70 on the back surface of the substrate 61, it is possible to produce a surface emitting laser diode having the configuration shown in FIG.
- the positive and negative carriers are injected into the p-side electrode 69 and the n-side electrode 70, respectively, so that the laser light having a wavelength of 780 nm is applied to the upper electrode.
- the light is emitted in a direction perpendicular to the substrate 61 from an opening formed in the pole 69.
- the entire cavity structure 64 is favorably etched. 64 can be detected, so that the second lower semiconductor DBR 63 can be formed with a smaller number of layers than 4/7 of the entire lower semiconductor DBR. As a result, the temperature rise of the element is suppressed, and the surface emitting laser diode can be driven with higher output.
- the mesa etching is performed with high reproducibility, the mesa height becomes uniform, and a surface emitting laser diode having uniform laser characteristics can be obtained with a high yield.
- the surface emitting laser diode 80 of the second embodiment also has the same configuration as that of FIG.
- Example 2 the n-AlAs / Al Ga As pair was repeatedly stacked 47.5 times on the n-GaAs single crystal (100) substrate 61 by MBE method.
- Lower semiconductor DB Lower semiconductor DB
- 0.95 0. 05 0.5 0.5 s pairs are repeatedly stacked 40.5 times, and the upper semiconductor DBR 66 and the ⁇ -GaAs contact layer 67 are sequentially stacked to form a VCSEL stacked structure.
- a circular mesa mask is patterned with a photoresist on the VCSEL laminated structure thus formed, C1 gas is introduced, and mesa etching is performed by an ICP etching method.
- the emission intensity of In was measured by the plasma emission spectrometer.
- the AlAs selectively oxidized layer 65 was subjected to a heat treatment at 400 ° C. in water vapor so that the non-oxidized AlAs region was 25 / im 2.
- Selectable acid A current confinement structure is formed in the passivation layer 65, and the periphery of the mesa structure is filled with a polyimide protective film 68 except for an electrode extraction portion and a light output portion.
- a p-side electrode film 69 is deposited on the upper surface of the mesa structure M by vapor deposition so as to be in contact with the p-type contact layer 67, and an opening for light output is formed by a lift-off method. Further, by forming an n-side electrode 70 on the back surface of the substrate 61, it is possible to produce a surface emitting laser diode having the configuration shown in FIG.
- the laser light having a wavelength of 650 nm is applied to the upper electrode.
- the light is emitted in a direction perpendicular to the substrate 61 from an opening formed in the substrate 69.
- the surface emitting laser diode 100 of the third embodiment also has the same configuration as that of FIG.
- Example 3 the first lower semiconductor D in which the n_AlAs / AlGaAs pair was repeatedly stacked 40.5 times on the n_GaAs single crystal (100) substrate 61 by MOCVD.
- the layers 67 are sequentially laminated to form a VCSEL laminated structure.
- the VCSEL laminated structure was mesa-etched in the same manner as in Example 2, further subjected to the same thermal oxidation treatment, and after filling the periphery of the mesa structure M with a polyimide film 68, an electrode was formed.
- the surface emitting laser diode 100 of 3 is obtained.
- the p-side electrode 69 and the n-side electrode By injecting the positive carrier and the negative carrier, respectively, a laser beam having a wavelength of 850 nm is emitted from the opening formed in the upper electrode 69 to the substrate 61 in the vertical direction.
- a surface emitting laser diode having excellent heat radiation characteristics and uniform element characteristics can be obtained with a high yield.
- the surface emitting laser diode 120 according to the fourth embodiment has the same configuration as that of FIG.
- Example 4 the first lower semiconductor in which the n—AlAs / GaAs pair was repeatedly laminated 32.5 times on the n—GaAs single crystal (100) substrate 61 by the MOCVD method was used.
- an upper semiconductor DBR66 consisting of 26 repeated GaAs pairs and p
- the GaAs contact layer 67 is sequentially laminated to form a VCSEL laminated structure.
- the VCSEL laminated structure was mesa-etched in the same manner as in Example 2 to form a mesa structure M, and further subjected to the same thermal oxidation treatment. After filling the periphery of the mesa structure M with a polyimide film 68, Then, electrodes are formed, and the surface emitting laser diode 120 of FIG. 3 is obtained.
- the laser light having a wavelength of 1300 nm is applied to the upper electrode.
- the light is emitted in a direction perpendicular to the substrate 61 from an opening formed in the substrate 69.
- the active layer contains GalnNAs
- even a 1.3 zm band laser device can be formed on a GaAs substrate.
- a high performance AlGaAs DBR can be used, and a selective oxidation confinement structure can be adopted.
- the band gap between the barrier layer and the spacer layer and the GalnNAs active layer is large. Carrier confinement efficiency is improved, so the characteristic temperature is further improved, and the applicability as a light source for optical transmission is high. A light emitting laser diode is obtained.
- the surface emitting laser diode of this embodiment is a device in the 1.3 / im band, the DBR6 Even if the thickness of the second lower DBR 63, in which the semiconductor layers constituting the layers 63 are thick, is set to a thickness corresponding to three pairs, the mesa etching is performed so that the lower end of the etching is located in the second lower DBR 63. It is possible to execute As a result, the heat radiation characteristics and the temperature characteristics are further improved, and the surface emitting laser diode can be driven with higher output.
- FIG. 5 shows the configuration of a surface emitting laser diode 140 according to the fifth embodiment.
- Example 5 a p-AlAs / p—AlGaAs pair was repeatedly laminated 39.5 times on a p-GaAs single crystal (100) substrate 81 by MOCVD. 1st lower half
- Conductor DBR82 and p-AlGaAs / p-AlGaAs pair were repeatedly laminated six times
- the tatto layers 87 are sequentially laminated to form a VCSEL laminated structure.
- the lower spacer layer 85A, the active layer 85B, and the upper spacer layer 84C form an active structure portion 85 serving as a resonator.
- the VCSEL laminated structure was mesa-etched in the same manner as in Example 2 to form a mesa structure M, and further subjected to the same thermal oxidation treatment. After the periphery of the mesa structure M was filled with a polyimide film 90, Then, electrodes are formed, and the surface emitting laser diode 120 of FIG. 3 is obtained. However, in this embodiment, the p-side electrode 89 is formed on the back surface of the substrate 81, and the n-side electrode 88 is formed on the contact layer 87.
- the n-side electrode 88 and the p-side electrode 89 are injected with negative and positive carriers, respectively, so that a laser beam having a wavelength of 850 nm is applied to the upper electrode.
- the light is emitted in a direction perpendicular to the substrate 81 from an opening formed in the substrate 88.
- the AlAs selectively oxidized layer 84 is made to have the above active property. It must be provided on the substrate side rather than the structural part 85. This is because, in a compound semiconductor, the mobility of the p-type conduction type layer is smaller than that of the n-type conduction type layer. The reason for this is that the stenosis effect is greater in the case of (1).
- the substrate-side semiconductor layer is formed to be a p-type conductivity type, more accurate etching control is required.
- the progress of the etching is monitored by using the plasma emission spectroscopy, so that the mesa etching can be stably performed even if the substrate-side semiconductor layer is a p-type conduction type surface emitting laser diode. Can be executed.
- FIGS. 6 to 7 show the configuration of the surface emitting laser diode 160 according to Embodiment 6 of the present invention.
- FIG. 7 is an enlarged view of a region A around the active layer of the surface emitting laser diode 160 of FIG.
- the surface emitting laser diode of the sixth embodiment oscillates at a wavelength of 780 nm.
