Abstract: A circular resonator, and an optical modulator and an optical element comprising same. The circular resonator includes a first material, formed in a circular shape, including a plurality of nano holes and having a thermo-optic coefficient varying at a predetermined ratio according to temperature, and a second material having a thermo-optic coefficient varying in a direction opposite to the direction of change of the thermo-optic coefficient of the first material depending on temperature, the second material being filled in the plurality of nano holes, wherein an interval between the plurality of nano holes is formed at a pitch shorter than the wavelength of incident light.

Abstract: The present disclosure is directed to methods for producing a photovoltaic junction that can include coating a bare junction with a composition. In one embodiment, the composition includes a plurality of quantum dots to create a film; exposing the film to a ligand to create a first layer; coating the first layer with the composition to form a film on the first layer; and exposing the film on the first layer to the ligand to create a second layer.

Abstract: Microwave photonic devices use light to carry and process microwave signals over a photonic link. Light can be used as a stimulus to microwave devices that directly control microwave signals. Previous optically controlled devices suffer from large footprint, high optical power level required for switching, lack of scalability and complex integration requirements, restricting their implementation in practical microwave systems. Disclosed are monolithic optically reconfigurable integrated microwave switches (MORIMSs) built on a CMOS compatible silicon photonic chip. The disclosed scalable micrometer-scale switches provide higher switching efficiency and operate using optical power that is orders of magnitude lower than previous devices. The disclosed devices and techniques provide examples of silicon photonic platforms integrating microwave circuitry.

Abstract: A solid-state image pickup device includes a plurality of pixels, a pixel connection section, and a pixel reset section. The plurality of pixels each include a photoelectric conversion section that generates a charge according to irradiated light, a charge holding section that holds the generated charge, and a signal generation section that generates as an image signal a signal according to the held charge. The pixel connection section conducts between charge holding sections of the plurality of pixels and thereby allows each of the charge holding sections of the plurality of pixels to hold the charge that has been generated by the photoelectric conversion section of one pixel of the plurality of pixels. The pixel reset section discharges and resets the charge of the respective charge holding sections of the plurality of pixels when the pixel connection section conducts between the respective charge holding sections of the plurality of pixels.

Abstract: In at least one embodiment, the optoelectronic semiconductor chip comprises a semiconductor layer sequence with a radiation side, a first semiconductor layer of a first conductivity type, an active layer, a second semiconductor layer of a second conductivity type, and a rear side, which are arranged one above the other in this order. The active layer generates or absorbs primary electromagnetic radiation in the intended operation. Further, the optoelectronic semiconductor chip comprises a first contact structure and a second contact structure for electrically contacting the semiconductor layer sequence. The second contact structure is arranged on the rear side and is in electrical contact with the second semiconductor layer. The radiation side is configured for coupling in or coupling out primary radiation into or out of the semiconductor layer sequence. The rear side is structured and includes scattering structures configured to scatter and redirect the primary radiation.

Abstract: Described herein is an optical sensor, a detector including the optical sensor for an optical detection of at least one object, and a method for manufacturing the optical sensor. The optical sensor (110) includes a substrate (120); a photoconductive layer (112) applied to a first portion (116) of a surface (118) of the substrate (120); and at least one electrode layer (124) applied to a second portion (126) of the surface (118) of the substrate (120). The optical sensor (110) exhibits a linear current-voltage characteristic according to Ohm's law.

Abstract: According to the present invention, an optical latch circuit includes a voltage detector configured to compare a first power generation voltage input from a first input terminal with a preset first threshold voltage and output a set signal from a determination output terminal when the first power generation voltage exceeds the first threshold voltage, a first photovoltaic element connected between the first input terminal and a grounding point in a forward direction and configured to output a first power generation voltage to the first input terminal according to photovoltaic power when light is radiated, and a feedback resistor inserted between the first input terminal and the determination output terminal.

Abstract: An image sensor includes a plurality of unit pixels, each including: a substrate including first and second sides which are opposite to each other, a photoelectric conversion layer in the substrate, and a wiring structure on the first side of the substrate. The wiring structure may include: a first capacitor, a second capacitor spaced from the first capacitor, a plurality of edge vias arranged along edges of the unit pixel, and a plurality of central vias interposed between the first capacitor and the second capacitor.

