JP7166882B2 - Electromagnetic wave detection device and electromagnetic wave detection system - Google Patents

Description

The present invention relates to an electromagnetic wave detection device and an electromagnetic wave detection system.

Patent Literature 1 discloses a wireless transmission device having a terahertz detection element. Further, as an example of the terahertz detection element in this document, a Schottky Barrier Diode (hereinafter referred to as SBD) is described.

JP 2013-005115 A

An electromagnetic wave detection element such as a terahertz detection element preferably has high electromagnetic wave detection sensitivity (detection output). However, since the electromagnetic waves that can be detected by the electromagnetic wave detection element itself are determined by its structure, there is a limit to the detection output.
However, the inventor of the present application has found a configuration that improves the detection output of electromagnetic waves by devising the configuration around the electromagnetic wave detecting element through test research.

One example of the problem to be solved by the present invention is to improve the detection output of electromagnetic waves.

The invention according to claim 1,
a substrate;
an electromagnetic wave detecting element grounded to the substrate and having a Schottky junction and a pair of conductive portions joined to each other via the Schottky junction;
It is arranged on the substrate at a position spaced apart from the Schottky junction, and has at least a portion along the direction in which the pair of conductive portions are arranged at an end on the electromagnetic wave detecting element side, and the width in the direction of the arrangement is the width of the electromagnetic wave detecting element. A floating conductive portion having a width equal to or larger than the width in the row direction of
with
When the center wavelength of the detection wavelength band of the electromagnetic wave detecting element is the wavelength λ and the separation distance between the Schottky junction and the floating conductive portion is the distance L, L is 90% of an odd multiple of (λ/4). above 110% or less,
It is an electromagnetic wave detector.

The invention according to claim 2,
a substrate;
an electromagnetic wave detecting element grounded to the substrate and having a Schottky junction and a pair of conductive portions joined to each other via the Schottky junction;
It is arranged on the substrate at a position spaced apart from the Schottky junction, and has at least a portion along the direction in which the pair of conductive portions are arranged at an end on the electromagnetic wave detecting element side, and the width in the direction of the arrangement is the width of the electromagnetic wave detecting element. A floating conductive portion narrower than the width in the row direction of
with
When the center wavelength of the detection wavelength band of the electromagnetic wave detecting element is the wavelength λ and the distance between the Schottky junction and the floating conductive portion is the distance L, L is 90% of an integral multiple of (λ/2). above 110% or less,
It is an electromagnetic wave detector.

1 is a schematic diagram of an electromagnetic wave detection system of a first embodiment; FIG. FIG. 2 is a partially enlarged view of an electromagnetic wave detection section that constitutes the electromagnetic wave detection device of the first embodiment; FIG. 3 is a partial cross-sectional view of the electromagnetic wave detection unit cut along the 3-3 cutting line in FIG. 2; FIG. 4 is a schematic diagram illustrating re-radiation between the electromagnetic wave detecting element and the floating conductive portion in the first embodiment; FIG. 4 is a model diagram for explaining the electric field and current phases of the electromagnetic wave detecting element and the re-radiated electric field phase in the case of dielectricity. FIG. 5 is a model diagram for explaining the relationship between the separation distance between the electromagnetic wave detecting element and the floating conductive portion and the re-radiation phase in the case of dielectricity. FIG. 4 is a partially enlarged view of an electromagnetic wave detection element of a modified example of the first embodiment; FIG. 5 is a partially enlarged view of an electromagnetic wave detection element of a second embodiment; FIG. 4 is a model diagram for explaining the electric field and current phases of the electromagnetic wave detecting element and the re-radiated electric field phase in the case of capacitiveness; FIG. 5 is a model diagram for explaining the relationship between the separation distance between the electromagnetic wave detecting element and the floating conductive portion and the re-radiation phase in the case of capacitiveness; FIG. 11 is a partially enlarged view of an electromagnetic wave detection element of a modified example of the second embodiment; FIG. 5 is a partially enlarged view of an electromagnetic wave detection element of another modification of the first embodiment;

≪Overview≫
Hereinafter, a first embodiment, a modified example of the first embodiment, a second embodiment, and a modified example of the second embodiment, which are examples of the present invention, will be described with reference to the drawings. In all the drawings to be referred to, constituent elements having similar functions are denoted by the same reference numerals, and descriptions thereof are omitted as appropriate in the specification.

<<First embodiment>>
A first embodiment will be described below with reference to the drawings. First, the function and configuration of the electromagnetic wave detection system 10 (see FIG. 1) of this embodiment will be described. Next, the electromagnetic wave detection operation by the electromagnetic wave detection system 10 of this embodiment will be described. Next, the effects of this embodiment will be described.