- the surface emitting laser diode 160 has an n— (100) GaAs substrate 101 whose plane orientation is inclined at an inclination angle of 15 ° in the (111) A plane direction.
- a first lower semiconductor DBR (lower first reflecting mirror) 102 having a periodic structure of 30.5 stacked layers, an n—Al Ga As low refractive index layer and an n_Al Ga As high refractive index layer are placed in a medium.
- a second lower semiconductor DBR (lower second reflecting mirror) 103 having a periodic structure in which, for example, 10 periods are alternately stacked with a thickness of 1Z4 times the oscillation wavelength of the laser.
- DBR lower second reflecting mirror
- the thickness including the inclined layer is set to be 1/4 times the oscillation wavelength in the medium.
- an (AlGa) InP lower first spacer (cladding) layer 104A that is lattice-matched with the second lower semiconductor DBR103, and the (Al)
- the barrier layers 104b are alternately stacked, and the quantum well active layers 104C and the Ga
- the spacer layer 104D and the (AlGa) InP upper first spacer (cladding) layer 104E are sequentially arranged.
- the semiconductor layers 104A to 104E form a resonator 104 for one wavelength.
- An upper semiconductor DBR (upper reflecting mirror) 105 having a periodic structure in which, for example, 25 periods are alternately stacked with a refractive index layer is formed (details are omitted in FIG. 6).
- a composition gradient layer is inserted between the low refractive index layer and the high refractive index layer in the upper reflecting mirror 105.
- a p_GaAs contact layer 106 is formed on the upper reflecting mirror 105.
- a resonator 104 having a thickness corresponding to one oscillation wavelength is provided between the lower reflecting mirror 103 and the upper reflecting mirror 105. It is formed.
- the growth of the semiconductor layers 102-106 is performed by the MOCVD method.
- the raw materials are TMG (trimethylgallium), TMA (trimethylaluminum), TMI (trimethylindium), PH ( Phosphine) and AsH (arsine) are used as needed.
- n trimethylgallium
- TMA trimethylaluminum
- TMI trimethylindium
- PH Phosphine
- AsH arsine
- HSe hydrogen selenide
- CBr p-type dopant
- H is used as a carrier gas.
- the MOCVD method is particularly suitable as a crystal growth method for a surface emitting laser diode including a DBR because a composition such as a composition gradient layer can be easily formed by controlling the supply amount of the source gas.
- mass productivity is excellent.
- a part of the low-refractive-index layer is formed of the AlAs layer 107 in the p-side DBR (upper reflector) 105 near the active layer 104C.
- the space around the mesa structure M formed by the mesa etching is filled with the polyimide film 108 and flattened, and thereafter, the p-contact layer 106 and a predetermined light emission on the upper reflector are emitted.
- the polyimide film 108 is removed from the portion 109A, and a p-side electrode 109 is formed on the p-contact layer 106 while avoiding the light emitting portion 109A.
- an n-side electrode 110 is formed on the back surface of the substrate 101.
- the current is confined by the selective oxidation of the selectively oxidized layer 107 mainly containing A1 and As, so that the threshold current is reduced.
- the current confinement layer 107A can be formed close to the active layer 104C, and the diffusion of the injection holes is suppressed.
- carriers can be efficiently confined in a minute region that does not come into contact with the atmosphere.
- the refractive index is reduced, and light is efficiently confined to a small region in which carriers are confined by the convex lens effect. And the efficiency of stimulated emission is greatly improved. Accordingly, the threshold current is reduced.
- the structure for reducing the current can be easily formed, so that the manufacturing cost of the surface emitting laser diode can be reduced.
- (AlGa) InP which is a wide band gap material, is used as the spacer layers (cladding layers) 104A and 104E. For this reason,
- the band gap difference between the spacer layers 104A and 104E and the quantum well active layer 104a is 743meV compared to 466meV (in the case of Al composition 0.6) when the spacer layer is formed of AlGaAs. Increase.
- a band gear between the barrier layer 104b and the quantum well active layer 104a is also superior in the surface emitting laser diode 160, and good carrier confinement is realized.
- the quantum well active layer 104a accumulates compressive strain, an increase in gain due to band separation between heavy holes and light holes can be obtained.
- the surface emitting laser diode 160 has an extremely high gain and can operate at a high output with a low threshold value.
- the quantum well active layer 104a and the barrier layer 104b also have a material strength not including A1, the incorporation of oxygen into these layers is reduced, and the formation of a non-radiative recombination center is reduced. It can be suppressed. As a result, it is possible to realize a long-life surface emitting laser diode.
- the control of the polarization direction is realized by using the optical gain anisotropy due to the inclination of the substrate.
- the inclination angle of the surface emitting laser diode according to the present embodiment is smaller (15 °), and therefore the optical gain anisotropy must be reduced. Therefore, in the surface emitting laser diode 160 according to the sixth embodiment, the decrease in the optical gain anisotropy is compensated for by increasing the optical gain anisotropy by applying compressive strain to the quantum well active layer. With such a configuration, satisfactory polarization control can be realized.
- the gain of the active layer 104a is large and the heat radiation is improved, whereby the threshold value of laser oscillation is low and the reliability is excellent.
- a high-output surface-emitting laser diode with a wavelength of 780 nm can be realized.
- the effect of the present invention described above is reduced in a shorter wavelength band, but is remarkable in a longer wavelength band than 680 nm.
- Al has the largest band gap in the typical composition range of an AlGaAs (0 x x ⁇ 1) -based spacer layer.
- the band gap difference with the active layer is about 200 meV, which is almost the same as that of the 780 nm surface emitting laser diode using the AlGaAs / AlGaAs active layer.
- the AlGalnP-based spacer layer is used, and if the composition wavelength is longer than 680 nm, the AlGaAs / AlG layer can be used even if the A1 free active layer (quantum well active layer and barrier layer) is used. This means that carrier confinement equal to or greater than that of a 780 nm surface-emitting laser diode using an aAs-based active layer is possible. Taking into account the effect of the strained quantum well active layer, the surface emitting laser diode according to the present embodiment has characteristics equal to or better than those of the 780 nm band surface emitting laser diode using the conventional AlGaAs / AlGaAs-based active layer. Power to gain S
- FIG. 8 is a top view of a surface emitting laser diode 180 according to the seventh embodiment.
- the surface emitting laser diode 180 according to the seventh embodiment has the same cross-sectional structure as the surface emitting laser diode 160 according to the sixth embodiment, but the mesa structure M viewed from the light emitting direction of the surface emitting laser diode is different from the (111) A plane. It is different in that it is formed with anisotropy so as to have a long elliptical shape long in the direction. Therefore, description of the cross-sectional structure of the surface emitting laser diode 180 will be omitted.
- the shape of the current injection region 107 defined by the A1 oxide film 107A also becomes longer in the (ll) A plane direction.
- the anisotropic shape is not limited to the oblong shape, but may be another shape such as a rectangle.
- the optical gain anisotropy due to the inclination of the substrate 101 is used for polarization control.
- the tilt angle is smaller (15 °) than when the (311) B substrate (tilt angle is 25 °), which is currently regarded as the most promising, is used for polarization control. It must be.
- Example 7 the decrease in optical gain anisotropy was increased by compressive strain in the quantum well active layer 104a.
- the outer peripheral shape of the active layer viewed from the light emitting direction force of the surface emitting laser diode 180 is given anisotropy. More specifically, (111) Compensation by increasing the optical gain in the substrate tilt direction ((111) A-plane direction) by making the shape longer in the A-plane direction. (311) The polarization control is not inferior to that using the B-substrate. realizable.
