JPWO2010038785A1 - Optical sensor and manufacturing method thereof - Google Patents

Abstract

Provided are an optical sensor excellent in responsiveness to long-wavelength light and a method for manufacturing the same. An electrical conductivity change body whose electrical conductivity changes by receiving light, the first electrode and the second electrode provided on the light receiving surface of the electrical conductivity change body, and the first electrode and the second electrode An optical sensor having a current detecting means for detecting a current, wherein the electrical conductivity changing body is composed of a compound having a layered triangular lattice structure containing a rare earth element. In the compound, R is at least one element selected from In, Sc, Y, Dy, Ho, Er, Tm, Yb, Lu, Ti, Ca, Sr, Ce, Sn, and Hf, Ma and Mb, At least one element selected from Ti, Mn, Fe, Co, Cu, Ga, Zn, Al, Mg, and Cd, allowing overlap, n is an integer of 1 or more, m is an integer of 0 or more, and δ is 0 or more A compound having a layered triangular lattice structure represented by (RMbO3-δ) n (MaO) m as a real number of 0.2 or less, or a compound obtained by substituting a part of R of the compound with an element not more than positive divalent.

Description

  The present invention relates to an optical sensor and a method for manufacturing the same.

  Conventionally, in an optical sensor, light is detected using a pn junction interface formed by stacking a p-type semiconductor layer and an n-type semiconductor layer.

  That is, in the optical sensor, when light is applied to the pn junction interface, electrons at the pn junction interface are excited to generate free electrons and holes.

  Then, the generated free electrons move to the n-type semiconductor layer, and the generated holes move to the p-type semiconductor layer, so that a predetermined potential difference is generated between the n-type semiconductor layer and the p-type semiconductor layer. The light is detected by detecting this potential difference.

  Silicon is generally used for the p-type semiconductor layer and the n-type semiconductor layer. However, the pn junction interface formed using silicon has a large energy band gap and receives light with energy smaller than the energy band gap. However, free electrons and holes are not generated, and the optical sensor is not sensitive. That is, in the photosensor using silicon, the sensitivity to light on the long wavelength side is not sufficient.

  In view of this, an optical sensor has been proposed in which a light absorption part is provided in a semiconductor layer to improve absorption efficiency for light on the long wavelength side.

Specifically, in the case of a p-type semiconductor layer formed of silicon, it has been proposed to form a light absorption part by adding an additive such as Cu, Zn, Au, Fe, Mn (for example, (See Patent Document 1).
JP 09-321327 A

  However, the sensitivity on the long wavelength side in the optical sensor is still not sufficient, and further improvement in sensitivity has been demanded.

  Therefore, in the optical sensor of the present invention, the electrical conductivity change body whose electrical conductivity changes by receiving light, the first electrode and the second electrode provided on the light receiving surface of the electrical conductivity change body, the first electrode, An optical sensor having a current detecting means for detecting a current generated between the second electrode and the second electrode, wherein the electrical conductivity changing body is composed of a compound having a layered triangular lattice structure containing a rare earth element.

Furthermore, the optical sensor of the present invention is also characterized by the following points. That is,
(1) In the compound, R is at least one element selected from In, Sc, Y, Dy, Ho, Er, Tm, Yb, Lu, Ti, Ca, Sr, Ce, Sn, and Hf, Ma, and Mb is at least one element selected from Ti, Mn, Fe, Co, Cu, Ga, Zn, Al, Mg, and Cd, n is an integer of 1 or more, m is an integer of 0 or more, δ A compound having a layered triangular lattice structure represented by (RMbO _{3 -δ} ) _n (MaO) _m , wherein R is a real number of 0 or more and 0.2 or less, or a compound in which a part of R of the compound is substituted with an element less than or equal to positive Be.
(2) The first electrode and the second electrode are provided in a comb shape.

