JP2007109766A - Optical semiconductor and optical transmission module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical semiconductor such as a surface-emitting laser and a light receiving element which can be reduced in leakage current, and also to provide an optical transmission module using the same. <P>SOLUTION: The optical semiconductor is formed of a multilayer structure comprising an active layer 13, a bottom DBR 12 formed on the lower layer side of the active layer 13, and a top DBR 14 formed on the upper layer side of the active layer 13. Further, the semiconductor comprises a multilayer structure and the whole or part of the multilayer structure constituting a pillar of a columnar shape; an oxidation-narrowed layer 18 formed of an insulating material which is formed in a shape of a doughnut immediately above the active layer; and an insulation layer 16 including an insulating region which is formed in a shape of a doughnut immediately below the active layer 13, has its periphery reaching the side wall of the pillar, and has a thickness larger than that of the oxidation-narrowed layer 18. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical semiconductor and an optical transmission module.

  In recent years, a surface emitting laser (VCSEL) having features of being capable of high-speed operation and low power consumption has been attracting attention as the amount of communication data increases. As an advantage of the surface emitting laser, it can be easily inspected, and it is inexpensive as compared with the edge emitting semiconductor laser. In order to take advantage of this feature, it is necessary to improve the yield without investing expensive production equipment in the manufacturing process.

Further, as a surface-emitting laser that can be easily manufactured with relatively high reliability, an oxidized constricted surface-emitting laser has been researched and developed. The oxidation confinement type surface emitting laser includes an oxide confinement layer (current confinement layer) formed by oxidizing a part of a layer in a convex column portion forming at least a part of a resonator. The density of the current flowing through the active layer in the column portion is improved by the oxidized constricting layer, and the efficiency of the laser output can be improved (for example, see Patent Documents 1 to 3).
JP 2003-168845 A JP 2004-207536 A Japanese Patent Laid-Open No. 2004-253408

  However, in the conventional surface emitting lasers including the surface emitting lasers described in Patent Documents 1 to 3, a leak current that flows through the side surface (outer peripheral surface) of the column of the resonator is generated to some extent, and the threshold value of the laser oscillation operation is lowered. There is a problem of obstructing. This increase in threshold value hinders the increase in the modulation driving speed and the reduction in power consumption of the surface emitting laser.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical semiconductor and an optical transmission module capable of reducing a leakage current in an optical semiconductor such as a surface emitting laser or a light receiving element.
It is another object of the present invention to provide an optical semiconductor and an optical transmission module that can reduce the threshold for the operation of an optical semiconductor such as a surface emitting laser or a light receiving element.

In order to achieve the above object, an optical semiconductor of the present invention has an active layer, a lower reflective layer formed on a lower layer side of the active layer, and an upper reflective layer formed on an upper layer side of the active layer. And a laminated structure part in which all or part of the laminated structure constitutes a pillar-shaped column part, and a planar shape formed in a donut shape directly above or directly below the active layer A current confinement layer made of a conductive material, and a layer having an insulating region in which a planar shape is formed in a donut shape immediately above or directly below the active layer or the current confinement layer, and the outer periphery of the layer is the pillar portion And an insulating layer having a thickness of the layer larger than that of the current confinement layer. The donut shape is, for example, a ring shape, and it is preferable that the plane where the ring shape exists and the plane of the active layer are arranged in parallel.
According to the present invention, the leakage current flowing through the side wall (outer periphery) of the column portion can be significantly reduced by the insulating layer. For example, the leakage current of the optical semiconductor becomes a flow path from the side surface of the upper reflective layer, through the side surface of the active layer, and through the side surface of the lower reflective layer. In the optical semiconductor of the present invention, since the end face of the insulating layer is exposed at the side wall portion of the column portion, the leakage current flowing through the side surface of the column portion can be blocked by the insulating layer. Furthermore, since the insulating layer is disposed immediately above or immediately below the active layer or the current confinement layer, and the insulating layer has a thickness larger than that of the current confinement layer, the leakage current flowing in the outer periphery of the active layer is reduced. It can block more effectively. Therefore, according to the present invention, leakage current in an optical semiconductor such as a surface emitting laser or a light receiving element can be reduced.