- FIG. 9 shows a configuration of a surface emitting laser diode 200 according to the eighth embodiment.
- FIG. 9 is an enlarged view of the area around the active layer of the surface emitting laser diode of Example 8 corresponding to FIG. 7 described above.
- the surface-emitting laser diode 200 of the eighth embodiment is different from the surface-emitting laser diode 160 of the sixth embodiment in that Ga In P having tensile strain is used as the barrier layer 104b.
- Example 8 the failure of Ga In P having tensile strain was observed.
- the wall layer 104b is provided below the first quantum well active layer 104a and also above the third quantum well active layer 104a.
- Other structures are the same as those of the surface emitting laser diode 160 in FIG.
- the band gap of GalnP is the largest when compared with the same lattice constant.
- a composition having a smaller lattice constant can secure a larger band gap, so that the band discontinuity with the quantum well active layer 104a can be further increased, and the gain is further increased.
- Low threshold operation and high output operation are possible.
- the band gap of the Ga InP tensile strain layer used in Example 8 is 2.02 eV
- the band gap is Ga In P of Example 6 with a band gap of 1.87 eV.
- FIG. 10 is a top view showing a configuration of a surface emitting laser diode ray 220 according to Embodiment 9 of the present invention.
- the surface emitting laser diode ray 220 the surface emitting laser of Example 8 was used.
- Laser diodes 200 are one-dimensionally arranged on a substrate 101 in ten elements.
- the p-side and the n-side of the surface emitting laser diode 220 are opposite to the surface emitting laser diode of the eighth embodiment. That is, in the ninth embodiment, the GaAs substrate 101 on which the surface emitting laser diode 220 is formed is a substrate, and the n-side individual electrode pad 109 is formed on the upper surface and the p-side common electrode 110 is formed on the back surface. .
- a force in which a plurality of surface emitting laser diodes 200 are arranged one-dimensionally may be arranged two-dimensionally.
- FIG. 11 shows an optical transmission module 240 according to Embodiment 10 of the present invention.
- the optical transmission module 240 has a configuration in which an inexpensive acrylic POF (plastic optical fiber) 240 is combined with the surface emitting laser diode laser chip 220 of FIG.
- the laser light 241A from the surface emitting laser diode 200 is injected into the corresponding POF 241 and transmitted.
- the acrylic POF has a minimum absorption loss at a wavelength of 650 nm, and therefore, a 650 nm surface-emitting laser diode has been conventionally studied.
- conventional surface-emitting laser diodes in the 650 nm band have not been put into practical use due to poor high-temperature characteristics. Under such circumstances, it is difficult to perform high-speed modulation with a power LED that uses an LED in an optical transmitter module using such a P ⁇ F.
- Semiconductor lasers are considered indispensable for high-speed transmission exceeding lGbps.
- the laser oscillation wavelength is 780 nm.
- the heat radiation characteristics are excellent and the active layer gain is large, high output operation is possible.
- because of its excellent high-temperature characteristics even if there is a problem of absorption loss due to POF, it is possible to transmit light sufficiently over short distances.
- each surface emitting laser diode element 200 of the surface emitting laser diode ray and the optical fiber 241 correspond to each other on a one-to-one basis. It is also possible to further increase the transmission speed by arranging the surface emitting laser diode elements in a one-dimensional or two-dimensional array and performing wavelength-division multiplexing transmission via a single optical fiber.
- the inexpensive surface-emitting laser diode element 200 and the inexpensive POF241 are combined, so that a low-cost optical transmission module can be realized, and a low-cost optical communication system can be realized using this module. it can.
- Powerful optical communication systems are extremely low-cost and are effective for short-distance data communication such as home use, indoor use in offices, and use in equipment.
- FIG. 12 shows a configuration of an optical transceiver module 260 according to Embodiment 11 of the present invention.
- an optical transceiver module 260 has a configuration in which the surface emitting laser diode element 200 of the eighth embodiment, a receiving photodiode 261, and an acrylic POF 262 are combined.
- the surface emitting laser diode element 200 and the POF 262 according to the present invention are both inexpensive, and the light transmitting / receiving system 260 using the surface emitting laser diode element 200 according to the present invention in an optical communication system, as shown in FIG.
- a surface emitting laser diode element 200 for transmission and a photodiode 261 for reception with a single POF 262 to form an optical transmission / reception module, a low-cost optical communication system can be realized.
- the cost of the optical transceiver module 260 can be further reduced.
- the surface emitting laser diode element 200 of the present invention has excellent temperature characteristics and a low laser oscillation threshold value, so that a low-cost optical communication system that can be used to a high temperature with little heat generation and without cooling can be realized.
- the optical communication system 260 performs optical transmission between devices such as a computer such as a LAN (Local Area Network) using a P ⁇ F, optical transmission between boards in the device, and It is particularly effective for short-distance communication, such as optical transmission between LSIs and optical interconnection between elements in the LSI.
- devices such as a computer such as a LAN (Local Area Network) using a P ⁇ F
- P ⁇ F Local Area Network
- P ⁇ F Local Area Network
- optical transmission between boards in the device and It is particularly effective for short-distance communication, such as optical transmission between LSIs and optical interconnection between elements in the LSI.
- an ultra-high-speed network system can be constructed.
- surface-emitting laser diode elements are extremely suitable for constructing a parallel transmission type optical communication system because power consumption can be reduced by orders of magnitude compared to edge-emitting laser diodes and two-dimensional arrays can be easily formed. .
- FIG. 13 shows a configuration of a laser printer 280 according to the twelfth embodiment.
- the laser printer 280 shown in FIG. 13 has a surface emitting laser diode array chip in which the surface emitting laser diode 200 having an oscillation wavelength of 780 nm is arranged in a 4 ⁇ 4 two-dimensional array on the GaAs substrate 101 (16 beam emitting chip).
- VCSEL array) 281 is combined with a photosensitive drum 282.
- FIG. 13 shows an outline of the optical scanning portion of the laser printer 280 in particular.
- FIG. 14 is a top view showing a schematic configuration of the surface emitting laser diode ray chip (16-beam VCSEL array) 281 used in the laser printer 280 of FIG.
- a surface emitting laser diode ray chip (16-beam VCSEL array) 281 adjusts the lighting timing so that the light source on the photoconductor 282 moves in the sub scanning direction V-SCAN as shown in FIG. It is possible to realize a situation equivalent to a system 1J at 10 ⁇ m intervals.
- a plurality of light beams of a plurality of surface emitting laser diode rays 200 are focused on a running polygon mirror 284 by using an optical system including a lens 283 as described above.
- the polygon mirror 284 is rotated at a high speed, and the timing of lighting is adjusted to form a plurality of light spots arranged in the sub-scanning V-SCAN direction, and these are spotted through a so-called f_ lens 285.
- the light is condensed on the photosensitive member 282, which is the scanning surface, to form an image. That is, according to the present embodiment, image formation is performed by scanning a plurality of beams at a time.
- optical writing can be performed on the photosensitive member 282 at an interval of about 10 / im on the V-SCAN in the sub-scanning direction, which is 2400 DPI (dots / inch). resolution It corresponds to.
- the writing interval in the main scanning direction HSCAN can be easily controlled by turning on the light source.
- the laser printer 280 of the present embodiment 16 dots can be simultaneously written, and high-speed printing is possible. Further, by increasing the number of surface emitting laser diodes 200 in the array, higher speed printing becomes possible. In addition, by adjusting the interval between the surface emitting laser diode elements 200, the dot interval in the sub-scanning H_SCAN direction can be adjusted, and high-density printing, for example, higher quality printing than 2400 DPI becomes possible.