<Functions and Configuration of Electromagnetic Wave Detection System of First Embodiment>
FIG. 1 is a schematic diagram of an electromagnetic wave detection system 10 of this embodiment. The electromagnetic wave detection system 10 includes an electromagnetic wave generator 20 and an electromagnetic wave detector 30 . The electromagnetic wave detection system 10 has a function of detecting the electromagnetic wave W generated by the electromagnetic wave generator 20 with the electromagnetic wave detection device 30 .

Here, the electromagnetic waves W generated by the electromagnetic wave generator 20 of the present embodiment are terahertz waves, for example. Terahertz waves are said to be electromagnetic waves with shorter wavelengths than infrared rays and longer wavelengths than millimeter waves. Terahertz waves are electromagnetic waves that have the properties of both light waves and radio waves. hard to penetrate). Generally, the frequency of the terahertz wave is said to be an electromagnetic wave with a frequency of around 1 THz (corresponding to a wavelength of around 300 μm), but there is generally no clear definition of that range. Therefore, in this specification, the wavelength range of the terahertz wave is defined as the range of 100 GHz or more and 10 THz or less.

[Electromagnetic wave generator]
The electromagnetic wave generator 20 has a function of generating an electromagnetic wave W to which a modulated signal is added. The generated wavelength band of the electromagnetic wave W is a wavelength band within the wavelength range of the terahertz wave described above, and the center wavelength is defined as the wavelength λ in this specification.

[Electromagnetic wave detector]
The electromagnetic wave detection device 30 has a function of detecting the electromagnetic wave W generated by the electromagnetic wave generation device 20 . The electromagnetic wave detector 30 has an electromagnetic wave detector 32, a spectrum analyzer 34, and a condenser lens 36, as shown in FIG. The condenser lens 36 converges the electromagnetic waves W generated by the electromagnetic wave generator 20 toward the electromagnetic wave detector 32 . The electromagnetic wave detector 32 detects and demodulates the electromagnetic waves W condensed through the condensing lens 36 . The spectrum analyzer 34 uses the electromagnetic wave W demodulated by the electromagnetic wave detector 32 to calculate a signal on the frequency axis.

Next, the electromagnetic wave detector 32 will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is a partially enlarged view of the electromagnetic wave detector 32 of this embodiment. FIG. 3 is a partial cross-sectional view of the electromagnetic wave detector 32 cut along the 3-3 cutting line in FIG.
As shown in FIG. 2, the electromagnetic wave detection section 32 includes a substrate 40, a Schottky barrier diode structure section 50 (hereinafter referred to as an SBD structure section 50 (an example of an electromagnetic wave detection element)), and a floating conductive section 60. have.

<Substrate and SBD structure>
The SBD structure 50 has a Schottky junction 51, a pair of pads 56A and 56B, and a pair of extensions 58A and 58B. The SBD structure 50 is grounded to the substrate 40 .

(Schottky junction)
The substrate 40 and the SBD structure 50 have a layered structure as shown in FIG. Specifically, the substrate 40 is a substrate obtained by cutting a semiconductor wafer. A semiconductor layer 52 containing impurities is formed on the substrate 40 . A metal layer 54A and a semiconductor layer 53 containing impurities are formed on the semiconductor layer 52 with a gap therebetween so as to face each other. A pad 56A is formed on the metal layer 54A. A metal layer 55 is formed on the semiconductor layer 53, and a metal layer 54B is formed on the metal layer 55. As shown in FIG. Finger electrodes 57 are arranged on the metal layer 54B. In this specification, a structure composed of a combination of the semiconductor layer 52, the metal layer 54A, the semiconductor layer 53, the metal layer 54A, the metal layer 55, the metal layer 54B, and the finger electrodes 57 formed on the substrate 40 is described. , is defined as the Schottky junction 51 . Note that the finger electrodes 57 are elongated as shown in FIG. In this embodiment, the longitudinal direction of the finger electrodes 57 (and the direction in which pads 56A and 56B are arranged, which will be described later) is the X direction.

