Colloidal quantum dot photodetectors

Abstract

A colloidal quantum dot device is provided that includes an integrated circuit, a colloidal quantum dot structure on the integrated circuit, and an encapsulation layer on the colloidal quantum dot structure, the encapsulation layer having a thickness of about .5 nm to about 500 nm.

Description

Priority claims

[0001]

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 138,977, filed January 19, 2021, entitled COLLOIDAL QUANTUM DOT (CQD) PHOTODETECTORS HAVING THIN ENCAPSULATION LAYERS DEPOSITED THEREON AND METHODS OF FABRICATING THE SAME, the contents of which are incorporated herein by reference in their entirety. [Technical Field]

[0002] FIELD OF THE INVENTION

[0002] The present concepts relate generally to photodetectors, and more particularly to colloidal quantum dot photodetectors including thin encapsulation layers thereon, and related methods. [Background technology]

[0003] Colloidal quantum dot photodetectors are photodetectors that use a thin film composed of a collection of small particles of semiconductor material to absorb photons and detect light. Unlike some crystalline photodetector materials, such as silicon (Si) and gallium arsenide (GaAs), colloidal quantum dot photodetectors generally experience changes in device performance when exposed to air, moisture, or high temperatures. These performance changes generally limit the operating conditions under which colloidal quantum dot detectors can be deployed and limit the usable lifetime of colloidal quantum dot-containing sensors and systems. Therefore, fabrication parameters for colloidal quantum dot photodetectors are being investigated to reduce or potentially eliminate their sensitivity to air, moisture, and high temperatures (e.g., 40°C to 125°C).

[0004] For example, some existing methods use visible and infrared (IR) transparent materials, such as glass, sapphire, quartz, and silicon, bonded to the colloidal quantum dot detector. Typical bonding materials can include polymer-based adhesives, epoxies, and / or metal-based soldering or welding materials. Adhesive- and epoxy-based solutions are generally not very hermetic, i.e., they are not airtight, sealed, or watertight, and allow some air and / or moisture to eventually reach the colloidal quantum dot detector. Transparent epoxies generally have low glass transition temperatures, which may reduce their potential for use in consumer electronics and automotive applications requiring long lifetimes at high temperatures. While metal-based solutions can be very hermetic and reliable, these solutions are generally not cost-effective and may be bulky for consumer applications. Finally, solutions that use layers of glass-like materials, such as glass, sapphire, and quartz, between the ambient environment and the photodetector can produce undesirable optical interference artifacts that may hinder or even prevent their use in laser detection applications such as those used for three-dimensional (3D) depth sensing, light detection and ranging (LIDAR), structured light, etc. Improved methods and devices are desirable. Summary of the Invention

[0005]

[0005] Some embodiments of the present concept provide a colloidal quantum dot device including an integrated circuit, a colloidal quantum dot structure on the integrated circuit, and an encapsulation layer on the colloidal quantum dot structure, the encapsulation layer having a thickness of about 0.5 nm to about 500 nm.

[0006]

[0006] In a further embodiment of the inventive concept, the colloidal quantum dot device may be an optoelectronic device comprising a first electrode, a first quantum dot layer on the first electrode, the first quantum dot layer comprising a plurality of quantum dots, a second quantum dot layer comprising a plurality of quantum dots and located directly on the first quantum dot layer, and a second electrode on the second quantum dot layer.

[0007] In still further embodiments, an electron blocking layer is provided on the first electrode between the first electrode and the first quantum dot layer.

[0008] In some embodiments, a colloidal quantum dot device comprises an optoelectronic device including a first electrode, a quantum dot layer on the first electrode, the quantum dot layer comprising a plurality of quantum dots, a fullerene layer directly on the quantum dot layer, and a second electrode on the fullerene layer, wherein the quantum dot layer and the fullerene layer form an electronic heterojunction.

[0009] In a further embodiment, the sealing layer may be an atomic layer deposition (ALD) layer.

[0010] In still further embodiments, the ALD layer may be located directly on the colloidal quantum dot structure. The colloidal quantum dot device may further include an epoxy layer on the ALD layer and a glass layer on the epoxy layer.