  Further, in the method for manufacturing an optical sensor according to the present invention, the current generated between the first electrode and the second electrode provided on the light receiving surface of the electrical conductivity changing body whose electrical conductivity changes by receiving light is detected. A method of manufacturing an optical sensor for detecting by means, comprising the step of forming an electrical conductivity change body with a compound having a layered triangular lattice structure containing a rare earth element.

  According to the present invention, the electrical conductivity change body whose electrical conductivity changes by receiving light, the first electrode and the second electrode provided on the light receiving surface of the electrical conductivity change body, the first electrode, and the second electrode In an optical sensor having a current detecting means for detecting a current generated between the electrode and the electrode, the electrical conductivity change body is made of a compound having a layered triangular lattice structure containing a rare earth element, thereby forming a semiconductor pn junction. It is possible to provide an optical sensor with improved response to light having a longer wavelength than the optical sensor used.

FIG. 1 is a schematic explanatory diagram of the arrangement of each element in a plan view of a compound having a layered triangular lattice structure. FIG. 2 is a schematic explanatory diagram of the arrangement of each element in a side view of a compound having a layered triangular lattice structure. FIG. 3 is a graph showing a change state of electric conductivity with light irradiation of LuFe ₂ O ₄ . It is a schematic explanatory drawing of the optical sensor concerning embodiment of this invention.

10 Insulating substrate
20 Electric conductivity change body
31 First electrode
31a First base
31b First tooth
32 Second electrode
32a Second base
32b Second tooth
40 Current detection means
41 Bias power supply
42 Current detection circuit

  The optical sensor of the present invention is characterized in that an electrical conductivity change body whose electrical conductivity changes by receiving light is used. In particular, the electrical conductivity change body is a layered triangular lattice structure containing a rare earth element. It is comprised with the compound which has this.

Specifically, the electrical conductivity change body is at least one selected from R, In, Sc, Y, Dy, Ho, Er, Tm, Yb, Lu, Ti, Ca, Sr, Ce, Sn, and Hf. Elements, Ma and Mb, at least one element selected from Ti, Mn, Fe, Co, Cu, Ga, Zn, Al, Mg, and Cd, allowing overlap, n is an integer greater than or equal to 1, and m is 0 A compound represented by (RMbO _{3 -δ} ) _n (MaO) _m , or a compound in which a part of R of the compound is substituted with an element less than or equal to a positive divalent, is there.

Hereinafter, a compound having a layered triangular lattice structure will be described with LuFe ₂ O _{4 in} which R is Lu and Ma and Mb are Fe as representative examples.

LuFe ₂ O ₄ can be produced by the following procedure.
(1) Lutetium oxide (Lu ₂ O ₃ ) and iron (III) oxide (Fe ₂ O ₃ ) are mixed at a ratio of 1: 2 and mixed with a ball mill for about 1 hour to form a mixture.
(2) The mixture is formed into a predetermined shape and heated to 800 ° C. for 24 hours in an oxygen atmosphere to form a pre-fired body.
(3) The temporary fired body is fired by the FZ (Floating Zone) method to obtain single crystal LuFe ₂ O ₄ . At this time, crystals are grown in an atmosphere of a CO—CO ₂ mixed gas that is a mixed gas of carbon monoxide and carbon dioxide.

In the main firing for producing a single crystal, a CO ₂ —H ₂ mixed gas may be used instead of the CO—CO ₂ mixed gas, and the amount of oxygen is obtained by firing while controlling the oxygen partial pressure in a reducing atmosphere. Is adjusted.

The crystal structure of single crystal LuFe ₂ O ₄ will be described with reference to FIGS. For convenience of explanation, the crystal structure of LuFe ₂ O ₄ is in a state before so-called charge ordering, in which the ordered structure of Fe ³⁺ and Fe ²⁺ does not appear in Fe ions in the crystal.

  FIG. 1 is a schematic explanatory diagram of the arrangement of each element in plan view, and shows the positional relationship between the triangular lattice of element A, the triangular lattice of element B, and the triangular lattice of element C. In the following, the position of the lattice point in the triangular lattice of element A is “A position”, the position of the lattice point in the triangular lattice of element B is “B position”, and the position of the lattice point in the triangular lattice of element C is “C position”. I will call it.