Abstract: The present disclosure relates to a CMOS image sensor, and an associated method of formation. In some embodiments, the CMOS image sensor comprises a substrate and a transfer gate disposed from a front-side surface of the substrate. The CMOS image sensor further comprises a photo detecting column disposed at one side of the transfer gate within the substrate. The photo detecting column comprises a doped sensing layer comprising one or more recessed portions along a circumference of the doped sensing layer in parallel to the front-side surface of the substrate. By forming the photo detecting column with recessed portions, a junction interface is enlarged compared to a previous p-n junction interface without recessed portions, and thus a full well capacity of the photodiode structure is improved.

Abstract: Disclosed herein are a radiation detector and a method of making it. The radiation detector is configured to absorb radiation particles incident on a semiconductor single crystal of the radiation detector and to generate charge carriers. The semiconductor single crystal may be a CdZnTe single crystal or a CdTe single crystal. The method may comprise forming a recess into a substrate of semiconductor; forming a semiconductor single crystal in the recess; and forming a heavily doped semiconductor region in the substrate. The semiconductor single crystal has a different composition from the substrate. The heavily doped region is in electrical contact with the semiconductor single crystal and embedded in a portion of intrinsic semiconductor of the substrate.

Abstract: An image sensor with high quantum efficiency is provided. In some embodiments, a semiconductor substrate includes a non-porous semiconductor layer along a front side of the semiconductor substrate. A periodic structure is along a back side of the semiconductor substrate. A high absorption layer lines the periodic structure on the back side of the semiconductor substrate. The high absorption layer is a semiconductor material with an energy bandgap less than that of the non-porous semiconductor layer. A photodetector is in the semiconductor substrate and the high absorption layer. A method for manufacturing the image sensor is also provided.

Abstract: A photoconductive switch that uses materials that support negative differential mobility, whose operation leverages the pulse compression of a charge could to generate the “on” time of the pulse in combination with the speed of light to generate the “off” time of the pulse, is described. In one example, a method of operating a photoconductive switch, which includes two electrodes and a light absorbing material positioned therebetween, includes selecting a value for one or more parameters comprising a voltage for generation of an electric field, a spot size of a laser pulse, a temporal pulse width of the laser pulse, or an intensity of the laser pulse, wherein the selected value(s) for the one or more parameters enable the switch to operate in a region where the light absorbing material exhibits negative differential mobility, and illuminating the light absorbing material with the laser pulse to generate a charge cloud within the light absorbing material.

Abstract: A sensor lens assembly having a non-reflow configuration is provided. The sensor lens assembly includes a circuit board, an electronic chip assembled to the circuit board, a sensor chip, a die attach film (DAF) pre-bonded onto the sensor chip, a plurality of wires electrically coupling the electronic chip and the sensor chip to the circuit board, a supporting adhesive layer, a light-permeable sheet, and an optical module that is fixed to the circuit board for surrounding the above components. The sensor chip is adhered to the electronic chip through the DAF such that a sensing region of the sensor chip is perpendicular to a central axis of the optical module. The supporting adhesive layer is in a ringed shape and is disposed on a top surface of the sensor chip. The light-permeable sheet is disposed on the supporting adhesive layer and faces the sensor chip.

Abstract: Structures and formation methods of a chip package are provided. The chip package includes a semiconductor die having a conductive element and an antenna element over the semiconductor die. The chip package also includes a first conductive feature electrically connecting the conductive element of the semiconductor die and the antenna element. The chip package further includes a protective layer surrounding the first conductive feature. In addition, the chip package includes a second conductive feature over the first conductive feature. A portion of the second conductive feature is between the first conductive feature and the protective layer.

Abstract: An optical device includes an intermetallic compound of a first metal and a second metal having a lower work function than the first metal, or a solid-solution alloy of the first metal and the second metal and includes an n-type semiconductor in Schottky junction with the intermetallic compound or the solid-solution alloy.

Abstract: A photo-sensitive device includes a uniform layer, a gradated buffer layer over the uniform layer, a silicon layer over the gradated buffer layer, a photo-sensitive light-sensing region in the uniform layer and the silicon layer, a device layer on the silicon layer, and a carrier wafer bonded to the device layer.

Abstract: An image sensor includes an array of readout circuits in non-organic technology and photodiodes made of organic materials.