[0011] In some embodiments, the device may further include an epoxy layer on the colloidal quantum dot structure and a glass layer on the epoxy layer, with the ALD layer on the glass layer.

[0012] In further embodiments, the colloidal quantum dot device may be one of a photodiode device and a photodetector device.

[0013] In still further embodiments, the colloidal quantum dot device can detect light with sensitivity over a spectral range from about 250 nm to about 2400 nm.

[0014] In some embodiments, the encapsulating layer can include multiple alternating layers having a combined thickness of from about 5 nm to about 500 nm.

[0015]

[0015] A further embodiment of the present concept provides a die including an integrated circuit, a plurality of colloidal quantum dot devices on the integrated circuit, and an encapsulation layer over the plurality of colloidal quantum dot devices, the encapsulation layer having a thickness of about 0.5 nm to about 500 nm.

[0016] In still further embodiments, the die may be configured to be separated into a plurality of individual colloidal quantum dot devices.

[0017] In some embodiments, the encapsulation layer can be an ALD layer.

[0018] In a further embodiment, the ALD layer may be located directly on the plurality of colloidal quantum dot devices, and the die may further include an epoxy layer on the ALD layer and a glass layer on the epoxy layer.

[0019] In still further embodiments, the die may further include an epoxy layer on the plurality of colloidal quantum dot devices and a glass layer on the epoxy layer, with the ALD layer on the glass layer.

[0020] Some embodiments of the present inventive concepts provide methods of fabricating colloidal quantum dot devices, the method including providing an integrated circuit including a plurality of colloidal quantum dot structures thereon, and forming an encapsulation layer over the plurality of colloidal quantum dot structures, the encapsulation layer having a thickness of about 0.5 nm to about 500 nm, separating the plurality of colloidal quantum dot structures into individual colloidal quantum dot devices.

[0021]

[0021] In further embodiments, the encapsulation layer may include one or more of Al2O3, Zr2O3, ZnO, InO, SiO2, Si3N4, Hf2O3, TiO2, Ti3N4, SiO, Al2N3, and TaO2.

[0022] In still further embodiments, forming the encapsulation layer may include depositing the encapsulation layer using ALD.

[0023] In some embodiments, the encapsulating layer can be deposited at a temperature of from about 25°C to about 150°C.

[0024] In a further embodiment, the ALD layer may be formed directly on the plurality of colloidal quantum dot structures. The method may further include forming an epoxy layer on the ALD layer and forming a glass layer on the epoxy layer.

[0025]

[0025] In still further embodiments, the method may further include forming an epoxy layer on the plurality of colloidal quantum dot structures and forming a glass layer on the epoxy layer, wherein the ALD layer is formed on the glass layer.

[0026] In some embodiments, each of the plurality of colloidal quantum dot structures may include one of a photodiode device and a photodetector device.

[0027] In further embodiments, forming the encapsulating layer can include forming a plurality of alternating layers having a combined thickness of from about 5 nm to about 500 nm. [Brief explanation of the drawings]

[0028] [Figure 1A]

[0028] Figure 1 illustrates a cross section of a die including multiple colloidal quantum dot photodiodes having an encapsulation layer thereon in accordance with some embodiments of the inventive concept. [Figure 1B]

[0029] 1B is a more detailed diagram illustrating a cross section of the die of FIG. 1A including exemplary layers according to some embodiments of the inventive concepts. [Figure 2]

[0030] FIG. 1 illustrates a cross section of a die with an atomic layer deposition (ALD) encapsulation layer on glass and epoxy on top of a colloidal quantum dot detector structure according to some embodiments of the inventive concepts. [Figure 3]

[0031] 1A-1D illustrate microscopic images of fabricated ALD sealing structures according to some embodiments of the inventive concepts. [Figure 4]

[0032] FIG. 1 illustrates a cross section of a die having an atomic layer deposition (ALD) encapsulation layer under epoxy and glass in accordance with some embodiments of the inventive concepts. [Figure 5]