FIG. 2 is a schematic explanatory diagram of the arrangement of each element in a side view, and each element is located at a predetermined position in the following order from the uppermost layer downward.
Lu-B position
OC position
Fe-C position
O-B position
OC position
Fe-B position
O-B position
Lu-C position
O-A position
Fe-A position
O-C position ○
O-A position ○
Fe-C position ○
OC position
Lu-A position
O-B position
Fe-B position
O-A position
O-B position
Fe-A position
O-A position
Lu-B position

Among these, a portion composed of four layers marked with a circle is called a W layer (W-Layer), and having this W layer is a characteristic point of LuFe ₂ O ₄ .

Further, it is known that a W layer is also formed in a compound having a layered triangular lattice structure other than LuFe ₂ O ₄ .

The W layer has a triangular lattice laminated structure, and the presence of the same number of Fe ²⁺ and Fe ³⁺ in LuFe ₂ O ₄ causes frustration of charges.

As a result, in LuFe ₂ O ₄ , the Fe ³⁺ region in the W layer has a positive charge role, while the Fe ²⁺ region has a negative charge role. It has become.

  This charge order is easily disturbed by an external field due to incident light, and this disorder of charge order appears as a change in electrical conductivity.

FIG. 3 shows the electrical conductivity when LuFe ₂ O ₄ is irradiated with white light, white light through a filter that cuts infrared light, and white light through a filter that transmits only visible light. It is the graph which showed the change.

From the graph of FIG. 3, it can be seen that in LuFe ₂ O ₄ , the electrical conductivity changes greatly even for incident light having a wavelength in the infrared region, and the electrical conductivity changes over a wide wavelength region. .

  In this way, by using an optical conductivity change body composed of a compound having a layered triangular lattice structure containing a rare earth element, a response to incident light with energy smaller than the band gap of silicon can be obtained. It is possible to provide an optical sensor that can be obtained and has improved response to long-wavelength light.

  That is, as shown in FIG. 4, the optical sensor of the present invention includes an insulating substrate 10 serving as a support base, a layered or film-like electric conductivity changing body 20 formed on the insulating substrate 10, and the electric conductivity. The first electrode 31 and the second electrode 32 provided on the light receiving surface of the change body 20 and current detection means 40 for detecting a current generated between the first electrode 31 and the second electrode 32 are configured.

The insulating substrate 10 is a substrate that supports the electrical conductivity changing body 20, and it is desirable to use a material having a similar crystal orientation of the electrical conductivity changing body 20 formed on the insulating substrate 10. In the present embodiment, as will be described later, since the electrical conductivity change body 20 is made of LuFe ₂ O ₄ , it is desirable to use ScAlMgO ₄ or the like for the insulating substrate 10.

The electrical conductivity changing body 20 is LuFe ₂ O ₄ in this embodiment. The electrical conductivity changing body 20 is not limited to LuFe ₂ O ₄ , and R is changed to In, Sc, Y, Dy, Ho, Er, Tm, Yb, Lu, Ti, Ca, Sr, Ce, Sn. , Hf, at least one element selected from Hf, Ma, Mb, at least one element selected from Ti, Mn, Fe, Co, Cu, Ga, Zn, Al, Mg, Cd allowing duplication, n A compound having a layered triangular lattice structure represented by (RMbO3 _-δ ) _n (MaO) _m , wherein R is an integer of 1 or more, m is an integer of 0 or more, δ is a real number of 0 to 0.2, or R of the compound A compound in which a part of is substituted with an element having a positive divalent value or less can be used. Hereinafter, the electrical conductivity changing body 20 will be described as LuFe ₂ O ₄ .

The electrical conductivity changing body 20 is formed on the insulating substrate 10 by using fine particles of LuFe ₂ O ₄ by CVD (Chemical Vapor Deposition), sputtering, MBE (Molecular Beam Epitaxy), or aerosol deposition. It is formed into a film or layer. The electrical conductivity changing body 20 is preferably a single crystal of LuFe ₂ O ₄ , but may be polycrystalline.

