JP5443602B2 - Photoelectric conversion element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a photoelectric conversion element applied to, for example, a photodiode or a solar cell and a method for manufacturing the photoelectric conversion element, and more particularly to a photoelectric conversion element using the Schottky effect and the surface plasmon effect synergistically and a manufacturing method therefor.

For example, Patent Document 1 describes a photoelectric conversion element using surface plasmon resonance. An uneven structure having a uniform period is formed on the surface of the metal layer of the element. A semiconductor layer is laminated on the concavo-convex structure, and a transparent electrode is further laminated thereon. Another electrode is laminated on the back surface of the metal layer. When light is incident on the element, electrons on the surface of the metal layer on the concave-convex structure side vibrate in resonance with the incident light, and a current is generated.
In the photoelectric conversion element described in Patent Document 2, two or more kinds of fine particles are provided on the surface, and surface plasmon resonance is caused in at least two wavelength bands.

Further, it has been known since the 1960s that visible light can be detected by a Schottky optical sensor in which Au having a thickness of several μm or more is stacked on n-type Si.
Non-Patent Document 1 describes that near-infrared light of 1 μm to ₂ μm can be detected by an optical sensor in which CoSi ₂ is laminated on n-type Si.
Non-Patent Document 2 describes that infrared light of 1 μm to 5 μm can be detected by an optical sensor in which CoSi ₂ is laminated on p-type SiGe.
Non-Patent Document 3 describes that infrared light of 1 μm to 6 μm can be detected by an optical sensor in which Pt is stacked on p-type Si.
Non-Patent Document 4 describes that light of 10 μm or less can be detected by an optical sensor in which Ir is laminated on Si.

JP 2007-073794 A JP 2010-021189 A

Roca, Elisenda, et al., Proceedings of SPIE-The International Society for Optical Engineering 2525 (2), 456 (1995) S. Kolondinski, et al., Proceedings of SPIE-The International Society for Optical Engineering 2554, 175 (1995) J.M.Mooney and J.Silverman, IEEE Trans.Electron DevicesED-32, 33-39 (1985) B-Y.Tsaur, M.M.Weeks, R.Trubiano and P.W.Pellegrini, IEEE Electron Device Left.9,650-653 (1988)

  However, a photoelectric conversion element that is sensitive to a wide band from visible light to infrared light is not known. Also, in any photoelectric conversion element, it is not easy to reduce the thickness because carriers flow in the stacking direction (thickness direction) of the elements.

  Therefore, it is conceivable to stack a conductive layer on the semiconductor layer, dispose a pair of electrodes on this conductive layer, and dispose a plasmon resonance structure on the surface of the conductive layer between the electrodes. However, it is uncertain which of the pair of electrodes becomes the anode and which becomes the cathode, and the direction of the current cannot be determined. Each electrode can be an anode or a cathode due to contamination or disturbance incidentally or inevitably mixed in the manufacturing process, and there is no guarantee that the current-voltage characteristics are asymmetric between the positive side and the negative side.

In order to solve the above problems, the photoelectric conversion element according to the present invention is:
An n-type or p-type semiconductor layer formed so that a convex layer protrudes from the surface;
A conductive layer laminated on the surface and in contact with one side surface of the convex layer;
A first electrode provided on the opposite side of the conductive layer across the convex layer on the surface and in contact with the opposite side surface of the convex layer;
A second electrode provided on the conductive layer;
A metal nanostructure including a plurality of (preferably many) periodic structures laminated on the convex layer or the conductive layer;
Wherein the respective periodic structure comprises a plurality of first protrusions, the arrangement interval of the first protrusion is characterized not claimed to vary depending on the periodic structure.
The claimed feature of the photoelectric conversion element according to the present invention is that an n-type or p-type semiconductor layer formed so that a convex layer protrudes on the surface, and one side surface of the convex layer laminated on the surface, and A conductive layer in Schottky contact with the surface; a first layer in ohmic contact with the opposite side surface of the convex layer and the surface; An electrode, a second electrode provided on the conductive layer, and a metal nanostructure including a plurality of periodic structures stacked on the convex layer or the conductive layer, each periodic structure including a plurality of first convex The arrangement interval of the first convex portions is different depending on the periodic structure.

According to the photoelectric conversion element, the first Schottky junction is formed between the surface of the semiconductor layer and the conductive layer. In addition, a second Schottky junction is formed between one side surface of the convex layer and the end surface of the conductive layer on the convex layer side.
When light enters the photoelectric conversion element, photocarriers (electron-hole pairs) are generated by photoelectric conversion at the first and second Schottky junctions.
When the semiconductor layer is an n-type semiconductor, the electrons of the photocarrier move to the semiconductor layer side by the electric field of the depletion layer in the first Schottky junction. Along with this, electrons flow from the second electrode into the conductive layer. In the second Schottky junction, the electrons of the carriers move to the convex layer side and thus to the first electrode side. As a result, electrons flow toward the first electrode along the conductive layer. Thus, the first electrode becomes the cathode and the second electrode becomes the anode.
When the semiconductor layer is a p-type semiconductor, in the first Schottky junction, photocarrier holes move to the semiconductor layer side by the electric field of the depletion layer. Along with this, holes flow from the second electrode into the conductive layer. In the second Schottky junction, the positive holes of the carriers move to the convex layer side and thus to the first electrode side. As a result, holes flow along the conductive layer toward the first electrode. Thus, the first electrode becomes the anode and the second electrode becomes the cathode.
In this way, the electrode to be the anode and the electrode to be the cathode can be determined, and the direction of the photoinduced current can be controlled. Therefore, the current-voltage characteristic is reliably asymmetric between the positive side and the negative side, and a clean diode characteristic can be obtained. Furthermore, the sensitivity of photoelectric conversion can be increased by the metal nanostructure.

  One side surface and the opposite side surface of the convex layer may be substantially orthogonal to the surface of the semiconductor layer, or may be oblique to the surface of the semiconductor layer. One side surface and the opposite side surface of the convex layer may approach each other toward the projecting end of the convex layer, and the cross section of the convex layer may be trapezoidal or triangular. The protruding height of the convex layer is, for example, about 1 to 10 nm, and preferably about several nm (2 nm to 3 nm). The width between one side surface of the convex layer and the opposite side surface is, for example, 0. It is several mm to several mm. Preferably, the convex layer has a trapezoidal cross section, and the upper bottom surface has a width of about 1 mm.

The first electrode is preferably in ohmic contact with the semiconductor layer. Furthermore, it is more preferable that the first electrode is in ohmic contact with the opposite side surface of the convex layer.
It is preferable that the second electrode is in ohmic contact with the conductive layer. The second electrode is preferably not in direct contact with the semiconductor layer.

