JP2005159002A - Light receiving element, optical module, and optical transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light receiving element having high light reception sensitivity, an optical module, and an optical transmission device. <P>SOLUTION: The light receiving element comprises a substrate 10, an optical absorption layer 40 disposed above the substrate 10 for absorbing light of a given wavelength band, and a one-dimensional or two-dimensional photonic crystal 50a disposed above the optical absorption layer 40 having a periodical refractive index distribution in a plane intersecting an incident direction of light Pin. The photonic crystal 50a is formed such that at least part of the incident light Pin distributes and propagates in the plane of the optical absorption layer 40 as even numbered order diffraction lights. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light receiving element, an optical module, and an optical transmission device.

  The surface-type light receiving element is superior to the edge-type light receiving element in terms of compatibility with the VCSEL, coupling efficiency with the fiber, compatibility with the IJ lens, etc., but it absorbs because the light travel distance is short. There is also a drawback of inefficiency.

  Further, when the absorption efficiency of the light absorption layer is relatively high as in the example using GaAs as the material of the light absorption layer shown in FIG. 11, the efficiency can be increased by increasing the thickness of the absorption layer to some extent. However, since the drive bias voltage increases when the light absorption layer is formed thick, it is desirable to make the light absorption layer as thin as possible for low bias drive.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a light receiving element, an optical module, and an optical transmission device with high light receiving sensitivity.

  (1) The present invention includes a substrate, a light absorbing layer disposed above the substrate and absorbing light in a given wavelength band, disposed above the light absorbing layer, and intersecting the incident direction of the light. A one-dimensional or two-dimensional photonic crystal portion having a periodic refractive index distribution in the plane of the photonic crystal, wherein at least a part of the incident light becomes even-order diffracted light. The present invention relates to a light receiving element formed so as to be distributed and propagated in a plane of a light absorption layer.

  According to the present invention, since the photonic crystal portion disposed above the light absorption layer has a periodic refractive index distribution in a plane intersecting the light incident direction, at least part of the incident light is even-ordered. The diffracted light can be distributed so as to be distributed in the in-plane direction of the light absorption layer, and the light incident on the light absorption layer can be spread in the in-plane direction. Thereby, incident light can be efficiently absorbed by the light absorption layer. For example, even if the light absorption layer is formed thin, the light receiving efficiency can be improved.

  (2) The present invention provides a substrate, a light absorption layer that is disposed above the substrate and absorbs light in a given wavelength band, a surface that is formed in the light absorption layer and intersects the incident direction of the light. A one-dimensional or two-dimensional photonic crystal portion having a periodic refractive index distribution, wherein at least part of incident light becomes even-order diffracted light and absorbs the light The present invention relates to a light receiving element formed so as to be distributed and propagate in the plane of a layer.

  According to the present invention, since the photonic crystal portion is formed in the light absorption layer itself, the light incident on the light absorption layer can be spread in the in-plane direction as in the above case. Thereby, incident light can be efficiently absorbed by the light absorption layer. For example, even if the light absorption layer is formed thin, the light receiving efficiency can be improved.

  (3) In the light receiving element of the present invention, a light reflecting film for reflecting the light transmitted through the light absorbing layer may be disposed on the side opposite to the incident surface of the incident light with respect to the light absorbing layer. In this way, light that has been transmitted without being absorbed by the light absorption layer can be reflected and returned to the light absorption layer, so that the light receiving efficiency can be improved.

  (4) In the light receiving element of the present invention, a non-reflective coating film may be disposed on the incident surface side of the incident light with respect to the light absorption layer. In this way, it is possible to prevent front-surface reflection of incident light that occurs on the light incident surface side, and to improve light receiving efficiency.

  (5) According to the present invention, a semiconductor substrate, a first contact layer made of a first conductivity type semiconductor disposed above the semiconductor substrate, and a first wavelength layer disposed above the first contact layer are provided. A light absorbing layer made of a semiconductor that absorbs light, a second contact layer made of a second conductivity type semiconductor disposed above the light absorbing layer, and a first electrode provided in contact with the first contact layer And a second electrode provided in contact with the second contact layer, the second contact layer having periodically arranged grooves, holes, or columnar protrusions, and intersecting a light incident direction. Including a one-dimensional or two-dimensional photonic crystal portion having a periodic refractive index distribution in a plane, wherein the photonic crystal portion includes at least a part of incident light as even-order diffracted light. Formed to propagate in the plane of The present invention relates to light-receiving element.