[0033] FIG. 1 illustrates a photograph of a colloidal quantum dot image sensor fabricated using an ALD encapsulation structure according to some embodiments of the inventive concepts. [Figure 6A]

[0034] 10 is a graph illustrating the change in sensor dark signal as a function of high temperature and humidity stress time for sensors fabricated without a thin film ALD encapsulation structure in accordance with an embodiment of the inventive concepts. [Figure 6B]

[0035] 10 is a graph illustrating the change in sensor optical response signal as a function of high temperature and humidity stress time for sensors fabricated without a thin film ALD encapsulation structure according to some embodiments of the inventive concepts. [Figure 7A]

[0036] 1 is a graph illustrating the change in sensor dark signal as a function of high temperature and humidity stress time for sensors fabricated using ALD film encapsulation structures according to some embodiments of the inventive concepts. [Figure 7B]

[0037] 1 is a graph illustrating the change in sensor optical response signal as a function of high temperature and humidity stress time for sensors fabricated using ALD film encapsulation structures according to some embodiments of the inventive concepts. [Figure 8A]

[0038] 1A-1D are cross-sectional views illustrating processing steps in the fabrication of colloidal quantum dot sensors according to various embodiments of the inventive concepts. [Figure 8B] 1A-1D are cross-sectional views illustrating processing steps in the fabrication of colloidal quantum dot sensors according to various embodiments of the inventive concepts. [Figure 8C]1A-1D are cross-sectional views illustrating processing steps in the fabrication of colloidal quantum dot sensors according to various embodiments of the inventive concepts. [Figure 9]

[0039] 1 illustrates a multi-layer encapsulation layer according to some embodiments of the inventive concept. [Figure 10]

[0040] 1 illustrates a cross section of an exemplary colloidal quantum dot device according to some embodiments of the inventive concepts. DETAILED DESCRIPTION OF THE INVENTION

[0029]

[0041] The inventive concepts are described more fully below with reference to the accompanying drawings, which show embodiments of the inventive concepts, however, the inventive concepts may be embodied in many alternate forms and should not be construed as limited to the embodiments set forth herein.

[0030]

[0042] Accordingly, while the inventive concepts are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that there is no intention to limit the inventive concepts to the particular forms disclosed, but on the contrary, the inventive concepts are intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the inventive concepts as defined by the appended claims. Like numbers refer to like elements throughout the description of the figures.

[0031]

[0043] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the concepts of the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Furthermore, when an element is referred to as "responsive to" or "connected to" another element, it may be directly responsive to or connected to the other element, or intervening elements may be present. In contrast, when an element is referred to as "directly responsive to" or "directly connected to" another element, there are no intervening elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated list items and may be abbreviated as " / ."

[0032]

[0044] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the inventive concept belongs. Furthermore, it will be understood that terms used herein should be interpreted to have a meaning consistent with the meaning in the context of the present specification and the related art, and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0033]

[0045] While terms such as "first," "second," etc. may be used herein to describe various elements, it should be understood that these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, a first element could be referred to as a second element, and similarly, a second element could be referred to as a first element, without departing from the teachings of this disclosure. Some figures include arrows on communication paths to indicate the primary direction of communication, but it should be understood that communication may occur in the opposite direction to the illustrated arrows.

[0034]

[0046] As used herein, the term "optoelectronic device" generally refers to any device that acts as an optical-to-electrical or electrical-to-optical transducer. Thus, the term "optoelectronic device" may refer, for example, to photovoltaic (PV) devices (e.g., solar cells), photodetectors, thermovoltaic cells, or electroluminescent (EL) devices such as light-emitting diodes (LEDs) and laser diodes (LDs). In a general sense, EL devices operate inversely to PV and photodetector devices. Electrons and holes are injected from their respective electrodes into a semiconductor region under the influence of an applied bias voltage. One of the semiconductor layers is selected for its light-emitting properties rather than its light-absorbing properties. Radiative recombination of the injected electrons and holes causes light emission in this layer. Many of the same types of materials used in PV and photodetector devices may also be used in EL devices, although the layer thicknesses and other parameters must be adapted to achieve the different goals of the EL device.

