Abstract:
A microcavity-controlled two-dimensional carbon lattice structure device selectively modifies to reflect or to transmit, or emits, or absorbs, electromagnetic radiation depending on the wavelength of the electromagnetic radiation. The microcavity-controlled two-dimensional carbon lattice structure device employs a graphene layer or at least one carbon nanotube located within an optical center of a microcavity defined by a pair of partial mirrors that partially reflect electromagnetic radiation. The spacing between the mirror determines the efficiency of elastic and inelastic scattering of electromagnetic radiation inside the microcavity, and hence, determines a resonance wavelength of electronic radiation that is coupled to the microcavity. The resonance wavelength is tunable by selecting the dimensional and material parameters of the microcavity. The process for manufacturing this device is compatible with standard complementary metal oxide semiconductor (CMOS) manufacturing processes.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to an optoelectronic device, and particularly to an optoelectronic device employing a microcavity and a two-dimensional lattice structure embedded therein, and methods of manufacturing the same. 
         [0002]    Current optoelectronic technologies based on silicon and group III-V semiconductor compounds have large device footprints. For example, typical optoelectronic devices currently available have an average device area on the order of a square millimeter. Further, current optoelectronic devices also have a limited switching speed. For example, on-chip optoelectronic components operating in the terahertz regime are not currently available. 
         [0003]    Two-dimensional carbon lattice structures include sp 2 -bonded carbon atoms that are densely packed in a hexagonal lattice structure. If the two-dimensional carbon lattice structure is topologically planar, the two-dimensional carbon lattice structure constitutes a graphene layer. If the two-dimensional carbon lattice structure includes a curvature in one direction and the two-dimensional carbon lattice structure wraps around to form a topologically tube-shaped structure, the two-dimensional carbon lattice structure constitutes a carbon nanotube. 
         [0004]    A graphene layer and a carbon nanotube allow for modulating charge carrier densities at a very high speed. Moreover, a graphene layer and a carbon nanotube absorb and emit light across the entire range of the electromagnetic spectrum, and sustain high electrical current densities and extreme temperatures. Despite the superior performance potential of a graphene layer and a carbon nanotube relative to silicon and group III-V semiconductor compounds in terms of such properties, formation of a compact optoelectronic device based on a graphene layer or a carbon nanotube and smaller than currently available optoelectronic technologies based on silicon and group III-V semiconductor compounds is a significant challenge because coupling between electromagnetic radiation and charge carriers of the graphene layer and/or the carbon nanotube is relatively weak. 
       BRIEF SUMMARY 
       [0005]    A microcavity-controlled two-dimensional carbon lattice structure device selectively modifies to reflect or to transmit, or emits, or absorbs, electromagnetic radiation depending on the wavelength of the electromagnetic radiation. The microcavity-controlled two-dimensional carbon lattice structure device employs a graphene layer or at least one carbon nanotube located within an optical center of a microcavity defined by a pair of partial mirrors that partially reflect electromagnetic radiation. The spacing between the mirrors determines the efficiency of elastic and inelastic scattering of electromagnetic radiation inside the microcavity, and hence, determines a resonance wavelength of electronic radiation that is coupled to the microcavity. The resonance wavelength is tunable by selecting the dimensional and material parameters of the microcavity. The process for manufacturing this device is compatible with standard complementary metal oxide semiconductor (CMOS) manufacturing processes. 
         [0006]    According to an aspect of the present disclosure, an electromagnetic radiation detector is provided, which includes: a stack, from bottom to top, of a first partial mirror, a first transparent layer, a second transparent layer, and a second partial mirror; at least one two-dimensional carbon lattice structure embedded in the second transparent layer; a first contact electrode in contact with one end of the at least one two-dimensional carbon lattice structure and embedded within the second transparent layer; a second contact electrode in contact with an opposite end of the at least one two-dimensional carbon lattice structure and embedded within the second transparent layer; and a circuit connected across the first contact electrode and the second contact electrode and configured to provide an electrical bias voltage across the first contact electrode and the second contact electrode and to measure electrical current that passes through the at least one two-dimensional carbon lattice structure upon irradiation of the at least one two-dimensional carbon lattice structure with electromagnetic radiation. 
         [0007]    According to another aspect of the present disclosure, an electromagnetic radiation emitter is provided, which includes: a stack, from bottom to top, of a first partial mirror, a first transparent layer, a second transparent layer, and a second partial mirror; at least one two-dimensional carbon lattice structure embedded in the second transparent layer; a first contact electrode in contact with one end of the at least one two-dimensional carbon lattice structure and embedded within the second transparent layer; a second contact electrode in contact with an opposite end of the at least one two-dimensional carbon lattice structure and embedded within the second transparent layer; and a circuit connected across the first contact electrode and the second contact electrode and configured to provide an electrical bias voltage across the first contact electrode and the second contact electrode and to switch electrical current that passes through the at least one two-dimensional carbon lattice structure, wherein electromagnetic radiation is emitted from the at least one two-dimensional carbon lattice structure while electrical current passes through the at least one two-dimensional carbon lattice structure. 
         [0008]    According to yet another aspect of the present disclosure, an electromagnetic radiation modulator is provided, which includes: a stack, from bottom to top, of a first partial mirror, a first transparent layer, a second transparent layer, and a second partial mirror; at least one two-dimensional carbon lattice structure embedded in the second transparent layer; a first contact electrode in contact with one end of the at least one two-dimensional carbon lattice structure and embedded within the second transparent layer; a second contact electrode in contact with an opposite end of the at least one two-dimensional carbon lattice structure and embedded within the second transparent layer; and a circuit configured to apply electrical bias to one of the first partial mirror and the second partial mirror relative to the first contact electrode, and to modulate electrical current through the at least one two-dimensional carbon lattice structure, wherein a transmission coefficient of electromagnetic radiation passing through the stack is modulated by electrical current passing through the at least one two-dimensional carbon lattice structure. 