  (6) The present invention covers a substrate having a recess having protrusions periodically arranged on the bottom surface, at least a first electrode disposed in the recess of the substrate, and a protrusion on the bottom surface of the recess of the substrate. A light absorption layer made of an organic material that absorbs light in a given wavelength band, and a second electrode disposed above the light absorption layer, the light absorption layer comprising A one-dimensional or two-dimensional photonic crystal portion having a periodic refractive index distribution in a plane intersecting a light incident direction in a boundary region with the bottom surface of the concave portion of the substrate, and the photonic crystal portion includes incident light The light receiving element is formed so that at least a part of the light becomes even-order diffracted light and propagates in the plane of the light absorption layer.

  (7) The present invention relates to a substrate having a recess, at least a first electrode disposed in the recess of the substrate, and an organic material that is disposed above the first electrode and absorbs light in a given wavelength band. And a second electrode disposed above the light absorption layer, wherein the light absorption layer is formed by periodically arranging grooves or columnar protrusions on the light incident surface side. Including a one-dimensional or two-dimensional photonic crystal portion having a periodic refractive index distribution in a plane intersecting with the incident direction of light, wherein at least part of the incident light is an even number. The present invention relates to a light receiving element formed so as to be distributed as a next diffracted light and propagate in the plane of the light absorption layer.

  (8) The present invention provides a substrate having a recess, at least a first electrode disposed in the recess of the substrate, and an organic material that is disposed above the first electrode and absorbs light in a given wavelength band. A light absorbing layer comprising: a second electrode disposed above the light absorbing layer; between the first electrode and the light absorbing layer; and between the second electrode and the light absorbing layer. A charge transport layer disposed on at least one of the first and second charge transport layers, the charge transport layer having grooves, holes, or columnar protrusions arranged periodically, and having a periodic shape in a plane intersecting a light incident direction. It includes a one-dimensional or two-dimensional photonic crystal part having a refractive index distribution, and at least a part of incident light becomes even-order diffracted light and is distributed in the plane of the light absorption layer. The present invention relates to a light receiving element formed so as to propagate.

  (9) The present invention can be applied to an optical module including any one of the light receiving elements described above. The optical module of the present invention can be applied to an optical transmission device.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

1. First Light Receiving Element FIG. 1A is a cross-sectional view schematically showing a first light receiving element according to an embodiment of the present invention.

  In the first light receiving element, the semiconductor multilayer reflective film 20, the n-type contact layer (first contact layer) 30, the light absorption layer 40, and the p-type contact layer (second contact layer) 50 are sequentially formed on the semiconductor substrate 10. It is constructed by stacking. The first light receiving element includes a ring-shaped p-type electrode (second electrode) 62 formed on the p-type contact layer and a ring-shaped n-type electrode formed on the exposed surface of the n-type contact layer. (First electrode) 64. For example, the p-type electrode 62 may be a laminated film of an alloy of Au and Zn and Au. The n-type electrode 64 can be, for example, a laminated film of an alloy of Au and Ge and an alloy of Au and Ni.

  For the semiconductor substrate 10, for example, a Si substrate, a GaAs substrate, an InP substrate, or the like can be used according to the material of the light absorption layer 40 formed thereabove.

  The semiconductor multilayer reflective film 20 is provided between the semiconductor substrate 10 and the light absorption layer 40 as necessary. The semiconductor multilayer reflective film 20 can reflect the light transmitted without being absorbed by the light absorption layer 40 and return it to the light absorption layer 40 side again. The semiconductor multilayer reflective film 20 can be formed by alternately laminating a plurality of types of semiconductor films having different refractive indexes, such as GaAs and AlGaAs.

  The n-type contact layer 30 is a semiconductor layer doped with impurities that can ensure ohmic contact with the n-type electrode 64. For example, the n-type contact layer 30 can be made n-type by doping Si into GaAs.

  The light absorption layer 40 is made of a non-doped semiconductor layer and is made of Si, GaAs, InGaAs, GaInNAs, or the like. That is, the p-type contact layer 50, the light absorption layer 40, and the n-type contact layer 30 constitute a pin diode. The light absorption layer 40 is not limited to a single semiconductor layer, and has a quantum well structure in which a plurality of types of semiconductor layers are stacked (including a so-called multiple quantum well structure and a superlattice structure). Also good.