[0035]

[0047] As used herein, the term "fullerene" refers to buckminsterfullerene C 60 , and C 70 , C 84 and other forms of molecular carbon such as olefins and similar cage-like carbon structures, more commonly ranging from 20 to several hundred carbon atoms, i.e., where n is 20 or greater. nFullerenes can be functionalized or chemically modified as needed for specific purposes, such as, for example, improving solubility or dispersibility or altering the electrical properties of the fullerene. The term "fullerene" can also refer to endohedral fullerenes, in which a non-carbon atom or cluster of atoms is encapsulated in a carbon cage. The term "fullerene" can also refer to fullerene derivatives. Some non-limiting examples of fullerene derivatives include [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) and phenyl-C 61 -butyric acid cholestryl ester (PCBCR). The term "fullerene" may also refer to a mixture of the above forms of fullerene.

[0036]

[0048] As used herein, the term "quantum dot" or "QD" refers to a semiconductor nanocrystalline material in which excitons are confined in all three spatial dimensions, and is distinguished from quantum wires (quantum confined in only two dimensions), quantum wells (quantum confined in only one dimension), and bulk semiconductors (unconfined). Furthermore, many optical, electrical, and chemical properties of quantum dots can be strongly dependent on their size; therefore, such properties can be modified or tuned by controlling their size. Quantum dots may generally be characterized as particles, and their shape may be spheroidal, ellipsoidal, or other shapes. The "size" of a quantum dot may refer to its shape or an approximate dimensional characteristic of its shape, and thus may be the diameter, major axis, major length, etc. The size of a quantum dot is on the order of nanometers, i.e., generally in the range of 1.0 to 1000 nm, but more typically in the range of 1.0 to 100 nm, 1.0 to 20 nm, or 1 to 10 nm. In a plurality of quantum dots or a collection thereof, the quantum dots may be characterized as having an average size. The size distribution of the plurality of quantum dots may or may not be monodisperse. The quantum dots may have a core-shell configuration, where the core and surrounding shell may have distinct compositions. The quantum dots may also include ligands attached to their outer surface or may be functionalized with other chemical moieties for specific purposes.

[0037]

[0049] Plasma synthesis has become one of the most common gas-phase approaches for the fabrication of quantum dots, especially those with covalent bonds. For example, silicon (Si) and germanium (Ge) quantum dots have been synthesized using non-thermal plasma. The size, shape, surface, and composition of quantum dots can all be controlled in non-thermal plasma. Doping, which is considered very difficult for quantum dots, has also been achieved in plasma synthesis. Quantum dots synthesized by plasma are usually in the form of a powder, which can be subjected to surface modification. This can result in excellent dispersion of quantum dots in either organic solvents or water, i.e., colloidal quantum dots. An embodiment of the inventive concept uses colloidal quantum dot films, as described below.

[0038]

[0050] For purposes of this disclosure, spectral ranges or bands of electromagnetic radiation may generally be considered as follows, with the understanding that adjacent spectral ranges or bands may be considered to overlap one another to some extent. Ultraviolet (UV) radiation may be considered to fall within the range of approximately 10-400 nm, although for practical applications (above vacuum) the range is approximately 200-400 nm. Visible light radiation may be considered to fall within the range of approximately 380-760 nm. Infrared (IR) radiation may be considered to fall within the range of approximately 750-100,000 nm. IR radiation may also be considered in terms of subranges, examples of which are as follows: Short-wavelength infrared (SWIR) radiation may be considered to fall within the range of approximately 1,000-3,000 nm. Mid-wavelength infrared (MWIR) radiation may be considered to fall within the range of approximately 3,000-5,000 nm. Long-range infrared (LWIR) radiation may be considered to fall within the range of approximately 8,000-12,000 nm.