         [0009]    According to still another aspect of the present disclosure, a method of forming an optoelectronic device is provided, which includes: forming a first transparent layer on a substrate; placing at least one two-dimensional carbon lattice structure on a top surface of the first transparent layer; forming a first contact electrode on one end of the at least one two-dimensional carbon lattice structure and a second contact electrode on another end of the at least one two-dimensional carbon lattice structure; forming a second transparent layer on the at least one two-dimensional carbon lattice structure, the first and second contact electrodes, and the first transparent layer; forming a first partial mirror on a bottom surface of the first transparent layer and a second partial mirror on a top surface of the second transparent layer; and forming a circuit that electrically biases the second contact electrode relative the first contact electrode. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0010]      FIG. 1A  is a top-down view of a first exemplary structure after formation of a first transparent layer on a substrate according to a first embodiment of the present disclosure. 
           [0011]      FIG. 1B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 1A  along the plane B-B′ in  FIG. 1A . 
           [0012]      FIG. 2A  is a top-down view of the first exemplary structure after formation of a trench within the substrate and exposure of a bottom surface of the first transparent layer according to the first embodiment of the present disclosure. 
           [0013]      FIG. 2B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 2A  along the plane B-B′ in  FIG. 2A . 
           [0014]      FIG. 3A  is a top-down view of the first exemplary structure after attachment of at least one graphene layer on a top surface of the first transparent layer according to the first embodiment of the present disclosure. 
           [0015]      FIG. 3B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 3A  along the plane B-B′ in  FIG. 3A . 
           [0016]      FIG. 4A  is a top-down view of the first exemplary structure after application and patterning of a mask layer over the at least one graphene layer and the first transparent layer according to the first embodiment of the present disclosure. 
           [0017]      FIG. 4B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 4A  along the plane B-B′ in  FIG. 4A . 
           [0018]      FIG. 5A  is a top-down view of the first exemplary structure after formation of contact electrodes by a masked deposition according to the first embodiment of the present disclosure. 
           [0019]      FIG. 5B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 5A  along the plane B-B′ in  FIG. 5A . 
           [0020]      FIG. 6A  is a top-down view of the first exemplary structure after a lift-off of the mask layer according to the first embodiment of the present disclosure. 
           [0021]      FIG. 6B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 6A  along the plane B-B′ in  FIG. 6A . 
           [0022]      FIG. 7A  is a top-down view of the first exemplary structure after formation of a second transparent layer according to the first embodiment of the present disclosure. 
           [0023]      FIG. 7B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 7A  along the plane B-B′ in  FIG. 7A . 
           [0024]      FIG. 8A  is a top-down view of the first exemplary structure after formation of a front-side partial mirror and a back-side partial mirror according to the first embodiment of the present disclosure. 
           [0025]      FIG. 8B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 8A  along the plane B-B′ in  FIG. 8A . 
           [0026]      FIG. 9A  is a top-down view of the first exemplary structure after formation contact via structures that provide electrical contact to the contact electrodes according to the first embodiment of the present disclosure. 
           [0027]      FIG. 9B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 9A  along the plane B-B′ in  FIG. 9A . 
           [0028]      FIG. 10  is a schematic view of a first exemplary structure after formation of a first bias and current measurement circuit for operation of the first exemplary structure as a light detector according to the first embodiment of the present disclosure. 
           [0029]      FIG. 11  is a schematic view of a second exemplary structure, which is derived from the first exemplary structure of  FIGS. 9A and 9B , after formation of a second bias and current measurement circuit for operation of the second exemplary structure as a light detector according to a second embodiment of the present disclosure. 
           [0030]      FIG. 12  is a schematic view of a third exemplary structure, which is derived from the first exemplary structure of  FIGS. 9A and 9B , after formation of a first bias and switching circuit for operation of the third exemplary structure as a light emitter according to a third embodiment of the present disclosure. 
           [0031]      FIG. 13  is a schematic view of a fourth exemplary structure, which is derived from the first exemplary structure of  FIGS. 9A and 9B , after formation of a second bias and switching circuit for operation of the fourth exemplary structure as a light emitter according to a fourth embodiment of the present disclosure. 
           [0032]      FIG. 14  is a schematic view of a fifth exemplary structure, which is derived from the first exemplary structure of  FIGS. 9A and 9B , after formation of a bias and signal amplification circuit for operation of the fifth exemplary structure as a light modulator according to a fifth embodiment of the present disclosure. 
           [0033]      FIG. 15A  is a top-down view of a sixth exemplary structure that is derived from the first exemplary structure of  FIGS. 2A and 2B  by placing at least one carbon nanotube on the first transparent layer according to a sixth embodiment of the present disclosure. 
           [0034]      FIG. 15B  is a vertical cross-sectional view of the sixth exemplary structure of  FIG. 15A  along the plane B-B′ in  FIG. 15A . 
           [0035]      FIG. 16A  is a top-down view of the sixth exemplary structure after formation of a second transparent layer according to the sixth embodiment of the present disclosure. 
           [0036]      FIG. 16B  is a vertical cross-sectional view of the sixth exemplary structure of  FIG. 16A  along the plane B-B′ in  FIG. 16A . 
           [0037]      FIG. 17  is a schematic view of the sixth exemplary structure after formation of a first bias and current measurement circuit for operation of the sixth exemplary structure as a light detector according to the sixth embodiment of the present disclosure. 
           [0038]      FIG. 18  is a schematic view of a seventh exemplary structure, which is derived from the sixth exemplary structure of  FIGS. 16A and 16B , after formation of a second bias and current measurement circuit for operation of the seventh exemplary structure as a light detector according to a seventh embodiment of the present disclosure. 
           [0039]      FIG. 19  is a schematic view of an eighth exemplary structure, which is derived from the sixth exemplary structure of  FIGS. 16A and 16B , after formation of a first bias and switching circuit for operation of the eighth exemplary structure as a light emitter according to an eighth embodiment of the present disclosure. 
           [0040]      FIG. 20  is a schematic view of a ninth exemplary structure, which is derived from the sixth exemplary structure of  FIGS. 16A and 16B , after formation of a second bias and switching circuit for operation of the ninth exemplary structure as a light emitter according to a ninth embodiment of the present disclosure. 