Abstract: The present disclosure is directed to an infrared sensor that includes a plurality of pairs of support structures positioned on the substrate, each pair including a first support structure adjacent to a second support structure. The sensor includes plurality of pixels, where each pixel is associated with one of the pairs of support structures. Each pixel includes a first infrared reflector layer on the substrate between the first and the second support structures, a membrane formed on the first and second support structures, a thermally conductive resistive layer on the membrane and positioned above the first infrared reflector layer, a second infrared reflector layer on the resistive layer, and an infrared absorption layer on the second infrared reflector layer.

Abstract: A photodiode, a light sensor and a fabricating method thereof are disclosed. An n-type semiconductor layer and an intrinsic semiconductor layer of the photodiode respectively comprise n-type amorphous indium gallium zinc oxide (IGZO) and intrinsic IGZO. The oxygen content of the intrinsic amorphous IGZO is greater than the oxygen content of the n-type amorphous IGZO. A light sensor comprise the photodiode is also disclosed.

Abstract: An optoelectronic device, including a semiconductor body having a surface to receive photons and a plurality of doped regions of opposite doping polarities, the doped regions extending substantially from the surface of the semiconductor body and into the semiconductor body, and being arranged in one or more pairs of opposite doping polarities such that each pair of doped regions forms a corresponding space charge region having a corresponding electric field therein, the space charge region extending substantially from the surface of the semiconductor body and into the semiconductor body such that photons entering the semiconductor body through the surface and travelling along paths within the space charge region generate electron-hole pairs in the space charge region that are separated in opposing directions substantially orthogonal to the photon paths by the electric field and collected by the corresponding pair of doped regions, thereby providing an electrical current to be conducted from the device.

Abstract: An absorber is disclosed. The disclosed absorber contains a base layer, and a plurality of pillars disposed above the base layer and composed of material configured to absorb an incident light and generate minority electrical carriers and majority electrical carrier, wherein the height of the pillars is predetermined to provide a common pyramidal outline shared by the pillars in the plurality of pillars.

Abstract: The present invention provides templating methods for replicating patterned metal films from a template substrate such as for use in plasmonic devices and metamaterials. Advantageously, the template substrate is reusable and can provide plural copies of the structure of the template substrate. Because high-quality substrates that are inherently smooth and flat are available, patterned metal films in accordance with the present invention can advantageously provide surfaces that replicate the surface characteristics of the template substrate both in the patterned regions and in the unpatterned regions.

Abstract: Methods and structures for providing single-color or multi-color photo-detectors leveraging plasmon resonance for performance benefits. In one example, a radiation detector includes a semiconductor absorber layer having a first electrical conductivity type and an energy bandgap responsive to radiation in a first spectral region, a semiconductor collector layer coupled to the absorber layer and having a second electrical conductivity type, and a plasmonic resonator coupled to the collector layer and having a periodic structure including a plurality of features arranged in a regularly repeating pattern.

Abstract: A touch sensing substrate includes a substrate, a first light sensing element, a second light sensing element and a first bias line. The first light sensing element includes a first gate electrode, a first active pattern overlapping with the first gate electrode, a first source electrode partially overlapping with the first active pattern and a first drain electrode partially overlapping with the first active pattern. The second light sensing element includes a second gate electrode, a second active pattern overlapping with the second gate electrode, a second source electrode partially overlapping with the second active pattern and a second drain electrode partially overlapping with the second active pattern. The first bias line is connected to the first and second gate electrodes.

Abstract: A dual-band infrared detector structure based on Type-II superlattices (T2SL) has been developed and experimentally validated. The structure according to the principles of the present invention is designed for a single Indium bump architecture and utilizes a T2SL barrier design that omits the traditional p-n junction region. The barrier design comprises multiple periods where each period comprises multiple monolayers doped P type. By selecting the composition, number of monolayers per period and number of periods, a transition region is created in the conduction band between a first absorber layer and a second absorber layer that allows operation at low biases (<100 mV for both bands) and exhibits a dark current density in the longer wavelength band comparable to that obtained with single-color detectors.

Abstract: An image sensor having a wave guide includes a semiconductor substrate formed with a photodiode and a peripheral circuit region; an anti-reflective layer formed on the semiconductor substrate; an insulation layer formed on the anti-reflective layer; a wiring layer formed on the insulation layer and connected to the semiconductor substrate; at least one interlayer dielectric stacked on the wiring layer; and a wave guide connected to the insulation layer by passing through the interlayer dielectric and the wiring layer which are formed over the photodiode.