  Examples of the metal component constituting the conductive layer include Co, Fe, W, Ni, Al, and Ti. These metal elements listed have relatively high melting points and excellent mechanical properties at high temperatures. The conductive layer may be a metal, or a mixture or alloy of a metal and a semiconductor. Examples of the metal or semiconductor mixture or alloy include metal silicide. When the semiconductor layer is made of silicon, the conductive layer may be a metal silicide formed by diffusing the metal component and the surface layer portion of the semiconductor layer. The diffusion and thus silicidation can be performed, for example, by annealing. The metals listed above (Co, Fe, W, Ni, Al, Ti) are suitable for silicidation.

The metal nanostructure is preferably an aggregate of nanosized metal fine particles.
Plasmon resonance occurs when light enters the metal nanostructure. Thereby, the metal nanostructure contributes to the increase of the light-induced electric field.
As the metal constituting the metal nanostructure, Au, Ag, Pt, Cu, or Pd is preferably used. These listed metal elements have relatively high chemical stability, are not easily alloyed, and are not easily combined with a semiconductor such as Si. Therefore, surface plasmon can be formed reliably.

  The metal nanostructure is provided on the convex layer or the conductive layer. The metal nanostructure may be provided mainly on the convex layer, may be provided mainly on the conductive layer, or may be provided across the convex layer and the conductive layer. It is more preferable that the metal nanostructure is widely distributed on the convex layer or the conductive layer. When the metal nanostructure is provided on the convex layer, the carrier can be promoted to move to the side of the convex layer and thus to the side of the first electrode in the second Schottky junction. Therefore, the rectifying action of the second Schottky junction can be enhanced. Providing the metal nanostructure on the conductive layer can promote the movement of carriers toward the semiconductor layer at the first Schottky junction. Therefore, the photo-induced current can be reliably increased.

  In the metal nanostructure, it is preferable that the periodic structure has a random period. It is preferable that the period of the periodic structure is changed. That is, it is preferable that the arrangement interval of the first protrusions differs according to the periodic structure. Thereby, it can respond to the light of a different wavelength according to a periodic structure. Therefore, the wavelength range in which the metal nanostructure can be sensitive as a whole can be widened. Therefore, it is possible to provide a photoelectric conversion element that can cope with a wide band extending from the visible light region to the infrared light region.

The arrangement interval (period) of the first protrusions is preferably about 0.1 to 1 times the wavelength λ of the incident light, and more preferably about 0.1 times the wavelength λ. Alternatively, the arrangement interval (period) of the first protrusions is preferably about 0.1 to 1 times the sensitive wavelength of the Schottky element formed by the semiconductor layer (including the protrusion layer) and the conductive layer. The periodic structure is sensitively sensitive to incident light having a wavelength λ of about 1 to 10 times (particularly about 10 times the period) of the period of the first convex portion constituting the periodic structure, and plasmon resonance. This contributes to the amplification of the light-induced electric field. It is preferable that the period of the periodic structure of the n-type element in the semiconductor layer (arrangement interval of the first protrusions) is smaller than the period of the periodic structure of the p-type element in the semiconductor layer (arrangement interval of the first protrusions). In an element having an n-type semiconductor layer, the arrangement interval (period) of the first protrusions is more preferably about 100 nm or less. Thereby, it can have a favorable sensitivity with respect to the light of the infrared light range-visible light range whose wavelength is about 1 micrometer or less. In an element having a p-type semiconductor layer, the arrangement interval (period) of the first protrusions is more preferably about 150 nm or less. Thereby, it can have a favorable sensitivity with respect to the infrared light whose wavelength is about 1 micrometer-4 micrometers.
The protruding height of the first convex portion is preferably about 10 nm to 20 nm.

  At least one of the periodic structures is about 0.1 to 1 times as large as any wavelength within a certain wavelength range (preferably from the visible light region to the infrared light region) (particularly about 0.1 times the size). ) Is preferably provided. Thus, if the incident light is included in the wavelength range, at least one periodic structure of the metal nanostructure can be sensitive to the incident light.

The metal nanostructure further includes a plurality of second protrusions protruding larger than the first protrusions, the second protrusions are dispersed from each other, and each second protrusion is one of the periodic structures. It is preferable that they are arranged on top of each other or close to each other.
When light enters the metal nanostructure, near-field light is generated around the second convex portion. Due to the synergistic effect of this near-field light and plasmon resonance due to the periodic structure, a photo-induced electric field can be amplified with high sensitivity and output (K. Kobayashi, et.al., Progress in Nano-Electro-Optecs I. ed. M See Ohtsu, p.119 (Sptinger-Verlag, Berlin, 2003). Even if the incident light is weak, the photovoltaic force can be generated with high sensitivity.

The protrusion height of the second protrusion is preferably about 50 nm to 200 nm.
The dispersion interval of the second protrusions (the distance between adjacent second protrusions) is preferably greater than the wavelength of incident light, and is greater than the sensitive wavelength of a Schottky element formed by the semiconductor layer and the conductive layer. preferable.
It is preferable that the dispersion interval of the 2nd convex part of the element whose semiconductor layer is n type is smaller than the dispersion interval of the 2nd convex part of the element whose semiconductor layer is p type. For example, when the semiconductor layer is n-type, the dispersion interval of the second protrusions is preferably 1 μm or more, and more preferably about 2 μm to 3 μm. When the semiconductor layer is p-type, it is preferable that the dispersion interval of the second protrusions is about 3 μm to 5 μm. Thereby, it can avoid that the adjacent 2nd convex part interferes and weakens an electric field.
The upper limit of the dispersion interval of the second protrusions is preferably about 3 μm to 5 μm for the n-type, and preferably about 5 μm to 6 μm for the p-type. As a result, the existence density of the second protrusions can be ensured, the number of periodic structures that can cause interaction with the second protrusions can be ensured, and the sensitive band can be reliably widened.

  An insulator such as a carbon compound may be mixed in the metal nanostructure to form an MIM structure.

The method for producing a photoelectric conversion element according to the present invention is as follows.
A convex layer forming step of forming a convex layer on the surface by etching the surface of the semiconductor layer;
A conductive layer forming step of laminating the conductive layer on the surface so as to be in contact with one side surface of the convex layer;
An electrode forming step in which a first electrode is provided on the surface so as to contact a side surface opposite to the one side surface of the convex layer, and a second electrode is provided on the conductive layer;
By laminating a metal on the convex layer or the conductive layer and heat-treating, a plurality of (preferably many) periodic structures are included, and each periodic structure includes a plurality of first convex portions, and the first convex portions A nanostructure forming step of forming metal nanostructures having different arrangement intervals according to the periodic structure;
It is the feature which does not claim including.
The claimed feature of the method for producing a photoelectric conversion element according to the present invention is that a surface of the semiconductor layer is etched to form a convex layer on the surface, and a conductive layer is formed on the convex layer. Conductive layer forming step of laminating on the surface so as to make Schottky contact with the side surface and the surface, and ohmic contact with the side surface opposite to the one side surface of the convex layer and the surface An electrode forming step of providing the second electrode on the conductive layer provided on the surface, and laminating a metal on the convex layer or the conductive layer and heat-treating, thereby including a plurality of periodic structures, And a nanostructure forming step that includes a plurality of first protrusions, and a metal nanostructure in which an interval between the first protrusions is different depending on the periodic structure.