The p-type contact layer 50 is a semiconductor layer doped with impurities that can ensure ohmic contact with the p-type electrode 62. The p-type contact layer 50 can be made p-type by doping C into GaAs, for example. Further, as shown in FIG. 1B, the p-type contact layer 50 disposed closer to the light incident surface than the light absorption layer 40 is made of a material of the p-type contact layer 50 and a medium (such as air) inside the groove 50b. ), A photonic crystal portion 50a having a two-dimensional photonic crystal structure having a periodic refractive index distribution in a plane intersecting the traveling direction of the incident light Pin is formed. The photonic crystal part 50a is realized, for example, by providing grooves 50b periodically arranged at intervals of about the wavelength of the incident light Pin. The photonic crystal part 50a is formed so that at least a part of the incident light Pin is an even-numbered diffracted light, more preferably a second-order diffracted light, and is distributed in the plane and propagates inside the device. The For example, if having a one-dimensional photonic crystal structure photonic crystal portion 50a is made of a medium having a refractive index n ₂ and a medium of refractive index n _1, periodic interval D of the refractive index distribution, the absorption wavelength of the light absorbing layer 40 If λ is λ, D = λ / 2n ₁ + λ / 2n ₂ can be formed. Further, even in the case of a two-dimensional photonic crystal structure, it is sufficient that the refractive index distribution is formed at a similar periodic interval.

  The arrangement of the grooves 50b can be, for example, a triangular lattice shape or a square lattice shape. Further, the cross-sectional shape of the groove 50b is not limited to a symmetrical shape such as a cylindrical shape, and may be an asymmetric shape having a taper such as a conical shape. Further, the planar shape of the groove 50b is not limited to a circle but may be a polygon. Further, in order for the photonic crystal portion 50a to have a one-dimensional photonic crystal structure, the groove 50b is patterned into a slit shape so as to function as a diffraction grating in which slits are arranged in parallel to the light incident surface. What is necessary is just to form. In addition, when a protective film or a non-reflective coating film is formed on the photonic crystal part 50a and another material is filled in the groove 50b, refraction with the material of the p-type contact layer 50 is performed. It is preferable to select one having a high rate difference.

  In the first light receiving element of the present embodiment, in the photonic crystal part 50a provided in the p-type contact layer 50, at least a part of incident light having a predetermined wavelength to be absorbed by the light absorption layer 40 is an even order. It propagates as diffracted light so that it is distributed in the plane. Thereby, the incident light is spread in the plane of the light absorption layer 40 and can efficiently absorb the light. Further, in order to realize the low voltage operation of the element, it is desired to make the light absorption layer 40 thin. In this case, the light absorption rate in the light absorption layer 40 is lowered. However, in the first light receiving element of this embodiment, the light receiving sensitivity can be maintained high even if the light absorption layer 40 is thinned.

  Further, in the first light receiving element of the present embodiment, a non-reflective coating film (not shown) is set on the p-type contact layer 50 as required so that the reflectance with respect to the incident light Pin is lowered. May be provided. The non-reflective coating film can be formed from, for example, a known material used for a light emitting surface of a semiconductor optical amplifier. In this way, it is possible to reduce the front reflection of incident light on the light incident surface and to take in a large amount of light inside the device.

  Next, an example of a manufacturing process of the first light receiving element will be described with reference to FIGS. 2 (A) to 2 (D).

  First, as shown in FIG. 2A, a semiconductor multilayer reflective film 20 is formed on a semiconductor substrate 10 by epitaxial growth. Examples of the film forming method include MBE method and MOCVD method. Hereinafter, when various semiconductor layers are formed by epitaxial growth, the above method can be used. Next, as shown in FIG. 2B, the n-type contact layer 30, the light absorption layer 40, and the p-type contact layer 50 are sequentially epitaxially formed on the semiconductor multilayer reflective film 20.

  Then, as shown in FIG. 2C, the stacked structure including the n-type contact layer 30, the light absorption layer 40, and the p-type contact layer 50 is etched using a photolithography technique to form a columnar structure. To do. Furthermore, for the p-type contact layer 50, a photonic crystal part 50a is formed by providing periodically arranged grooves by applying a photolithography technique, an EB (Electron Beam) processing technique, or the like. Finally, a ring-shaped p-type electrode 62 is formed on the p-type contact layer 50 and a ring-shaped n is formed on the n-type contact layer 30 by using a mask vapor deposition method or a mask sputtering method. The mold electrode 64 can be formed to obtain the first light receiving element.

