Patent Publication Number: US-2022231182-A1

Title: Terahertz and sub-terahertz devices

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Application No. 62/839,830, filed Apr. 29, 2019, which is incorporated by reference as if disclosed herein in its entirety. 
    
    
     FIELD 
     The present disclosure relates to devices, in particular to, terahertz and sub-terahertz devices. 
     BACKGROUND 
     Terahertz (THz) technology has found numerous applications ranging from nondestructive remote sensing to the detection of chemical agents, radio astronomy, nondestructive VLSI (very large scale integration) testing, concealed weapons and object detection, gasoline and oil quality testing, biotechnology, medical diagnostics, cancer detection, explosive detection, THz spectroscopy of explosives and drugs, THz communications, and imaging. THz imaging and sensing are based on the interaction of the THz radiation with phonons, hydrogen bonds, and bond and molecular vibrations. THz absorption, reflection, and polarization are also affected by chemical changes, changes in polarizability or protein density or conformation and are relatively highly sensitive to water content. 
     Plasma waves propagating in the channel of a field effect transistor (FET) with a continuous flow of electrons from the source to the drain have been used to detect, mix, and frequency multiply THz and sub-THz radiation including using homodyne or heterodyne detection. While the feature sizes of these devices may be scaled to obtain the device parameters close to the THz gap (i.e., frequencies from a few hundred gigahertz to 30 THz), contact parasitic impedances, electron ballistic scattering by contacts, and viscosity of the electronic fluid limit the performance of such devices. 
     SUMMARY 
     In some embodiments, there is provided a semiconducting device for at least one of detecting, producing or manipulating electromagnetic radiation having a frequency of at least 100 gigahertz (GHz). The semiconducting device includes a heterodimensional plasmonic structure, and an active layer. The heterodimensional plasmonic structure includes at least one nanostructure configured to form a heterodimensional junction with the active layer and having a tunable resonant plasmon frequency. 
     In some embodiments of the semiconducting device, the nanostructure is selected from the group comprising a nanodot, a nanoparticle, a nanocolumn, a nanocone, a nanowire, a nanotube, or a combination thereof. In some embodiments of the semiconducting device, the active layer is selected from the group comprising a two-dimensional electron gas, a three-dimensional electron gas, a two-dimensional hole gas and a three-dimensional hole gas. 
     In some embodiments of the semiconducting device, at least one of the active layer and the heterodimensional plasmonic structure is fabricated with a material selected from the group comprising silicon (Si), gallium-nitride (GaN), indium gallium arsenide (InGaAs), and graphene. 
     In some embodiments, the semiconducting device includes a gate coupled to the active layer. The gate is configured receive a bias voltage. The bias voltage is configured to tune the resonant plasmon frequency. In some embodiments, the semiconducting device includes a drain contact and a source contact contacting the active layer. A configuration of the drain contact and the source contact is selected from the group including continuous side contacts, split side contacts, side contacts in an opposing configuration and side contacts in a cross configuration. 
     In some embodiments of the semiconducting device, at least one of the heterodimensional plasmonic structure and the gate include an asymmetric feature configured to provide an asymmetry between the gate and the drain. 
     In some embodiments of the semiconducting device, the heterodimensional plasmonic structure includes a plurality of nanostructures. A first portion of the plurality of nanostructures is fabricated with a first set of parameters and a second portion of the plurality of nanostructures is fabricated with a second set of parameters. A selected first parameter of the first set differs from a selected second parameter of the second set by at least one percent (%). 
     In some embodiments of the semiconducting device, the active layer is periodically modulated. In some embodiments of the semiconducting device, the heterodimensional plasmonic structure includes a plurality of nanostructures. The plurality of nanostructures are periodically modulated. 
     In some embodiments, there is provided a field effect device for at least one of detecting, producing or manipulating electromagnetic radiation having a frequency of at least 100 gigahertz (GHz). The field effect device includes a heterodimensional plasmonic structure, an active layer, and a gate, a drain, and a source coupled to the active layer. The heterodimensional plasmonic structure includes at least one nanostructure configured to form a heterodimensional junction with the active layer and having a tunable resonant plasmon frequency. 
     In some embodiments of the field effect device, the nanostructure is selected from the group including a nanodot, a nanoparticle, a nanocolumn, a nanocone, a nanowire, a nanotube, or a combination thereof. 
     In some embodiments of the field effect device, the active layer is selected from the group including a two-dimensional electron gas, a three-dimensional electron gas, a two-dimensional hole gas and a three-dimensional hole gas. 
     In some embodiments of the field effect device, at least one of the active layer and the heterodimensional plasmonic structure is fabricated with a material selected from the group including silicon (Si), gallium-nitride (GaN), indium gallium arsenide (InGaAs), and graphene. 
     In some embodiments of the field effect device, the gate is configured receive a bias voltage. The bias voltage is configured to tune the resonant plasmon frequency. 
     In some embodiments, the field effect device includes a drain contact and a source contact contacting the active layer. A configuration of the drain contact and the source contact is selected from the group including continuous side contacts, split side contacts, side contacts in an opposing configuration and side contacts in a cross configuration. 
     In some embodiments of the field effect device, each nanostructure is capacitively coupled to the gate. In some embodiments of the field effect device, at least one of the heterodimensional plasmonic structure and the gate include an asymmetric feature configured to provide an asymmetry between the gate and the drain. In some embodiments of the field effect device, the heterodimensional plasmonic structure includes a plurality of nanostructures. A first portion of the plurality of nanostructures is fabricated with a first set of parameters and a second portion of the plurality of nanostructures is fabricated with a second set of parameters. A selected first parameter of the first set differs from a selected second parameter of the second set by at least one percent (%). 