After the first electrode is coated on the surface, heat treatment is performed at a first temperature, and thereafter, after the metal component of the conductive layer is coated on the surface, heat treatment is performed at a second temperature lower than the first temperature. Is preferred. Thereby, it can prevent that the junction part of a conductive layer and a semiconductor layer is alloyed by the heat processing of the said electrode formation process, and can obtain a favorable Schottky junction part.
In the electrode forming step, it is not necessary to simultaneously form the first electrode and the second electrode. After forming the first electrode, another process (such as a conductive layer forming process or a nanostructure forming process) may be performed, and then the second electrode may be formed.
It is preferable to heat-treat after coating the first electrode on the surface. The first electrode and the semiconductor layer can be in ohmic contact by the heat treatment.
In the conductive layer forming step, heat treatment may be performed after the metal component of the conductive layer is coated on the surface. Thereby, a conductive layer formed by diffusing the metal component and the surface component of the semiconductor layer can be formed, and the conductive layer and the semiconductor layer can be in Schottky contact.

  In the nanostructure forming step, after the metal nanostructure base is disposed on the convex layer or the conductive layer, the base is diffused along the surface of the convex layer or the surface of the conductive layer by heat treatment. Preferably, the metal nanostructure is naturally formed. An annealing treatment is preferably applied as the heat treatment. The shape or property of the original is not particularly limited, and may be any of a thin film shape, a small piece shape, a small lump shape, a granular shape, a powder shape, a colloidal shape, a fiber shape, a wire shape, a dot shape, and other shapes or It may be a property. By the heat treatment, the base material is diffused so as to branch in multiple stages or multiple, and becomes an aggregate of a fractal structure. Thereby, the metal nanostructure can be naturally formed. Sub-micron or nano-order irregularities are formed on the surface of the metal nanostructure. The surface of the metal nanostructure includes a large number of protrusions protruding in the stacking direction and has a cluster shape. The multiple convex portions include the first convex portion and the second convex portion. Each of the periodic structures is constituted by a plurality of convex portions arranged at substantially equal intervals among the plurality of convex portions.

  An annealing treatment is preferably applied as the heat treatment in each step. The temperature condition for the annealing process in the electrode forming step is preferably about 600 ° C. to 1000 ° C., for example, and more preferably about 800 ° C. The temperature condition of the annealing process in the conductive layer forming step is, for example, about 400 ° C. to 800 ° C., and more preferably about 600 ° C.

  The heat treatment in the nanostructure forming step is preferably performed at a lower temperature than the heat treatment in the electrode forming step. An annealing treatment is preferably applied as the heat treatment in the nanostructure forming step. The annealing temperature condition in the nanostructure forming step is, for example, about 400 ° C. to 800 ° C., and preferably about 600 ° C.

The heat treatment in the electrode formation step, the heat treatment in the conductive layer formation step, and the heat treatment in the nanostructure formation step may be performed simultaneously by a single common heat treatment operation.
The heat treatment in the electrode forming step and the heat treatment in the conductive layer forming step may be performed simultaneously by a single common heat treatment operation.
The heat treatment in the conductive layer formation step and the heat treatment in the nanostructure formation step may be performed simultaneously by a single common heat treatment operation.
The heat treatment in the electrode formation step and the heat treatment in the nanostructure formation step may be performed simultaneously by a single common heat treatment operation.

  Either or both of the pair of electrodes may be used as a metal raw material of the metal nanostructure. The metal constituting the electrode may be diffused around the electrode in a cluster shape or a fractal shape by annealing. Then, the metal nanostructure can be formed in the vicinity of the electrode. In this case, the electrode and the metal nanostructure include the same metal component.

  A nanostructure made of a semiconductor having sensitivity in the ultraviolet region or infrared region may be further provided on the surface of the photoelectric conversion element. In particular, when the semiconductor layer is an n-type semiconductor, it is preferable to provide a nanostructure made of a semiconductor having sensitivity in the ultraviolet region on the surface of the photoelectric conversion element. A semiconductor having sensitivity in the ultraviolet region refers to a semiconductor having a property that carriers are excited when irradiated with ultraviolet light having a wavelength of 0.4 μm or less. As such a semiconductor, for example, zinc oxide (ZnO) which is an n-type semiconductor can be given, and in addition, n-type gallium nitride (n-GaN) and the like can be mentioned. When the semiconductor layer is a p-type semiconductor, it is preferable to provide a nanostructure made of a semiconductor having sensitivity in the infrared region on the surface of the photoelectric conversion element. A semiconductor having sensitivity in the infrared region refers to a semiconductor having a property in which carriers are excited when irradiated with infrared light having a wavelength of, for example, 0.7 μm or more. Examples of such a semiconductor include p-type gallium nitride (p-GaN) and carbon. Examples of nanostructures include nanowires, nanotubes, nanoneedles, and nanorods. The nanostructure can increase the sensitivity of photoelectric conversion. When the nanostructure is made of a semiconductor having sensitivity in the ultraviolet region, the photoelectric conversion sensitivity to incident light in the ultraviolet region can be increased. When the nanostructure is made of a semiconductor having sensitivity in the infrared region, the photoelectric conversion sensitivity to incident light in the infrared region can be increased. By configuring the nanostructure with nanowires, nanotubes, or the like, the quantum efficiency can be increased, and the sensitivity of the photoelectric conversion element can be reliably increased.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode used as the positive electrode of the photoelectric conversion element and the electrode used as a negative electrode can be determined reliably, and an asymmetric diode characteristic can be acquired.