           [0041]      FIG. 21  is a schematic view of a tenth exemplary structure, which is derived from the sixth exemplary structure of  FIGS. 16A and 16B , after formation of a bias and signal amplification circuit for operation of the tenth exemplary structure as a light modulator according to a tenth embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0042]    As stated above, the present disclosure relates to an optoelectronic device employing a microcavity and a two-dimensional lattice structure embedded therein, and methods of manufacturing the same, which are now described in detail with accompanying figures. It is noted that like reference numerals refer to like elements across different embodiments. 
         [0043]    Referring to  FIGS. 1A and 1B , a first exemplary structure according to a first embodiment of the present disclosure includes a substrate  10 . The substrate  10  can include a conductive material, an insulator material, a semiconductor material, or any solid material provided that the substrate  10  can provide structural support to layers to be subsequently formed. 
         [0044]    A first transparent layer  20  having a first thickness t 1  is formed on the top surface of the substrate  10 . The first transparent layer  20  includes a material that is optically transparent within a wavelength range, which is herein referred to as a first transparent wavelength range. The first transparent layer  20  can be formed, for example, by chemical vapor deposition, physical vapor deposition, vacuum evaporation or evaporation at subatomic pressure, atomic layer deposition, spin coating, layer transfer and bonding from another substrate, or a combination thereof. The first transparent layer  20  has a first refractive index of n 1 . 
         [0045]    A first wavelength λ 1  is herein defined as the product of 4 and the first thickness t 1  and the first refractive index n 1 , i.e., λ 1 =4×t 1 ×n 1 . If the first refractive index n 1  is a function of wavelength of electromagnetic radiation, the first refractive index n 1  herein refers to value at the first wavelength λ 1 . It is noted that a refractive index of a material is a slowly varying function of the wavelength of electromagnetic radiation, and thus, the first wavelength λ 1  can be defined for any given value of the first thickness t 1 . 
         [0046]    The material of the first transparent layer  20  is optically transparent at the first wavelength λ 1 , i.e., has a transmission coefficient that is substantially equal to 1 at the first wavelength λ 1 . The first refractive index n 1  can have a value from 1.0 to 10, although greater values for the first refractive index n 1  can also be employed. The first thickness t 1  can be from 2.5 nm to 1 cm, although lesser and greater values can be employed for the first thickness t 1 . In one embodiment, the first wavelength λ 1  can be in the ultraviolet range, i.e., from 10 nm to 400 nm, in the visible range, i.e., from 400 nm to 800 nm, or in the infrared range, i.e., from 800 nm to 1 mm. 
         [0047]    The material of the first transparent layer  20  can be, for example, silicon oxide, silicon nitride, silicon oxynitride, a dielectric oxide of an alkali metal, a dielectric oxide of an alkaline earth metal, a dielectric oxide of a transition metal, a dielectric oxide of a Lanthanide, a dielectric oxide of an Actinide, a dielectric nitride of a metallic element, or an alloy thereof. 
         [0048]    Referring to  FIGS. 2A and 2B , a trench  11  is formed through a portion of the substrate  10  so that a bottom surface of the first transparent layer  20  is physically exposed within the trench  11 . The area of the trench  11  is schematically illustrated with a dotted rectangle in  FIG. 2A . 
         [0049]    The trench  11  can be formed, for example, by flipping the first exemplary structure upside down, applying a photoresist (not shown) on the substrate  10 , patterning the photoresist by lithographic exposure and development, transferring the pattern in the photoresist through the substrate  10  by an etch process that employs the patterned photoresist as an etch mask, and removing the photoresist selective to the first transparent layer  20 . The etch process can include an anisotropic etch such as a reactive ion etch, and/or an isotropic etch such as a wet etch. For example, if the first transparent layer  20  includes silicon oxide or silicon nitride and the substrate  10  includes a semiconductor material, an anisotropic etch or a wet etch that removes the semiconductor material selective to silicon oxide or silicon nitride can be employed. 
         [0050]    The etch process continues until a physically exposed surface of the first transparent layer  20  is detected at a bottom surface of the trench  11  (while the first exemplary structure is upside down). The end portion of the etch process employs an etch chemistry that etches the material of the substrate  10  selective to the material of the first transparent layer  20 , i.e., etches the material of the substrate  10  while not etching the material of the first transparent layer  20 . The removal of the photoresist can be effected, for example, by ashing. 
         [0051]    The lateral dimensions of the trench  11  (e.g., the length of a side for a trench  11  having a rectangular cross-sectional area or a diameter for a trench  11  having a circular horizontal cross-sectional area) is greater than the first wavelength λ 1 , and can be from 50 nm to 1 cm, although lesser and greater lateral dimensions can also be employed. 
         [0052]    Referring to  FIGS. 3A and 3B , at least one two-dimensional carbon lattice structure  30  is placed on the top surface of the first transparent layer  20 . As used herein, a two-dimensional carbon lattice structure refers to any carbon lattice structure in which sp 2 -bonded carbon atoms are densely packed in a hexagonal lattice structure. Two-dimensional carbon lattice structures include, for example, a graphene monolayer, a carbon nanotube or a film or array thereof. 
         [0053]    In the first embodiment, the at least one two-dimensional carbon lattice structure can be at least one graphene layer  30 , which is attached to the top surface of the first transparent layer  20  by a layer transfer process. The at least one graphene layer  30  can be a monolayer of graphene, or can be a stack of a plurality of graphene monolayers. If the at least one graphene layer  30  includes a stack of a plurality of graphene monolayers, the total number of the graphene monolayers within the at least one graphene layer  30  can be, for example, from 2 to 10, although a greater number can also be employed. The at least one graphene layer  30  can be mechanically exfoliated from any structure including one or more graphene layers, and can be transferred onto the top surface of the first transparent layer  20 . 