     In some embodiments of the field effect device, the active layer is periodically modulated. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The drawings show embodiments of the disclosed subject matter for the purpose of illustrating features and advantages of the disclosed subject matter. However, it should be understood that the present application is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein: 
         FIG. 1  illustrates an isometric view of a semiconducting device consistent with several embodiments of the present disclosure; 
         FIG. 2  illustrates a side view of a semiconducting device including a three-dimensional (3D) gas, consistent with some embodiments of the present disclosure; 
         FIG. 3  illustrates a top view of a semiconducting device consistent with several embodiments of the present disclosure; 
         FIG. 4A  illustrates a side view of a semiconducting device including an ungated two-dimensional (2D) gas, consistent with some embodiments of the present disclosure; 
         FIG. 4B  illustrates a side view of a semiconducting device including a gated 2D gas, consistent with some embodiments of the present disclosure; 
         FIGS. 5A and 5B  illustrate top views of a semiconducting device with continuous side contacts and continuous side contacts in a cross configuration, respectively, consistent with several embodiments of the present disclosure; 
         FIGS. 6A and 6B  illustrate a top view of a semiconducting device with split side contacts split side contacts in a cross configuration, respectively, consistent with several embodiments of the present disclosure; 
         FIG. 7  illustrates a top view of a semiconducting device with a periodic array of nanostructures, periodically modulated, consistent with several embodiments of the present disclosure; 
         FIG. 8  illustrates a side view of a semiconducting device including a periodically modulated active layer, consistent with some embodiments of the present disclosure; 
         FIG. 9  illustrates a side view of a semiconducting device including a substrate having a microfluidic channel, consistent with some embodiments of the present disclosure; 
         FIGS. 10A through 10C  illustrate respective side views of three example semiconducting devices that each include a respective passivating layer, consistent with some embodiments of the present disclosure; 
         FIGS. 11A and 11B  illustrate two example systems including a semiconducting device and one or a plurality of scanning detectors, respectively, consistent with some embodiments of the present disclosure; 
         FIGS. 12A and 12B  illustrate a top view of a semiconducting device and a side view cross-section (A-A′) of the semiconducting device, respectively, consistent with some embodiments of the present disclosure; 
         FIG. 13  illustrates is a top view of a semiconducting device that includes a nanostructure capacitively coupled to a gate, consistent with some embodiments of the present disclosure; 
         FIG. 14  illustrates an isometric view of a semiconducting device that includes embedded generally conical nanostructures; 
         FIG. 15  illustrates an isometric view of a semiconducting device that includes an insulating layer; 
         FIG. 16  illustrates an isometric view of a semiconducting device that includes a plurality of stacked lattices; and 
         FIGS. 17A through 17D  illustrate example semiconducting devices that include asymmetry between a drain and source configured to enhance detections, consistent with some embodiments of the present disclosure. 
     
    
    
     Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. 
     DETAILED DESCRIPTION 
     Generally, this disclosure relates to semiconducting devices configured to operate at THz and sub-THz frequencies. A semiconducting device consistent with the present disclosure may be configured to at least one of detect, produce, or manipulate electromagnetic radiation. The semiconducting device includes a heterodimensional plasmonic structure and an active layer. The heterodimensional plasmonic structure includes at least one nanostructure configured to form a heterodimensional junction with the active layer and to have a tunable resonant plasmon frequency. The resonant coupling may be achieved at or near room temperature and at sub-THz and THz frequencies. As used herein, a nanostructure is a structure with at least one dimension having a maximum size on the order of tens of nanometers (nm). Nanostructures may include, but are not limited to, nanodots, nanoparticles, nanowires, nanocones, nanotubes, nanocolumns and/or a combination thereof. The active layer may be two-dimensional (2D) or three-dimensional (3D). For example, the active layer may include, but is not limited to, a 2D electron gas (2 DEG), a 2D hole gas (2 DHG), a 3D electron gas (3 DEG) and/or a 3D hole gas (3 DHG). 
     It may be appreciated that the feature sizes of modern field effect transistors (FETs) have reached dimensions as low as 7 nanometers (nm). Such FETs may then be suitable as nanoscale detectors for sub-wavelength sub-THz and THz imaging. Plasmonic resonant properties of nanostructures forming heterodimensional junctions with a 2D gas (electron or hole) enable local resonant coupling and may be used for sub-wavelength imaging. In one nonlimiting example, the resonant plasmon frequency of a nanostructure may be tuned by varying a bias of a gate capacitively coupled to the nanostructures. 
     The plasmonic properties of nanostructures accounting for the boundary scattering and for the carrier fluid velocity indicate that the plasma oscillations in silicon (Si), gallium nitride (GaN), and indium gallium arsenide (InGaAs) and nanostructures may achieve high quality factors. For example, a single embedded nanostructure or an array of embedded nanostructures placed into a perforated asymmetrical 2 DEG or/and 2 DHG structures or superlattices may be used for detection, mixing, or frequency multiplication of sub-THz, THz or infrared (IR) radiation. In another example, embedded nanostructure arrays, as described herein, may be used as active elements of THz emitters and as sub-THz, THz, or IR sensitive photodetector layers for pixelless THz to visible converters. 
     In another example, combining impinging beams of the different frequencies may facilitate frequency mixing due to nonlinearity of a semiconducting device that includes a heterodimensional plasmonic structure and active layer, as described herein. At high intensity of an impinging THz electromagnetic radiation beam, frequency multiplication is achieved in some embodiments. Possible applications include THz and sub-THz components of THz imaging and sensing systems for THz and sub THz communication, beyond 5G Wi-Fi technology, biotechnology and medical THz, IR, and sub-THz systems. 
     The basic mechanism of the plasmonic detection is rectification of plasma waves excited by impinging radiation. These waves decay due to the electron (or hole for p-channel devices) scattering by impurities and lattice vibrations and due to the viscosity of the electrons (or holes) forming the electron or hole fluid if the electron-electron (or hole-hole) collisions are often enough. 
     If the decay time τ is long, the plasma waves may be resonant with the resonance plasma frequency ω p  determined by the device (e.g., transistor) size (for ω p τ&gt;&gt;1). The opposite case of decayed (overdamped) plasma waves when ω p τ&lt;1 is relatively more common. For short device sizes, parasitic and contact impedances start playing a dominant role. 
     When the electron-electron or hole-hole collisions are frequent enough, so that τ ee &lt;&lt;τ p , where 
     
       
         
           
             
               
                 
                   
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     is the electron collision time for the non-degenerate gas and for the degenerate gas, respectively, τ p  is the momentum relaxation time, q is the electronic charge, N˜n s /d ee  is the electron (or hole) concentration, n s  is the sheet carrier density, d ee  is the effective thickness of the 2 DEG or 2 DHG, his the Plank constant, ε o  is the dielectric permittivity of vacuum, ε is the relative dielectric relative constant, k B  is the Boltzmann constant, E F =n s /D 2  is the Fermi level, 
     
       
         
           
             
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     is the two-dimensional density of states. 
     For a nanostructure that corresponds to a nanoparticle, the plasma frequency for an ungated nanoparticle is given by 
       ω p =√{square root over (2ak)}  (3)
 
     Here a=n s q 2 /(4εε o m), k=π/(2R) is the wave vector, and R is the radius of the nanoparticle. 
     The quality factor is defined as Q=ω p /γ. Here γ=1/τ+v F /(2R), v F =√{square root over (2qE F /m)} are the effective scattering rate and the Fermi velocity, respectively. 
     For example, for GaN, InGaAs, and Si nanodots, resonant coupling may be achieved at room temperature at relatively high frequencies (all calculations are done for T=300 K). The GaN nanoparticles have a slightly larger quality factor, thus relatively higher sheet carrier densities may be achieved in GaN (e.g., n s= 4.16×10 12  cm −2  has been demonstrated). For InGaAs, the largest quality factor was achieved for 200 nm nanoparticles at approximately 7.6 THz. For Si and GaN, the largest quality factor was achieved for 40 nm nanoparticles at approximately 8.6 THz. Thus, these structures facilitate scanning THz images at relatively higher frequencies in some embodiments than have been achieved for typical plasmonic detectors. It is contemplated that these frequencies may reach the values suitable for applications in thermal imaging devices. 