FIG. 1 is a cross-sectional view showing a schematic structure of a photoelectric conversion element according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a convex layer forming step in the method for manufacturing a photoelectric conversion element. FIG. 3 is a cross-sectional view showing a step of forming an ohmic contact promoting layer of the first electrode in the method for manufacturing a photoelectric conversion element. FIG. 4 is a cross-sectional view showing a process of coating the first electrode and the material of the metal nanostructure in the method for manufacturing a photoelectric conversion element. FIG. 5 is a cross-sectional view showing a step of coating the metal component of the conductive layer in the method for manufacturing a photoelectric conversion element. FIG. 6 is a cross-sectional view showing a step of forming a second electrode in the method for manufacturing a photoelectric conversion element. FIG. 7 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to the second embodiment of the present invention. FIG. 8 is a cross-sectional view illustrating a schematic configuration of a photoelectric conversion element according to the third embodiment of the present invention. FIG. 9 is a cross-sectional view showing a convex layer forming step in the method of manufacturing a photoelectric conversion element according to the third embodiment. FIG. 10 is a cross-sectional view illustrating a process of coating the first electrode material in the method for manufacturing a photoelectric conversion element according to the third embodiment. FIG. 11 is a cross-sectional view illustrating a process of coating a metal component of a conductive layer in the method for manufacturing a photoelectric conversion element according to the third embodiment. FIG. 12 is a cross-sectional view showing a step of arranging the metal nanostructure base and the second electrode in the method of manufacturing a photoelectric conversion element according to the third embodiment. FIG. 13A is an image obtained by observing one part of the surface of the metal nanostructure in Example 1 with an SEM (scanning electron microscope). FIG.13 (b) is the image which observed the location different from Fig.13 (a) by the SEM of the surface of the metal nanostructure in Example 1. FIG. FIG. 14 is a stereoscopic image obtained by observing a place on the surface of the metal nanostructure in Example 1 with an AFM (atomic force microscope). FIG. 15 is an explanatory diagram of the stereoscopic image of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a photoelectric conversion element 1 according to the first embodiment of the present invention. The photoelectric conversion element 1 includes a semiconductor layer 10, a pair of electrodes 21 and 22, a metal nanostructure 30, and a conductive layer 40.

  As shown in FIG. 1, the semiconductor layer 10 is composed of silicon (Si). However, the present invention is not limited to this, and the semiconductor layer 10 may be composed of another semiconductor such as Ge or GaAs. The semiconductor layer 10 is doped with an n-type impurity such as P (phosphorus). The semiconductor layer 10 constitutes an n-type semiconductor.

  As shown in FIG. 1, the semiconductor layer 10 also serves as a substrate for the photoelectric conversion element 1. The semiconductor layer 10 is composed of a silicon substrate. The silicon substrate is doped with n-type impurities. A silicon wafer or the like can be used as the silicon substrate. The silicon substrate ensures the shape retention and mechanical rigidity of the photoelectric conversion element 1. The substrate may be provided separately from the semiconductor layer 10. For example, the n-type semiconductor layer 10 may be coated on a substrate made of glass or a resin film. The n-type semiconductor layer 10 may be formed on the surface of the separate substrate by CVD or the like.

  A convex layer 11 is formed on the surface of the semiconductor layer 10. The convex layer 11 protrudes in the thickness direction of the semiconductor layer 10 (the stacking direction of the elements 1). The convex layer 11 is constituted by a part of the semiconductor layer 10 and is integrated with the semiconductor layer 10. Both side surfaces of the convex layer 11 in the width direction (left and right in FIG. 1) are inclined with respect to the surface of the semiconductor layer 10. Note that the both side surfaces may be substantially vertical.

  The protruding height of the convex layer 11 is, for example, about 1 nm to 10 nm, and preferably about several nm. The width dimension (left and right dimensions in FIG. 1) of the convex layer 11 is, for example, 0. It is several mm to several mm. Preferably, the width of the upper surface (projecting end surface) of the convex layer 11 is about 1 mm. In the figure, the protruding height (vertical dimension) of the convex layer 11 is exaggerated with respect to the width (horizontal dimension).

  The conductive layer 40 is laminated on the surface portion of the semiconductor layer 10 on one side (left side in FIG. 1) from the convex layer 11. The bottom surface (lower surface) of the conductive layer 40 and the semiconductor layer 10 are in Schottky contact. A first Schottky junction 41 is formed between the conductive layer 40 and the semiconductor layer 10. Furthermore, the right end surface (convex layer side end surface) of the conductive layer 40 is joined to the left side surface (one side surface) of the convex layer 11 and is in Schottky contact. A second Schottky junction 42 is formed between the conductive layer 40 and the convex layer 11.

The conductive layer 40 is made of metal silicide and has conductivity. The silicon of the surface layer of the semiconductor layer 10 is self-organized and constitutes the silicon component of the conductive layer 40. Examples of the metal component constituting the conductive layer 40 include Co, Fe, W, Ni, Al, Ti, and the like. However, the metal component is not limited to these. Here, Co is used as the metal component of the conductive layer 40. Conductive layer 40 is formed by CoSix, preferably are composed of CoSi _2. Thereby, good Schottky interfaces are formed between the conductive layer 40 and the semiconductor layer 10 and between the conductive layer 40 and the convex layer 11. The conductive layer 40 may be composed of only a metal component. The thickness of the conductive layer 40 is approximately the same as the protruding height of the convex layer 11. The upper surface (front side surface) of the conductive layer 40 is substantially flush with the upper surface (projecting end surface) of the convex layer 11. Note that the upper surface of the conductive layer 40 may protrude from the convex layer 11 or may be recessed. For example, the thickness of the conductive layer 40 is about 1 nm to 10 nm, preferably about several nm. The width dimension (dimension in the left-right direction) of the conductive layer 40 is, for example, about 3 mm to 5 mm. However, it is not restricted to this, The said width dimension may be 3 mm or less, and may be 5 mm or more.
In the drawing, the thickness of the conductive layer 40 and the protruding amount of the convex layer 11 are exaggerated with respect to the thickness of the semiconductor layer 10, the electrodes 21, 22, the metal nanostructure 30, and the like.

  The first electrode 21 is arranged on the right side of the convex layer 11 on the surface of the semiconductor layer 10, that is, on the opposite side of the conductive layer 40 with the convex layer 11 in between. The first electrode 21 is in contact with the surface of the semiconductor layer 10 and is also in contact with the right side surface (opposite side surface) of the convex layer 11.

  The surface portion where the electrode 21 is disposed on the surface of the semiconductor layer 10 is slightly depressed (for example, about 1 nm or less) downward from the portion where the conductive layer 40 is disposed. This recessed portion is continuous with the right side surface (opposite side surface) of the convex layer 11. The bottom portion of the first electrode 21 is in ohmic contact with the recessed portion of the semiconductor layer 10. Further, the first electrode 21 is in ohmic contact with the right side surface (opposite side surface) of the convex layer 11.

  The second electrode 22 is disposed on the conductive layer 40 so as to be separated from the convex layer 11 on the left side (one side).

  Each of the electrodes 21 and 22 is made of a metal such as Au, Ag, Pt, Cu, or Pd. Here, Au is used as the metal constituting the electrodes 21 and 22. The two electrodes 21 and 22 may be composed of different metal components.

  The ohmic junction between the first electrode 21 and the semiconductor layer 10 (including the convex layer 11) is made of an alloy of Au, Co, and Si, and preferably made of an Au-rich alloy.