  The first electrode 31 and the second electrode 32 are made of a highly conductive metal such as Au or Cu. Specifically, a predetermined metal film is formed on the upper surface of the electrical conductivity changing body 20 by sputtering or the like, an etching mask is formed on the upper surface of the metal film, and the first electrode 31 portion and the first metal film are etched. The metal film other than the two-electrode 32 portion is removed and formed.

  In particular, the first electrode 31 and the second electrode 32 are comb-shaped as shown in FIG.

  That is, the first electrode 31 of the present embodiment includes a linear first base portion 31a and a plurality of first tooth portions 31b protruding from the first base portion 31a toward the second electrode 32. The second electrode 32 of the embodiment includes a linear second base portion 32a and a plurality of second tooth portions 32b protruding from the second base portion 32a toward the first electrode 31. The first tooth portions 31b and the second tooth portions 32b are alternately arranged along the direction orthogonal to the protruding direction of the tooth portions 31b and the second tooth portions 32b.

  By making each of the first electrode 31 and the second electrode 32 comb-like, it is possible to easily detect a change in electrical conductivity between the first electrode 31 and the second electrode 32, and to improve the sensitivity of the optical sensor. Can be improved.

  The current detection means 40 includes a bias power source 41 that applies a predetermined bias voltage to the first electrode 31 and the second electrode 32, and a current detection circuit 42 that detects a current flowing between the first electrode 31 and the second electrode 32. I have.

  In the optical sensor of the present embodiment, the current detection circuit 42 indicates that the electrical conductivity of the electrical conductivity change body 20 increases with light reception, and the current flowing between the first electrode 31 and the second electrode 32 increases. It is possible to detect light by detecting with.

  In particular, in the optical sensor of the present invention, the electrical conductivity changing body 20 is formed of a compound having a layered triangular lattice structure containing a rare earth element, so that light having a wavelength longer than that using a semiconductor pn junction is used. The sensitivity of the optical sensor can be increased.

  In the optical sensor of the present embodiment, the electrical conductivity change body 20 has a rectangular shape in plan view as shown in FIG. 4, but the shape of the electrical conductivity change body 20 is not limited to a rectangular shape in plan view, The shape may be

  ADVANTAGE OF THE INVENTION According to this invention, the optical sensor excellent in the responsiveness with respect to the light of a long wavelength can be provided.

Claims (4)

An electrical conductivity change body whose electrical conductivity changes by receiving light; and
A first electrode and a second electrode provided on a light receiving surface of the electric conductivity change body;
An optical sensor having current detection means for detecting a current generated between the first electrode and the second electrode,
An optical sensor in which the electrical conductivity changing body is composed of a compound having a layered triangular lattice structure containing a rare earth element. The compound is
R is at least one element selected from In, Sc, Y, Dy, Ho, Er, Tm, Yb, Lu, Ti, Ca, Sr, Ce, Sn, and Hf,
Ma and Mb, at least one element selected from Ti, Mn, Fe, Co, Cu, Ga, Zn, Al, Mg, and Cd, allowing duplication,
n is an integer of 1 or more,
m is an integer greater than or equal to 0,
A compound having a layered triangular lattice structure represented by (RMbO _{3 -δ} ) _n (MaO) _m or a part of R of the compound was substituted with an element less than positive divalent, where δ is a real number between 0 and 0.2. The optical sensor according to claim 1, which is a compound.   The optical sensor according to claim 1, wherein the first electrode and the second electrode are each provided in a comb shape. A method of manufacturing an optical sensor, wherein a current detection means detects a current generated between a first electrode and a second electrode provided on a light receiving surface of an electrical conductivity change body whose electrical conductivity changes by receiving light. ,
A method of manufacturing an optical sensor, comprising: forming the electric conductivity change body with a compound having a layered triangular lattice structure containing a rare earth element.

Images