Abstract: A center region of conductive material/s may be disposed or “sandwiched” between transition regions of relatively lower conductivity materials to provide substantially low defect density interfaces for the sandwiched material. The center region and surrounding transition regions may in turn be disposed or sandwiched between dielectric insulative material to form a sandwiched and transitioned device structure. The center region of such a sandwiched structure may be implemented, for example, as a device layer such as conductive microbolometer layer for a microbolometer detector structure.

Abstract: A photodetector is formed from a body of semiconductor material substantially surrounded by dielectric surfaces. A passivation process is applied to at least one surface to reduce the rate of carrier generation and recombination on that surface. Photocurrent is read out from at least one electrical contact, which is formed on a doped region whose surface lies entirely on a passivated surface. Unwanted leakage current from un-passivated surfaces is reduced through one of the following methods: (a) The un-passivated surface is separated from the photo-collecting contact by at least two junctions; (b) The un-passivated surface is doped to a very high level, at least equal to the conduction band or valence band density of states of the semiconductor; (c) An accumulation or inversion layer is formed on the un-passivated surface by the application of an electric field.

Abstract: Microelectronic imagers, methods for packaging microelectronic imagers, and methods for forming electrically conductive through-wafer interconnects in microelectronic imagers are disclosed herein. In one embodiment, a microelectronic imaging die can include a microelectronic substrate, an integrated circuit, and an image sensor electrically coupled to the integrated circuit. A bond-pad is carried by the substrate and electrically coupled to the integrated circuit. An electrically conductive through-wafer interconnect extends partially through the substrate and is in contact with the bond-pad.

Abstract: A solid-state imaging device includes: a gate electrode arranged over an upper surface of a semiconductor substrate; a photoelectric conversion portion formed over the semiconductor substrate to position under the gate electrode; an overflow barrier formed over the semiconductor substrate to position in a portion other than a position facing the gate electrode in a planar direction and adjoin a side face of the photoelectric conversion portion; and a drain formed over the semiconductor substrate to adjoin a side face of the overflow barrier opposite to a side face adjoining the photoelectric conversion portion.

Abstract: A device includes a semiconductor substrate and implant isolation region extending from a top surface of the semiconductor substrate into the semiconductor substrate surrounding an active region. A gate dielectric is disposed over an active region of the semiconductor substrate, wherein the gate dielectric extends over the implant isolation region. A gate electrode is disposed over the gate dielectric and an end cap dielectric layer is between the gate dielectric and the gate electrode over the implant isolation region.

Abstract: Disclosed are minority carrier based mercury-cadmium telluride (HgCdTe) infrared detectors and arrays, and methods of making, are disclosed. The constructions provided by the invention enable the detectors to be used at higher temperatures, and/or be implemented on less expensive semiconductor substrates to lower manufacturing costs. An exemplary embodiment a substrate, a bottom contact layer disposed on the substrate, a first mercury-cadmium telluride layer having a first bandgap energy value disposed on the bottom contact layer, a second mercury-cadmium telluride layer having a second bandgap energy value that is greater than the first bandgap energy value disposed on the first mercury-cadmium telluride layer, and a collector layer disposed on the second mercury-cadmium telluride layer, wherein the first and second mercury-cadmium telluride layers are each doped with an n-type dopant.

Abstract: A solid-state imaging device and a method for manufacturing the same are provided. The solid-state imaging device includes a structure that provides a high sensitivity and high resolution without variations in spectral sensitivity and without halation of colors, and prevents light from penetrating into an adjacent pixel portion. A plurality of photodiodes are formed inside a semiconductor substrate. A wiring layer includes a laminated structure of an insulating film and a wire and is formed on the semiconductor substrate. A plurality of color filters are formed individually in a manner corresponding to the plurality of photodiodes above the wiring layer. A planarized film and a microlens are sequentially laminated on each of the color filters. In the solid-state imaging device, each of the color filters has an refraction index higher than that of the planarized film and has, in a Z-axis direction, an upper surface in a concave shape.

Abstract: Here, an apparatus is provided. The apparatus generally comprises a substrate and a thermopile. The thermopile includes a cavity that is etched into the substrate, a functional area that is formed over the substrate (where the cavity is generally coextensive with the functional area), and a metal ring formed over the substrate along the periphery of the functional area (where the metal ring is thermally coupled to the substrate).