  Metal nanostructures 30 are laminated on the upper surface of the convex layer 11. The metal nanostructure 30 is provided in the vicinity of the first electrode 21.

  The metal nanostructure 30 is composed mainly of a metal such as Au, Ag, Pt, Cu, or Pd. Here, Au is used as the metal constituting the metal nanostructure 30. The metal nanostructure 30 is an Au-rich structure. Therefore, the metal nanostructure 30 is composed of the same metal component as the electrode 21. The metal nanostructure 30 is integrally connected to the first electrode 21.

  The metal component constituting the metal nanostructure 30 and the metal component constituting the electrodes 21 and 22 may be different from each other. An insulator such as a carbon compound may be mixed in the metal constituting the metal nanostructure 30, and the metal nanostructure 30 has a metal-insulator-metal (MIM) metal-insulator-metal (MIM) structure. It may be.

  The surface of the metal nanostructure 30 has submicron or nano-order irregularities. Specifically, the metal nanostructure 30 has a structure in which metals (Au) are gathered in a cluster shape or a fractal shape (see FIGS. 13 and 14). The aggregate of the metal nanostructures 30 includes a large number or innumerable protrusions protruding in the thickness direction (upward) of the element 1. These convex portions are gathered in a cluster. Alternatively, it has a fractal structure in which an aggregate of Au nanoparticles is diffused so as to branch multiple times. The metal nanostructure 30 includes a large number of first protrusions 31 and second protrusions 32. A part of the many convex parts constitutes the first convex part 31, and the other part constitutes the second convex part 32.

  The metal nanostructure 30 has at least one periodic structure 30. Preferably, the metal nanostructure 30 has a large number or innumerable (plural) periodic structures 33. Each periodic structure 33 is constituted by several (plural) convex portions 31, 31... Adjacent to each other in the large number of convex portions of the metal nanostructure 30. The first protrusions 31, 31... Constituting each periodic structure 33 are arranged at a certain interval (period) along the surface direction of the element 1 (direction orthogonal to the stacking direction). The arrangement interval (period) of the first convex portions 31 differs depending on the periodic structure 33. The arrangement interval (period) of the first protrusions 31 in these periodic structures 33 is preferably about several tens of nm to several μm, and more preferably about 40 nm to 100 nm. This arrangement interval (period) is preferably about 0.1 to 1 times the wavelength of the incident light L, and more preferably about 0.1 times. Further, the arrangement interval (period) is about 0.1 to 1 times the sensitive wavelength (visible light region to infrared light region) of the Schottky element composed of the n-type semiconductor layer 10 and the conductive layer 40. It is preferable. The metal nanostructure 30 preferably includes at least one periodic structure having an arrangement interval that is approximately 0.1 to 1 times the arbitrary wavelength within the sensitive region of the Schottky element.

  Furthermore, a plurality of second convex portions 32 are arranged in the metal nanostructure 30 in a dispersed manner. Each 2nd convex part 32 is arrange | positioned so that one of the periodic structures 33 may overlap. Or each 2nd convex part 32 is arrange | positioned in the vicinity of one of the periodic structures 33. FIG. The second convex portion 32 has a protruding height larger than that of the first convex portion 31 and has a sharpness (ratio of the protruding height and the width of the bottom portion) larger than that of the first convex portion 31. The protruding height of the second convex portion 32 is preferably about 50 nm to 200 nm. The dispersion interval between the second convex portions 32 is preferably larger than the wavelength of the incident light. For example, the dispersion interval is preferably 1 μm or more, and preferably about 2 μm to 3 μm. The upper limit of the dispersion interval between the second convex portions 32 is preferably about 3 μm to 5 μm.

A method for manufacturing the photoelectric conversion element 1 will be described.
A P (phosphorus) -doped n-type silicon substrate is prepared as the semiconductor layer 10. As shown in FIG. 2, the surface of the semiconductor layer 10 is etched to form the convex layer 11 (convex layer forming step). Further, the etching is performed so that the right side portion where the electrode 21 on the surface of the semiconductor layer 10 is to be disposed is slightly recessed (about 1 nm or less) from the left side portion of the convex layer 11. Etching may be performed by wet etching or dry etching.

  As shown in FIG. 3, a film 25 made of Co is coated on the recessed portion on the right side of the semiconductor layer 10. The Co film 25 also coats the right side surface (one side surface) of the convex layer 11. The coating of the Co film 25 can be performed by various film forming methods such as sputtering and vapor deposition. The thickness of the Co film 25 is preferably 1 nm or less. It is preferable that the upper surface of the Co film 25 be substantially flush with the central portion of the surface of the semiconductor layer.

  Next, as shown in FIG. 4, a film 26 made of Au serving as a first electrode and a metal nanostructure is stacked on the Co film 25. The Au film 26 is in contact with the right side surface (one side surface) of the convex layer 11. Furthermore, the Au film 26 is also coated on at least a part of the upper surface of the convex layer 11. The Au film 26 can be coated by various film forming methods such as sputtering and vapor deposition.

  Next, as shown in FIG. 5, a film 43 made of Co is formed on the surface portion of the semiconductor layer 10 on the left side of the convex layer 11. The coating of the Co film 43 can be performed by various film forming methods such as sputtering and vapor deposition.

  Next, as shown in FIG. 6, the second electrode 22 made of Au is laminated on the left side of the surface of the Co film 43 (second electrode formation step). The coating of the second electrode 22 can be performed by various film forming methods such as sputtering and vapor deposition. Note that the step of forming the second electrode may be performed after the next annealing treatment.

Next, the substrate 10 is put in an annealing treatment tank, and annealing treatment (heat treatment) is performed. The temperature condition for the annealing treatment is preferably about 400 ° C. to 800 ° C., more preferably about 600 ° C. The annealing treatment is performed in a 100% inert gas atmosphere as much as possible. As the inert gas for the annealing treatment, a rare gas such as He, Ar, Ne or the like can be used, and N ₂ may also be used. The pressure condition for the annealing treatment is in the vicinity of atmospheric pressure, for example, about several Pa lower than atmospheric pressure.

  By the annealing process, the Au film 26 is in ohmic contact with the semiconductor layer 10 (including the convex layer 11) through the thin Co film 25 to form the first electrode 21 (first electrode forming step). At the junction between the first electrode 21 and the semiconductor layer 10, Au and Si are diffused and alloyed with each other across Co. Thereby, the first electrode 21 and the semiconductor layer 10 can be reliably brought into ohmic contact.