  Next, a modified example of the first light receiving element will be described. FIG. 3A and FIG. 3B are cross-sectional views showing a modification of the first light receiving element of this embodiment. Members having substantially the same functions as those of the first light receiving element shown in FIG. 1A are denoted by the same reference numerals, detailed description thereof will be omitted, and main differences will be described.

  First, in the embodiment shown in FIG. 3A, the intermediate layer 72 is provided between the light absorption layer 40 and the p-type contact layer 50. The intermediate layer 72 preferably has a sufficiently small film thickness compared to other epitaxial layers. The intermediate layer 72 can be a semiconductor layer doped with impurities. The intermediate layer 72 is preferably made of a material that can use an etchant having an etching selectivity smaller than that of the p-type contact layer 50. In this case, when the through-holes are periodically formed in the p-type contact layer 50 to form the photonic crystal structure, the intermediate layer 72 serves as an etch stopper, so that a technique such as wet etching is used. Will be able to. Moreover, the light absorption layer 40 and the photonic crystal part 50a can be brought close to each other by providing the photonic crystal part 50a through the through hole with the intermediate layer 72 being thin.

  Next, in the embodiment shown in FIG. 3B, the photonic crystal structure is not provided in the p-type contact layer 50 itself, but a region where light is incident on the p-type contact layer 50 is removed by etching. For example, a protective film 74 made of polyimide or the like is formed, and a photonic crystal portion 74 a is formed in the protective film 74. In this way, the range of selectivity for the material constituting the photonic crystal structure is widened. For example, by selecting a resin material having excellent moldability, the processing process can be facilitated. Become.

2. Second Light Receiving Element FIG. 4A is a plan view schematically showing a second light receiving element of the present embodiment. FIG. 4B is a cross-sectional view taken along line XX in FIG.

  The second light receiving element is formed so as to cover the cathode (first electrode) 68 formed from the main surface of the substrate 12 to the inside of the recess 12a and the protrusion 12b formed on the bottom surface of the recess 12a of the substrate 12. And the anode (second electrode) 66 formed on the light absorption layer 42.

  As the substrate 12, a glass substrate, a resin substrate, a semiconductor substrate, or the like that is suitable for the application can be adopted. For example, when light is desired to enter from the back surface (surface opposite to the main surface) of the substrate 12, a transparent substrate made of quartz glass, transparent plastic such as polycarbonate, polyimide, or PET is used. be able to. Further, the second light receiving element of the present embodiment employs a configuration in which the protrusion 12b is provided on the substrate 12 to pattern the light absorption layer 42 covering the protrusion 12b to provide the photonic crystal portion 42a. For this reason, it is preferable to select a material for the substrate 12 that has a sufficient refractive index difference with the material for the light absorption layer 42.

  As the cathode 68, a metal, an alloy, an electrically conductive compound, or a mixture thereof having a low work function can be used. As such an electrode substance, for example, those disclosed in JP-A-8-248276 can be used.

  As the anode 66, a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function can be used. When an optically transparent material is used as the anode 66, a conductive compound such as CuI, ITO, SnO2, or ZnO can be used. When transparency is not required, a metal such as gold is used. Can do.

  The light absorption layer 42 is made of an organic material having a light absorption property (or photoelectric conversion property). For example, an organic material disclosed in Japanese Patent Application Laid-Open No. 2001-297874 or Japanese Patent Application Laid-Open No. 2003-101060 is used. Can be formed. The light absorption layer 42 has a plurality of periodically arranged grooves 42 b patterned by the protrusions 12 b of the substrate 12. In the second light receiving element of the present embodiment, there is a difference in refractive index between the protrusion 12b of the substrate 12 and the groove 42b of the light absorption layer 42, so that the period is within the plane intersecting the incident direction of the incident light Pin. A refractive index profile. And the photonic crystal part 42a which has a photonic crystal structure in the boundary area | region with the board | substrate 12 of the light absorption layer 42 is formed. The photonic crystal portion 42a can have a one-dimensional photonic crystal structure by providing the protruding portions 12b of the substrate 12 so that the plurality of grooves 42b function as diffraction gratings. The photonic crystal part 42a can also have a two-dimensional photonic crystal structure by providing the protrusion 12b of the substrate 12 so that the planar shape of the groove 42b is circular or polygonal. Alternatively, the groove 42b of the light absorption layer 42 may be formed to have an asymmetric cross-sectional shape by forming the protrusion 12b with an asymmetric cross-sectional shape. The photonic crystal portion 42a is formed so that at least a part of the incident light Pin is an even-numbered diffracted light, more preferably a second-order diffracted light, and is distributed in the plane and propagates inside the device. The