(pair of pads)
Further, as shown in FIG. 2, a pad 56A is arranged on one side of the Schottky junction 51, and a pad 56B is arranged on the other side. The pads 56A and 56B (an example of a pair of conductive portions) have a rectangular shape when viewed from the plate thickness direction of the substrate 40, and are arranged along the longitudinal direction of the finger electrodes 57 to form the Schottky junctions 51. are connected to each other through As described above, the metal layer 54A on the semiconductor layer 52 is in contact with the bottom of the pad 56A (see FIG. 3). On the other hand, the pad 56B is connected to one longitudinal end of the finger electrode 57 (the end opposite to the pad 56A side) (see FIG. 3). A metal layer 54B on the semiconductor layer 52 is in contact with the bottom of the pad 56B (not shown).
In this embodiment, the longitudinal direction of the finger electrodes 57, that is, the direction in which the pads 56A and 56B are arranged is the X direction. In this embodiment, the X direction is the polarization direction of the electromagnetic wave W. FIG. Further, in the present embodiment, the length LA from the end of the pad 56A opposite to the Schottky junction 51 side to the end of the pad 56B opposite to the Schottky junction 51 is LA. The width LA (see FIG. 2) is set to 440 μm as an example.

(a pair of extensions)
At the end of the pad 56A opposite to the Schottky junction 51 side in the X direction, an extending portion 58A extending along a direction orthogonal to the X direction (referred to as the Y direction) is arranged. . The extending portion 58A has the same layer structure as the pad 56A. An extension portion 58B extending along the Y direction is arranged at the end portion of the pad 56B on the side opposite to the Schottky junction 51 side in the X direction. The extending portion 58B has the same layer structure as the pad 56B. The extension portion 58A and the extension portion 58B are each connected to a detection circuit (not shown).

<Floating conductive part>
As shown in FIG. 2, the floating conductive portion 60 of the present embodiment has, for example, a rectangular shape when viewed from the thickness direction of the substrate 40 . In addition, the floating conductive portion 60 is arranged along the X direction at a position opposite to the side on which the pair of extension portions 58A and 58B are arranged in the Y direction with respect to the Schottky junction portion 51. there is That is, the floating conductive portion 60 is arranged at a position separated from the Schottky junction 51 on the substrate 40 . The floating conductive portion 60 is in a floating state without being grounded to the substrate 40 .
As shown in FIG. 2, the floating conductive portion 60 overlaps the SBD structure portion 50 in the Y direction and protrudes outside both ends of the SBD structure portion 50 in the X direction. That is, the width of the floating conductive portion 60 in the X direction is equal to or greater than (or greater than) the width of the SBD structure portion 50 in the X direction.
In this embodiment, the length LB of the floating conductive portion 60 in the X direction, in other words, the width LB of the floating conductive portion 60 (see FIG. 2) is set to 820 μm as an example. That is, in this embodiment, the width LB of the floating conductive portion 60 is set longer than the width LA.

Further, as described above, the floating conductive portion 60 has a rectangular shape when viewed from the thickness direction of the substrate 40 and is arranged along the X direction. Therefore, both edges (both ends in the short direction) of the floating conductive portion 60 in the Y direction are arranged along the X direction. Here, in the present embodiment, the portion on the side of the SBD structure portion 50 among the portions at both ends of the floating conductive portion 60 in the short direction is referred to as a portion 62 (an example of a portion along the direction in which the pair of conductive portions are arranged). A distance L is the distance from the center position of the Schottky junction 51 to the portion 62 in the Y direction (the distance between the Schottky junction 51 and the floating conductive portion 60). Further, the distance L in this embodiment has the following relationship with the wavelength λ of the electromagnetic wave W:

(Formula 1) {(λ/4)×n}×0.9≦L≦{(λ/4)×n}×1.1
where n is an odd number.

That is, according to (Equation 1), the distance L is 90% or more and 110% or less of an odd multiple of (λ/4).

The above is the description of the function and configuration of the electromagnetic wave detection system 10 of the present embodiment.

<Electromagnetic wave detection operation by the electromagnetic wave detection system of the first embodiment>
Next, the electromagnetic wave detection operation by the electromagnetic wave detection system 10 of this embodiment will be described with reference to FIGS. 1 and 2. FIG.

First, the electromagnetic wave generator 20 generates an electromagnetic wave W with a wavelength λ to which a modulated signal is added.
The electromagnetic wave W generated by the electromagnetic wave generator 20 is then condensed by the condensing lens 36 . Then, the electromagnetic waves W condensed by the condensing lens 36 are irradiated to the electromagnetic wave detector 32 .
Next, the electromagnetic wave W irradiated to the electromagnetic wave detection section 32 is detected by the electromagnetic wave detection section 32 . Then, the electromagnetic waves W detected by the electromagnetic wave detector 32 are demodulated by the electromagnetic wave detector 32 .
Next, the electromagnetic wave W demodulated by the electromagnetic wave detector 32 is calculated by the spectrum analyzer 34 as a signal on the frequency axis.
The detection operation of the electromagnetic wave W by the electromagnetic wave detection unit 32 will be described in the description of the effects of the present embodiment.