In the optical semiconductor of the present invention, it is preferable that the laminated structure portion constitutes a resonator of a surface emitting laser.
According to the present invention, the leakage current of the surface emitting laser can be greatly reduced, and the threshold value of the laser oscillation operation can be lowered. Thereby, a surface emitting laser that performs a modulation operation at high speed can be provided.

In the optical semiconductor of the present invention, it is preferable that the laminated structure portion constitutes a light receiving element (for example, a photodiode).
According to the present invention, in an optical semiconductor that forms a light receiving element such as a photodiode, leakage current can be significantly reduced, and high speed operation and improved light receiving sensitivity can be achieved. Here, the optical semiconductor constituting the light receiving element may not have the current confinement layer. Further, the surface emitting laser and the light receiving element may be provided on one substrate.

In the optical semiconductor of the present invention, it is preferable that the optical film thickness of the region other than the insulating region in the insulating layer is set to an odd multiple of 1/4 of the wavelength (λ) of the surface emitting laser. .
According to the present invention, for example, when the lower reflective layer and the upper reflective layer are configured by distributed reflective multilayer mirrors (DBR mirrors), the thickness of the insulating layer is equal to the thickness (λ / 4) of each layer of the DBR mirror. It becomes an odd multiple. Therefore, the insulating layer can be formed by oxidizing an odd layer of the DBR mirror, and an optical semiconductor with little leakage current can be provided simply and at low cost.

In the optical semiconductor of the present invention, the laminated structure is formed by laminating a layer containing aluminum and a semiconductor material as an element, and the aluminum is lower than the aluminum low composition layer and the aluminum low composition layer. The insulating layer has a structure in which a plurality of aluminum high composition layers having a high content ratio are stacked, and the insulating layer is formed by oxidizing a layer including aluminum and a semiconductor material as elements. It is preferable that
According to the present invention, a lower reflective layer and an upper reflective layer that constitute a DBR mirror can be configured by a structure in which an aluminum low composition layer and an aluminum high composition layer are alternately laminated. In addition, the insulating layer can be formed by oxidizing part of the lower reflective layer or the upper reflective layer. Therefore, the present invention can provide an optical semiconductor with little leakage current easily and at low cost.

In the optical semiconductor of the present invention, the current confinement layer is formed immediately above the active layer, forms a part of the insulating layer, and is a first insulating layer formed immediately below the active layer. And a second insulating layer that forms part of the insulating layer and is formed immediately above the current confinement layer. In the optical semiconductor of the present invention, the current confinement layer is formed immediately below the active layer, forms a part of the insulating layer, and is a first insulating layer formed immediately above the active layer. And a second insulating layer that forms part of the insulating layer and is formed immediately below the current confinement layer.
According to the present invention, the active layer and the current confinement layer can be sandwiched between the first insulating layer and the second insulating layer. Therefore, the leakage current flowing through the side surface of the active layer can be more effectively blocked by the first insulating layer and the second insulating layer.

In the optical semiconductor of the present invention, it is preferable that the aluminum content ratio of the insulating layer is higher than the aluminum content ratio of the lower reflective layer and the upper reflective layer.
According to the present invention, for example, an insulating layer can be formed by oxidizing a layer containing aluminum. That is, when the column portion including the layer to be the insulating layer is oxidized, the lower reflective layer and the upper reflective layer having a relatively low aluminum content ratio are hardly oxidized, and an insulating layer having a relatively high aluminum content ratio is obtained. In the vicinity of the outer periphery of the layer, aluminum is oxidized and becomes a highly insulating region. Thereby, it is possible to form a good insulating layer while maintaining a good DBR mirror configuration. Therefore, the present invention can provide an optical semiconductor with little leakage current easily and at low cost.