  Therefore, also in the second light receiving element according to the present embodiment, the incident light Pin is in a state of spreading in the plane of the light absorption layer 42 and can efficiently absorb light. In the second light receiving element, since an organic material is used as the material of the light absorption layer 42, it is desired that the light absorption layer 42 has a high insulating property and is thin. If the light absorption layer 42 is made thinner, the light absorption region becomes smaller, so that the light absorption efficiency is lowered. However, in the second light receiving element of the present embodiment, the incident light Pin is propagated so as to be distributed in the plane of the light absorbing layer 42, so that the light receiving sensitivity can be maintained high even if the light absorbing layer 42 is thinned. it can.

  In the second light receiving element of the present embodiment, in order to further increase the light receiving sensitivity, incident light is incident on the back surface side of the substrate 12, specifically, on the surface opposite to the surface on which the light absorption layer 42 is formed. A metal film having a reflectivity for Pin, a dielectric multilayer reflective film, or a semiconductor multilayer reflective film can be provided. If it does in this way, the light which was not absorbed in the light absorption layer 42 but permeate | transmitted can be reflected, and can enter into the light absorption layer 42 again.

  Further, in the second light receiving element of the present embodiment, when the carrier transport capability in the light absorption layer 42 is low, as shown in FIG. 8A, the light is interposed between the light absorption layer 42 and the cathode 68. A charge transport layer 82 that transports carriers generated by light absorption in the absorption layer 42 to the electrode side may be provided. The charge transport layer 82 may be provided between the light absorption layer 42 and the anode 66. As a material for forming the charge transport layer 82, for example, those disclosed in JP-A-8-248276 or JP-A-2003-101060 can be used. When the charge transport layer 82 is provided as in this example, the incident light Pin is distributed in the plane of the light absorption layer 42 by patterning the grooves 82b periodically arranged in the charge transport layer 82. Therefore, a photonic crystal portion 82a can be formed.

  Next, an example of a manufacturing process of the second light receiving element will be described with reference to FIGS. 5 (A) to 5 (D).

  First, as shown in FIG. 5A, a recess 12a is provided in the substrate 12, and patterning is performed so that a plurality of protrusions 12b are periodically arranged on the bottom surface of the recess 12a. The patterning can be performed using, for example, reactive ion etching (RIE) or electron beam drawing. When the one-dimensional photonic crystal structure is formed in the light absorption layer 42, the protrusion 12b can be patterned in a stripe shape. In addition, when the two-dimensional photonic crystal structure is formed in the light absorption layer 42, the protruding portion 12b can be patterned into a square lattice shape or a triangular lattice shape, for example, in a circular or polygonal planar shape. .

  Next, as shown in FIG. 5B, a cathode 68 is formed from the main surface of the substrate 12 to the inside of the recess 12a by vapor deposition or sputtering. If it is desired to form the cathode 68 so that the electrode material does not adhere to the protrusion 12b in order to obtain the patterning dimension accuracy of the photonic crystal structure formed in the light absorption layer 42, the mask vapor deposition method or A mask sputtering method may be used.

  Next, as shown in FIG. 5C, the light absorption layer 42 is formed so as to cover the protrusion 12b of the recess 12a of the substrate 12 with the organic material described above. The light absorption layer 42 can be formed by vapor deposition as disclosed in Japanese Patent Application Laid-Open No. 2003-101060, but an organic material is made into a solution and dropped into the recess 12a using an inkjet device or a dispenser. You may use the method of hardening | curing a solution-form organic material after filling with a method. In this case, examples of the method for curing the organic material include a method of irradiating ultraviolet rays and a method of applying heat according to the properties of the material. By this step, the light absorption layer 42 is also patterned in accordance with the pattern shape of the protrusion 12b to form a periodic groove 42b, and the photonic crystal part 42a is provided in the boundary region with the substrate 12.

  Next, as shown in FIG. 5D, the second light receiving element of this embodiment can be obtained by forming the anode 66 on the light absorption layer 42. The anode 66 can also be formed by the same film formation method as the cathode 68.

3. Third Light Receiving Element FIG. 6A is a plan view schematically showing a third light receiving element of the present embodiment. FIG. 6B is a cross-sectional view taken along line XX in FIG. 6A and 6B, members having substantially the same functions as those of the second light receiving element shown in FIGS. 4A and 4B are denoted by the same reference numerals. In the following, detailed description will be omitted, and the main differences will be described.