The above is the description of the electromagnetic wave detection operation of the electromagnetic wave detection system 10 of the present embodiment.

<Effects of the first embodiment>
Next, the effects of this embodiment will be described with reference to FIGS. 4 to 6. FIG. The effect of this embodiment is the effect of the electromagnetic wave detecting section 32 having the floating conductive section 60 . The effect of this embodiment will be described by comparing this embodiment with a comparative embodiment (not shown) described below. In the comparative embodiment, components having the same function, structure, etc. as those of the present embodiment will be described using the same names, symbols, etc. as those of the present embodiment.
Here, FIG. 4 is a schematic diagram illustrating re-radiation between the SBD structure portion 50 and the floating conductive portion 60 in this embodiment.

The electromagnetic wave detection system (not shown) of the comparative example has the same configuration as that of the present embodiment except that the electromagnetic wave detection unit does not have the floating conductive portion 60 . That is, the electromagnetic wave detecting device (not shown) of the comparative form detects the electromagnetic wave W generated by the electromagnetic wave generating device 20 and condensed by the condensing lens 36 only with the SBD structure portion 50 .
In the case of the electromagnetic wave detection portion of the comparative form, when the SBD structure portion 50 is irradiated with the electromagnetic wave W, the pair of pads 56A and 56B function as antennas, and current flows along the X direction. Thus, the electromagnetic wave detector of the comparative form detects the electromagnetic wave W. FIG.
Hereinafter, the detection output of the electromagnetic wave W having the wavelength λ in the electromagnetic wave detection device of the comparative form will be described as a reference (100%).

On the other hand, in the case of the present embodiment, when the SBD structure 50 is irradiated with the electromagnetic waves W as in the case of the comparative embodiment, the pair of pads 56A and 56B function as antennas, and the current IA flows along the X direction. flows (Fig. 4). In addition, an induced current IB flows through the floating conductive portion 60 due to the electromagnetic wave W re-radiated by the current IA. During the period when the electromagnetic wave detector 32 detects the electromagnetic wave W, re-radiation of the electromagnetic wave W caused by the current IA and re-radiation of the electromagnetic wave W caused by the induced current IB occur simultaneously. As a result, the SBD structure 50 receives current IA plus the current due to re-radiation from the floating conductive portion 60 . More specifically, it will be described with reference to FIGS. 5 and 6. FIG.

FIG. 5 is a model diagram for explaining the electric field and current phases of the SBD structure 50 and the re-radiated electric field phase in the case of dielectricity, which will be described later. FIG. 6 is a model diagram for explaining the relationship between the separation distance (distance L) between the SBD structure portion 50 and the floating conductive portion 60 and the re-radiation phase in the dielectric case.
This embodiment corresponds to the case where the width LB of the floating conductive portion 60 is equal to or greater than the resonance length (λ/2). Such a case is said to be a case where the impedance is "dielectric".

Each code|symbol in FIG. 5 has shown the following parameters.
li: inductive reactance lc: capacitive reactance E: electric field Ei: electric field generated with respect to li Ec: electric field generated with respect to lc

Next, the model diagrams of FIGS. 5A and 5B will be described. Here, the combination of the SBD structure portion 50 and the floating conductive portion 60 will be explained by replacing each with a capacitor.
As described above, in the case of the present embodiment, the impedance is "inductive" because it corresponds to the case where the width LB of the floating conductive portion 60 is equal to or greater than the resonance length (λ/2). Therefore, when the reference electric field E is reached, the phase of the current is delayed by 90 (°) (λ/4) with respect to the formed electric field E (see FIG. 5A). Furthermore, the re-radiated electric field from the state of FIG. 5(A) lags behind the current by 90 (°). As described above, the electric field E (see FIG. 5(A)) and the electric field Ei (see FIG. 5(B)) propagate in the leading direction and the lagging direction, respectively.

Next, the model diagram of FIG. 6 will be described. The model diagram of FIG. 6 is a model diagram of changes in the reradiation phase with respect to the distance L. In FIG.
As shown in FIG. 6A, the distance L is λ/4 (equivalent to 90 (°) in terms of phase), 3λ/4, 5λ/4, . In the case of λ/4×(2n−1), the electric field E and the electric field Ei are in phase with each other and reinforce each other.
On the other hand, as shown in FIG. 6B, the distance L is λ/2, λ (=2λ/2), 3/λ, 2λ (=4λ/2), . is a positive integer, the electric field E and the electric field Ei are out of phase with each other and weaken each other.
As described above, since the distance L and the wavelength λ in this embodiment have the relationship of the above-described (Equation 1), the relationship is as shown in FIG. 6A.
In this embodiment, the detection output was 166% (experimental result) when the detection output in the above-described comparative embodiment was taken as the standard (100%).