In the optical semiconductor of the present invention, the insulating layer is formed by laminating a layer containing aluminum and a semiconductor material as an element, and is made of aluminum in comparison with the aluminum low composition layer and the aluminum low composition layer. It is preferable to have a structure in which a plurality of aluminum high composition layers having a high content ratio are stacked.
In the optical semiconductor of the present invention, the insulating layer, the lower reflective layer, and the upper reflective layer include an aluminum low composition layer and an aluminum high composition layer having a higher aluminum content ratio than the aluminum low composition layer, respectively. The insulating layer has a structure in which a plurality of sets are laminated, and the aluminum low composition layer of the insulating layer has a higher aluminum content than the aluminum low composition layer of the lower reflective layer and the upper reflective layer, and the insulating layer The aluminum high composition layer preferably has a higher aluminum content than the aluminum high composition layers of the lower reflective layer and the upper reflective layer.
According to the present invention, the insulating layer can be formed, for example, by oxidizing a part of a DBR mirror, and an optical semiconductor with little leakage current can be provided simply and at low cost.

In the optical semiconductor of the present invention, it is preferable that all of the portions in the vicinity of the side wall of the column portion are oxidized to form an insulating region.
According to the present invention, it is possible to make a structure in which all of the DBR mirror constituting the pillar part and the vicinity of the outer periphery of the active layer (part near the side wall of the pillar part) are made of insulating materials. Therefore, the present invention can provide an optical semiconductor with very little leakage current easily and at low cost.

In order to achieve the above object, an optical transmission module of the present invention comprises the optical semiconductor.
According to the present invention, it is possible to provide an optical transmission module having good high frequency characteristics and low power consumption. Therefore, the optical transmission module of the present invention can increase the speed of communication and the like.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing referred to below, the scale of each component is appropriately changed and displayed for easy understanding of the drawing. In the following embodiments, a surface emitting laser is described as an example of an optical semiconductor, but the present invention can also be applied to a light receiving element such as a photodiode.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing a surface emitting laser according to a first embodiment of the present invention. The surface emitting laser 10 includes a semiconductor substrate 11, a lower DBR (lower reflective layer) 12, an active layer 13, an upper DBR (upper reflective layer) 14, an insulating layer 16, and an oxidized constricting layer (current confining layer). 18, an insulating layer 19, a first electrode 20, and a second electrode 21. The insulating layer 16 is an insulating layer according to the present invention.

The semiconductor substrate 11 is made of a compound semiconductor, for example, an n-type GaAs substrate. The lower DBR 12 is formed in the upper layer of the semiconductor substrate 11. The lower DBR 12 is composed of a reflective layer in which layers having different refractive indexes are alternately stacked. For example, the lower DBR 12 includes 40 pairs of distributed reflective multilayer mirrors (DBR mirrors) in which n-type Al _0.9 Ga _0.1 As layers and n-type Al _0.15 Ga _0.85 As layers are alternately stacked. It is composed. The active layer 13 is formed on the upper layer side of the lower DBR 12. The active layer 13 is composed of, for example, a 3 nm thick GaAs well layer and a 3 nm thick Al _0.3 Ga _0.7 As barrier layer, and the well layer is composed of three layers. Make up layer.

The upper DBR 14 is provided on the upper layer side of the active layer 13. And upper DBR14 is comprised by the reflection layer which laminated | stacked the layer from which a refractive index differs alternately. For example, the upper DBR 14 has 25 pairs in which p-type Al _0.9 Ga _0.1 As layers (aluminum high composition layer) and p-type Al _0.15 Ga _0.85 As layers (aluminum low composition layer) are alternately laminated. The distributed reflection type multilayer mirror (DBR mirror) is constructed.

  The lower DBR 12 is made an n-type semiconductor by doping Si. The upper DBR 14 is made into a p-type semiconductor by doping C. The active layer 13 is not doped with impurities. Accordingly, the lower DBR 12, the active layer 13, and the upper DBR 14 constitute a pin diode, and constitute a resonator of the surface emitting laser 10. The active layer 13 and the upper DBR 14 in this resonator constitute a cylindrical column portion formed in a convex shape on the upper surfaces of the semiconductor substrate 11 and the lower DBR 12. The lower DBR 12 may also have a convex shape, and a part of the upper side of the lower DBR 12 may be a part of the column part. The upper surface and the lower surface of the column portion become the laser light emission surface of the surface emitting laser 10.