     Varying the gate bias may change the surface depletion region for the nanoparticles enabling resonance tuning in some embodiments. Estimating the coupling capacitance between the nanoparticle and the 2 DEG as C c ˜2λRεε o , the modulation change is Q m ˜2πRεε o ΔV g , where ΔV g  is the variation of the gate bias. For a nanodot disk, this leads to the relative change in the nanodisk radius ΔR/R˜εε o ΔV g /(qn s R). For example, for ΔV g =0.1 V and ε=11.7, a frequency modulation Δf/˜ΔR/(2R) of ˜10% or more may be achieved. 
     Heterodimensional plasmonic structures with a single embedded nanoparticle may be configured to achieve imaging resolution at the nanoscale either by scanning or making multi pixel arrays. In some embodiments, such arrays may be used as the THz or infrared detector layers for pixelless image converters. 
     Analyses of the plasmonic properties of nanoparticles accounting for the boundary scattering and for the carrier fluid velocity indicate that the plasma oscillations in Si, GaN, and InGaAs and nanoparticles may achieve high quality factors. Other materials including, but not limited to, diamond, graphene or graphene heterostructures with van der Waals materials may be used for heterodimensional devices, consistent with the present disclosure. Advantageously, these oscillations are not impeded by contact resistances. This enables resonant response to the THz radiation inducing polarization dependent resonant dipole moment in some embodiments. An array of such particles placed into perforated asymmetrical 2 DEG or/and 2 DHG structures or superlattices may be used for detection, mixing, or frequency multiplication of sub-THz, THz or IR radiation in some embodiments. These structures may be used as elements of sub-THz or THz emitting devices enabling a better impedance matching for extracting the electromagnetic radiation in other embodiments. The embedded nanoparticle arrays capacitively coupled to 2 DEG or 2 DHG systems could be also used as sub-THz, THz, or IR sensitive photodetector layer for pixelless THz to visible converters. 
     Other embodiments of the technology include tunable THz and infrared field effect and field effect array detectors, mixers, phase shifters, delay lines, frequency multipliers operating in resonant and/or non-resonant regimes using nanostructures, e.g., nanoscale conducting dots, with floating potential capacitively coupled to the transistor gate. The response of such devices may be tunable by the gate bias in some embodiments and may be resonant even when the transistor operates in the collision dominated regime. According to some embodiments, the devices may be capable of detecting frequency and/or amplitude modulated signals. The ultimate modulation frequency could also reach the THz range and may increase performance of selected THz and sub-THz devices and components. 
     It is understood, that for purposes of this description Al means Aluminum, Ga means Gallium, N means Nitrogen, In means Indium, Si means Silicon, O means Oxygen, C means Carbon, As means Arsenic, Li means Lithium, Nb means Niobium, Ge means Germanium, Sb means Antimony, and P means Phosphorus. Further, it is understood that “group III elements” include the elements Al, Ga, In, Boron (B), and Thallium (Ti), and “group IV elements” include the elements C, Si, Ge, Tin (Sn), and Lead (Pb). Still further, it is understood that “THz radiation” includes radiation having a frequency between approximately 0.1 and 100 terahertz (THz, b  10   12  hertz), and “microwave radiation” includes radiation having a frequency between approximately 1 and 100 gigahertz (GHz, 10 9  hertz). It is further understood that “infrared radiation” includes radiation having a frequency between approximately 300 GHz and 430 THz. 
     Embodiments of the technology include semiconducting devices operating in the microwave and/or THz ranges and/or infrared range for the generation, adjustment, and/or detection by adjusting a voltage applied to the semiconducting device. In some embodiments, the semiconducting device has an active layer that includes a two-dimensional (electron or hole) gas. As such, active layers may include any compound capable of including the two-dimensional carrier gas, including, for example, Si, SiGe, Ge, AlGaAs, GaAs, AIN, GaN, InN, AlInAs, InSb, InP, etc. Barrier layers may include, for example, SiO 2 , SiN, a binary, ternary, or quaternary compound that includes one, two, or three group III elements, respectively, and N or a group IV element, a compound that includes elements of groups II and VI, or a combination of layers of different compositions. 
     Generally, embodiments of the technology include heterodimensional systems that include semiconducting devices configured to at least one of detect, produce or manipulate electromagnetic radiation. A semiconducting device may include a heterodimensional plasmonic structure and an active layer. The heterodimensional plasmonic structure contains one or more nanostructures configured to form a heterodimensional junction with the active layer. A plurality of nanostructures included in the heterodimensional plasmonic structure may be arranged in a two dimensional array or a three-dimensional array. As used herein, a heterodimensional plasmonic structure is a 2D or 3D array of nanostructures. The active layer may include, but is not limited to, a 2D gas (electron or hole), and/or a 3D gas (electron or hole). At least a portion of the heterodimensional plasmonic structure may be embedded into and isolated from the active layer. Such nanostructures exhibiting a resonance response at room temperature may be capacitively coupled to the active layer and may thus produce detected signals. 
       FIG. 1  illustrates an isometric view of a semiconducting device  100  consistent with several embodiments of the present disclosure. In an embodiment, semiconducting device  100  may correspond to THZ field effect transistor. Device  100  may be configured to detect, produce and/or manipulate THz electromagnetic radiation, as described herein. Device  100  includes a heterodimensional plasmonic structure  102 , an active layer  104  and a substrate  108 . Device  100  further includes a gate layer  110  and side contacts  112 ,  114 . For example, the side contacts may correspond to a source  112  and drain  114  of a field effect transistor. The source  112  and drain  114  are positioned adjacent and on opposing sides of the heterodimensional plasmonic structure  102  and of the gate layer  110 . The source  112  and the drain  114  are each separated from the gate layer  110  by a respective gap  113 ,  115 . The gaps may  113 ,  115  facilitate capture of impinging electromagnetic radiation. 
     The heterodimensional plasmonic structure  102  includes a plurality of nanostructures, e.g., nanostructure  106 , as described herein. The nanostructures may be arranged in an array. 
     In one nonlimiting example, each nanostructure may correspond to a nanocolumn. However, this disclosure is not limited in this regard. The gate layer  110  defines a plurality of voids, e.g., void  111 . Each void, e.g., void  111 , is configured to align with a corresponding nanostructure, e.g., nanostructure  106 , and may be sized to accommodate the nanostructure  106  and a depletion region  107 . For example, each nanostructure, e.g., nanostructure  106 , may be surrounded by a depletion region, e.g., depletion region  107 , separating the nanostructure  106  from the gate layer  110 . In one nonlimiting example, the void and/or depletion region may be configured to facilitate capacitive coupling between the nanostructure and the gate. 
     A shape of the nanostructure  106  and/or the void  107  may be generally circular, generally ellipsoidal with a long axis generally parallel to a side of the gate  110 , generally ellipsoidal with the long axis at an angle with respect to the side of the gate, and/or may have a compound shape that includes a plurality of generally circular and/or ellipsoidal shapes. However, this disclosure is not limited in this regard. 
     It may be appreciated that the nanostructures, e.g., nanostructure  106 , may be positioned below the void  111  defined in the gate layer  110 . The void  111  may generally align with the depletion region  107 . 