Further, Si of the semiconductor layer 10 diffuses into the Co film 43 by the annealing treatment. Thereby, the conductive layer 40 made of CoSix, preferably CoSi ₂ can be formed (conductive layer forming step). A Schottky junction 41 can be formed by the Schottky junction between the bottom surface of the conductive layer 40 and the semiconductor layer 10. And the Schottky junction part 42 can be formed because the right end surface (convex layer side end surface) of the conductive layer 40 and the left side surface (other side surface) of the convex layer 11 join. By setting the annealing temperature to about 600 ° C., the component of the conductive layer 40 can be made of CoSi ₂ . Therefore, the semiconductor layer 10 and the conductive layer 40 can be securely Schottky joined, and good Schottky junctions 41 and 42 can be obtained.

  Further, as shown in FIG. 1, the fine particles of the Au film 26 are diffused along the upper surface of the convex layer 11 by the annealing treatment so as to form clusters or fractals. That is, Au fine particles diffuse so as to branch into multiple, and become an aggregate of a fractal structure. The surface of the aggregate has sub-micron or nano-order irregularities and is clustered. Thereby, the metal nanostructure 30 can be naturally formed (nanostructure formation process).

The operation of the photoelectric conversion element 1 will be described.
When light having a wavelength in the visible region to the infrared region (specifically, about 0.4 μm to 2 μm) is incident on the photoelectric conversion element 1, the first Schottky junction between the bottom surface of the conductive layer 40 and the semiconductor layer 10. In the part 41, photocarriers are generated by photoelectric conversion. In addition, photocarriers (electron-hole pairs) are also generated by photoelectric conversion at the second Schottky junction 42 between the right end surface of the conductive layer 40 and the convex layer 11.

  In the first Schottky junction 41, the electrons of the photocarrier move to the semiconductor layer 10 side by the electric field of the depletion layer. Along with this, electrons flow from the second electrode 22 into the conductive layer 40. In the second Schottky junction 42, the electrons of carriers move to the convex layer 11 side and thus to the first electrode 21 side. Thereby, electrons flow along the conductive layer 40 toward the first electrode 21. Accordingly, the first electrode 21 becomes a cathode and the second electrode 22 becomes an anode. In this way, the electrode 22 that becomes the anode and the electrode 21 that becomes the cathode can be determined, and the direction of the photoinduced current can be controlled. Therefore, the current-voltage characteristic can be reliably asymmetrical between the positive side and the negative side, and a clean diode characteristic can be obtained.

  Furthermore, the sensitivity of photoelectric conversion can be increased by the metal nanostructure 30 on the surface of the element 1. Moreover, the wavelength range of light that can be photoelectrically converted can be expanded by the metal nanostructure 30.

  The operation of the metal nanostructure 30 will be described in detail. Plasmons are localized on the surface of the Au nanoparticle constituting the metal nanostructure 30. The surface plasmon and incident light resonate to generate a large electric field. The periodic structure 33 of the metal nanostructure 30 enhances the sensitivity of photoelectric conversion with respect to incident light having a wavelength corresponding to the period (the arrangement interval of the first protrusions 31). That is, the periodic structure 33 is sensitively sensitive to incident light having a wavelength of about 1 to 10 times, particularly about 10 times the period, and causes plasmon resonance. Since the period of the 1st convex part 31 changes according to the periodic structure 33, the wavelength range which the metal nanostructure 30 can respond can be widened. Further, near-field light is generated around the second convex portion 32. A large light-induced electric field can be generated by a synergistic effect of the near-field light and the plasmon resonance by the periodic structure 33. As a result, it is possible to provide the photoelectric conversion element 1 that is sensitive to a wide band extending from the visible light region to the infrared light region. Even if the incident light is weak, the photovoltaic force can be generated with high sensitivity. By making the dispersion interval of the second convex portions 32 larger than the wavelength of incident light (visible light region to infrared light region), preferably 1 μm or more, more preferably 2 μm to 3 μm, adjacent second convex portions 32. , 32 can interfere with each other and weaken the electric field. By setting the upper limit of the dispersion interval of the second convex portions 32 to 3 μm to 5 μm, the existence density of the second convex portions 32 can be maintained high, and the number of the periodic structures 33 that can cause the interaction with the second convex portions 32 is increased. Can be secured, and the sensitive band can be reliably widened.

When the photoelectric conversion element 1 is used as a light detection sensor, it is possible to provide a light detection sensor having excellent sensitivity characteristics and capable of detecting broadband light.
When using the photoelectric conversion element 1 as a solar cell, it is possible to provide a solar cell that can be used for electric power by photoelectrically converting sunlight in a wide band. Sufficiently large electric power can be obtained not only in fine weather but also in cloudy weather. Furthermore, even after sunset, power can be obtained by photoelectrically converting infrared light scattered in the atmosphere. By absorbing infrared light, thermal conversion of infrared light can be prevented, and it can also be expected as a measure against global warming.

Since the pair of electrodes 21 and 22 are disposed on the same surface (upper surface) of the element 1, the photoelectric conversion element 1 can be thinned.
Since the photo-induced electric field is formed along the surface of the element 1, carriers are accelerated along the surface of the element 1 and can move at a high speed of the compound semiconductor level. Therefore, it is possible to realize an ultra-high-speed imaging sensor or a photodetection sensor that can cope with light modulation waves in the GHz to THz band. Since the photoelectric conversion element 1 is a thin film type, it can also be used as a CCD sensor array.

Next, another embodiment of the present invention will be described. In the following embodiments, the same reference numerals are attached to the drawings for the same contents as those already described, and the description thereof is omitted.
FIG. 7 shows a second embodiment of the present invention. A photoelectric conversion element 1A according to the second embodiment includes a p-type semiconductor layer 10A instead of the n-type semiconductor layer 10 of the first embodiment. The p-type semiconductor layer 10A is made of p-type silicon doped with a p-type impurity such as B (boron). The p-type semiconductor layer 10A is the same as the first embodiment in that it also serves as a substrate.

  The arrangement interval (period) of the first protrusions 31 in the periodic structure 33 of the p-type element 1 </ b> A is preferably slightly larger than that of the n-type element 1. For example, the arrangement interval (period) is more preferably about 60 nm to 150 nm. The dispersion interval of the second convex portions 32 in the periodic structure 33 of the p-type element 1A is preferably slightly larger than that of the n-type element 1. For example, the dispersion interval is preferably about 3 μm to 5 μm, and the upper limit is preferably about 5 μm to 6 μm.

  The sensitive region of the p-type photoelectric conversion element 1A is shifted to a longer wavelength side than the sensitive region of the n-type photoelectric conversion element 1, and is sensitive to light in the infrared region (specifically, a wavelength of about 1 μm to 4 μm). . When light in the infrared region is incident on the photoelectric conversion element 1A, photocarriers are generated by photoelectric conversion at the first Schottky junction 41 between the bottom surface of the conductive layer 40 and the semiconductor layer 10A. In addition, photocarriers (electron-hole pairs) are also generated by photoelectric conversion at the second Schottky junction 42 between the right end surface (convex layer side end surface) of the conductive layer 40 and the left side surface (one side surface) of the convex layer 11. Occur.