  A contact layer (not shown) is formed on the upper DBR 14. The contact layer is made of, for example, a p-type GaAs layer. The insulating layer 19 is a layer for insulating the second electrode 21 from the lower DBR 12 and the active layer 13. The first electrode 20 forms a cathode electrode of the surface emitting laser 10. The first electrode 20 is electrically connected to the lower DBR 12 through the semiconductor substrate 11. The The second electrode 21 forms an anode electrode of the surface emitting laser 10. The second electrode 21 is electrically connected to the upper DBR 14 via the contact layer 15.

  The oxidized constricting layer 18 forms an insulating region that restricts a flow path of current flowing through the active layer. In other words, the oxidized constricting layer 18 is intended to improve the current density by narrowing the flow region of the current flowing in the resonator of the surface emitting laser 10. By increasing the current density, a high-performance surface-emitting laser 10 capable of laser oscillation at a low current can be configured. The oxidized constricting layer 18 is disposed immediately above the active layer 13. The planar shape of the oxidized constricting layer 18 is a donut shape.

  The oxidized constricting layer 18 is formed of an insulating layer mainly composed of Al oxide, for example. The oxidized constricting layer 18 is provided with a layer that is easily oxidized (mainly a layer containing a large amount of Al, for example, an AlGaAs layer having an Al composition of 0.95 or more) in the vicinity of the active layer 13, for example, and high-temperature water vapor (about 400 ° C.) It can be formed by an oxidation reaction using an oxidizing gas. As a result, the easily oxidized layer in the columnar column portion is oxidized from the side surface of the column portion, and the oxidized portion becomes a donut-shaped insulator and becomes the oxidized constriction layer 18.

  The insulating layer 16 is formed immediately below the active layer 13 and has a donut-shaped insulating region. The outer periphery of the insulating region of the insulating layer 16 reaches the side wall of the column portion. The thickness of the insulating layer 16 is larger than the thickness of the oxidized constricting layer 18. Alternatively, the insulating layer 16 may be disposed immediately above the active layer 13 and the oxidized constricting layer 18 may be disposed directly below the active layer 13.

  As a result, according to the surface emitting laser 10 of the present embodiment, the end portion of the insulating layer 16 is widely exposed on the side wall of the column portion immediately below or immediately above the active layer 13. Therefore, the leakage current flowing through the side wall (outer periphery) of the column portion can be significantly reduced by the insulating layer 16. Therefore, the surface emitting laser 10 can realize a low threshold of the laser oscillation operation and can perform a high-speed modulation operation.

  Further, in the region other than the insulating region in the insulating layer 16, the optical film thickness is preferably set to an odd multiple of ¼ of the wavelength λ of the surface emitting laser 10. Here, the thickness of each layer of the multilayer film of the lower DBR 12 and the upper DBR 14 is ¼ of the wavelength λ of the surface emitting laser 10. Therefore, the thickness of the insulating layer 16 is an odd multiple of the thickness of each layer (one layer) of the multilayer film of the lower DBR 12 and the upper DBR 14. As a manufacturing method having such a configuration, there is a method of forming the insulating layer 16 by oxidizing an odd layer of the multilayer film to form an insulator.

The composition of the insulating layer 16 is, for example, X = 0.12 to 0.98 when composed of “Al _X Ga _1-X As”. In this way, the Al component can be oxidized to form an insulator. The insulating layer 16 is a layer having a donut-shaped insulating region, but the interval (width) between the inner periphery and the outer periphery of the donut shape may be, for example, 0.001 μm or more. In this way, the effect of preventing leakage current can be enhanced.

The diameter of the donut-shaped opening in the insulating layer 16 is preferably smaller than the diameter of the donut-shaped opening in the oxidized constricting layer 18. In this way, the leakage current can be reduced without hindering the current density improvement effect by the oxidized constricting layer 18.
In the surface emitting laser 10, the first electrode 20 may be arranged on the upper surface side of the semiconductor substrate 11 (the surface side of the second electrode 21).