     Device  100  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. The heterodimensional plasmonic structure  102  and/or the nanostructures are configured to form a heterodimensional junction with the active layer  104  and to have a tunable resonant plasmon frequency. For example, the plasmon frequency may be tuned by application of a bias voltage to the gate  110 . The resonant coupling may be achieved at or near room temperature and at sub-THz and THz frequencies. In some embodiments, device  100  may be configured with an asymmetry between the source  112  and drain  114 , configured to enhance detections. For example, the gate layer  110  and/or the heterodimensional plasmonic structure  102  may include one or more asymmetric features, as described herein. 
       FIG. 2  illustrates a side view of a semiconducting device  200  including a three-dimensional (3D) gas, consistent with some embodiments of the present disclosure. Device  200  includes a heterodimensional plasmonic structure  202  and an active layer  204 . The heterodimensional plasmonic structure  202  includes a plurality of nanostructures  206 - 1 , . . . ,  206 - n.  In this embodiment, the active layer  204  corresponds to a three-dimensional (3D) gas. For example, the active layer  204  may correspond to a 3D electron gas (3 DEG). In another example, the active layer  204  corresponds to a 3D hole gas (3 DHG). The nanostructures  206 - 1 , . . . ,  206 - n  may include, but are not limited to, nanodots, nanoparticles, nanowires, nanocones, nanotubes, nanocolumns and/or a combination thereof. In one nonlimiting example, the nanostructures  206 - 1 , . . . ,  206 - n  may correspond to nanotubes with each nanotube containing a plurality of nanowires, e.g., an array of nanowires. 
     The nanostructures  206 - 1 , . . . ,  206  - n  are configured to form a heterodimensional junction with the active layer  204 . The nanostructures  206 - 1 , . . . ,  206  - n  may be configured to have a tunable resonant plasmon frequency. The plasmon resonant frequency may be tuned by application of a voltage to device  200 . In some embodiments, the heterodimensional plasmonic structure  202  and the plurality of nanostructures  206 - 1 , . . . ,  206  - n  may be configured to form a heterodimensional contact with the active layer  204 . 
     Device  200  may be configured to support plasma waves. Device  200  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. In other words, the electromagnetic radiation may have a frequency of at least 100 gigahertz (GHz). 
       FIG. 3  illustrates a top view  300  of a semiconducting device consistent with several embodiments of the present disclosure. Device  300  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range, as described herein. 
     Device  300  includes a heterodimensional plasmonic structure  302  and a base layer  304 . The heterodimensional plasmonic structure  302  includes a plurality of nanostructures  306 - 1 , . . . ,  306 - q,  . . . ,  306 - z , as described herein. The nanostructures  306 - 1 , . . . ,  306 - q,  . . . ,  306 - z  may be arranged in an array. In an embodiment, a first portion of the plurality of nanostructures may be fabricated with a first set of parameters and a second portion of the plurality of nanostructures may be fabricated with a second set of parameters where a selected first parameter of the first set differs from a selected second parameter of the second set by at least one percent (%). Parameters may include, but are not limited to, physical dimensions, materials and/or material properties, etc. For example, one nanostructure, e.g., nanostructure  306 - q,  may be fabricated with at least one parameter that differs from the parameters of the other nanostructures by at least one percent. In another example, a portion of nanostructures, e.g., column of nanostructures  308 , may be fabricated with at least one parameter that differs from the parameters of the other nanostructures by at least one percent. In another example, nanostructures  306 - 1 , . . . ,  306 - q,  . . . ,  306 - z may be arranged in a periodic array with a portion  310  of rows and/or columns configured to form a plasmonic waveguide. 
     In an embodiment, the base layer  304  may correspond to an active layer, e.g., a 2D electron gas (2 DEG), a 3 DEG, a 2D hole gas (2 DHG), or a 3 DHG. In another embodiment, the base layer  304  may correspond to a passivation layer. 
       FIG. 4A  illustrates a side view of a semiconducting device  400  including an ungated two-dimensional (2D) gas, consistent with some embodiments of the present disclosure. Device  400  includes a heterodimensional plasmonic structure  402 , an active layer  404  and a substrate  408 . The active layer  404  is positioned between the heterodimensional plasmonic structure  402  and the substrate  408 . The heterodimensional plasmonic structure  402  includes a plurality of nanostructures  406 - 1 , . . . ,  406 - n , as described herein. In this embodiment, the active layer  404  corresponds to a 2D gas. For example, the active layer  404  may correspond to a 2DEG. In another example, the active layer  404  corresponds to a 2 DHG. 
     The nanostructures  406 - 1 , . . . ,  406 - n  are configured to form a heterodimensional junction with the active layer  404  (i.e., with the ungated 2D gas). Device  400  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range, as described herein. 
       FIG. 4B  illustrates a side view of a semiconducting device  401  including a gated 2D gas, consistent with some embodiments of the present disclosure. Similar to device  400 , device  401  includes the heterodimensional plasmonic structure  402 , the active layer  404  and the substrate  408 . Device  401  further includes a gate  410  and a gate electrode  412 . The active layer  404  is positioned between the heterodimensional plasmonic structure  402  and the substrate  408 . The gate  410  is positioned opposite the active layer  404  with the substrate  408  sandwiched therebetween. The heterodimensional plasmonic structure  402  includes a plurality of nanostructures  406 - 1 , . . . ,  406 - n,  as described herein. In this embodiment, the active layer  404  corresponds to a 2D gas. For example, the active layer  404  may correspond to a 2 DEG. In another example, the active layer  404  corresponds to a 2 DHG. 
     The nanostructures  406 - 1 , . . . ,  406 - n  are configured to form a heterodimensional junction with the active layer  404  (i.e., with the gated 2D gas). In some embodiments, the heterodimensional plasmonic structure  402  and the plurality of nanostructures  406 - 1 , . . . ,  406 - n  may be configured to form a heterodimensional contact with the active layer  404 . The nanostructures  406 - 1 , . . . ,  406 - n  may be configured to have a tunable resonant plasmon frequency. For example, the resonant plasmon frequency may be tuned via a bias voltage applied to the gate  410 . Device  400  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. 
       FIGS. 5A and 5B  illustrate top views of a semiconducting device with continuous side contacts  500  and continuous side contacts in a cross configuration  501 , respectively, consistent with several embodiments of the present disclosure. Devices  500 ,  501  include a heterodimensional plasmonic structure  502 , a base layer  504  and a first pair of side contacts  508 - 1 ,  508 - 2 . The heterodimensional plasmonic structure  502  includes a plurality of nanostructures  506 - 1 , . . . ,  506 - m , as described herein. The side contacts  508 - 1  and  508 - 2  are positioned adjacent and on opposing sides of the array of nanostructures  506 - 1 , . . . ,  506 - m  that form the heterodimensional plasmonic structure  502 . 