  In the third light receiving element of the present embodiment, the photonic crystal part 42 a is formed in the boundary region between the light absorption layer 42 and the substrate 12 by using the protrusions provided on the substrate 12 by the second light receiving element described above. In contrast, the groove 42b is patterned on the upper surface (the surface opposite to the substrate 12) of the light absorption layer 42 to form a photonic crystal portion 42a. In this case, the anode 66 can be a ring electrode.

  In the third light receiving element of the present embodiment, a difference in refractive index is generated between the air in the groove 42b and the organic material constituting the light absorption layer 42, and the photonic crystal portion 42a has a two-dimensional photonic crystal structure. Constitute. Further, if the groove 42b is patterned in a stripe shape, the photonic crystal part 42a can function as a diffraction grating to form a one-dimensional photonic crystal structure. As in the case of the second light receiving element, the photonic crystal portion 42a is distributed in the plane as at least part of the incident light Pin becomes even-numbered diffraction light, more preferably second-order diffraction light. It is formed so as to propagate inside the element. Therefore, also in the third light receiving element according to the present embodiment, the incident light Pin is in a state of spreading in the plane of the light absorption layer 42 and can efficiently absorb the light. Even if the thickness is reduced, the light receiving sensitivity can be kept high.

  In the third light receiving element of the present embodiment, in order to further increase the light receiving sensitivity, incident light is incident on the back side of the substrate 12, specifically on the surface opposite to the surface on which the light absorption layer 42 is formed. A metal film having a reflectivity for Pin, a dielectric multilayer reflective film, or a semiconductor multilayer reflective film can be provided.

  Further, in the third light receiving element of the present embodiment, when the carrier transport capability in the light absorption layer 42 is low, as shown in FIG. 8B, the light is interposed between the light absorption layer 42 and the cathode 68. A charge transport layer 82 that transports carriers generated by light absorption in the absorption layer 42 to the electrode side may be provided. The charge transport layer 82 may be provided between the light absorption layer 42 and the anode 66. As a material for forming the charge transport layer 82, for example, those disclosed in Japanese Patent Application Laid-Open No. 8-248276 or Japanese Patent Application Laid-Open No. 2003-101060 can be used. When the charge transport layer 82 is provided as in this example, the photonic crystal portion for distributing the incident light Pin in the plane of the light absorption layer 42 by patterning the groove 82b in the charge transport layer 82. 82a can be formed.

  Next, an example of a manufacturing process of the third light receiving element will be described with reference to FIGS. 7 (A) to 7 (D).

  First, as shown in FIG. 7A, the substrate 12 is provided with a recess 12a. The recess 12a can be provided using, for example, reactive ion etching (RIE), electron beam drawing, or the like. Subsequently, as shown in FIG. 7B, the cathode 68 is formed from the main surface of the substrate 12 to the inside of the recess 12a by using an evaporation method, a sputtering method, or the like, and the recess 12a of the substrate 12 is made of the organic material described above. A light absorption layer 42 is formed therein. The light absorption layer 42 can be formed by vapor deposition as disclosed in Japanese Patent Application Laid-Open No. 2003-101060, but an organic material is made into a solution and dropped into the recess 12a using an inkjet device or a dispenser. You may use the method of hardening | curing a solution-form organic material after filling with a method. In this case, examples of the method for curing the organic material include a method of irradiating ultraviolet rays and a method of applying heat according to the properties of the material.

  Next, as shown in FIG. 7C, a periodic groove 42b is formed by patterning on the upper surface of the light absorption layer 42 to provide a photonic crystal portion 42a. The groove 42b can be formed by patterning in a stripe shape when a one-dimensional photonic crystal structure is formed in the light absorption layer 42. Further, when the two-dimensional photonic crystal structure is formed in the light absorption layer 42, the grooves 42b may be formed by patterning in a square lattice shape or a triangular lattice shape with a circular or polygonal planar shape, for example. it can. In addition, when forming the light absorption layer 42 from curable resin, it is necessary to perform the process shown to FIG. 7 (B) and FIG.7 (C) continuously. For example, a solution of an organic material is dropped into the recess 12a, and the resin is cured while being embossed with a stamper or the like on which a pattern for forming the groove 42b is formed. If such a method is used, the reproducibility of the pattern is high and the manufacturing cost can be reduced.