  In the first Schottky junction 41, the holes of the photocarrier move to the semiconductor layer 10 side by the electric field of the depletion layer. Along with this, holes flow from the second electrode 22 into the conductive layer 40. In the second Schottky junction 42, the carrier holes move toward the convex layer 11 and thus toward the first electrode 21. As a result, holes flow along the conductive layer 40 toward the first electrode 21. Therefore, the 1st electrode 21 becomes an anode and the 2nd electrode 22 becomes a cathode. In this way, the electrode 21 serving as the anode and the electrode 22 serving as the cathode can be determined, and the direction of the photoinduced current can be controlled. Therefore, the current-voltage characteristic can be reliably asymmetrical between the positive side and the negative side, and a clean diode characteristic can be obtained.

  FIG. 8 shows a photoelectric conversion element 1B according to the third embodiment of the present invention. In the third embodiment, the metal nanostructure 30 extends from the convex layer 11 to the conductive layer 40 and is widely distributed not only on the upper surface of the convex layer 11 but also on the surface of the conductive layer 40. The electrode 21 arrangement portion on the right side of the surface of the semiconductor layer 10 is flush with the conductive layer 40 arrangement portion (same height), but may be slightly recessed (about 1 nm) as in the first embodiment. Good.

A method for manufacturing the photoelectric conversion element 1B of the third embodiment will be described.
[Convex layer forming process]
As shown in FIG. 9, the surface of the semiconductor layer 10 is etched to form the convex layer 11. In the third embodiment, there is no need to further etch the right side portion of the convex layer 11 on the surface of the semiconductor layer 10.

[First electrode formation process]
In the third embodiment, the coating of the Co film 25 (see FIG. 3) on the left side of the convex layer 11 on the surface of the semiconductor layer 10 can be omitted. As shown in FIG. 10, an Au film 26 is directly laminated on the right portion of the semiconductor layer 10 by sputtering, vapor deposition, or the like. The Au film 26 may be coated so as to be in contact with the right side portion of the surface of the semiconductor layer 10 and the right side surface of the convex layer 11, and does not have to cover the upper surface of the convex layer 11.

  Next, the substrate 10 is put in an annealing treatment tank, and annealing treatment (heat treatment) is performed. The annealing temperature condition (first temperature) is about 800 ° C. Other conditions for the annealing treatment are the same as those in the first embodiment. As a result, the Au film 26 is in ohmic contact with the semiconductor layer 10 (including the convex layer 11) and becomes the first electrode 21. At the junction between the first electrode 21 and the semiconductor layer 10 (including the convex layer 11), Au and Si can be diffused and alloyed with each other, so that the electrode 21 and the semiconductor layer 10 (including the convex layer 11) can be reliably connected. Can make ohmic contact.

[Conductive layer forming step]
Next, as shown in FIG. 11, a Co film 43 serving as a metal component of the conductive layer 40 is coated on the left side of the convex layer 11 on the surface of the semiconductor layer 10 by sputtering, vapor deposition, or the like.

[Second electrode forming step]
Next, as shown in FIG. 12, the second electrode 22 made of Au is stacked on the left side of the surface of the Co film 43. The coating of the second electrode 22 can be performed by various film forming methods such as sputtering and vapor deposition.

[Nanostructure formation process]
In addition, the base material 34 (Au) to be the metal nanostructure 30 is disposed on the convex layer 11 and the Co film 43. The shape or property of the active material 34 (Au) is not particularly limited, and may be any of a thin film shape, a small piece shape, a small lump shape, a granular shape, a powder shape, a colloidal shape, a fiber shape, a wire shape, and a dot shape. The shape or property may be used. The base body 34 is preferably arranged so as to be dispersed and interspersed in a portion between the first electrode 21 and the second electrode 22 on the upper surface of the convex layer 11 and the Co film 43. The width W of each original material 24 is preferably about several hundred nm to 1 mm. The height H of each original material 24 is preferably about several hundred nm to 1 mm. The width D of the gap between the adjacent original materials 34 is preferably about several hundred nm to 1 mm. The coating of the original material 34 can be performed by various film forming methods such as sputtering and vapor deposition. The second electrode 22 and the original material 34 may be formed simultaneously.

Next, the substrate 10 is again placed in the annealing bath, and annealing (heat treatment) is performed. The temperature condition (second temperature) of the annealing treatment at this time is preferably lower than the annealing temperature (800 ° C.) in the electrode forming step, more preferably about 600 ° C. Other conditions for the annealing treatment are the same as those in the first embodiment. As a result, the conductive layer 40 made of CoSix, preferably CoSi ₂ can be reliably formed, and the first and second Schottky junctions 41 and 42 can be formed. In addition, the metal nanostructure 30 can be naturally formed by diffusing the fine particles of the base material (Au) so as to form clusters or fractals.

  In the third embodiment, the annealing process is performed in two steps, so that the first annealing process is performed at a temperature suitable for ohmic contact between the first electrode 21 and the semiconductor layer 10 (including the convex layer 11). In the second annealing treatment, the temperature can be set to a temperature suitable for making the Schottky contact between the conductive layer 40 and the semiconductor layer 10 and the temperature suitable for obtaining the cluster-like or fractal-shaped metal nanostructure 30. By coating the conductive layer 40 after the formation of the first electrode 21, it is possible to prevent the bonding portion between the conductive layer 40 and the semiconductor layer 10 from being alloyed by the annealing process of the first electrode formation step, and to ensure the Schottky interface. Can be formed.

The present invention is not limited to the above-described embodiment, and various modifications can be made without changing the gist of the invention.
For example, the metal nanostructure 30 may be provided only on the surface of the conductive layer 40. The metal nanostructure 30 may be stacked only on a part of the conductive layer 40.
A semiconductor nanostructure may be provided on the metal nanostructure 30. When the semiconductor layer 10 of the element 1 is n-type, the semiconductor nanostructure is preferably n-type, and more preferably a semiconductor nanostructure having sensitivity in the ultraviolet region. Examples of the component of the semiconductor nanostructure include ZnO, and other examples include n-type GaN. When the semiconductor layer 10A of the element 1A is p-type, the semiconductor nanostructure is preferably p-type, and more preferably a semiconductor nanostructure having sensitivity in the infrared region. Examples of the component of the semiconductor nanostructure include p-type GaN and C. Both the n-type semiconductor nanostructure and the p-type semiconductor nanostructure may be provided in one photoelectric conversion element 1, 1 </ b> A. The semiconductor nanostructure has a form such as a nanowire, a nanoneedle, a nanotube, or a nanorod, and is preferably protruded from the surface of the metal nanostructure 30. Such a semiconductor nanostructure can be formed by CVD, PVD, sol-gel method or the like.
The metal component constituting the metal nanostructure 30 is not limited to Au, and may be Ag, Pt, Cu, Pd, or the like.
The metal component constituting the conductive layer 40 is not limited to Co, but may be Fe, W, Ni, Al, Ti, or the like.
A plurality of embodiments may be combined with each other. For example, in the third embodiment, a p-type semiconductor layer 10A similar to the second embodiment may be used instead of the n-type semiconductor layer 10.
In the manufacturing process of the third embodiment, a Co layer 43 that promotes ohmic junction may be interposed at the junction between the electrodes 21 and 22 and the semiconductor layer 10 as in the first embodiment.
The manufacturing steps of the photoelectric conversion elements 1 and 1A may be changed or changed as appropriate.