     Device  501  further includes a second pair of continuous side contacts  510 - 1 ,  510 - 2 . The heterodimensional plasmonic structure  502  includes a plurality of nanostructures  506 - 1 , . . . ,  506 - m,  as described herein. The first pair of continuous side contacts  508 - 1  and  508 - 2  are positioned adjacent and on opposing sides (i.e., left side and right side) of the array of nanostructures  506 - 1 , . . . ,  506 - m  that form the heterodimensional plasmonic structure  502 . The second pair of continuous side contacts  510 - 1  and  510 - 2  are positioned adjacent and on opposing sides (i.e., top and bottom) of the array of nanostructures  506 - 1 , . . . ,  506 - m.    
     In an embodiment, the base layer  504  may correspond to an active layer, e.g., a 2 DEG, a 3 DEG, a 2 DHG, or a 3 DHG. In this embodiment, the plurality of nanostructures  506 - 1 , . . . ,  506 - m  may be configured to form heterodimensional contact with the active layer  504 . In another embodiment, the base layer  504  may correspond to a passivation layer. 
       FIGS. 6A and 6B  illustrate a top view of a semiconducting device with split side contacts  600  and split side contacts in a cross configuration  601 , respectively, consistent with several embodiments of the present disclosure. Devices  600 ,  601  include a heterodimensional plasmonic structure  602  and a base layer  604 . The heterodimensional plasmonic structure  602  includes a plurality of nanostructures  606 - 1 , . . . ,  606 - m,  as described herein. 
     Devices  600 ,  601  include a first pair of sets  608 - 1 ,  608 - 2  of split side contacts. Device  601  further includes a second pair of sets  610 - 1 ,  610 - 2  of split side contacts. Each set  608 - 1 ,  608 - 2 ,  610 - 1 ,  610 - 2  of split side contacts includes a plurality of contact portions. In one nonlimiting example, the number of contact portions in each plurality of split side contacts may be three. However, this disclosure is not limited in this regard. Other embodiments may include more or fewer contact portions. The first pair of sets  608 - 1  and  608 - 2  of split side contacts are positioned adjacent and on opposing sides (i.e., left side and right side) of the array of nanostructures  606 - 1 , . . . ,  606 - m  that form the heterodimensional plasmonic structure  602 . The second pair of sets  610 - 1  and  610 - 2  of split side contacts are positioned adjacent and on opposing sides (i.e., top and bottom) of the array of nanostructures  606 - 1 , . . . ,  606 - m.    
     In an embodiment, the base layer  604  may correspond to an active layer, as described herein. In this embodiment, the plurality of nanostructures  606 - 1 , . . . ,  606 - m  may be configured to form heterodimensional contact with the active layer  604  and the split side contacts may be configured to contact the active layer. In another embodiment, the base layer  604  may correspond to a passivation layer. 
     It may be appreciated that one or more of the configurations (e.g., plasmonic waveguide) of the array of nanostructures  302  of the semiconducting device of  FIG. 3  may be utilized in one or more embodiments of semiconducting devices  500 ,  501 ,  600 , and/or  601  of  FIGS. 5A, 5B, 6A and 6B , respectively. 
       FIG. 7  illustrates a top view  700  of a semiconducting device with a periodic array of nanostructures, periodically modulated, consistent with several embodiments of the present disclosure. Device  700  includes a heterodimensional plasmonic structure  702  and a base layer  704 . The heterodimensional plasmonic structure  702  includes a plurality of nanostructures, as described herein. In an embodiment, the heterodimensional plasmonic structure  702  may include a plurality of portions with each portion including a respective array of nanostructures. The plurality of arrays of nanostructures may be periodic and/or may be periodically modulated. For example, the heterodimensional plasmonic structure  702  may include an array of nanostructures arranged in a plurality of periodic portions  708 - 1 ,  708 - 2 , . . . ,  708 - r  that are periodically modulated in one direction. In another example, the heterodimensional plasmonic structure  702  may include the array of nanostructures arranged in a first plurality of periodic portions  708 - 1 ,  708 - 2 , . . . ,  708 - r  that are periodically modulated in a first direction. Continuing with this example, the array of nanostructures may be further arranged in a second plurality of portions  710 - 1 ,  710 - 2 , that are periodically modulated in a second direction. The second direction may differ from the first direction. In an embodiment, the base layer  704  may correspond to an active layer, e.g., a 2D electron gas (2 DEG), a 3 DEG, a 2D hole gas (2 DHG), or a 3 DHG. In this embodiment, the plurality of nanostructures may be configured to form heterodimensional contact with the active layer  704 . In another embodiment, the base layer  704  may correspond to a passivation layer. 
       FIG. 8  illustrates a side view  800  of a semiconducting device including a periodically modulated active layer, consistent with some embodiments of the present disclosure. Device  800  includes a heterodimensional plasmonic structure  802 , an active layer  804 , a substrate  808  and a gate  810 . The active layer  804  is positioned between the heterodimensional plasmonic structure  802  and the substrate  808 . The gate  810  is positioned opposite the active layer  804  with the substrate  808  sandwiched therebetween. The heterodimensional plasmonic structure  802  includes a plurality of nanostructures, as described herein. In this embodiment, the active layer  804  corresponds to a periodically modulated 2D gas. For example, the active layer  804  may correspond to a periodically modulated 2 DEG. In another example, the active layer  804  corresponds to a periodically modulated 2 DHG. 
     The heterodimensional plasmonic structure  802  and corresponding nanostructures are configured to form a heterodimensional junction with the active layer  804  (i.e., with the periodically modulated 2D gas). For example, the heterodimensional plasmonic structure  802  and corresponding nanostructures may be configured to form a heterodimensional contact with the periodically modulated 2D gas. The periodically modulated 2D gas may or may not be gated. 
     The heterodimensional plasmonic structure  802  and corresponding nanostructures may be configured to have a tunable resonant plasmon frequency. For example, the resonant plasmon frequency may be tuned via a bias voltage applied to the gate  810 . Device  800  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. 
       FIG. 9  illustrates a side view  900  of a semiconducting device including a substrate having a microfluidic channel, consistent with some embodiments of the present disclosure. Device  900  includes a heterodimensional plasmonic structure  902 , an active layer  904 , a substrate  908  and a gate  910 . The active layer  904  is positioned between the heterodimensional plasmonic structure  902  and the substrate  908 . The gate  910  is positioned opposite the active layer  904  with the substrate  908  sandwiched therebetween. In an embodiment, the device  900  includes a plurality of microfluidic channels  912 . The microfluidic channels may be defined by and/or included in the substrate  908 . The heterodimensional plasmonic structure  902  includes a plurality of nanostructures, as described herein. In this embodiment, the active layer  904  corresponds to a 2D gas. For example, the active layer  904  may correspond to a 2 DEG. In another example, the active layer  904  corresponds to a 2 DHG. 
     The heterodimensional plasmonic structure  902  and corresponding nanostructures are configured to form a heterodimensional junction with the active layer  904  (i.e., with the 2D gas). For example, the heterodimensional plasmonic structure  902  and corresponding nanostructures may be configured to form a heterodimensional contact with the 2D gas having microfluidic channels  912 . The heterodimensional plasmonic structure  902  and corresponding nanostructures may be configured to have a tunable resonant plasmon frequency. For example, the resonant plasmon frequency may be tuned via a bias voltage applied to the gate  910 . Device  900  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. 