  Next, as shown in FIG. 7D, the third light receiving element of the present embodiment can be obtained by forming a ring-shaped anode 66 on the light absorption layer 42. The anode 66 can also be formed by the same film formation method as the cathode 68.

4). Optical Module FIG. 9 is a diagram showing an optical module to which the light receiving element of this embodiment is applied.

  As shown in FIG. 9A, this optical module has a container 102 joined (or integrated) with a metal stem 101, and a lead 104 provided so as to protrude on the opposite side of the container 102. This is a so-called CAN package type optical module. The container 102 is provided with a light receiving window 103 made of glass for taking incident light on its upper surface. FIG. 9B shows a schematic cross-sectional view of the optical module of the present embodiment. In the container 102, the light receiving element 100 of the present embodiment is disposed on the stem 101, and the lead 104 and the electrode are connected by a bonding wire or the like. The light receiving element 100 may be disposed on the stem 101 via a metal submount. In this optical module, incident light can be taken from the light receiving window 103, and an optical signal can be converted into an electric signal by the light receiving element 100 and taken out from the lead 104. The optical module of the present embodiment is not limited to a CAN package type as shown in FIG. 9A, but is an SMD (surface mount device) type, an optical connector integrated type, and an optical fiber at the tip. May be a pigtail-type optical module.

5). Optical Transmission Device FIG. 10 is a diagram illustrating an optical transmission device to which the optical module of the present embodiment is applied.

  The optical transmission device 90 connects electronic devices 92 such as a computer, a display, a storage device, and a printer to each other. The electronic device 92 may be an information communication device. The optical transmission device 90 may be one in which plugs 96 are provided at both ends of the cable 94. The cable 94 is specifically a multimode optical fiber. The plug 96 is configured to include the optical module of the present embodiment as a receiving photodetector. According to this optical transmission device, data transmission between electronic devices can be performed by an optical signal.

  Note that electronic devices interconnected by the optical transmission device of this embodiment include a liquid crystal display monitor, a digital CRT (may be used in the fields of finance, mail order, medical care, and education), and a liquid crystal projector. Plasma display panel (PDP). It may be a digital TV, a retail store cash register (for POS), a video, a tuner, a game device, or the like.

  Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist of the invention.

  For example, in this embodiment, the case where the photonic crystal portion is formed exclusively by a periodic arrangement of grooves has been described. However, the present invention is not limited to this, and the refractive index distribution is also generated by the periodic arrangement of holes and columnar protrusions. Thus, a photonic crystal part can be realized.

  In addition, for example, the p-type electrode and the n-type electrode in the first light receiving element, and the cathode and the anode in the second and third light receiving elements can be provided interchangeably with each other depending on the layer structure employed.

  For example, in the second light receiving element and the third light receiving element, the case where the cathode is formed in the concave portion of the substrate has been described. However, the present invention is not limited to this, and the case where the substrate has conductivity. Can form a cathode on the back side of the substrate.

FIG. 1A is a cross-sectional view schematically showing the first light receiving element. FIG. 1B is a cross-sectional perspective view for explaining the photonic crystal portion of the first light receiving element. 2A to 2D are cross-sectional views schematically showing the manufacturing process of the first light receiving element. FIG. 3A and FIG. 3B are cross-sectional views schematically showing modified examples of the first light receiving element. FIG. 4A is a plan view schematically showing the second light receiving element. FIG. 4B is a cross-sectional view schematically showing the second light receiving element. FIG. 5A to FIG. 5D are cross-sectional views schematically showing manufacturing steps of the second light receiving element. FIG. 6A is a plan view schematically showing the third light receiving element. FIG. 6B is a cross-sectional view schematically showing the third light receiving element. FIG. 7A to FIG. 7D are cross-sectional views schematically showing the manufacturing process of the third light receiving element. FIG. 8A is a cross-sectional view schematically showing a modification of the second light receiving element. FIG. 8B is a cross-sectional view schematically showing a modification of the third light receiving element. FIG. 9A is an external view schematically showing an optical module. FIG. 9B is a cross-sectional view schematically showing the optical module. FIG. 10 is a diagram schematically illustrating an optical transmission apparatus. FIG. 11 is a diagram for explaining the relationship between the layer thickness of GaAs and the light absorption rate.