As described above, the electromagnetic wave detection section 32 (electromagnetic wave detection device 30) of the present embodiment can improve the detection output more than the electromagnetic wave detection section (electromagnetic wave detection device) of the comparative embodiment. In addition, the electromagnetic wave detection unit 32 (electromagnetic wave detection device 30) of the present embodiment has a detection output that is greater than when the distance L of the floating conductive unit 60 is λ/2×n, where n is a positive integer. can be improved.
In addition, according to the above-mentioned (Equation 1), the distance L may be 90% or more and 110% or less of an odd multiple of (λ/4). The reason why the range of ±10% with respect to odd multiples of (λ/4) is acceptable is that manufacturing variations of the electromagnetic wave detecting section 32 and the like are taken into consideration.

The above is the description of the effects of the present embodiment. Also, the above is the description of the first embodiment.

<<Modification of First Embodiment>>
Next, a modification of the first embodiment will be described with reference to FIG. Only the parts of this modification that differ from the first embodiment will be described below. In addition, in this modified example, the same names, symbols, etc. as in the first embodiment will be used for description of components having functions, structures, etc., equivalent to those in the first embodiment.

<Function and configuration, and electromagnetic wave detection operation>
The electromagnetic wave detection unit 32A (and the electromagnetic wave detection device 30A and the electromagnetic wave detection system 10A) of this modification includes an SBD structure unit 60A (structure an example of the body). Specifically, the SBD structure portion 60A includes a Schottky junction portion 51A (an example of another Schottky junction portion), a pair of pads 56A1 and 56B1 (an example of another pair of conductive portions), and a pair of extensions. It has parts 58A and 58B. Here, the shape and structure of the Schottky junction 51A are the same as the Schottky junction 51 (see FIG. 2) of the first embodiment. The pair of pads 56A1 and 56B1 differs from the pair of pads 56A and 56B only in that the length in the X direction is longer than the pair of pads 56A and 56B (see FIG. 2) of the first embodiment. The width of the SBD structure portion 60A is the same width (width LB) as the floating conductive portion 60 of the first embodiment. Also, the SBD structure portion 60A is not grounded to the substrate 40 and is in a floating state. Further, in the case of this modification, the distance L is the distance from the Schottky junction 51 to the Schottky junction 51A in the Y direction.

Further, the electromagnetic wave detection operation by the electromagnetic wave detection system 10A of this modified example is the same as in the case of the first embodiment.

<effect>
In this modification, the ungrounded SBD structure portion 60A that is not grounded to the substrate 40 forms a capacitor together with the SBD structure portion 50, like the floating conductive portion 60 of the first embodiment. Further, in the case of this modification, the impedance is "inductive" because it corresponds to the case where the width LB of the SBD structure portion 60A is equal to or greater than the resonance length (λ/2).
As described above, this modification has the same effect as the case of the first embodiment.
In addition, in the case of this modification, for example, switching of the grounding of the SBD structure portion 60A to the substrate 40 is made possible by a changeover switch (not shown), and in the grounded state, it is a single electromagnetic wave detection element, and in the ungrounded state It can be used as a substitute for the floating conductive portion 60 . Also, for example, by measuring two SBD structure portions (SBD structure portion 50 and SBD structure portion 60A) independently, it becomes easier to find out where the cutoff frequency is. Furthermore, when the peaks of the detection signals of the two SBD structures have a certain width near the center frequency and one becomes unusable due to damage or the like, the other can compensate. These points are effects that cannot be obtained in the case of the first embodiment.

The above is the description of the modification of the first embodiment.

<<Second embodiment>>
Next, a second embodiment will be described with reference to FIGS. 8 to 10. FIG. Only parts of this embodiment that differ from the first embodiment will be described below. In addition, in this embodiment, the same names, symbols, etc. as in the first embodiment will be used for description of components having functions, structures, etc., equivalent to those in the first embodiment.

<Function and configuration, and electromagnetic wave detection operation>
The electromagnetic wave detection section 32B (and the electromagnetic wave detection device 30B and the electromagnetic wave detection system 10B) of the present embodiment includes a floating conductive section 60B (see FIG. 8) instead of the floating conductive section 60 (see FIG. 2) of the first embodiment. have. Here, unlike the floating conductive portion 60, the floating conductive portion 60B is arranged inside both ends of the SBD structure portion 50 in the X direction. That is, the width LC of the floating conductive portion 60B is less than the width LA of the SBD structure portion 50. FIG.
In this embodiment, the width LB (see FIG. 2) of the floating conductive portion 60 is set to 380 μm as an example. That is, in this embodiment, the width LC of the floating conductive portion 60B is set narrower than the width LA.