       FIGS. 10A through 10C  illustrate respective side views  1000 ,  1030 ,  1050  of three example semiconducting devices that each include a respective passivating layer, consistent with some embodiments of the present disclosure.  FIGS. 10A through 10C  may be best understood when considered together. Each device  1000 ,  1030 ,  1050  includes a heterodimensional plasmonic structure  1002 , an active layer  1004 , a substrate  1008  and a gate  1010 . The active layer  1004  is positioned between the heterodimensional plasmonic structure  1002  and the substrate  1008 . The gate  1010  is positioned opposite the active layer  1004  with the substrate  1008  sandwiched therebetween. The heterodimensional plasmonic structure  1002  includes a plurality of nanostructures, e.g., nanostructure  1006 , as described herein. In this embodiment, the active layer  1004  corresponds to a 2D gas, as described herein. 
     The heterodimensional plasmonic structure  1002  and corresponding nanostructures are configured to form a heterodimensional junction with the active layer  1004  (i.e., with the periodically modulated 2D gas). The heterodimensional plasmonic structure  1002  and corresponding nanostructures may be configured to have a tunable resonant plasmon frequency. For example, the resonant plasmon frequency may be tuned via a bias voltage applied to the gate  1010 . Each of devices  1000 ,  1030 ,  1050  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. 
     Device  1000  of  FIG. 10A  includes a passiviting layer  1012 . In this example, the heterodimensional plasmonic structure  1002  is embedded in the passivating layer  1012  such that the passivating layer  1012  surrounds each nanostructure on their respective tops and sides but not on their respective bottoms where the nanostructures may contact the active layer  1004 . 
     Device  1030  of  FIG. 10B  includes a passiviting layer  1032 . In this example, the heterodimensional plasmonic structure  1002  is embedded in the passivating layer  1032  such that each nanostructure extends above the passivating layer  1032  on the top. The passivating layer  1032  then contacts the active layer  1004  at or near the bottom of the passivating layer  1032 . 
     Device  1050  of  FIG. 10C  includes the passiviting layer  1032 , as described herein, and further includes a plurality of microfluidic channels  1034 . The microfluidic channels are embedded in and/or defined by the passivating layer  1032 . In this example, the heterodimensional plasmonic structure  1002  is embedded in the passivating layer  1032  such that each nanostructure extends above the passivating layer  1032  on the top. The passivating layer  1032  then contacts the active layer  1004  at or near the bottom of the passivating layer  1032 . 
       FIGS. 11A and 11B  illustrate two example systems  1100 ,  1130  including a device under test (DUT) and one scanning detector or a plurality of detectors, respectively, consistent with some embodiments of the present disclosure. Example systems  1100 ,  1130  each includes a DUT  1101 . Example system  1100  further includes one scanning detector  1103 . Example system  1130  further includes a plurality of detectors  1103 - 1 , . . . ,  1103 - n.  The scanning detector  1103  and each of the plurality of detectors  1103 - 1 , . . . ,  1103 - n  are examples of a semiconducting device consistent with several embodiments of the present disclosure. The scanning detector  1103  and each of the plurality of detectors  1103 - 1 , . . . ,  1103 - n  may thus each include a heterodimensional plasmonic structure that includes one or more nanostructures and may further include an active layer, as described herein. 
     In an embodiment, the DUT  1101  may be an integrated circuit that is to be imaged by scanning detector  1103  or the plurality of detectors  1103 - 1 , . . . ,  1103 - n.  For example, the scanning detector  1103  may be moved to each of a plurality of positions in order to scan a portion or all the DUT  1101 . In another example, each detector of the array of detectors  1103 - 1 , . . . ,  1103 - n  may be configured to remain stationary and to capture a respective image of a portion of the DUT  1101 . 
       FIGS. 12A and 12B  illustrate a top view of a semiconducting device  1200  and a side view cross-section (A-A′)  1220  of the semiconducting device, respectively, consistent with some embodiments of the present disclosure.  FIGS. 12A and 12B  may be best understood when considered together. Device  1200  includes a heterodimensional plasmonic structure  1202 , a gate layer  1210  and side contacts  1212 ,  1214 . For example, the side contacts may correspond to a source  1212  and drain  1214  of a field effect transistor. The source  1212  and drain  1214  are positioned adjacent and on opposing sides of the heterodimensional plasmonic structure  1202  and of the gate layer  1210 . The source  1212  and the drain  1214  are each separated from the gate layer  1210  by a respective gap  1213 ,  1215 . Thus, device  1200  may correspond to a side contact configuration, as described herein. In another embodiment, device  1200  may be configured with side contacts in a cross configuration, as described herein. It may be appreciated that the gaps  1213 ,  1215  may facilitate receipt and capture of impinging electromagnetic radiation by the semiconducting device. In an embodiment, the gate material may transparent thus further facilitating capture of impinging electromagnetic radiation of a THz beam. 
     The heterodimensional plasmonic structure  1202  includes a plurality of nanostructures, e.g., nanostructure  1206 , arranged in an array, as described herein. In one nonlimiting example, each nanostructure may correspond to a nanodot. However, this disclosure is not limited in this regard. Each nanostructure  1206  is surrounded by a depletion region  1207 , separating the nanostructure  1206  from the gate layer  1210 . A shape of the nanostructure  1206  and/or the void  1207  may be generally circular, generally ellipsoidal with a long axis generally parallel to a side of the gate  1210 , generally ellipsoidal with the long axis at an angle with respect to the side of the gate, and/or may have a compound shape that includes a plurality of generally circular and/or ellipsoidal shapes. However, this disclosure is not limited in this regard. 
     It may be appreciated that the nanostructures, e.g., nanostructure  1206 , may be positioned below a void  1211  defined in the gate layer  1210 . The void  1211  may generally align with the depletion region  1207 . 
     Device  1200  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. 
       FIG. 13  illustrates is a top view of a semiconducting device  1300  that includes a nanostructure  1302  capacitively coupled to a gate  1310 , consistent with some embodiments of the present disclosure. In one nonlimiting example, the nanostructure  1302  may correspond to a nanodot. 
     The gate  1310  may define a void  1307  configured to accommodate the nanostructure  1302 . Device  1300  further includes side contacts  1312  and  1314 . For example, the side contacts  1312 ,  1314  may correspond to a source and drain, respectively, of a field effect transistor. The capacitive coupling is illustrated by a plurality of capacitances, e.g., capacitance  1309 . 
     A shape of the nanodot  1302  and/or the void  1307  may be generally circular, generally ellipsoidal with a long axis generally parallel to a side of the gate  1310 , generally ellipsoidal with the long axis at an angle with respect to the side of the gate, and/or may have a compound shape that includes a plurality of generally circular and/or ellipsoidal shapes. However, this disclosure is not limited in this regard. 