         [0054]    In one embodiment, the thickness of the at least one graphene layer  30  can be selected to be less than 25% of the first thickness t 1 . In one embodiment, the thickness the thickness of the at least one graphene layer  30  can be selected to be less than 10% of the first thickness t 1 . The smaller the ratio of the thickness of the at least one graphene layer  30 , the greater the fraction of the volume of the at least one graphene layer  30  that is placed near the peak of the amplitude of electromagnetic radiation that forms a standing wave within a microcavity that includes the first transparent layer  20  and a second transparent layer to be subsequently formed. Because the at least one graphene layer  30  is placed on a planar top surface of the first transparent layer, the bottom surface of the at least one graphene layer  30  is coplanar with the top surface of the first transparent layer  20 . 
         [0055]    Referring to  FIGS. 4A and 4B , a mask layer  37  is deposited over the physically exposed top surface of the at least one graphene layer  30  and the first transparent layer  20 , and is lithographically patterned. In one embodiment, the mask layer  37  is a soft mask layer including a carbon-based material. For example, the mask layer  37  can include a photoresist, a material sensitive to electron beam irradiation, i.e., an e-beam resist (e.g., poly(methyl methacrylate) or hydrogen silsesquioxane), or a carbon-based material that is not sensitive to irradiation by photons or electrons. Alternately, the mark layer  37  can be a hard mask layer including a material that is not carbon-based. For example, the mask layer  37  can include a dielectric material different from the dielectric material of the insulator layer, or can include a metallic material. The material of the mask layer  37  is selected such that an etch process exists that can etch the material of the mask layer  37  selective to the material of the at least one graphene layer  30  and the material of the first transparent layer  20 . For example, if the mask layer  37  includes an organic material such as a photoresist or an e-bean resist, the etch process to be subsequently used can employ an organic solvent such as acetone. 
         [0056]    If the mask layer  37  includes a photoresist, the mask layer  37  can be patterned by lithographic exposure and subsequent development. If the mask layer  37  includes an e-beam resist, the mask layer  37  can be patterned by exposure with electron beam and subsequent development. If the mask layer  37  is a hard mask layer or if the mask layer  37  includes a carbon-based material that is not sensitive to irradiation by photons or electrons, the mask layer  37  can be patterned by applying a photoresist layer (not shown) or an e-beam resist layer (not shown) thereupon, patterning the photoresist layer or the e-beam resist layer, transferring the pattern into the mask layer  37 , and optionally removing the photoresist layer or the e-beam resist layer. 
         [0057]    A first opening and a second opening laterally separated from the first opening are formed within the mask layer  37 . The mask layer  37  covers at least a center portion of the region of the at least one graphene layer overlying the trench  11 . In one embodiment, the mask layer  37  can cover the entirety of the region of the at least one graphene layer overlying the trench  11  as illustrated in  FIGS. 4A and 4B . In another embodiment, the mask layer  37  can cover a center portion of the region of the at least one graphene layer overlying the trench  11 , and at least one peripheral portion of the region of the at least one graphene layer overlying the trench  11  can be within the area of the openings in the mask layer  37  trench. 
         [0058]    Lateral dimensions of each of the first opening and the second opening (e.g., the length of a side for an opening having a rectangular cross-sectional area or a diameter for an opening having a circular horizontal cross-sectional area) can be 20 nm to 1 cm, although lesser and greater lateral dimensions can also be employed. The effective area of the optoelectronic device to be subsequently formed is determined by the common area between the area of the trench  11  and the area of the mask layer  37  as patterned. 
         [0059]    Referring to  FIGS. 5A and 5B , a conductive material is anisotropically deposited in the openings and over the mask layer  37  in a direction perpendicular to the top surface of the first transparent layer  20 . A portion of the conductive material deposited in the first opening forms a first contact electrode  32 . A portion of the conductive material deposited in the second opening forms a second contact electrode  34 . The conductive material deposited over the mask layer  37  is herein referred to an overlying conductive material layer  31 . The first contact electrode  32 , the second contact electrode  34 , and the overlying conductive material layer  31  are formed simultaneously. 
         [0060]    The first contact electrode  32 , the second contact electrode  34 , and the overlying conductive material layer  31  includes an elemental metal, an alloy of at least two elemental metals, a conductive metallic nitride, a conductive metallic carbide, a doped semiconductor material, an alloy thereof, and/or a stack thereof. The materials that can be employed for the first contact electrode  32 , the second contact electrode  34 , and the overlying conductive material layer  31  include, but are not limited to, Pd, Pt, Ni, Au, Ag, Cu, Al, Ti, Ta, W, TiN, TaN, WN, TiC, TaC, WC, doped silicon, an alloy thereof, and a stack thereof. 
         [0061]    The conductive material of the first contact electrode  32 , the second contact electrode  34 , and the overlying conductive material layer  31  can be deposited, for example, by vacuum evaporation, physical vapor deposition, or a combination thereof. 
         [0062]    The first contact electrode  32 , the second contact electrode  34 , and the overlying conductive material layer  31  have a same composition and a same thickness. The thickness of the first contact electrode  32  and the second contact electrode  34  can be from 5 nm to 1,000 nm, although lesser and greater thicknesses can also be employed. The thickness of the first contact electrode  32  and the second contact electrode  34  is less than the thickness of the mask layer  37 . Each of the first contact electrode  32  and the second contact electrode  34  has a bottommost surface that is coplanar with the top surface of the first transparent layer  20 . 
         [0063]    Referring to  FIGS. 6A and 6B , the mask layer  37  and the overlying conductive material layer  31  are lifted off the first transparent layer  20 , the at least one graphene layer  30 , the first contact electrode  32 , and the second contact electrode  34 , for example, by an etch. The etch can be a wet etch that dissolves the material of the mask layer  37  selective to the dielectric material of the first transparent layer  20  and selective to the conductive material of the first contact electrode  32  and the second contact electrode  34 . For example, if the mask layer  37  is a soft mask layer, an organic solvent that dissolves the carbon-based material of the soft mask layer selective to the dielectric material of the first transparent layer  20  and the conductive material of the first contact electrode  32  and the second contact electrode  34  can be employed. If the mask layer  37  is a hard mask layer, a wet etch chemistry that dissolves the material of the hard mask layer selective the dielectric material of the first transparent layer  20  and the conductive material of the first contact electrode  32  and the second contact electrode  34  can be employed. The overlying conductive material layer  31  is not dissolved during the lift-off process, but is physically separated from the first transparent layer  20 , the at least one graphene layer  30 , the first contact electrode  32 , and the second contact electrode  34  as the material of the mask layer  37  is etched or dissolved. The bottommost surfaces of the first contact electrode  32  and the second contact electrode  34  are coplanar with the top surface of the first transparent layer  20 . 