In addition, the distance L in this embodiment has the following relationship with the wavelength λ of the electromagnetic wave W:

(Formula 2) {(λ/2)×n}×0.9≦L≦{(λ/2)×n}×1.1
where n is a positive integer.

That is, according to (Equation 2), the distance L is 90% or more and 110% or less of an integral multiple of (λ/2).

Further, the electromagnetic wave detection operation by the electromagnetic wave detection system 10B of this embodiment is the same as in the case of the first embodiment.

<Effects of Second Embodiment>
Next, the effects of this embodiment will be described with reference to FIGS. 9 and 10. FIG. The effect of this embodiment is the effect of the electromagnetic wave detecting section 32 having the floating conductive section 60B. The effects of this embodiment will be described by comparing this embodiment with the aforementioned comparative example (not shown).

In the case of this embodiment, when the SBD structure 50 is irradiated with the electromagnetic waves W, the pair of pads 56A and 56B function as antennas, and current flows along the X direction, as in the case of the comparative embodiment. In addition, an induced current flows through the floating conductive portion 60B due to the electromagnetic wave W re-radiated by the current flowing through the SBD structure portion 50 . During the period in which the electromagnetic wave detector 32 is detecting the electromagnetic wave W, the electromagnetic wave W is re-radiated due to the current flowing through the SBD structure portion 50 and the electromagnetic wave W is re-radiated due to the induced current flowing through the floating conductive portion 60B. and occur at the same time. As a result, a current flowing through the SBD structure 50 is the sum of the current flowing through the SBD structure 50 and the current caused by the re-radiation from the floating conductive portion 60B. More specifically, it will be described with reference to FIGS. 9 and 10. FIG.

FIG. 9 is a model diagram for explaining the electric field and current phases of the SBD structure 50 and the re-radiated electric field phase in the capacitive case described later. FIG. 10 is a model diagram for explaining the relationship between the separation distance (distance L) between the SBD structure portion 50 and the floating conductive portion 60B and the re-radiation phase in the capacitive case.
This embodiment corresponds to the case where the width LC of the floating conductive portion 60B is less than the resonance length (λ/2). Such a case is referred to as a case where the impedance is "capacitive".

Each reference symbol in FIG. 9 is the same as in the description of FIG. 5 of the first embodiment.
li: inductive reactance lc: capacitive reactance E: electric field Ei: electric field generated with respect to li Ec: electric field generated with respect to lc

Next, the model diagrams of FIGS. 9A and 9B will be described. Here, the combination of the SBD structure portion 50 and the floating conductive portion 60B will be explained by replacing each with a capacitor.
As described above, in the case of this embodiment, the impedance is "capacitive" because it corresponds to the case where the width LC of the floating conductive portion 60B is less than the resonance length (λ/2). Therefore, when the reference electric field E is reached, the phase of the electric current advances by 90 (°) (λ/4) with respect to the formed electric field E (see FIG. 9A). Furthermore, the re-radiated electric field from the state of FIG. 9(A) lags behind the current by 90 (°). As described above, the electric field E (see FIG. 9(A)) and the electric field Ei (see FIG. 9(B)) propagate in the leading direction and the lagging direction, respectively.

Next, the model diagram of FIG. 10 will be described. The model diagram of FIG. 10 is a model diagram of changes in the reradiation phase with respect to the distance L. In FIG.
As shown in FIG. 10B, the distance L is λ/2 (equivalent to 180 (°) in terms of phase), λ (=2λ/2), 3/λ, 2λ (=4λ/2), . . , that is, in the case of λ/2×n where n is a positive integer, the electric field E and the electric field Ei are in phase with each other and reinforce each other.
On the other hand, as shown in FIG. 10A, when the distance L is λ/4 (equivalent to 90 (°) in terms of phase), 3λ/4, 5λ/4, . In the case of λ/4×(2n−1) when taken as a positive integer, the electric field E and the electric field Ei are in opposite phases and weaken each other.
As described above, since the distance L and the wavelength λ in this embodiment have the relationship of the above-described (Equation 2), the relationship is as shown in FIG. 10B.
In this embodiment, the detected output was 227% (experimental result) when the detected output in the above-described comparative embodiment was taken as the standard (100%).