       FIG. 14  illustrates an isometric view  1400  of a semiconducting device that includes embedded generally conical nanostructures. Device  1400  includes a heterodimensional plasmonic structure  1402  and an active layer  1404 . The heterodimensional plasmonic structure  1402  includes a plurality of nanostructures, e.g., nanostructure  1406 , arranged in an array, as described herein. In one nonlimiting example, each nanostructure may correspond to a nanocone, i.e., may have a generally conical shape. However, this disclosure is not limited in this regard. Each nanostructure  1406  may be embedded in the active layer  1404  resulting in a void  1407  surrounding the nanocone  1406  at a top surface  1405  of the active layer  1404 . A shape of the void  1407  may generally correspond to a shape of a cross section of the nanocone. However, this disclosure is not limited in this regard. The active layer  1404  may include, but is not limited to, a 2D electron gas (2 DEG), a 3 DEG, a 2D hole gas (2 DHG), or a 3 DHG. The active layer may thus correspond to an ungated gas. Device  1400  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. 
       FIG. 15  illustrates an isometric view  1500  of a semiconducting device that includes an insulating layer. Device  1500  includes a heterodimensional plasmonic structure  1502 , an insulating layer  1503  and an active layer  1504 . The insulating layer  1503  is positioned (i.e., sandwiched) between the heterodimensional plasmonic structure  1502  and the active layer  1504 . 
     The heterodimensional plasmonic structure  1502  includes a plurality of nanostructures, e.g., nanostructure  1506 , arranged in an array, as described herein. In one nonlimiting example, each nanostructure corresponds to a nanocolumn, i.e., may have a generally cylindrical shape. However, this disclosure is not limited in this regard. 
     Device  1500  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. 
       FIG. 16  illustrates an isometric view  1600  of a semiconducting device that includes a plurality of stacked lattices. Device  1600  includes a top lattice  1601 - 1 , a middle lattice  1601 - 2  and a bottom lattice  1601 - 3 . Each lattice  1601 - 1 ,  1601 - 2 ,  1601 - 3  includes a respective heterodimensional plasmonic structure  1602 - 1 ,  1602 - 2 ,  1602 - 3  and a corresponding respective active layer  1604 - 1 ,  1604 - 2 ,  1604 - 3 . Each respective heterodimensional plasmonic structure  1602 - 1 ,  1602 - 2 ,  1602 - 3  includes a plurality of nanostructures, e.g., nanostructure  1606 - 1 ,  1606 - 2 ,  1606 - 3 , respectively. In one nonlimiting example, each nanostructure corresponds to a nanocolumn, i.e., may have a generally cylindrical shape. However, this disclosure is not limited in this regard. In some embodiments, each nanostructure  1606 - 1 ,  1606 - 2 ,  1606 - 3  may be separated from the corresponding active layer  1604 - 1 ,  1604 - 2 ,  1604 - 3  by a respective region  1608 - 1 ,  1608 - 2 ,  1608 - 3 . For example, the region may be a void and/or may be configured to facilitate capacitive coupling. In another example, a nanostructure may extend from above the top lattice  1601 - 1  through a top active layer  1604 - 1  and a middle active layer  1604 - 2  at least into a bottom active layer  1604 - 3 . 
     In an embodiment, the active layers  1604 - 1 ,  1604 - 2 ,  1604 - 3  may correspond to 2D gases. For example, the active layers  1604 - 1 ,  1604 - 2 ,  1604 - 3  may all be a 2 DEG or a 2 DHG. In another example, one active layer may differ from at least one of the other two active layers. 
     In some embodiments, the device  1600  may correspond to a 3D semiconducting structure. In these embodiments, doping of one active layer may differ from the doping of at least one of the other two active layers. For example, the top active layer  1604 - 1  may include doping corresponding to p-type, the middle active layer  1604 - 2  may be undoped (i.e., intrinsic) and the bottom active layer  1604 - 3  may include doping corresponding to n-type. Thus, in this example, the device  1600  may correspond to a 3D p-i-n device. In another example, the top active layer  1604 - 1  may include doping corresponding to n-type, the middle active layer  1604 - 2  may include doping corresponding to p-type and the bottom active layer  1604 - 3  may include doping corresponding to n-type. Thus, in this example, the device  1600  may correspond to a 3D n-p-n device. 
     Device  1600  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. 
       FIGS. 17A through 17D  illustrate example semiconducting devices  1700 ,  1730 ,  1750 ,  1770  that include asymmetry between a drain and source configured to enhance detections, consistent with some embodiments of the present disclosure. The structures of semiconducting devices  1700 ,  1730 ,  1750 ,  1770  are configured to provide an asymmetry between gate and drain that may then enable detection of sub-THz and THz electromagnetic radiation. 
     Each semiconducting device  1700 ,  1730 ,  1750 ,  1770  includes a respective heterodimensional plasmonic structure  1702 ,  1732 ,  1752 ,  1772 . Each heterodimensional plasmonic structure  1702 ,  1732 ,  1752 ,  1772  includes a respective plurality of nanostructures, e.g., nanostructure  1706 ,  1736 ,  1756 ,  1776 . Each nanostructure may be surrounded by a respective region, e.g., region  1707 ,  1737 ,  1757 ,  1777 , that may correspond to a void, in some embodiments. Each semiconducting device  1700 ,  1730 ,  1750 ,  1770  includes a respective gate  1710 ,  1740 ,  1760 ,  1780 , respective source  1712 ,  1742 ,  1762 ,  1782  and respective drain  1714 ,  1744 ,  1764 ,  1784 . The structures of semiconducting devices  1700 ,  1730 ,  1750 ,  1770  are configured to provide an asymmetry between gate and drain that may then enable detection of sub-THz and THz electromagnetic radiation. In particular, each respective heterodimensional plasmonic structure  1702 ,  1732 ,  1752 ,  1772  and/or each respective gate  1710 ,  1740 ,  1760 ,  1780  may include an asymmetric feature configured to provide the asymmetry. 
     Turning now to  FIG. 17A ,  FIG. 17A  illustrates a top view of example semiconducting device  1700 . Semiconducting device  1700  is configured to provide the asymmetry via a variable cross-section of the gate  1710  between the drain  1714  and source  1712 . For example, a width, w 1 , of the drain  1714  is less than a width, w 2 , of the source  1712 . A width of the gate  1710  may thus vary linearly between the drain  1714  and source  1712 . 
     Turning now to  FIG. 17B ,  FIG. 17B  illustrates a side view of example semiconducting device  1730 . Device  1730  includes an active layer  1734  and a substrate  1738 . For example, the active layer  1734  may include a 2D gas, as described herein. The gate  1740  has a variable thickness such that a thickness t 1  near the drain  1744  is less than a thickness t 2  near the source  1742 . In this example, the thickness varies generally linearly between the source  1742  and drain  1744 . 