         [0064]    Referring to  FIGS. 7A and 7B , a second transparent layer  40  having a second thickness t 2  is formed on the physically exposed top surfaces of the first transparent layer  20 , the at least one graphene layer  30 , the first contact electrode  32 , and the second contact electrode  34 . The second transparent layer  40  includes a material that is optically transparent within a wavelength range, which is herein referred to as a second transparent wavelength range. The second transparent layer  40  can be formed, for example, by chemical vapor deposition, physical vapor deposition, vacuum evaporation or evaporation at subatomic pressure, atomic layer deposition, spin coating, or a combination thereof. The material of the second transparent layer  40  can be any of the material that can be employed for the material of the first transparent layer  20 . The second transparent layer  40  has a second refractive index of n 2 . 
         [0065]    A second wavelength λ 2  is herein defined as the product of 4 and the second thickness t 2  and the second refractive index n 2 , i.e., λ 2 =4×t 2 ×n 2 . If the second refractive n 2  is a function of wavelength of electromagnetic radiation, the second refractive index n 2  herein refers to value at the second wavelength λ 2 . The second wavelength λ 2  can be defined for any given value of the second thickness t 2 . 
         [0066]    The material of the second transparent layer  40  is optically transparent at the second wavelength λ 2 . The second refractive index n 2  can have a value from 1.0 to 10, although greater values for the second refractive index n 2  can also be employed. The second thickness t 2  can be from 2.5 nm to 2 cm, although lesser and greater values can be employed for the second thickness t 2 . In one embodiment, the second wavelength λ 2  can be in the ultraviolet range, i.e., from 10 nm to 400 nm, in the visible range, i.e., from 400 nm to 800 nm, or in the infrared range, i.e., from 800 nm to 2 mm. 
         [0067]    It is understood that the at least one graphene layer  30 , the first contact electrode  32 , and the second contact electrode  34  may, or may not, be visible through the second transparent layer  40  in the top-down view of  FIG. 7A  depending on whether the material of the second transparent layer  40  is optically transparent within the visible spectrum. For example, if the second wavelength λ 2  is within the infrared range or within the ultraviolet range and if the material of the second transparent layer  40  is not optically transparent in the visible spectrum (between 400 nm and 800 nm in wavelength), the at least one graphene layer  30 , the first contact electrode  32 , and the second contact electrode  34  may not be visible in the top-down view of  FIG. 7A . 
         [0068]    Further, while  FIG. 7B  illustrates an embodiment in which the topography of the top surface of the second transparent layer  40  is planar (which occurs, for example, when the thicknesses of the at least one graphene layer  30  and the first and second contact electrodes ( 32 ,  34 ) are negligible compared to the second thickness t 2 ), embodiments are also contemplated in which the thicknesses of the at least one graphene layer  30  and the first and second contact electrodes ( 32 ,  34 ) are not negligible compared to the second thickness t 2 , and the top surface of the second transparent layer  40  has a topography that reflects the underlying topography of the top surfaces of the at least one graphene layer  30  and the first and second contact electrodes ( 32 ,  34 ). 
         [0069]    The second wavelength λ 2  can be substantially the same as the first wavelength λ 1 , i.e., 4×t 1 ×n 1 ≅4×t 2 ×n 2 . In one embodiment, the second wavelength λ 2  can be within 25% of the first wavelength λ 1 , i.e., 0.75×λ 1 &lt;λ 2 &lt;1.25×λ 1 . In other words, the product of the first thickness t 1  and the first index of refraction n 1  can be within 25% of the product of the second thickness t 2  and the second index of refraction n 2 . In one embodiment, the second wavelength λ 2  can be within 10% of the first wavelength λ 1 , i.e., 0.90×λ 1 &lt;λ 2 &lt;1.10×λ 1 . In one embodiment, the second wavelength λ 2  can be within 1% of the first wavelength λ 1 , i.e., 0.99×λ 1 &lt;λ 2 &lt;1.01×λ 1 . In one embodiment, the second wavelength λ 2  can the same as the first wavelength λ 1  within the limit of measurement errors. 
         [0070]    In one embodiment, the material of the first transparent layer  20  can be the same as the material of the second transparent layer  40 . In this case, the first index of refraction n 1  is the same as the second index of refraction n 2 . In this case, the second thickness t 2  can be substantially the same as the first thickness t 1 . In one embodiment, the second thickness t 2  can be within 25% of the first thickness t 1 , i.e., 0.75×t 1 &lt;t 2 &lt;1.25×t 1 . In other words, the first thickness t 1  can be within 25% of the second thickness t 2 . In one embodiment, the second thickness t 2  can be within 10% of the first thickness t 1 , i.e., 0.90×t 1 &lt;t 2 &lt;1.10×t 1 . In one embodiment, the second thickness t 2  can be within 1% of the first thickness t 1 , i.e., 0.99×t 1 &lt;t 2 &lt;1.01×t 1 . In one embodiment, the second thickness t 2  can be the same as the first thickness t 1  within the limit of measurement errors. 
         [0071]    Referring to  FIGS. 8A and 8B , a first partial mirror  80 , a substrate partial mirror  80 ′, and a second partial mirror  70  are formed on the first exemplary structure. The first partial mirror  80  is formed on the bottom surface of the first transparent layer  20 , and the second partial mirror  70  is formed on the top surface of the second transparent layer  40 . The substrate partial mirror  80 ′ is formed on the back surface of the substrate  10 . 