As described above, the electromagnetic wave detection section 32B (electromagnetic wave detection device 30B) of the present embodiment can improve the detection output more than the electromagnetic wave detection section (electromagnetic wave detection device) of the comparative form. In addition, the electromagnetic wave detection unit 32B (electromagnetic wave detection device 30B) of the present embodiment is compared to the case where the distance L of the floating conductive unit 60B is λ/4×(2n−1) where n is a positive integer. , the detection output can be improved.
In addition, according to the above-described (Equation 2), the distance L may be 90% or more and 110% or less of the integral multiple of (λ/2). The reason why the range of ±10% with respect to integral multiples of (λ/2) is acceptable is that manufacturing variations of the electromagnetic wave detecting section 32B and the like are taken into consideration.

The above is the description of the second embodiment.

<<Modification of Second Embodiment>>
Next, a modified example of the second embodiment will be described with reference to FIG. In the following, this modified example will be described only with regard to portions that differ from the second embodiment. In addition, in this modified example, the same names, symbols, etc. as in the second embodiment will be used for the constituent elements having the same function, structure, etc. as those in the second embodiment.

<Function and configuration, and electromagnetic wave detection operation>
An electromagnetic wave detection unit 32C (and an electromagnetic wave detection device 30C and an electromagnetic wave detection system 10C) of this modification includes an SBD structure unit 60C (structure an example of the body). Specifically, the SBD structure 60C includes a Schottky junction 51C (an example of another Schottky junction), a pair of pads 56A2 and 56B2 (an example of another pair of conductive portions), and a pair of extensions. It has parts 58A and 58B. Here, the shape and structure of the Schottky junction 51C are the same as the Schottky junction 51 (see FIG. 8) of the second embodiment. The pair of pads 56A2 and 56B2 differs from the pair of pads 56A and 56B only in that the length in the X direction is shorter than the pair of pads 56A and 56B (see FIG. 8) of the second embodiment. The width of the SBD structure portion 60C is the same width (width LC) as the floating conductive portion 60B of the second embodiment. Also, the SBD structure portion 60C is not grounded to the substrate 40 and is in a floating state. Further, in the case of this modification, the distance L is the distance from the Schottky junction 51 to the Schottky junction 51C in the Y direction.

Further, the electromagnetic wave detection operation by the electromagnetic wave detection system 10C of this modified example is the same as in the case of the second embodiment.

<effect>
In this modification, the ungrounded SBD structure portion 60C that is not grounded to the substrate 40 forms a capacitor together with the SBD structure portion 50, like the floating conductive portion 60B of the second embodiment. Further, in the case of this modification, the impedance is "capacitive" because it corresponds to the case where the width LC of the SBD structure portion 60C is less than the resonance length (λ/2).
As described above, this modification has the same effect as the case of the second embodiment.
In addition, in the case of this modification, for example, it is possible to switch the grounding of the SBD structure portion 60C to the substrate 40 by a changeover switch (not shown), and in the grounded state it is a single electromagnetic wave detection element, and in the ungrounded state It can be used as a substitute for the floating conductive portion 60B. Also, for example, by measuring two SBD structure portions (SBD structure portion 50 and SBD structure portion 60C) independently, it becomes easier to find out where the cutoff frequency is. Furthermore, when the peaks of the detection signals of the two SBD structures have a certain width near the center frequency and one becomes unusable due to damage or the like, the other can compensate. These points are effects that cannot be obtained in the case of the second embodiment.

The above is the description of the modification of the second embodiment.

As described above, the present invention has been described by taking the first embodiment and its modifications and the second embodiment and its modifications as examples, but the present invention is not limited to these embodiments. The technical scope of the present invention includes, for example, the following forms (modifications).

For example, the length of the finger electrodes and the shape of the Schottky junction may be changed. Specifically, like the electromagnetic wave detection unit 32D (and the electromagnetic wave detection device 30D and the electromagnetic wave detection system 10D) of the modification shown in FIG. (See FIG. 7) may be replaced by the SBD structure portion 60D. Here, the SBD structure portion 60D has a width LA with respect to the SBD structure portion 60A, and the diameter of the Schottky electrode is extremely large (for example, about five times). The difference is that the curved diameter of the surface facing the finger electrodes 57 is extremely large (for example, about five times as large). That is, the SBD structure portion 60D of this modification has the same width LA as the SBD structure portion 50, and the shape of the Schottky junction portion 51D is different from those of the SBD structure portion 50 and the SBD structure portion 60A. Note that the Schottky electrode means the end portion of the finger electrode 57 on the pad 56A2 side. Moreover, since the width of the SBD structure portion 60D is LA, this modification corresponds to the case where the impedance is "dielectric".