     Turning now to  FIG. 17C ,  FIG. 17C  illustrates a side view of example semiconducting device  1750 . Device  1750  includes an active layer  1754  and a substrate  1758 . For example, the active layer  1754  may include a 2D gas, as described herein. The gate  1760  has a variable thickness such that a thickness t 1  near the drain  1764  is less than a thickness t 2  near the source  1762 . The thickness varies generally stepwise between the source  1762  and drain  1764 . 
     Turning now to  FIG. 17D ,  FIG. 17D  illustrates a side view of example semiconducting device  1770 . Device  1770  includes an active layer  1774  and a substrate  1778 . For example, the active layer  1774  may include a 2D gas, as described herein. The active layer  1774  includes a plurality of regions. The nanostructures of the heterodimensional plasmonic structure  1772  may be nonuniformly distributed between the source  1782  and the drain  1784  with the nonuniformity configured to provide and/or facilitate asymmetry between the gate and the drain, as described herein. 
     Devices  1700 ,  1730 ,  1750 ,  1770  may be configured to detect, produce or manipulate electromagnetic radiation having a frequency in the sub-THz, THz or infrared frequency range. The structures of semiconducting devices  1700 ,  1730 ,  1750 ,  1770  are configured to provide an asymmetry between gate and drain that may then enable detection of sub-THz and THz electromagnetic radiation. In particular, each respective heterodimensional plasmonic structure  1702 ,  1732 ,  1752 ,  1772  and/or each respective gate  1710 ,  1740 ,  1760 ,  1780  may include an asymmetric feature configured to provide the asymmetry. 
     Thus, a semiconducting device, consistent with the present disclosure, may be configured to at least one of detect, produce or manipulate electromagnetic radiation. Electromagnetic radiation having a frequency in the microwave and/or THz ranges may be detected by adjusting a voltage applied to the semiconducting device, e.g., a gate bias voltage. The semiconducting device may have an active layer that includes a two-dimensional carrier gas (electron or hole) whose density is controlled by a gate contact. The gate contact may be perforated (i.e., may define one or more voids). Nanostructures positioned in the perforations may be capacitively coupled to the gate. For example, the nanostructures may be coupled to the impinging sub-THz or THz radiation, inducing changes in the gate which change the device threshold voltage and, therefore, may be detected as the drain voltage. In another example, adjusting the gate bias may facilitate modulation of the detected signal. In another example, nonlinearity of the device may facilitate frequency mixing, combining impinging beams of electromagnetic radiation at different frequencies. At a relatively high intensity of the impinging THz beam, frequency multiplication may be achieved. Thus, embodiments of a semiconducting device consistent with the present disclosure may include tunable THz and infrared field effect and field effect array detectors, mixers, phase shifters, delay lines, and frequency multipliers. At least some embodiments may be capable of detecting frequency and/or amplitude modulated signals. At least some embodiments may have room temperature and elevated temperature detectivity, responsivity, and noise equivalent power. Embodiments are configured to be relatively low cost with all-electronic THz system capability. Some embodiments are configured to capture the entire THz beam. In some embodiments, the modulation frequency may reach the THz range. Semiconducting devices consistent with the present disclosure may thus correspond to THz and sub-THz components of THz sensing systems, THz and sub-THz communication systems, beyond 5G Wi-Fi technology, biotechnology and medical THz, IR, and sub-THz systems. 
     Some embodiments of the semiconducting device include, sub-THz and THz devices and systems for modulation, detection, and generation of sub-THz and THz radiation and for sensing gases, fluids, nanoparticles, mixtures, and biological fluids. Some embodiments may improve performance by capturing the entire electromagnetic beam, eliminating or decreasing contact and parasitic effects, and enabling cost-effective and accurate selective sensing. In some embodiments, common resonances of a nanostructure, e.g., a nanotube, and 2D or 3D electron gas plasma waves may be used, enabling modulation and sensing via heterodimensional junctions. At least some embodiments are compatible with VLSI technology and associated manufacturing process thus enabling cost reduction of THz components and systems. 
     Various embodiments may include heterodimensional plasmonic structures with nanostructures including, but not limited to, nanoparticles, nanodots, and nanowires of different shapes capacitively coupled to 2 DEG and 2 DHG layers or superlattices. These structures form parts of tunable THz and infrared field effect and field effect array detectors, mixers, phase shifters, delay lines, frequency multipliers operating in resonant and/or non-resonant regimes according to various embodiments of the technology. The response of such devices according to some embodiments is tunable by the gate bias and may be resonant even when the transistor operates in the collision dominated regime but the nanostructures response is resonant. Some embodiments of devices according to the present disclosure are capable of detecting frequency and/or amplitude modulated signal. In some embodiments, the modulation frequency may be in the THz range. 
     In some embodiments, the THz field may polarize the nanostructures and the response may be sensitive to radiation helicity. Radiation having a frequency in the microwave and/or THz ranges may be detected as the voltage induced between the source and drain contacts. Tuning may be accomplished by adjusting a voltage applied to the semiconducting device. The semiconducting device according to some embodiments, has an active layer or active layers that include 2 DEG or/and 2 DHG, whose density is controlled by the gate contact. The gate contact may be perforated and nanostructures, e.g., nanodots, may be positioned in the perforations and may be capacitively coupled to the gate. The nanodots may be coupled to impinging sub-THz or THz radiation inducing changes in the gate which change the device threshold voltage and, therefore, detected as the drain voltage. Changing the gate bias allows for the modulation of the detected signal. 
     In some embodiments, asymmetry between the drain and gate is configured to enable detection of impinging electromagnetic radiation. Such asymmetry may be achieved using the boundary conditions in some embodiments (ideally an open circuit between at the drain and short circuit at the source). However, a more efficient detection may be achieved in some embodiments when asymmetry is achieved by a bias drain current or built-in into some embodiments of the device structure. 
     In some embodiments, THz radiation may be shone onto a gate-drain spacing on the device, or simultaneously shone onto both gate-source spacing and gate drain spacing. Further, in some embodiments, the gate may include a material that allows radiation to pass through it (i.e., be transparent) and the device may include a substrate contact. 
     Some embodiments use two-dimensional electron or hole gas (or both) that are excited by impinging radiation. In some embodiments, characteristics of the two-dimensional carrier gas may be modified by adjusting the applied voltage, which in turn adjusts the frequency response of the device. In some embodiments, the frequency response of the device may further be adjusted by modifying various physical parameters of the semiconducting device. 
     When an array of devices (i.e., diodes, field effect transistors, etc.) is used, the same voltage may be applied to the various contacts or two or more different voltages may be applied to the various contacts. While devices are shown having a number and configuring gate, and the configuration of contacts, it is understood that these are presented for illustrative purposes only. Some embodiments of the technology include devices that include any number and/or configuration of contacts. 
     The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described (or portions thereof), and it is recognized that various modifications are possible within the scope of the claims. Accordingly, the claims are intended to cover all such equivalents. 
     Various features, aspects, and embodiments have been described herein. The features, aspects, and embodiments are susceptible to combination with one another as well as to variation and modification, as will be understood by those having skill in the art. The present disclosure should, therefore, be considered to encompass such combinations, variations, and modifications.