Explanation of symbols

10 substrate, 20 multilayer reflection film, 30 n-type contact layer, 40 light absorption layer, 50 p-type contact layer, 50a photonic crystal part, 62 p-type electrode, 64 n-type electrode

Claims (12)

A substrate,
A light-absorbing layer disposed above the substrate and absorbing light in a given wavelength band;
A one-dimensional or two-dimensional photonic crystal portion disposed above the light absorption layer and having a periodic refractive index distribution in a plane intersecting the incident direction of the light;
Including
The photonic crystal part is a light receiving element formed so that at least a part of incident light becomes even-order diffracted light and is distributed and propagated in a plane of the light absorption layer. A substrate,
A light-absorbing layer disposed above the substrate and absorbing light in a given wavelength band;
A one-dimensional or two-dimensional photonic crystal portion formed in the light absorption layer and having a periodic refractive index distribution in a plane intersecting the incident direction of the light;
Including
The photonic crystal part is a light receiving element formed so that at least a part of incident light becomes even-order diffracted light and is distributed and propagated in a plane of the light absorption layer. In claim 1 or 2,
A light receiving element, wherein a light reflection film that reflects light transmitted through the light absorption layer is disposed on a side opposite to the incident light incident surface with respect to the light absorption layer. In any one of Claims 1-3,
A light receiving element, wherein a non-reflective coating film is disposed on an incident surface side of the incident light with respect to the light absorption layer. A semiconductor substrate;
A first contact layer made of a first conductivity type semiconductor disposed above the semiconductor substrate;
A light absorption layer made of a semiconductor disposed above the first contact layer and absorbing light in a given wavelength band;
A second contact layer made of a second conductivity type semiconductor disposed above the light absorption layer;
A first electrode provided in contact with the first contact layer;
A second electrode provided in contact with the second contact layer;
Including
The second contact layer has a periodically arranged groove, hole, or columnar protrusion, and a one-dimensional or two-dimensional photonic crystal having a periodic refractive index distribution in a plane intersecting the light incident direction. Part
The photonic crystal part is a light receiving element formed so that at least a part of incident light becomes even-order diffracted light and is distributed and propagated in a plane of the light absorption layer. In claim 5,
A light receiving element in which a multilayer reflective film in which a plurality of types of semiconductor films having different refractive indexes are laminated is disposed between the semiconductor substrate and the light absorption layer. A substrate having a recess having protrusions periodically arranged on the bottom surface;
A first electrode disposed in at least a recess of the substrate;
A light absorption layer formed of an organic material that absorbs light of a given wavelength band, and is formed so as to cover the protrusion on the bottom surface of the concave portion of the substrate;
A second electrode disposed above the light absorption layer;
Including
The light absorption layer includes a one-dimensional or two-dimensional photonic crystal portion having a periodic refractive index distribution in a plane intersecting a light incident direction in a boundary region with the bottom surface of the concave portion of the substrate,
The photonic crystal part is a light receiving element formed so that at least a part of incident light becomes even-order diffracted light and is distributed and propagated in a plane of the light absorption layer. A substrate having a recess;
A first electrode disposed in at least a recess of the substrate;
A light absorption layer made of an organic material disposed above the first electrode and absorbing light in a given wavelength band;
A second electrode disposed above the light absorption layer;
Including
The light absorbing layer is formed by periodically arranging grooves or columnar protrusions on the light incident surface side, and has a one-dimensional or periodic refractive index distribution in a surface intersecting with the light incident direction. Including a two-dimensional photonic crystal part,
The photonic crystal part is a light receiving element formed so that at least a part of incident light becomes even-order diffracted light and is distributed and propagated in a plane of the light absorption layer. A substrate having a recess;
A first electrode disposed in at least a recess of the substrate;
A light absorption layer made of an organic material disposed above the first electrode and absorbing light in a given wavelength band;
A second electrode disposed above the light absorption layer;
A charge transport layer disposed between at least one of the first electrode and the light absorption layer and between the second electrode and the light absorption layer;
Including
The charge transport layer has a periodically arranged groove, hole, or columnar protrusion, and has a one-dimensional or two-dimensional photonic crystal portion having a periodic refractive index distribution in a plane intersecting the light incident direction. Including
The photonic crystal part is a light receiving element formed so that at least a part of incident light becomes even-order diffracted light and is distributed and propagated in a plane of the light absorption layer. In any one of Claims 7-9,
A light receiving element, wherein a light reflecting film for reflecting light transmitted through the light absorbing layer is disposed on a surface opposite to the main surface of the substrate.   The optical module containing the light receiving element in any one of Claims 1-10.   An optical transmission device comprising the optical module according to claim 11.

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