         [0072]    Each of the first partial mirror  80 , the substrate partial mirror  80 ′, and the second partial mirror  70  includes a metal layer of a specific but not necessarily the same thickness or a reflective stack of alternating dielectric thin films having different indices of refraction. Non-limiting exemplary materials that can be employed for the first partial mirror  80 , the substrate partial mirror  80 ′, and the second partial mirror  70  include Ag, Au, Cu, Al, Ta, Ti, and a superlattice of silicon oxide and silicon nitride. 
         [0073]    The composition of the metal layer or the reflective stack is selected so that the first partial mirror  80 , the substrate partial mirror  80 ′, and the second partial mirror  70  partially reflects electromagnetic radiation in the range between the first wavelength λ 1  and the second wavelength λ 2  (or at the common wavelength if the first wavelength λ 1  is the same as the second wavelength λ 2 ), and transmits a fraction of the electromagnetic radiation in that wavelength range. The reflectivity, i.e., the fraction of the reflected light relative to the incident light, of the first partial mirror  80  can be from 0.1 to 0.9, although lesser or greater values can be employed for the reflectivity. 
         [0074]    The first partial mirror  80  and the substrate partial mirror  80 ′ can be formed simultaneously by a deposition process that deposits a metal layer or a highly reflective stack of alternating dielectric thin films. For example, the first partial mirror  80  and the substrate partial mirror  80 ′ can be deposited, for example, by vacuum evaporation, atomic layer deposition, chemical vapor deposition, physical vapor deposition, or a combination thereof. Depending on the deposition process employed, materials may, or may not, be deposited on the sidewalls of the trench  11 . 
         [0075]    The second partial mirror  70  can be formed before, simultaneously with, or after formation of the first partial mirror  80  and the substrate partial mirror  80 ′. The same type of deposition processes can be employed to deposit a metal layer or a highly reflective stack of alternating dielectric thin films for the second partial mirror  70 . 
         [0076]    Optionally, an optically transparent capping layer (not shown) can be formed over the first partial mirror  80  and second partial mirror  70  to protect the first partial mirror  80  and the second partial mirror  70  during subsequent handling or operation. 
         [0077]    The stack of the first partial mirror  80 , the first transparent layer  20 , the second transparent layer  40 , and the second partial mirror  70  constitutes an optical microcavity that couples with electromagnetic radiation at a resonance wavelength λ. The first partial mirror  80  functions as a back-side partial mirror, and the second partial mirror  70  functions as a front-side partial mirror. If the first wavelength λ 1  is the same as the second wavelength λ 2 , the resonance frequency λ is the same as the first wavelength λ 1 . If the first wavelength λ 1  is not the same as the second wavelength λ 2 , the resonance frequency λ is between the first wavelength λ 1  and the second wavelength λ 2 . In general, the resonance frequency λ is a frequency at which the electromagnetic radiation of the corresponding wavelength forms a standing wave between the first partial mirror  80  and the second partial mirror  70 . If the percentage difference between the first wavelength λ 1  and the second wavelength λ 2  is small, the resonance frequency λ can be approximated by the mathematical average of the first wavelength λ 1  and the second wavelength λ 2 , i.e., λ≅(λ 1 +λ 2 )/2. 
         [0078]    In one embodiment, each of the first wavelength λ 1  and the second wavelength λ 2  can be substantially the same as the resonance frequency λ. In other words, four times the product of the first thickness t 1  and the first index of refraction n 1  can be substantially equal to the resonance wavelength λ, and four times the product of the second thickness t 2  and the second index of refraction n 2  can be substantially equal to the resonance wavelength λ. In one embodiment, each of the first wavelength λ 1  and the second wavelength λ 2  can be within 12.5% of the resonance frequency λ. In one embodiment, each of the first wavelength λ 1  and the second wavelength λ 2  can be within 5.0% of the resonance frequency λ. In one embodiment, each of the first wavelength λ 1  and the second wavelength λ 2  can be within 0.5% of the resonance frequency λ. 
         [0079]    Electromagnetic radiation can pass through the microcavity ( 80 ,  20 ,  40 ,  70 ) only if the electromagnetic radiation satisfies a resonance condition that is determined by optical thickness of the stack of the first transparent layer  20  and the second transparent layer  40 . The optical thickness of the stack of the first transparent layer  20  and the second transparent layer  40  is given by n 1 ×t 1 +n 2 ×t 2 . If the optical thickness of the stack of the first transparent layer  20  and the second transparent layer  40  equals integer multiples of one half of the resonance wavelength λ, the microcavity becomes optically transparent to that electromagnetic radiation. 
         [0080]    Referring to  FIGS. 9A and 9B , contact via structures are formed through the second partial mirror  70  and the optional optically transparent capping layer (not shown). The contact via structures include a first contact via structure  92  that contacts the first contact electrode  32  and a second contact via structure  94  that contacts the second contact electrode  34 . 
         [0081]    If the second partial mirror  70  includes at least one metallic material, a first dielectric liner  91  can be formed through the second partial mirror  70  and the optional optically transparent capping layer and around the first contact via structure  92 . Likewise, a second dielectric liner  93  can be formed through the second partial mirror  70  and the optional optically transparent capping layer and around the second contact via structure  94 . The first dielectric liner  91  and the second dielectric liner  93  can be formed by forming via cavities extending from the top surface of the second partial mirror  70  (or the top surface of the optional optically transparent capping layer, if present) to the top surfaces of the first and second contact electrodes ( 92 ,  94 ), depositing a dielectric material liner, and anisotropically etching horizontals of the dielectric material liner. Remaining portions of the dielectric material liner constitute the first and second dielectric liners ( 91 ,  93 ). 
         [0082]    The first contact via structure  92  and the second contact via structure  94  can be formed by filling the via cavities with a conductive material, and removing any excess conductive material from above the top surface of the second partial mirror  70  (or the top surface of the optional optically transparent capping layer, if present). The first contact via structure  92  and the second contact via structure  94  provide electrical contact to the first and second contact electrodes ( 32 ,  34 ), respectively. 
         [0083]    Referring to  FIG. 10 , a first bias and current measurement circuit is attached across the first and second contact via structures ( 92 ,  94 ) for operation of the first exemplary structure as a light detector, i.e., an electromagnetic radiation detector. The first bias and current measurement circuit includes a direct current voltage bias source  110 , which can be a battery or any other constant voltage generator, and a current measurement device  112 , which can be configured to measure any current that passes through the at least one graphene layer  30 . The current measurement device  112  can be configured to measure instantaneous current flow in any direction. 