[Second Embodiment]
FIG. 2 is a schematic cross-sectional view showing a surface emitting laser according to a second embodiment of the present invention. In FIG. 2, the same components as those in FIG. The surface emitting laser 10A of the present embodiment is different from the surface emitting laser 10 of the first embodiment in that the first insulating layer 16A and the second insulating layer 16B for preventing leakage current are arranged above and below the active layer 13. It is a point.

  That is, in FIG. 2, the first insulating layer 16A corresponds to the insulating layer 16 in FIG. 1, but the second insulating layer 16B is a component not included in the surface emitting laser 10 in FIG. The second insulating layer 16B is formed immediately above the oxidized constricting layer 18 formed immediately above the active layer 13. The planar shape and thickness of the second insulating layer 16B are preferably the same as or substantially the same as those of the first insulating layer 16A.

  As a result, according to the surface emitting laser 10A of the present embodiment, the active layer 13 and the oxidized constricting layer 18 are sandwiched between the first insulating layer 16A and the second insulating layer 16B. It is possible to more effectively reduce the leakage current flowing outside.

  Further, as a modification of the surface emitting laser 10A, an oxidized constricting layer 18 is disposed immediately below the active layer 13, a first insulating layer 16A is disposed immediately below the oxidized constricting layer 18, and the first insulating layer 16A is disposed immediately above the active layer 13. The structure which has arrange | positioned 2 insulating layers 16B is mentioned. In addition, a first oxidized constricting layer 18 is disposed immediately below the active layer 13, a second oxidized constricting layer (not shown) is disposed immediately above the active layer 13, and immediately below the first oxidized constricting layer 18. A configuration in which the first insulating layer 16A is disposed and the second insulating layer 16B is disposed immediately above the second oxidized constricting layer is also exemplified.

[Third Embodiment]
FIG. 3 is a schematic cross-sectional view showing a surface emitting laser according to a third embodiment of the present invention. 3, the same components as those in FIG. 2 are denoted by the same reference numerals. The surface emitting laser 10B of the present embodiment is different from the surface emitting laser 10A of the second embodiment in the first insulating layer 16A ′ and the second insulating layer 16B ′.

  The first insulating layer 16A 'corresponds to the first insulating layer 16A of FIG. 2, but is characterized by its composition and formation method. The second insulating layer 16B 'corresponds to the second insulating layer 16B in FIG. 2, but has a feature in its composition and formation method.

  The first insulating layer 16A ′ and the second insulating layer 16B ′ are made of a semiconductor containing Al (for example, AlGaAs), and the Al content ratio is higher than the Al content ratio of the multilayer film of the lower DBR 12 and the upper DBR 14. When the column portion having such a multilayer structure is oxidized, the first insulating layer 16A ′ and the second insulating layer 16B ′ have a high content ratio of Al that is oxidized and becomes an insulator, so that the side wall portion of the column portion is good. A simple insulating region is formed.

  As a result, according to the present embodiment, the first insulating layer 16A ′ and the second insulating layer having a good insulating property can be maintained while maintaining a good DBR mirror configuration by oxidizing the column part as a whole. 16B ′ can be formed. Therefore, according to the present embodiment, the surface emitting laser 10B with a small leakage current can be provided simply and at low cost.

  The first insulating layer 16A ′ and the second insulating layer 16B ′ are formed by stacking Al-containing semiconductor layers (for example, an AlGaAs layer), and are compared with the Al low composition layer and the Al low composition layer. It is also possible to have a structure in which a plurality of Al high composition layers having a high Al content ratio are stacked. In this case, the first insulating layer 16A 'and the second insulating layer 16B' can be formed by oxidizing a part of the lower DBR 12 and the upper DBR 14, for example. Therefore, the surface emitting laser 10B with a small leakage current can be provided simply and at low cost.