Abstract: A bolometer has a semiconductor membrane having a single-crystalline portion, and spacers so as to keep the semiconductor membrane at a predetermined distance from an underlying substrate. The complementarily doped regions of the single-crystalline portion form a diode and the predetermined distance corresponds to a fourth of an infrared wavelength.

Abstract: A solid-state imaging device in which a pixel circuit formed on the first surface side of a semiconductor substrate is shared by a plurality of light reception regions and second surface side of the semiconductor substrate is the light incident side of the light reception regions. The second surface side regions of the light reception regions are arranged at approximately even intervals and the first surface side regions of the light reception regions e are arranged at uneven intervals. Respective second surface side regions and first surface side regions are joined in the semiconductor substrate so that the light reception regions extend from the second surface side to the first surface side of the semiconductor substrate.

Abstract: A Schottky photodiode may include a monocrystalline semiconductor substrate having a front surface, a rear surface, and a first dopant concentration and configured to define a cathode of the Schottky photodiode, a doped epitaxial layer over the front surface of the monocrystalline semiconductor substrate having a second dopant concentration less than the first dopant concentration, and parallel spaced apart trenches in the doped epitaxial layer and having of a depth less than a depth of the doped epitaxial layer.

Abstract: A system, method, and apparatus for a lateral solar cell structure are disclosed herein. In particular, the present disclosure teaches a lateral solar cell structure that includes nanorods that are formed the during epitaxial growth process to produce electrodes extending into the absorber region. This structure allows for a long optical absorption length of the absorber, such as 0.5-3 microns, but also allows for carrier collection over sub-micron distances enabling high collection efficiency from materials with a sub-micron diffusion length. The disclosed method of manufacturing the lateral solar cell structure involves providing a substrate, and epitaxially growing an absorber region and an emitter region on the substrate. The emitter region comprises a plurality of nanorods extending into the absorber region. The absorber region and the nanorods are oppositely doped. The absorber region and the nanorods are also oppositely strained.

Abstract: According to one embodiment, an image detector comprises a plurality of photosensitive detector unit cells interconnected to a plurality of integrated circuits by a plurality of direct bond interconnects. Each unit cell includes an absorber layer and a separation layer. The absorber layer absorbs incident photons such that the absorbed photons excite photocurrent comprising first charged carriers and second charged carriers having opposite polarities. The separation layer separates the first charged carriers for collection at one or more first contacts and the second charged carriers for collection at one or more second contacts. The first and second contacts include the direct bond interconnects to conduct the first charged carriers and the second charged carriers from the unit cells in order to facilitate image processing.

Abstract: Graphene-based thermopiles are provided. The graphene-based thermopiles may include thermocouples having one or more graphene strips that may be polarized to adjust their Seebeck coefficients. The polarized graphene strips may have larger Seebeck coefficients than the materials conventionally used in thermopile devices. As a result, the graphene-based thermopiles may generate large output voltages using fewer thermocouples than conventional thermopile devices.

Abstract: A laminated module or panel of solar cells and a laminating method for making same comprise a top layer of melt flowable optically transparent molecularly flexible thermoplastic and a rear sheet of melt flowable insulating molecularly flexible thermoplastic both melt flowing at a temperature between about 80° C. and 250° C. and having a low glass transition temperature. Solar cells are encapsulated by melt flowing the top layer and rear sheet, and electrical connections are provided between front and back contacts thereof. Light passing through the transparent top layer impinges upon the solar cells and the laminated module exhibits sufficient flexural modulus without cross-linking chemical curing. Electrical connections may be provided by melt flowable electrically conductive molecularly flexible thermoplastic adhesive or by metal strips or by both.

Abstract: An infrared photodetector including a layer structure of an intermediate layer, and a quantum dot layer having a narrower band gap than the intermediate layer and including a plurality of quantum dots alternately stacked, and detecting photocurrent generated when infrared radiation is applied to the layer structure to thereby detect the infrared radiation, the infrared photodetector further including a first barrier layer provided on one side of the quantum dot layer and having a larger band gap than the intermediate layer; and a second barrier layer provided on the other side of the quantum dot layer and having a larger band gap than the intermediate layer.