         [0084]    The second contact electrode  34  is electrically biased relative to the first contact electrode  32  with a direct current (DC) voltage bias, i.e., a constant voltage bias. The DC voltage bias can be a positive voltage or a negative voltage. The magnitude of the DC voltage bias can be from 0.1 V to 100 V, although lesser and greater DC voltage bias can also be employed. 
         [0085]    The first bias and current measurement circuit is configured to measure electrical current that passes through the at least one graphene layer  30  upon irradiation of the at least one graphene layer  30  with electromagnetic radiation. The efficiency of coupling of the electromagnetic radiation is dependent upon the wavelength of the electromagnetic radiation, and is at a maximum at the resonance frequency λ. The Q-factor for the coupling, i.e., the narrowness of the width of the range of wavelength relative to the resonance frequency λ, is dependent upon the reflectivity of the first and second partial mirrors ( 80 ,  70 ). Thus, electrical photo-generated current flows through the at least one graphene layer  30  only when the wavelength of the electromagnetic radiation incident upon the optical microcavity is at the resonance frequency λ or around the resonance frequency λ such that the deviation of the wavelength of electromagnetic radiation from the resonance frequency λ is less than, or on the order of λ/Q, in which Q is the value of the Q-factor for the optical microcavity. 
         [0086]    If an external electric field is applied and/or an electrical current flows through the at least one graphene layer  30 , the optical properties of the optical microcavity changes reversibly. The property changes of the at least one graphene layer  30 , which is an intra-cavity optical medium, cause a modification of the optical properties of the optical device including the at least one graphene layer  30  and the microcacity, resulting in an angular and spectral redistribution, or filtering, of the electromagnetic radiation. This is the operational principle for microcavity-controlled switching and multiplexing of electromagnetic radiation. 
         [0087]    The current measurement device  112  can measure the presence or the magnitude of any additional current that flows in the at least one graphene layer  30  as a result of the microcavity-assisted absorption of electromagnetic radiation at, or near, the resonance wavelength λ. Thus, the first exemplary structure can be employed as an electromagnetic radiation detector for a narrow band of wavelength centered at the resonance wavelength λ. 
         [0088]    The electromagnetic radiation detector can detect light that impinges on the optical cavity from the front side F, or from the back side B. Optionally, a light shield  102  can be provided to filter out electromagnetic radiation that is outside a predetermined spherical angle. 
         [0089]    Referring to  FIG. 11 , the first bias and current measurement circuit of the first exemplary structure can be replaced with a second bias and current measurement circuit to provide a second exemplary structure. In the second bias and current measurement circuit, the direct current voltage bias source  110  in the first bias and current measurement circuit is replaced with an alternating current voltage bias source  120 , which applies an alternating current (AC) voltage bias across the at least one graphene layer  30  instead of a DC voltage bias. The amplitude of the AC voltage bias can be from 0.1 V to 100 V, and the frequency of the AC voltage bias can be from 1 Hz to 1 THz, although lesser and greater amplitudes and frequencies can also be employed. The second exemplary structure can be employed as an electromagnetic radiation detector as in the first embodiment. 
         [0090]    Referring to  FIG. 12 , a third exemplary structure can be derived from the first exemplary structure of  FIGS. 10A and 10B  by replacing the first bias and current measurement circuit with a first bias and switching circuit. The first bias and switching circuit includes a direct current (DC) voltage bias source  130  and a circuit switch  132 , which closes or opens the electrical circuit of a series connection of the DC voltage bias source  130 , the first contact structure  92 , the first contact electrode  32 , the at least one graphene layer  30 , the second contact electrode  34 , and the second contact structure  94 . While the circuit switch  132  is closed, a direct current (DC) electrical current flows through the at least one graphene layer  30 . The electrical current causes the at least one graphene layer  30  to emit light at various wavelengths. Only the electromagnetic radiation having wavelengths at which the optical microcavity is transparent can be emitted from the optical cavity. The wavelength range in which the electromagnetic radiation can escape the optical microcavity includes the wavelength range centered at the resonance wavelength λ. The third exemplary structure can operate as an electromagnetic radiation emitter that emits electromagnetic radiation only within a predetermined wavelength range centered around the resonance wavelength λ while direct current (DC) electrical current passes through the at least one graphene layer  30 . 
         [0091]    Thus, electromagnetic radiation can be generated by an electrical current flowing through the at least one graphene layer  30 . The electromagnetic radiation is coupled with high efficiency to internal photonic modes, i.e., the standing wave models that are provided by the optical microcavity. The integrated graphene-based microcavity emitter is an optoelectronic device that is configured to emit a spectrally narrow and highly directional light. 
         [0092]    Electromagnetic field confinement in a microcavity with a mirror spacing below one emission wavelength provides selective enhancement of the radiative emission rate of the at least one graphene layer  30  enclosed within the microcavity due to the Purcell Effect. Specifically, in the case of terahertz emission or thermal management applications for high-performance graphene transistors, the mirror spacing of the microcavity can be designed to match the resonance energy of principal lattice vibrations (phonons) in the at least one graphene sheet  30 . 
         [0093]    Referring to  FIG. 13 , the first bias and switching circuit of the third exemplary structure can be replaced with a second bias and switching circuit to provide a fourth exemplary structure. In the second bias and switching circuit, the DC voltage bias source  130  in the first bias and switching circuit is replaced with an alternating current voltage bias source  140 , which applies an alternating current (AC) voltage bias across the at least one graphene layer  30  instead of a DC voltage bias. The amplitude of the AC voltage bias can be from 0.1 V to 100 V, and the frequency of the AC voltage bias can be from 1 Hz to 1 THz, although lesser and greater amplitudes and frequencies can also be employed. The fourth exemplary structure can be employed as an electromagnetic radiation emitter as in the third embodiment. 