  Further, the surface emitting laser 10B may have a configuration in which all the portions near the side wall of the column portion are oxidized to form an insulating region. That is, not only the end portions of the first insulating layer 16A 'and the second insulating layer 16B' but also the end portions of the lower DBR 12, the active layer 13, and the upper DBR 14 may be oxidized to form an insulating member. In this way, a surface emitting laser with extremely little leakage current can be provided simply and at low cost.

[Fourth Embodiment]
FIG. 4 is a view showing a surface emitting laser according to a fourth embodiment of the present invention. 4A is a schematic plan view, and FIG. 4B is a schematic cross-sectional view of the position LL in FIG. 4A. 4, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals. The main difference between the surface emitting laser 10C of the present embodiment and the surface emitting laser 10 of the second embodiment is that the resonator does not constitute a column part.

The lower DBR 12 is formed in an upper layer of a semiconductor substrate (not shown). An active layer 13 and an upper DBR 14 are stacked on the lower DBR 12. The holes 301, 302, 303, and 304 are holes that are dug from the upper surface of the upper DBR 14 to the upper surface of the lower DBR 12. The first oxidized constricting layer 118A is a layer immediately below the active layer 13 and includes insulating regions formed around the holes 301, 302, 303, and 304, and corresponds to the oxidized constricting layer 18 in FIG.
The second oxide confinement layer 118B is a layer immediately above the active layer 13 and includes an insulating region formed around the holes 301, 302, 303, and 304. The holes 301, 302, 303, and 304 may be holes that are dug from the upper surface of the upper DBR 14 to a part of the first oxidized constricting layer 118 </ b> A. In other words, the holes 301, 302, 303, and 304 may be provided so as to form a recess in the first oxidized constricting layer 118A.

  The portion surrounded by the holes 301, 302, 303, 304 and the lower DBR 12 operate as a resonator of the surface emitting laser 10C. A portion surrounded by the holes 301, 302, 303, and 304 corresponds to the column portion of the surface emitting laser 10A of FIG. Further, the flow region of the current flowing through the resonator is limited by the first oxidized constricting layer 118A and the second oxidized constricting layer 118B. Thereby, the threshold value can be lowered.

  Further, in the surface emitting laser 10C, the first insulating layer 116A is disposed immediately below the first oxide constricting layer 118A and around the holes 301, 302, 303, and 304, and immediately above the second oxide constricting layer 118B. A second insulating layer 116B is disposed around the holes 301, 302, 303, and 304. The first insulating layer 116A and the second insulating layer 116B correspond to the first insulating layer 16A and the second insulating layer 16B in FIG.

  Therefore, according to the surface emitting laser 10C, the leakage current passing through the outside of the resonator (for example, the side surfaces of the holes 301, 302, 303, and 304) is significantly reduced by the first insulating layer 116A and the second insulating layer 116B. Can do. Thereby, the threshold value can be further lowered.

[Optical transmission module]
FIG. 5 shows an example of an optical transmission module using the surface emitting laser of this embodiment. An OSA (Optical Sub-Assembly) 100 as an optical transmission module has a surface emitting laser 10 (or surface emitting lasers 10A, 10B, 10C) described above mounted on a system 101. A lens 103 is disposed above the surface emitting laser 10 and on the optical axis of the surface emitting laser 10. Further, a cover 102 is formed from the base of the system 101 to a part of the optical fiber 104 in order to protect the surface emitting laser 10 and the like from the external environment. An optical fiber 104 is disposed on the optical axis of the lens 103. In the present embodiment, the cover 102 is made of resin and is formed integrally with the lens 103.

  When a voltage is applied between the first electrode 20 and the second electrode 21 of the surface emitting laser 10 via the pins of the system 101, the surface emitting laser 10 is driven. The light emitted from the surface emitting laser 10 reaches the lens 103. The reached light is collected by the lens 103 and enters the optical fiber 104.

  As a result, the OSA 100 of the present embodiment includes the surface emitting laser 10 having a small leakage current and a low threshold, and thus has good high-frequency characteristics and can reduce power consumption. Therefore, the OSA 100 according to the present embodiment can increase the speed of communication and the like.