- the surface emitting laser diode according to the twelfth embodiment has a constant efficiency compared with the conventional surface emitting laser diode, has excellent heat radiation characteristics, can maintain a high output even when a plurality of elements operate simultaneously, and has a high printing speed. Can be made faster than before.
- the surface emitting laser diode of the present invention can be applied to other image forming apparatuses. Further, it can be used as a light source for recording and reproduction of a CD or the like. That is, the present invention is applicable to an optical pickup system. Further, the present invention is also applicable to photoelectric fusion integrated circuits and the like.
- the surface-emitting laser diode of any of the embodiments described above or below can be used instead of the surface-emitting laser diode 200. .
- a twelfth embodiment of the present invention will be described with reference to FIGS.
- the twelfth embodiment of the present invention relates to a basic configuration example and an operation example of the surface emitting laser diode of the present invention.
- the surface emitting laser diode includes a GaAs substrate, at least one quantum well active layer formed on the GaAs substrate, and generating a laser beam, and a barrier.
- the lower reflector is a semiconductor distributed Bragg reflector At least a portion of the semiconductor distributed Bragg reflector comprises a semiconductor layer containing Al, Ga, As as a main component, between the active layer and the semiconductor layer containing Al, Ga, As as a main component.
- In, and P are surface emitting laser diodes formed so as to have an interface with the semiconductor layer containing P, In, and P as main components at positions of nodes of the electric field intensity distribution.
- the semiconductor layer containing Al, In, and P as a main component is, for example, (AlGa) InP (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1) Consists of a 1 ab 1 -b
- the conventional surface emitting laser diode is configured such that the interface between the resonator region and the reflector is located at the antinode of the electric field intensity distribution, and Al, In, A semiconductor layer containing P as a main component is provided. Therefore, the interface with the upper reflector made of a semiconductor layer containing Al, Ga, and As as a main component is formed at the antinode where the effect of light absorption greatly appears.
- a semiconductor layer containing Al, Ga, As as the main component is grown on a semiconductor layer containing Al, In, P as the main component, separation of In such as carry-over of In occurs immediately.
- the force S that needs to be suppressed, conventionally it was difficult to avoid a threshold rise. This problem is remarkable when a semiconductor layer containing Al, Ga, As as a main component is crystal-grown on a semiconductor layer containing Al, In, P as a main component.
- the semiconductor layer 1 containing Al, In, and P as main components and Al, Ga, As are mainly used.
- the semiconductor layer (part of upper mirror) 2 as a component at node AN in the electric field intensity distribution. Therefore, even if the above-described separation of In occurs to some extent, an increase in the laser oscillation threshold value can be significantly suppressed.
- the antinode of the electric field intensity distribution is represented by N.
- a thin In separation suppression is provided between the semiconductor layer 1 mainly containing Al, In, and P and the semiconductor layer 2 (part of the upper reflector) mainly containing Al, Ga, As. It is even better to provide a layer to reduce In separation.
- the semiconductor layer 1 containing Al, In, and P as main components for example, (Al Ga) In P
- a 1 ab 1 -b (0 ⁇ a ⁇ l, 0 ⁇ b ⁇ l) layers. Due to the powerful structure, it is necessary to use not only the surface emitting laser diode using the AlGalnP layer, such as the 780 nm band and the 850 nm band, but also the red emitting laser diode using the AlGalnP layer regardless of the wavelength, such as the 650 nm band and the 850 nm band. Thus, the effect of reducing the threshold value can be obtained.
- a surface emitting laser diode includes a GaAs substrate, at least one quantum well active layer and a barrier layer formed on the GaAs substrate and generating laser light.
- the mirror includes a semiconductor distributed Bragg reflector, and at least a part of the semiconductor distributed Bragg reflector comprises a semiconductor layer containing Al, Ga, As as a main component, and mainly includes the active layer and the Al, Ga, As.
- Zn (zinc) is generally used as a p-type dopant for a semiconductor layer containing Al, In, and P as a main component.
- Force Zn is an active layer with a large diffusion coefficient or close to an active layer. They are diffused and have a problem of deteriorating device characteristics due to a decrease in luminous efficiency due to deterioration of crystallinity and an increase in absorption loss.
- Mg which can be used as a p-type dopant, has a smaller diffusion coefficient than Zn.
- the ability to improve the above-mentioned problem is higher than that of Zn. Small, When Mg is added to a material containing As, the controllability of doping is deteriorated due to the memory effect.
- Mg is mainly added to the semiconductor layer containing Al, In, and P as main components
- C is mainly added to the semiconductor layer containing Al, Ga, and As as main components. I did it.
- dopant diffusion and memory effects can be reduced, doping controllability is improved, and a doping profile close to the design can be obtained.
- deterioration of the crystallinity of the active layer is suppressed, and a high output operation can be realized with a low level, a low threshold, and a high value.
- a surface emitting laser diode includes a GaAs substrate, at least one quantum well active layer and a barrier layer formed on the GaAs substrate and generating laser light. And an upper reflector and a lower reflector provided on the GaAs substrate and above and below the resonator region, wherein the upper reflector and / or the lower reflector are provided.
- the mirror includes a semiconductor distributed Bragg reflector, and at least a part of the semiconductor distributed Bragg reflector comprises a semiconductor layer containing Al, Ga, As as a main component, and the active layer and Al, Ga, As as main components.
- the semiconductor layer containing Al, Ga, and As as a main component and the semiconductor layer containing Al, In, and P as a main component (Al Ga) In P (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1) layer, and the (AlGa) InP (0 ⁇ a ⁇ l, 0 ⁇ b ⁇ l) layer is composed of AllnP and GalnP Characterized in that it is a surface emitting laser diode which is a semiconductor layer made of a more becomes short period superlattice structure.
- the thermal resistance of the ternary materials ⁇ and GalnP is smaller than that of the quaternary material AlGalnP. Adjustment Therefore, in this configuration example, in the surface emitting laser diode, at least two materials having a lower thermal resistance than the average composition are selected in place of the semiconductor layer, which was conventionally a uniform composition AlGal nP, and the super lattice structure is selected. Is formed, the thermal resistance is reduced.
- the heat generated in the active layer can be efficiently dissipated, the temperature rise of the active layer due to current injection can be reduced, the current can be injected to a higher level than before, the output increases, and as a result A surface-emitting laser diode capable of output operation can be obtained.
- a surface emitting laser diode includes a GaAs substrate, at least one quantum well active layer and a barrier layer formed on the GaAs substrate and generating laser light.
- An upper reflector and / or a lower reflector provided above and below the resonator region on the GaAs substrate, wherein the upper reflector and / or the lower reflector are provided.
- the reflector includes a semiconductor distributed Bragg reflector, and at least a portion of the semiconductor distributed Bragg reflector is a low-profile AlGaAs (0 ⁇ x ⁇ 1).
- An upper refractive mirror comprising a refractive index layer and a high refractive index layer of Al Ga As (0 ⁇ y ⁇ x ⁇ l).
- At least the low refractive index layer closest to the active layer has a lower refractive index than (Al Ga) In P (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1).
- the surface emitting laser diode is characterized in that the interface between the resonator region and the low refractive index layer closest to the active layer of the upper reflector and / or the lower reflector is located at the antinode of the electric field intensity distribution.
- FIG. 16 shows a configuration of a surface emitting laser diode according to the fourth configuration example.
- the interface 306 between the resonator region 304 including the active layer 307 and the upper reflecting mirror 305 is formed according to the conventional general configuration.