         [0094]    Referring to  FIG. 14 , a fifth exemplary structure is derived from the first exemplary structure of  FIGS. 9A and 9B  by connecting a bias and signal amplification circuit. The bias and signal amplification circuit includes a direct current (DC) drain voltage bias circuit  152 , a direct current (DC) gate voltage bias circuit  154 , and a signal amplification circuit  156 . The DC drain voltage bias circuit  152  applies a DC voltage bias across the first contact electrode  32  and the second contact electrode  34 , i.e., across the at least one graphene layer  30 . The DC gate voltage bias circuit  154  applies another DC voltage bias across one of the first contact electrode  32  and the second contact electrode  34  and one of the first partial mirror  80  and the second partial mirror  70 . 
         [0095]    The electrical current through the at least one graphene layer  30  can be modulated in a manner similar to current control in a field effect transistor. Specifically, the DC bias voltage applied by the DC drain voltage bias circuit  152  is analogous to a drain-to-source bias voltage, and the DC bias voltage applied by the DC gate voltage bias circuit  154  is analogous to a gate-to-source voltage. The electrical current through the at least one graphene layer  30  is analogous to a drain-to-source electrical current. The electrical current through the at least one graphene layer  30  can be detected by the signal amplification circuit  156 , which can include, for example, an operational amplifier. 
         [0096]    By modulating the electrical current through the at least one graphene layer  30 , the optical properties of the microcavity can be changed. Thus, in the absence of the electrical current through the at least one graphene layer  30 , the microcavity can be transparent at the resonance wavelength λ. By causing the electrical current to flow within the at least one graphene layer  30 , the microcavity can become opaque at the resonance wavelength λ. Thus, the fifth exemplary structure can be employed as an electromagnetic radiation modulator that modulates the transmission of light in a narrow wavelength range centered around the resonance wavelength λ through modulation of electrical current through the at least one graphene layer  30 . The transmission coefficient of electromagnetic radiation passing through the microcavity is modulated by electrical current passing through the at least one graphene layer  30 . The transmission coefficient is wavelength-dependent, and is at a maximum at the resonance wavelength λ while electrical current does not pass through the at least one graphene layer  30 . 
         [0097]    In general, each of the at least one graphene layer in any of the first, second, third, fourth, and fifth exemplary structures can be replaced with at least one carbon nanotube to provide optoelectronic devices that provide a same function, provided that the first contact electrode  32  and the second contact electrode  34  are formed on opposite ends of each carbon nanotube. 
         [0098]    Referring to  FIGS. 15A and 15B , a sixth exemplary structure according to a sixth embodiment of the present disclosure can be derived from the first exemplary structure of  FIGS. 2A and 2B  by placing at least one carbon nanotube  230  on the first transparent layer  130  in lieu of at least one graphene layer  30 . If the at least one carbon nanotube  230  is a plurality of carbon nanotubes, the plurality of carbon nanotubes can be aligned employing any method known in the art. Subsequently, processing steps of  FIGS. 4A ,  4 B,  5 A,  5 B,  6 A,  6 B,  7 A, and  7 B can be performed to provide the sixth exemplary structure illustrated in  FIGS. 16A and 16B . 
         [0099]    Processing steps of  FIGS. 8A ,  8 B,  9 A,  9 B, and  10  can be subsequently performed to provide the sixth exemplary structure of  FIG. 17 . The sixth exemplary structure of  FIG. 17  is an electromagnetic radiation detector having the same operational principle as the electromagnetic radiation detector of  FIG. 10  except for the difference of employing at least one carbon nanotube  230  instead of the at least one graphene layer  30 . 
         [0100]    A seventh exemplary structure illustrated in  FIG. 18  can be derived from the second exemplary structure of  FIG. 11  by replacing the at least one graphene layer  30  with at least one carbon nanotube  230 . The seventh exemplary structure of  FIG. 18  is an electromagnetic radiation detector having the same operational principle as the electromagnetic radiation detector of  FIG. 11 . 
         [0101]    An eighth exemplary structure illustrated in  FIG. 19  can be derived from the third exemplary structure of  FIG. 12  by replacing the at least one graphene layer  30  with at least one carbon nanotube  230 . The eighth exemplary structure of  FIG. 19  is an electromagnetic radiation emitter having the same operational principle as the electromagnetic radiation emitter of  FIG. 12 . 
         [0102]    A ninth exemplary structure illustrated in  FIG. 20  can be derived from the forth exemplary structure of  FIG. 13  by replacing the at least one graphene layer  30  with at least one carbon nanotube  230 . The ninth exemplary structure of  FIG. 20  is an electromagnetic radiation emitter having the same operational principle as the electromagnetic radiation emitter of  FIG. 13 . 
         [0103]    A tenth exemplary structure illustrated in  FIG. 21  can be derived from the fifth exemplary structure of  FIG. 14  by replacing the at least one graphene layer  30  with at least one carbon nanotube  230 . The tenth exemplary structure of  FIG. 21  is an electromagnetic radiation modulator having the same operational principle as the electromagnetic radiation emitter of  FIG. 14 . 
         [0104]    The methods of the present disclosure employ scalable, CMOS-compatible processes to provide an optoelectronic device employing a two-dimensional lattice structure. The disclosed optoelectronic devices consume less power and have smaller footprints compared with known optoelectronic devices known in the art. Further, the disclosed optoelectronic devices can provide a high operating speed across the entire electromagnetic spectral range as long as the dimensions of the microcavity can be adjusted to provide a matching resonance wavelength. 
         [0105]    Applications of the devices of the present disclosure include, but are not limited to, microcavity-controlled multiplexers, switches, detectors, and emitters of electromagnetic radiation operating in the visible, the infrared, and the terahertz spectral regime. Also, the method of the present disclosure can be adapted for the thermal management of high-performance electronic devices, such as field effect transistors, that employs a two-dimensional lattice structure. 
         [0106]    While the disclosure has been described in terms of specific embodiments, it is evident in view of the foregoing description that numerous alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the disclosure is intended to encompass all such alternatives, modifications and variations which fall within the scope and spirit of the disclosure and the following claims.