[Optical transmission device]
FIG. 6 is a diagram showing a light transmission device including the surface emitting laser 10 (or the surface emitting lasers 10A, 10B, and 10C) according to the embodiment of the present invention. The light transmission device 200 connects electronic devices 202 such as a computer, a display, a storage device, and a printer to each other. The electronic device 202 may be an information communication device. The optical transmission device 200 may be one in which plugs 206 are provided at both ends of the cable 204. The cable 204 includes an optical fiber. The plug 206 contains the surface emitting laser 10 (or the surface emitting lasers 10A, 10B, 10C) shown in FIG. The plug 206 may further incorporate a semiconductor chip.

  The plug 206 provided at one end of the cable 204 incorporates the surface emitting laser 10 according to the above-described embodiment, and the plug 206 provided at the other end of the cable 204 may incorporate a light receiving element. Good. By using two sets of such cables 204 and plugs 206, bidirectional communication can be performed. That is, the electrical signal output from the electronic device 202 is converted into an optical signal at the plug 206 at one end of the cable 204. This optical signal passes through the cable 204 and is converted into an electrical signal at the plug 206 at the other end of the cable 204. This electric signal is taken into the electronic device 202 to which the plug 206 at the other end is connected. Similarly, signal transmission in the reverse direction is also performed. Thus, according to the optical transmission device 200 according to the present embodiment, information transmission can be performed between the electronic devices 202 using the optical signal.

[Usage of optical transmission device]
FIG. 7 is a diagram illustrating a usage pattern of the optical transmission device illustrated in FIG. 6. The light transmission device 212 corresponds to the light transmission device 200 of FIG. The optical transmission device 212 connects the electronic devices 210. As the electronic device 210, a liquid crystal display monitor or a digital CRT (may be used in the fields of finance, mail order, medical care, education), a liquid crystal projector, a plasma display panel (PDP), a digital TV, a retail store A cash register (for POS (Point of Sale Scanning)), a video, a tuner, a game device, a printer, and the like can be given.

  The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention, and the specific materials and layers mentioned in the embodiment can be added. The configuration is merely an example, and can be changed as appropriate.

  For example, in the above embodiment, even if the p-type and n-type in each semiconductor layer are interchanged, it does not depart from the spirit of the present invention. The electro-optic element according to the present invention can be widely applied to electronic devices using light. That is, as an application circuit or electronic device provided with the electro-optic element according to the present invention, an optical interconnection circuit, an optical fiber communication module, a laser printer, a laser beam projector, a laser beam scanner, a linear encoder, a rotary encoder, a displacement sensor , Pressure sensor, gas sensor, blood blood flow sensor, fingerprint sensor, high-speed electrical modulation circuit, wireless RF circuit, mobile phone, wireless LAN, and the like.

  In the above embodiment, a surface emitting laser is used as an example of an optical semiconductor. However, the present invention can also be applied to a light receiving element (for example, a photodiode). For example, when the present invention is applied to a PIN photodiode, in a p-layer, i-layer and n-layer columnar stacked structure, the p-layer corresponds to the upper DBR 12, the i-layer corresponds to the active layer 13, and the n-layer Corresponds to the lower DBR 14. Then, an insulating layer (corresponding to the insulating layer 16) is disposed on the columnar side wall portion immediately above or directly below the i layer. With such a configuration, in an optical semiconductor that forms a light receiving element such as a photodiode, leakage current can be significantly reduced, and high speed operation and improved light receiving sensitivity can be achieved. Here, the optical semiconductor forming the light receiving element may have a configuration including a current confinement layer. Alternatively, the surface emitting laser and the light receiving element may be provided on one substrate.