Abstract: An infrared detector including a reflection portion which transmits far- and middle-infrared rays and which reflects near-infrared and visible rays; a photo-current generating portion having a plurality of layered quantum dot structures in each of which electrons are excited by the far- and middle-infrared rays having passed through the reflection portion so as to generate photo-current; a light emitting portion having a plurality of layered quantum well structures into each of which electrons of the photo-current generated by the photo-current generating portion are injected and in each of which the electrons thus injected thereinto are recombined with holes so as to emit near-infrared and visible rays; and a photo-detecting portion which detects the near -infrared and visible rays emitted from the light emitting portion and which detects the near-infrared and visible rays emitted from the light emitting portion and then reflected by the reflection portion.

Abstract: A method of forming a focal plane array by: preparing a first wafer having sensing material provided on a surface, which is covered by a sacrificial layer; preparing a second wafer including read-out integrated circuit and a contact pad, which is covered by another sacrificial layer into which are formed support legs in contact with the contact pad, the support legs being covered with a further sacrificial layer; bonding the sacrificial layers of the first and second wafers together such that the sensing material is transferred from the first wafer to the second wafer when a sacrificial bulk layer of the first wafer is removed; defining a pixel in the sensing material and forming a conductive via through the pixel for providing a connection between an uppermost surface of the pixel and the supporting legs; and removing the sacrificial layers to release the pixel, with the supporting legs underneath it.

Abstract: According to one embodiment, an image detector comprises a plurality of photosensitive detector unit cells interconnected to a plurality of integrated circuits by a plurality of direct bond interconnects. Each unit cell includes an absorber layer and a separation layer. The absorber layer absorbs incident photons such that the absorbed photons excite photocurrent comprising first charged carriers and second charged carriers having opposite polarities. The separation layer separates the first charged carriers for collection at one or more first contacts and the second charged carriers for collection at one or more second contacts. The first and second contacts include the direct bond interconnects to conduct the first charged carriers and the second charged carriers from the unit cells in order to facilitate image processing.

Abstract: An imaging element includes a plurality of pixels. Each of the plurality of pixels includes the following element. A photoelectric transducer is disposed in each of the plurality of pixels and is configured to generate electric charge corresponding to received light. A storage unit has a predetermined capacitance and is configured to store therein electric charge transferred from the photoelectric transducer. A capacitor is disposed separate from a silicon substrate with an interlayer insulating film therebetween, the photoelectric transducer and the storage unit being formed in the silicon substrate. A connecting unit is disposed separate from the silicon substrate with the interlayer insulating film therebetween and is configured to connect the storage unit and the capacitor.

Abstract: An infrared (IR) radiation sensor device (27) includes an integrated circuit radiation sensor chip (1A) including first (7) and second (8) temperature-sensitive elements connected within a dielectric stack (3) of the chip, the first temperature-sensitive element (7) being more thermally insulated from a substrate (2) than the second temperature-sensitive element (8). Bonding pads (28A) on the chip (1) are coupled to the first and second temperature-sensitive elements. Bump conductors (28) are bonded to the bonding pads (28A), respectively, for physically and electrically connecting the radiation sensor chip (1) to corresponding mounting conductors (23A). A diffractive optical element (21,22,23,31,32 or 34) is integrated with a back surface (25) of the radiation sensor chip (1) to direct IR radiation toward the first temperature-sensitive element (7).

Abstract: A detector array for an imaging system may exploit the different sensitivities of array pixels to an incident flux of low energy photons with a wavelength falling near the high end of the range of sensitivity of the semiconductor. The detector array may provide the de-multiplexable spatial information. The detector array may include a two-terminal multi-pixel array of Schottky photodiodes electrically connected in parallel.

Abstract: A photodiode, a light sensor and a fabricating method thereof are disclosed. An n-type semiconductor layer and an intrinsic semiconductor layer of the photodiode respectively comprise n-type amorphous indium gallium zinc oxide (IGZO) and intrinsic IGZO. The oxygen content of the intrinsic amorphous IGZO is greater than the oxygen content of the n-type amorphous IGZO. A light sensor comprise the photodiode is also disclosed.

Abstract: A device that includes a signal generating unit having a surface that can receive photons, a first metal structure located on the surface of the signal generating unit, and a second metal structure located on the surface of the signal generating unit. The second metal structure being spaced apart from the first metal structure.