- the force that is configured to match the antinode AN of the electric field intensity distribution In particular, in the configuration of FIG. ) In P (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1), the (AlGa) Ia1ab1ba1abnP (0 ⁇ a ⁇ l, 0 ⁇ b ⁇ l) layer A semiconductor layer containing Al, Ga, As as a main component
- the interface 309 in the case of crystal growth of the partial reflecting mirror 305) matches the node N of the electric field intensity distribution.
- reference numeral 310 denotes a lower reflector (part). In FIG. 16, only a part of the upper reflecting mirror 305 is shown.
- the lower reflecting mirror 310 is, in order from the substrate side, a first lower reflecting mirror in which the low refractive index layer is made of AlAs, and the low refractive index layer is Al Ga As (0 xl ⁇ l)
- the thermal resistance of AlAs increases sharply with a small amount of Ga.
- the low refractive index layer contains AlAs having low thermal resistance, the heat radiation of the heat generated in the active layer 307 is improved, and the temperature rise during driving is suppressed. In addition, a high-output surface emitting laser diode having excellent temperature characteristics can be obtained.
- an AlGaAs low refractive index having a small A1 composition is placed between the first lower reflector using an AlAs low refractive index layer and the layer containing In.
- the etching for forming the mesa stops between the selectively oxidized layer that becomes the A1 oxide film and the AlAs of the first lower reflector, and the etching is easily controlled. be able to.
- a high-refractive-index layer made of Al Gya As (0 ⁇ y ⁇ x ⁇ l) and (Al Ga) In P (0 A ⁇ 1, 0 ⁇ b ⁇ 1)
- An Al Ga As (0 ⁇ y x x ⁇ l) high refractive index layer can be easily formed on the layer in a wide range of conditions.
- the semiconductor distributed Bragg reflector constituting the p-type reflector has an Al Ga As (0 x x ⁇ l) low refractive index layer and
- C (carbon) is added as a p-type dopant to the Al Ga As (0 ⁇ y ⁇ x ⁇ l) high refractive index layer, and y i-y
- the low refractive index layer 308 made of (AlGa) InP (0 ⁇ a ⁇ l, 0 ⁇ b ⁇ 1) has p a 1 -a b 1 -b
- Mg manganesium
- the (AlGa) InP (0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1) low refractive index layer 308 is composed of AllnP and G a 1 -a b 1 -b
- a semiconductor layer having a short-period superlattice structure made of alnP may be used.
- the surface emitting laser diode according to a fifth configuration example of the twelfth embodiment of the present invention is the same as the surface emission laser diode according to the fourth configuration example, except that the active layer, the upper reflector, and / or the lower layer are formed.
- a spacer layer is provided between the reflector and a part of the spacer layer, and a part of the spacer layer has a band gap smaller than that of the AlGalnP low refractive index layer (Al Ga,) In P (0 ⁇ a ' ⁇ l, 0 ⁇ b' ⁇ l) layers, and the quantum well active layer has a compressive strain of Ga.
- the barrier layer is Ga In P As c 1-c d 1-d e 1- e f 1-
- At least the low refractive index layer closest to the active layer 307 is an AlGalnP layer, and the barrier layer and the quantum well active layer are Uses GalnPAs-based materials.
- the spacer layer can be used as a cladding layer for confining carriers, and the cladding layer and the quantum well active layer can be used compared to the case where the cladding layer for confining carriers is formed of AlGaAs. Can be further increased.
- the spacer layer is a layer between the active layer and the reflector in the case of a normal configuration, and refers to a layer having a function as a cladding layer for confining carriers. .
- a low refractive index layer of the DBR closest to the active layer may have a function in addition to the spacer layer.
- the low refractive index layer can have a function as a cladding layer.
- the band gap is formed in the spacer layer.
- the spacer layer and the quantum layer can be reduced more than AlGaAs / AlGaAs-based 850 nm surface-emitting laser diodes as well as AlGaAs / ZAlGaAs-based 850 nm surface-emitting laser diodes. It can be seen that a large band gap difference can be secured between the well layer and the barrier layer and the quantum well layer.
- the active layer 307 by forming the active layer 307 from a quantum well layer having a compressive strain composition, the band separation between the heavy hole and the light hole is increased as described in the previous embodiment. As a result, the gain is increased, the threshold value is reduced, the laser oscillation efficiency is improved, and the laser output is increased. It should be noted that this effect cannot be obtained with the AlGaAs / AlGaAs 850 nm surface emitting laser diode.
- a high-efficiency, high-output surface-emitting laser having a threshold lower than that of an AlGaAs / AlGaAs-based 850-nm surface-emitting laser diode It can be seen that a diode is obtained.
- the carrier confinement efficiency is improved, and the threshold value is also reduced due to the increase in gain due to the use of the strained quantum well active layer, whereby the reflectance of the DBR305 on the light extraction side can be reduced. It becomes. Thereby, the output of the surface emitting laser can be further increased.
- the quantum well layer in the quantum well active layer 307 is defined as Ga in P As (0 ⁇ c ⁇ l, 0
- the barrier layer in the quantum well active layer 307 is Ga In P As (0
- the active layer 307 can be composed of a material not containing A1.
- the incorporation of oxygen into the active layer 307 is reduced, the formation of non-radiative recombination centers is suppressed, and a long-life surface-emitting laser diode is manufactured. realizable.
- the active layer is formed by using the AlGalnP material for a part of the spacer layer and using GalnP As for the barrier layer and the quantum well active layer. The layer gain is large, the threshold is reduced, and a high-power surface-emitting laser diode operating at a wavelength shorter than 850 nm, which is excellent in reliability, can be realized.
- the same lattice as that of the GalnPAs-based material used as the barrier layer in the quantum well active layer of the surface emitting laser diode is used.
- the band gap of GalnP is the largest.
- a material having a smaller lattice constant can secure a larger band gap.
- a large band discontinuity can be realized between the barrier layer and the quantum well active layer, and the gain of the surface emitting laser diode can be increased. it can. This allows the surface emitting laser diode to operate at a high output with a low threshold.
- the band gap of the Ga In P tensile strained layer is 202 eV
- the band gap of the In P lattice matching layer is 1.87 eV, and the Ga In P
- the band gap is 150meV larger.
- the fifth configuration example has been described based on the fourth configuration example in which the AlGalnP layer is used as the low refractive index layer closest to the active layer, the first to third configuration examples are described.
- a part of the spacer layer provided between the active layer and the reflecting mirror is composed of an AlGalnP layer, and the quantum well active layer is formed of Ga In P As (0 ⁇ c ⁇ 1
- the barrier layer is formed of Ga in P As (0 ⁇ e ⁇ 1
- a spacer layer is provided between the active layer and the upper reflecting mirror and / or the lower reflecting mirror in the surface emitting laser diode.
- the quantum well active layer is formed of Ga in P As (0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1) having accumulated compressive strain
- the barrier layer is formed of Ga In P As c 1 -cd 1 -de 1 -ef 1 (0 ⁇ e ⁇ l, 0 ⁇ f ⁇ l).
- a spacer layer having a composition of (Al Ga) In P (0 ⁇ a, ⁇ l, 0 ⁇ b, ⁇ l) is used.
- the improvement of the carrier confinement efficiency and the reduction of the threshold realized by the gain increase by using the strained quantum well active layer enable the reflection coefficient of the DBR 305 on the light extraction side to be reduced.
- the light output can be increased.
- Ga in P As (0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1) was used as the quantum well active layer, and Ga In was used as the barrier layer.