Examples will be described. Needless to say, the present invention is not limited to the following examples.
In Example 1, fabrication and observation of metal nanostructures were performed. The metal nanostructure was produced as follows.
A Co film was formed on the entire surface of a substantially square n-type Si substrate by sputtering. The thickness of the Co film was 8 nm.
Next, after organic cleaning for 5 minutes, mask printing was performed, and Au films having a thickness were formed by sputtering at the four corners and the center of the surface of the Co film. The thickness of the Au film was about 10 nm.
Next, annealing treatment was performed. The atmosphere gas for the annealing treatment was He 100%. The annealing temperature was 600 ° C. The annealing time was 3 minutes. By annealing, Co diffused in the surface layer portion of the n-type Si substrate to form CoSix.

  Two places in the vicinity of the Au film were observed with an SEM (scanning electron microscope). FIGS. 13A and 13B show the images. It was confirmed that the fine particles of the Au film diffused along the surface of the CoSix film, and a metal nanostructure was naturally formed around the Au film. The morphology of the metal nanostructure was different depending on the location. As shown in FIG. 2B, a fractal structure was formed in the metal nanostructure depending on the location.

Further, laser light (wavelength 635 nm) was irradiated to several points of the structure, and the surface structure at the point where the photoinduced current at zero bias was maximized was observed three-dimensionally with an AFM (atomic force microscope). .
FIG. 14 shows the image. FIG. 15 duplicates and explains the image of FIG.
Sub-order or nano-order irregularities were formed on the surface of the metal nanostructure, and a cluster structure or fractal structure was confirmed. Furthermore, a large number of periodic structures 33 and a large number of second convex portions 32 were confirmed in the above-described uneven shape. Each periodic structure 33 includes a plurality of first protrusions 31, and the first protrusions 31 are arranged at a period (arrangement interval) according to the periodic structure 33. The period of the periodic structure 33 was approximately 100 nm or less. The protrusion height of each first protrusion 31 was about 10 nm to 20 nm. Each of the second convex portions 32 is disposed so as to overlap with a certain periodic structure 33 or is disposed in the vicinity of the periodic structure 33. The protrusion height of the second protrusion 32 was larger than the protrusion height of the first protrusion 31 and was about 50 nm to 200 nm. The dispersion interval of the second protrusions 32 was approximately 2 μm to 3 μm.

  The present invention is applicable to, for example, an optical sensor and a solar cell.

DESCRIPTION OF SYMBOLS 1 Photoelectric conversion element 10 Semiconductor layer 11 Convex layer 21 1st electrode 22 2nd electrode 25 Co layer (ohmic contact promotion layer)
26 Au film (first electrode material)
30 Metal nanostructure 31 First convex portion 32 Second convex portion 33 Periodic structure 34 Base body 40 Conductive layer 41 First Schottky junction portion 42 Second Schottky junction portion 43 Co film (conductive layer metal component)

Claims (6)

An n-type or p-type semiconductor layer formed so that a convex layer protrudes from the surface;
And a conductive layer laminated on the surface, and contacting one side and the surface Schottky of the convex layer,
A first electrode provided on the opposite side of the conductive layer across the convex layer on the surface and in ohmic contact with the opposite side surface of the convex layer and the surface ;
A second electrode provided on the conductive layer;
A metal nanostructure including a plurality of periodic structures laminated on the convex layer or the conductive layer;
The photoelectric conversion element is characterized in that each periodic structure includes a plurality of first protrusions, and an arrangement interval of the first protrusions varies depending on the periodic structure.   The at least one of the periodic structures has an arrangement interval that is 0.1 to 1 times as large as an arbitrary wavelength within a certain wavelength range from a visible light region to an infrared light region. The photoelectric conversion element as described.   The metal nanostructure further includes a plurality of second protrusions that protrude larger than the first protrusions, the second protrusions are dispersed from each other, and each second protrusion overlaps with any periodic structure. The photoelectric conversion element according to claim 1, wherein the photoelectric conversion elements are arranged close to each other. A convex layer forming step of forming a convex layer on the surface by etching the surface of the semiconductor layer;
A conductive layer forming step of laminating a conductive layer on one surface of the convex layer and Schottky contact with the surface; and
An electrode forming step of providing a first electrode on the surface so as to be in ohmic contact with the side surface opposite to the one side surface of the convex layer and providing the second electrode on the conductive layer;
By laminating a metal on the convex layer or the conductive layer and performing a heat treatment, the periodic structure includes a plurality of periodic structures, each of the periodic structures includes a plurality of first convex portions, and the arrangement interval of the first convex portions is the A nanostructure formation step of forming different metal nanostructures according to the periodic structure;
The manufacturing method of the photoelectric conversion element characterized by including. A convex layer forming step of forming a convex layer on the surface by etching the surface of the semiconductor layer;
A conductive layer forming step of laminating the conductive layer on the surface so as to be in contact with one side surface of the convex layer;
An electrode forming step in which a first electrode is provided on the surface so as to contact a side surface opposite to the one side surface of the convex layer, and a second electrode is provided on the conductive layer;
By laminating a metal on the convex layer or the conductive layer and performing a heat treatment, the periodic structure includes a plurality of periodic structures, each of the periodic structures includes a plurality of first convex portions, and the arrangement interval of the first convex portions is the A nanostructure formation step of forming different metal nanostructures according to the periodic structure;
After the first electrode is coated on the surface, heat treatment is performed at a first temperature, and then the metal component of the conductive layer is coated on the surface, and then at a second temperature lower than the first temperature. A method for producing a photoelectric conversion element, characterized by performing a heat treatment.   In the nanostructure forming step, after the metal nanostructure base is disposed on the convex layer or the conductive layer, the base is diffused along the surface of the convex layer or the surface of the conductive layer by heat treatment. The method for producing a photoelectric conversion element according to claim 4, wherein the metal nanostructure is naturally formed.