1 is a schematic cross-sectional view showing a surface emitting laser according to a first embodiment of the present invention. It is a schematic cross section which shows the surface emitting laser which concerns on 2nd Embodiment of this invention. It is a schematic cross section which shows the surface emitting laser which concerns on 3rd Embodiment of this invention. It is a figure which shows the surface emitting laser which concerns on 4th Embodiment of this invention. It is a schematic cross section which shows an example of the optical transmission module which concerns on embodiment of this invention. It is a figure which shows the optical transmission apparatus which concerns on embodiment of this invention. It is a figure which shows the usage condition of an optical transmission apparatus same as the above.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 10A, 10B, 10C ... Surface emitting laser, 11 ... Semiconductor substrate, 12 ... Lower DBR (lower reflective layer), 13 ... Active layer, 14 ... Upper DBR (upper reflective layer), 16 ... Insulating layer, 16A, 16A '... first insulating layer, 16B, 16B' ... second insulating layer, 18 ... oxidized constriction layer (current confinement layer), 19 ... insulating layer, 20 ... first electrode, 21 ... second electrode, 100 ... light transmission Module, 101 ... system, 102 ... cover, 103 ... lens, 104 ... optical fiber

Claims (12)

An active layer, a lower reflective layer formed on the lower layer side of the active layer, and an upper reflective layer formed on the upper layer side of the active layer form a laminated structure, and all or part of the laminated structure A laminated structure part forming a pillar-shaped pillar part;
A current confinement layer made of an insulating material in which a planar shape is formed in a donut shape immediately above or immediately below the active layer;
A layer having an insulating region whose planar shape is formed in a donut shape immediately above or immediately below the active layer or the current confinement layer, the outer periphery of the layer reaching the side wall of the pillar portion; And an insulating layer having a thickness greater than that of the current confinement layer.   The optical semiconductor according to claim 1, wherein the stacked structure portion constitutes a resonator of a surface emitting laser.   The optical semiconductor according to claim 1, wherein the laminated structure portion constitutes a light receiving element.   3. The optical semiconductor according to claim 2, wherein the region other than the insulating region in the insulating layer has an optical film thickness set to an odd multiple of ¼ of the wavelength of the surface emitting laser. The layered structure portion is formed by laminating layers including aluminum and a semiconductor material as elements, and an aluminum high composition layer having a higher aluminum content ratio than the aluminum low composition layer and the aluminum low composition layer. Has a structure in which a plurality of sets are stacked.
5. The optical semiconductor according to claim 1, wherein the insulating layer is formed by oxidizing a layer including aluminum and a semiconductor material as elements. 6. The current confinement layer is formed immediately above the active layer,
A first insulating layer that forms part of the insulating layer and is formed immediately below the active layer;
The optical semiconductor according to claim 1, further comprising: a second insulating layer that forms a part of the insulating layer and is formed immediately above the current confinement layer. . The current confinement layer is formed immediately below the active layer,
A first insulating layer that forms part of the insulating layer and is formed directly on the active layer;
The optical semiconductor according to claim 1, further comprising: a second insulating layer that forms a part of the insulating layer and is formed immediately below the current confinement layer. .   The optical semiconductor according to claim 1, wherein an aluminum content ratio of the insulating layer is higher than an aluminum content ratio of the lower reflective layer and the upper reflective layer.   The insulating layer is formed by laminating layers containing aluminum and a semiconductor material as elements, and an aluminum low composition layer and an aluminum high composition layer having a higher aluminum content ratio than the aluminum low composition layer, 9. The optical semiconductor according to claim 1, wherein a plurality of sets of the optical semiconductors are stacked. Each of the insulating layer, the lower reflective layer, and the upper reflective layer is formed by laminating a plurality of sets each composed of a low aluminum composition layer and a high aluminum composition layer having a higher aluminum content ratio than the low aluminum composition layer. Having a structured
The aluminum low composition layer of the insulating layer has a higher aluminum content than the aluminum low composition layer of the lower reflective layer and the upper reflective layer,
10. The optical semiconductor according to claim 1, wherein the high aluminum composition layer of the insulating layer has a higher aluminum content than the high aluminum composition layers of the lower reflective layer and the upper reflective layer. .   11. The optical semiconductor according to claim 1, wherein all of the portions in the vicinity of the side wall of the column portion are oxidized to form an insulating region. An optical transmission module comprising the optical semiconductor according to any one of claims 1 to 11.

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