- the active layer 307 is made of a material that does not contain Al.
- the surface emitting laser diode according to the sixth configuration example of the twelfth aspect of the present invention is the surface emitting laser diode of the fifth configuration example, wherein the oscillation wavelength is longer than about 680 nm. It is characterized by.
- the band gap difference between the active layer and the active layer is determined by using (Al Ga) In P (0 ⁇ a ⁇ l, 0 ⁇ b ⁇ ) used in the surface emitting laser diode in this embodiment.
- the band gap is the largest in the typical composition range of the spacer layer, (Al Ga) In
- the band gap difference with the active layer is about 200 meV, which is almost the same as that of a 780 nm surface emitting laser diode using an AlGaAsZAlGaAs-based active layer.
- a surface emitting laser diode according to a seventh configuration example of the twelfth aspect of the present invention is the same as the surface emitting laser diode according to any one of the first to sixth configuration examples, except that the plane orientation of the substrate to be grown is the same. It is characterized in that it is configured as a (100) plane inclined at 5 ° in the direction of the (111) A plane within a range of 20 °.
- the substrate plane orientation affects the crystal growth.
- the substrate plane orientation is (111) A
- the substrate plane orientation is (100) GaAs substrate inclined at an angle (inclination angle) in the range of 5 ° to 20 ° in the plane direction as the substrate 41. This is because when the plane orientation of the substrate is close to (100), the band gap decreases due to the formation of a natural superlattice, the surface shape deteriorates due to the generation of hillocks (hill-shaped defects), and non-radiative recombination centers occur. This is because there is a possibility that device characteristics such as a semiconductor laser formed on the substrate may be adversely affected.
- the band gap has a tilt angle of 10 ° 15. , And then gradually approach the normal band gap (band gap value of the mixed crystal), and hillocks gradually disappear.
- the growth of these materials requires the plane orientation to be in the range of 5 ° to 20 ° in the (111) A plane direction. It is preferable to use a (100) GaAs substrate inclined at an angle (more preferably, an angle in the range of 7 ° to 15 °).
- Japanese Patent Application Laid-Open No. 2001-60739 discloses that the plane orientation of the substrate is from 15 to 40 from (100) in the direction of the (ll) A plane or (lll) B plane.
- Polarization control technology that increases the optical gain in the tilt direction by using a tilted substrate, utilizing optical gain anisotropy, and employing a multiple quantum well active layer composed of InAlGaAs and InGaAsP with compressive strain. Is described.
- 2001-168461 discloses a configuration in which the mesa shape is circular, elliptical, or oblong, and the direction of the long axis is set from (100) to the (lll) A plane direction or (lll) B plane direction.
- the substrate plane orientation is 2 ° off (including 15 ° to + 5 °) from the (100) direction to the [110] direction, and is not a substrate inclined in the A-plane or B-plane direction.
- the optical gain anisotropy generated by inclining the substrate plane in the (111) A plane direction is used for polarization control. I do.
- this configuration example it is currently considered to be the most promising (311)
- the use of a B substrate and the use of polarization control technology are not possible.
- the substrate tilt angle is smaller than the (311) B substrate (25 °) (within a range of 5 ° and 20 °) (within a range of 5 ° and 20 °), the cost of the substrate can be reduced and cleavage can be easily performed. Despite the advantages, the obtained optical gain anisotropy must be reduced.
- this reduction is compensated for by increasing the optical gain anisotropy by applying compressive strain to the quantum well active layer.
- the outer peripheral shape of the active layer viewed from the light emitting direction is given a shape anisotropy such that the (lll) A plane direction becomes longer.
- the outer shape of the active layer viewed from the light emission direction of the surface emitting laser diode The optical gain in the tilt direction ((111) A-plane direction) is further increased by providing anisotropy and having a long shape in the (111) A-plane direction, and improving the deflection controllability. Can be. (Thirteenth embodiment)
- FIG. 17 is a principle sectional view showing a structural example of the surface emitting laser diode 400.
- FIG. 18 is a cross-sectional view showing, in an enlarged scale, the structure around the active layer of the surface-emitting laser diode 400, and
- FIG. 19 is a plan view showing a part of the surface-emitting laser diode 400.
- a surface emitting laser diode 400 uses an n_ (100) GaAs substrate 411 inclined at 15 ° in the (111) A-plane direction with a plane azimuth force. Sets the n-AlGaAs layer and the n-AlGaAs layer to have an oscillation wavelength of 1 in the medium.
- Periodic structure 412 alternately stacked with, for example, 35 periods with a thickness of / 4 times, and n- (AlGa) InP low refractive index layer (cladding layer) formed on top of it with a quarter wavelength thickness 413,
- n-AlGaAs constituting one unit of the repetition period in the periodic structure 412
- the Al composition gradually changes from one value to the other between the n-AlGaAs layer and the 1-layer
- a composition gradient layer (not shown) having a thickness of 20 nm is inserted, and the thickness of one unit of the repetition period is 1/4 times the oscillation wavelength in the medium including the composition gradient layer. Is set.
- the periodic structure 412 is lattice-matched to the substrate 411 (A1
- a p-semiconductor distributed Bragg reflector (upper reflector) 422 composed of a periodic structure 421 laminated with 24.5 periods is formed (details are omitted in FIG. 1).
- a composition gradient layer similar to that of the lower reflecting mirror 414 is inserted between the high refractive index layer and the low refractive index layer.
- a ⁇ -GaAs contact layer 423 for forming an ohmic contact with an electrode is formed on the uppermost part of the upper reflector 422.
- a resonator region 424 having a thickness of one oscillation wavelength is formed between the lower reflecting mirror 414 and the upper reflecting mirror 422.
- the resonator area 424, the lower reflector 414, and the upper reflector 422 form a resonator structure of the surface emitting laser 400.
- an AlGalnP cladding layer (spacer layer) is provided at the top of the resonator region.
- the interface between the resonator region and the upper reflector made of an AlGaAs-based material is formed at the antinode where the effect of light absorption is large.
- the interface 426 is made to coincide with the node of the electric field intensity distribution, the influence of light absorption at the interface 426 is greatly reduced, and the separation of In at this portion is reduced. Even if it occurs to some extent, it is possible to effectively suppress an increase in the threshold value.
- the p_ (AlGa) InP low refractive index layer 420 and the p_AlGaAs (x 0.
- the Al composition is smaller than or not contained in the low refractive index layer. Reducing the In separation by providing a thin (Al) GalnP further effectively suppresses the increase in threshold voltage.
- the low refractive index layer closest to the active layer 18 of the lower reflector 414 is also an (AlGa) InP layer.
- AlGaAs-based materials can be used if only the problem of In separation can be improved.
- the semiconductor multilayer structure forming the surface emitting laser diode 400 is formed by MOCVD.
- TMG trimethylgallium
- TMA trimethylaluminum
- TMI trimethylindium
- PH phosphine
- AsH AsH
- H Se hydrogen selenide
- the MOCVD method is suitable as a crystal growth method for a surface emitting laser diode including a DBR, which can easily form a composition such as a composition gradient layer by controlling the supply amount of a source gas.
- mass productivity is excellent.
- a part of the low refractive index layer near the active layer 418 in the p-side DBR is an AlAs layer.
- the mesa structure 426 having a predetermined size is formed such that at least the side wall surface of the p-AlAs selectively oxidized layer 427 is exposed by further mesa etching the laminated structure thus formed. Then, the exposed AlAs layer is oxidized from the side wall surface in water vapor to form an A1O current confinement layer 428.