By having the configuration as described above, this modified example has the following effects that are not found in each of the above-described embodiments and their modified examples.
For example, the cutoff frequency fc (see (Equation 3) described later) is generally designed to be higher than the target center frequency. In the case of this modification, the shape of the Schottky junction 51D is changed to remove unnecessary peaks (components) that appear in a frequency band that is higher than the target center frequency but lower than the cutoff frequency. can change the cutoff frequency.
In addition, in the case of this modified example, the detected output was 227% when the detected output in the above-described comparative embodiment was taken as the reference (100%) (result of experiment).
As described above, in the case of this modified example, it is possible to intentionally lower the sensitivity of unnecessary peak frequency bands.

(Formula 3) fc=1/(2πRC)
Here, each parameter is as follows.
R: electrical resistance of Schottky junction
C: Capacitance of Schottky junction

By the way, the cut-off frequency can be changed by changing the value of the resistance component by changing the film formation conditions of the semiconductor layer, for example, by changing the doping concentration, or by cutting the substrate to reduce the thickness to reduce the capacitance component. can. However, if the conditions of the semiconductor layer are changed, the detection output will decrease (deviate from the optimum film formation conditions), and if the substrate is thinned, the processing cost will increase and the strength of the semiconductor chip will decrease.
On the other hand, in the case of this modification, basically, the shape of the Schottky junction 51D can be changed simply by changing the design of the mask pattern used in manufacturing. That is, in the case of this modified example, it is possible to easily (or at low cost) achieve intentional reduction in the sensitivity of the unnecessary peak frequency band.
The above is the description of the effects of this modification.
It should be noted that the modified example shown in FIG. 12 has been described as corresponding to the case where the impedance is "dielectric". That is, the modification of FIG. 12 has been described as another modification of the first embodiment. However, as described above, the shape of the SBD structure 60D intentionally lowers the sensitivity of the unnecessary peak frequency band. good too.

Moreover, although one floating conductive portion 60 or the like is provided in each embodiment, one floating conductive portion 60 or the like may be arranged on both sides of the SBD structure portion 50 in the Y direction.

10 Electromagnetic wave detection system 20 Electromagnetic wave generator 30 Electromagnetic wave detector 32 Electromagnetic wave detector 34 Spectrum analyzer 36 Condensing lens 40 Substrate 50 Schottky barrier diode structure (SBD structure)
51 Schottky junction 52 Semiconductor layer 53 Semiconductor layer 54A Metal layer 54B Metal layer 55 Metal layer 56A Pad 56B Pad 57 Finger electrode 58A Extended portion 58B Extended portion 60 Floating conductive portion 60A SBD structure portion 60B Floating conductive portion 60C SBD structure Department

Claims (6)

a substrate;
an electromagnetic wave detecting element grounded to the substrate and having a Schottky junction and a pair of conductive portions joined to each other via the Schottky junction;
It is arranged on the substrate at a position spaced apart from the Schottky junction, and has at least a portion along the direction in which the pair of conductive portions are arranged at an end on the electromagnetic wave detecting element side, and the width in the direction of the arrangement is the width of the electromagnetic wave detecting element. A floating conductive portion having a width equal to or larger than the width in the row direction of
with
When the center wavelength of the detection wavelength band of the electromagnetic wave detecting element is the wavelength λ and the separation distance between the Schottky junction and the floating conductive portion is the distance L, L is 90% of an odd multiple of (λ/4). above 110% or less,
Electromagnetic wave detector. a substrate;
an electromagnetic wave detecting element grounded to the substrate and having a Schottky junction and a pair of conductive portions joined to each other via the Schottky junction;
It is arranged on the substrate at a position spaced apart from the Schottky junction, and has at least a portion along the direction in which the pair of conductive portions are arranged at an end on the electromagnetic wave detecting element side, and the width in the direction of the arrangement is the width of the electromagnetic wave detecting element. A floating conductive portion narrower than the width in the row direction of
with
When the center wavelength of the detection wavelength band of the electromagnetic wave detecting element is the wavelength λ and the distance between the Schottky junction and the floating conductive portion is the distance L, L is 90% of an integral multiple of (λ/2). above 110% or less,
Electromagnetic wave detector. The floating conductive portion is a structure having another Schottky junction and another pair of conductive portions joined to each other via the other Schottky junction.
The electromagnetic wave detection device according to claim 1 or 2. The shape of the other Schottky junction is different from the shape of the Schottky junction,
The electromagnetic wave detection device according to claim 3. The wavelength λ is a wavelength in the range of 100 GHz or more and 10 THz or less,
The electromagnetic wave detection device according to any one of claims 1 to 4. The electromagnetic wave detection device according to any one of claims 1 to 5;
an electromagnetic wave generator that generates an electromagnetic wave to be detected by the electromagnetic wave detection element;
An electromagnetic wave detection system comprising:

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