- the periphery of the mesa structure 426 is buried with a polyimide film 432 and flattened, and the polyimide film 432 is removed from a portion of the contact layer 423 corresponding to the light exit window 429. Further, a p-side electrode 430 is formed on the p-type contact layer 423 while avoiding the light emitting portion 29, and an n-side electrode 431 is formed on the back surface of the substrate 411.
- the current is confined by selective oxidation of the selectively oxidized layer 427 mainly composed of A1 and As, so that the threshold current is greatly reduced.
- the current confinement layer 428 can be formed close to the active layer 418. In other words, diffusion of the injected current can be suppressed, and the carrier can be efficiently confined to a small region that does not come into contact with the atmosphere.
- the oxidized portion 428 changes to an A1 oxide film, whereby the refractive index is reduced. Due to the effect of the convex lens, light is efficiently confined in the small region in which the carriers are confined. It is possible to achieve extremely high efficiency. This also reduces the threshold current. Further, such a current confinement structure can be easily formed, and the manufacturing cost of the laser diode can be greatly reduced.
- the mesa shape as viewed from the light emitting direction of the surface emitting laser diode is anisotropic so as to have a long elliptical shape long in the (ll) A plane direction as shown in FIG. To form.
- the anisotropic shape is not limited to the elliptical shape, but may be another shape such as a rectangle.
- the current injection region defined by the A1 oxide film 428 also has a shape elongated in the (111) A plane direction.
- an AlGalnP-based material is used for the low refractive index layer 425 and the spacer layer 419 of the reflector 422 closest to the active layer 418.
- GalnPAs is used for the 417 and the quantum well active layer 416.
- the band gap decreases due to the formation of a natural superlattice, and the hillock (hill) It is possible to reduce the deterioration of the surface shape due to the occurrence of shape defects) or the influence of the non-radiative recombination center due to such deterioration of the surface shape.
- the wide gap material (AlGa) In is used as the clad layer (low refractive index layer in the reflector 422 closest to the active layer 418) 420 for confining carriers.
- a band gap difference of 743 meV which is much larger than a band gap difference of 466 meV when the cladding layer 420 is formed of AlGaAs (in the case of an Al composition of 0.6) is obtained.
- a larger band gap difference is ensured between the barrier layer 417 and the active layer 418 according to the above configuration, so that very good carrier confinement is realized.
- the active layer 418 since the active layer 418 has a compressive strain, an increase in gain due to band separation of heavy holes and light holes can be obtained.
- the AlGalnP low refractive index layer 420 and the AlGalnP spacer layer 419 may contain trace amounts of other constituent elements.
- the active layer 418 and the barrier layer 417 also have a material strength not including A1 and have an A1 free active region (a quantum well active layer and a layer adjacent thereto).
- the uptake of oxygen is reduced, the formation of a non-radiative recombination center can be suppressed, and a long-life laser diode can be realized.
- the polarization is controlled using the optical gain anisotropy caused by the inclination of the substrate 411.
- the substrate tilt angle is smaller (15 °) than in the case where a (311) B substrate (25 °), which is currently regarded as the most promising, is used. Therefore, the optical gain anisotropy must be reduced.
- the outer peripheral shape of the quantum well active layer 416 is elongated in the (lll) A plane direction and is anisotropic when viewed from the light emitting direction.
- a polarization control that is not inferior to that using a B substrate is realized by increasing the optical gain in the substrate tilt direction (the (111) A plane direction). ing.
- the gain of the active layer 418 is large, the threshold is small, the reliability is excellent, and the polarization direction can be controlled in the 780 nm band.
- a high output surface emitting laser diode can be realized.
- the surface emitting laser diode 400 of the present embodiment is used for growing a semiconductor layer 425 containing Al, Ga, As as a main component on a semiconductor layer 420 containing Al, In, P as a main component. Even if separation occurs, It is designed to have a structure that does not easily raise the threshold value, and can easily manufacture laser diodes.
- the surface emitting laser diode of the present embodiment is compared with the case of a 780 nm surface emitting laser diode having an AlGaAs / AlGaAs-based active layer, the AlGa-As (0 K) used in the AlGaAsZAlGaAs-based surface emitting laser diode is compared.
- the band gap difference with the active layer is about 200 meV, which is almost the same as that of the 780 nm surface emitting laser diode using the AlGaAs / AlGaAs active layer.
- a red surface emitting laser diode having a wavelength shorter than 680 nm, such as a 650 nm band can be manufactured. In this case, the effect when the active layer is A1-free is not obtained, but it becomes possible to improve the problem of In separation described above.
- the fourteenth embodiment relates to a configuration example that further embodies the third configuration example described above.
- FIG. 20 is a cross-sectional view showing an enlarged structure around the active layer of the surface emitting laser diode 500 of the present embodiment.
- the present embodiment is basically the same as the configuration of the thirteenth embodiment in FIG. 18, except that the barrier layer 417 is replaced by a force S, More than In P
- a barrier layer 417a is used.
- the band gap of GalnP is the largest when compared with the same lattice constant.
- a material having a smaller lattice constant can ensure a larger band gap. That is, by using a GalnP-based material having a small lattice constant as the barrier layer 417a, a large band discontinuity can be realized between the barrier layer and the quantum well active layer, and the gain of the surface emitting laser diode 500 can be reduced. Can be increased. As a result, the surface emitting laser diode can operate at high output with a low threshold value. For example, Ga In P tensile strained layer 417a band
- the gap is 2.02 eV, and the band gap of Ga In P lattice matching layer 417 is 1.87 eV.
- the band gap of the Ga In P tensile strained layer 417a is larger by 150meV.
- the effect of increasing the band discontinuity by using the tensile strain composition layer as the barrier layer is due to the lattice matching composition and the tensile strain composition that are not only available when the quantum well active layer has the compressive strain composition. Note that you can still get
- the surface emitting laser diode according to the fifteenth embodiment of the present invention has the same configuration as the surface emitting laser diode 400 according to the thirteenth embodiment described above with reference to FIG. , P-Al
- Mg is used as the dopant for the P low refractive index layer.
- Mg is considered to be able to improve the above-mentioned problem in that the diffusion coefficient is smaller than that of Zn.
- the diffusion coefficient of C is smaller than that of Mg. It is also known that adding Mg to an As-based material deteriorates controllability due to the memory effect.
- Mg is added to the AlGalnP layer, and C is added to the AlGaAs multilayer film.
- the effect of using the dopant of the AlGalnP film as Mg and the dopant of the AlGaAs film as C is not limited to the case where the AlGalnP film is used as the low refractive index layer of the reflector as shown in FIG. This is obtained even when the AlGalnP film is provided in the resonator region sandwiched between the upper and lower reflectors.
- the surface emitting laser diode in the visible region such as the 650 nm band
- the surface emitting laser diode in which the cavity region is formed of AlGalnP-based material and the reflecting mirror is formed of A1 GaAs-based material as in the present embodiment A similar effect can be obtained.
- ⁇ _ ⁇ 1 constituting the uppermost low refractive index layer of the n-type lower reflecting mirror
- n— (AlGa) InP cladding layer 512 is formed on the GaAs layer 511,
- the active layer is formed by alternately stacking the GalnPAs quantum well active layers 514 and the GaO.5InO.5P barrier layers 515 that have accumulated therein only the active layer, and the (AlGa) InP A p- (AlGa) InP cladding layer 517 was formed via a spacer layer 516, and
- the P-A1 which constitutes the lowermost low refractive index layer of the p-type upper reflecting mirror 518
- a Ga As layer 518 is formed.
- n-AlGaAs layer 511 and the p-AlGaAs layer 518 form a laser beam in a medium.
- the semiconductor layers 512 to 517 form a resonator 519 for one wavelength between the upper and lower reflecting mirrors 511 and 518. . (Sixteenth embodiment)
- the surface emitting laser according to the sixteenth embodiment of the present invention has a force similar to that of the surface emitting laser diode 400 of FIG.
- the thermal resistance of the semiconductor layer increases as the number of elements included in the semiconductor material increases.
- AlGalnP which is a quaternary material, has a large thermal resistance.
- the heat generated in such an active layer is not easily dissipated, but is accumulated in the active layer, causing an increase in the temperature of the active layer.
- the thermal resistance of ternary materials ⁇ and GalnP is smaller than that of quaternary material AlGalnP. Because of the matching, in this configuration example, in the surface emitting laser diode, at least two materials whose thermal resistance is smaller than the average composition are selected instead of the semiconductor layer, which was conventionally a uniform composition AlGal nP, and the superlattice is used. Forming the structure reduces thermal resistance. As a result, the heat generated in the active layer can be efficiently dissipated, and the temperature rise of the active layer due to current injection can be reduced. The current can be reduced, the current can be injected to a higher level than before, the output increases, and as a result, a surface emitting laser diode that can operate at a high output can be obtained.
- the effect of reducing the thermal resistance when AlGalnP is formed in a short-period superlattice structure using AllnP and GalnP is not limited to the case where AlGalnP is used as the low refractive index layer of the reflecting mirror, as shown in FIG. It should be noted that this is obtained even when this is provided in the resonator region 519 sandwiched between the upper and lower reflecting mirrors 511 and 518 as shown in FIG. Similar effects can be obtained in a surface emitting laser diode in which the cavity region is formed of an AlGalnP-based material, such as a surface emitting laser diode in the visible region such as the 650 nm band.
- the heat radiation from the active layer is mainly on the substrate side
- the above configuration is preferably applied to at least the AlGaln P layer on the substrate side.
- a surface emitting laser diode 600 according to a seventeenth embodiment of the present invention will be described with reference to FIG. However, in FIG. 22, the same reference numerals are given to the parts described above, and description thereof will be omitted.
- the surface emitting laser diode 600 according to the present embodiment is different from the surface emitting laser diode 500 according to the fourteenth embodiment in the following two points.
- the lower reflecting mirror 414 is composed of a first lower reflecting mirror 412A in which the n-AlAs low refractive index layer and the n-A1 Ga As high refractive index layer are stacked 31 times in order from the substrate side 411. And n—Al
- a second lower anti-reflection layer consisting of 9 layers of Ga As low refractive index layer and n-Al Ga As high refractive index layer
- the lower reflector 414 includes AlAs having a low thermal resistance as a low refractive index layer, the heat dissipation of the heat generated in the active layer 416 is improved, and the temperature rise during driving is suppressed. As a result, a surface emitting laser diode having good temperature characteristics and high output can be obtained.
- the AlAs layer exposed on the mesa side wall is oxidized in the subsequent step of oxidizing the AlAs selectively oxidized layer. Oxidation also proceeds simultaneously from the end face of the laser diode, and the active layer 416 is insulated, or the electrical resistance of the laser diode increases. This is the oxidation rate of AlGaAs In this case, the dependence on Al composition is extremely large, and the oxidation rate increases as the A1 composition increases. The oxidation rate is maximized with AlAs.
- a second lower reflecting mirror 412B using A1 GaAs having a low oxidation rate is provided on the lower reflecting mirror 412A.
- the second lower reflecting mirror 412B needs to be provided when the oxidation rate S of the low refractive index layer in the first lower reflecting mirror 412A is higher than that of the material to be selectively oxidized. come.
- the selectively oxidized layer 427 is made of a material in which Ga is slightly added to AlAs, even if Ga is contained in the low refractive index layer of the first lower reflecting mirror 412A, the oxidation rate is reduced. May be faster than Even in this case, the second lower reflecting mirror 412B is required. If the low refractive index layer in the first lower reflecting mirror 412A has a composition (material) having a lower thermal resistance than the low refractive index layer in the second lower reflecting mirror 412B, efficient heat radiation is realized. .
- the mesetsuting is performed so as to stop between the selectively oxidized layer 427 to be the A1 oxide film and the AlAs412A of the first lower reflecting mirror. Les ,.
- a C1 gas is applied to a dry etching apparatus that holds a substrate to be processed.
- RIBE reactive ion beam etching
- the second point is that the n-side and p-side Al Ga As high refractive index layers and (Al Ga) In
- a (AlGa) InP intermediate layer 60 having a thickness of 20 nm
- the intermediate layer 601 having a small A1 composition by introducing the intermediate layer 601 having a small A1 composition, particularly, the p_AlGaAs high refractive index layer is formed on the p_ (AlGa) InP low refractive index layer.
- the range of growth conditions under which flat growth can be achieved with good crystallinity is expanded, and a high refractive index layer can be easily formed.
- the heterojunction of AlGaAs-based material and AlGalnP-based material if the Al composition of the AlGalnP-based material is large, the band discontinuity of the valence band increases, but an intermediate layer with a small A1 composition is introduced. As a result, such band discontinuity of the valence band can be reduced, and the electric resistance can be reduced.
- the intermediate layer 601 may contain As.
- a system 260, a laser printer 280 using a surface emitting laser array chip 281 and the like can be configured.
Abstract
Description
Claims
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US12/691,476 US8199788B2 (en) | 2004-06-11 | 2010-01-21 | Surface-emission laser diode and fabrication process thereof |
US13/459,333 US8401049B2 (en) | 2004-06-11 | 2012-04-30 | Surface-emission laser diode and fabrication process thereof |
US13/764,167 US8743924B2 (en) | 2004-06-11 | 2013-02-11 | Surface-emission laser diode and fabrication process thereof |
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JP2005088188A JP5057354B2 (ja) | 2004-04-30 | 2005-03-25 | 面発光レーザの製造方法 |
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JP2005101765A JP4950432B2 (ja) | 2004-06-11 | 2005-03-31 | 面発光型半導体レーザ、面発光型半導体レーザアレイ、画像形成装置、光ピックアップ、光送信モジュール、光送受信モジュール及び光通信システム |
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TWI464985B (zh) * | 2006-08-23 | 2014-12-11 | Ricoh Co Ltd | 表面發光雷射陣列,光學掃描裝置,及成像裝置 |
JP2008060459A (ja) * | 2006-09-01 | 2008-03-13 | Canon Inc | 半導体レーザ装置 |
JP2009277781A (ja) * | 2008-05-13 | 2009-11-26 | Ricoh Co Ltd | 面発光型レーザーアレイ素子、光走査装置及び画像形成装置 |
JP2010021521A (ja) * | 2008-06-11 | 2010-01-28 | Ricoh Co Ltd | 面発光レーザ素子、面発光レーザアレイ、光走査装置及び画像形成装置 |
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US20080212636A1 (en) | 2008-09-04 |
US20120263206A1 (en) | 2012-10-18 |
US8743924B2 (en) | 2014-06-03 |
EP1780849B1 (en) | 2013-01-30 |
US8401049B2 (en) | 2013-03-19 |
US20100118907A1 (en) | 2010-05-13 |
EP1780849A1 (en) | 2007-05-02 |
US7684458B2 (en) | 2010-03-23 |
US20140064313A1 (en) | 2014-03-06 |
EP1780849A4 (en) | 2009-07-15 |
US8199788B2 (en) | 2012-06-12 |
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