[0039]

[0051] Colloidal quantum dot photodetectors are described, for example, in commonly assigned U.S. patent application Ser. No. 17 / 199,971 (Attorney Docket No. 190823-00008), filed March 12, 2021, entitled "Colloidal Quantum Dot (CQD) Photodetectors and Related Devices," U.S. Patent No. 8,729,528, entitled "Quantum Dot-Fullerene Junction Optoelectronic Devices," and U.S. Patent No. 8,742,398, entitled "Quantum Dot-Fullerene Junction Based Photodetectors," the contents of which are incorporated herein by reference in their entireties. It will be understood that colloidal quantum dot photodetectors can be photoconductors or photodiodes. A photoconductor is a conductor / resistor that changes in response to light. A photodiode is a diode that changes in response to light. While embodiments of the inventive concepts will be described primarily with reference to photodiodes, it will be understood that embodiments of the inventive concepts are not limited thereto.

[0040]

[0052] Quantum dot photodiode / photodetector (QDP) technology is implemented to provide low-cost nanotechnology-enabled photodetectors. In some implementations, the photodetectors can be configured to efficiently detect light with sensitivity across a spectral range of approximately 250 to 2400 nm. Thus, the photodetectors can be configured as multispectral devices capable of generating images from incident ultraviolet (UV), visible, and / or infrared (IR) electromagnetic radiation. In some implementations, the spectral range of sensitivity may extend down to X-ray energies and / or up to IR wavelengths longer than 2400 nm. The photodetectors taught herein are cost-effective, scalable to large-area arrays, and applicable to flexible substrates.

[0041]

[0053] As used herein, "quantum efficiency" (QE) refers to the ratio of incident photons to measured electrons, with optimal efficiency being substantially 100% for a structure with no internal amplification (i.e., gain). "Hermetic" refers to a device that is hermetically sealed, sealed, and / or watertight.

[0042]

[0054] "Dark current" refers to the current that flows through a photoelectric device in the absence of incident illumination. In physics and electronics, dark current is the relatively small current that flows through a photosensitive device, such as a photomultiplier tube, photodiode, or charge-coupled device, even when no photons are incident on the device. Dark current generally consists of charge generated within the detector when no external radiation is incident on the detector. This is sometimes called reverse bias leakage current in non-optical devices and is generally present in all diodes. Physically, one cause of dark current in a diode is the random thermal generation of excited electrons and holes within the depletion region of the device.

[0043]

[0055] There is a fundamental trade-off between dark current and QE for photodetector sensor materials, which is directly related to the thickness of the photodetector material. In particular, varying the material thickness, i.e., making the material thicker or thinner, improves one attribute at the expense of another. Furthermore, unlike well-known crystalline photodetector materials such as silicon (Si) and gallium arsenide (GaAs), colloidal quantum dot photodetectors generally experience undesirable changes in device performance upon exposure to air, for example. Therefore, fabrication parameters for colloidal quantum dot photodetectors have been investigated to reduce or even eliminate air sensitivity. However, fabrication processes that result in air-stable colloidal quantum dot devices rarely exhibit superior photodetector performance, such as photoresponse, quantum efficiency, and dark current.

[0044]

[0056] For example, in an attempt to combine excellent photodetector performance with air stability, some existing methods use visible-IR transparent materials, such as glass, sapphire, quartz, and silicon, bonded to colloidal quantum dot detectors. Typical bonding materials can include polymer-based adhesives, epoxies, and / or metal-based soldering or welding materials. Adhesive- and epoxy-based solutions are generally not very hermetic (not airtight, sealed, or watertight) and allow some air and / or moisture to eventually reach the colloidal quantum dot detector. Transparent epoxies tend to have low glass transition temperatures, which may make them less suitable for use in consumer applications requiring long lifetimes at high temperatures. Metal-based solutions tend to be very hermetic and reliable, but they are generally too expensive and bulky for consumer applications. Finally, solutions that use layers of glass-like materials, such as glass, sapphire, and quartz, between the external environment and the photodetector can produce undesirable optical interference artifacts that may hinder or even prevent their use in laser detection applications such as those used for three-dimensional (3D) depth sensing, light detection and ranging (LIDAR), and structured light.

[0045]

[0057] Therefore, to address some of the above-mentioned shortcomings of existing methods, embodiments of the inventive concepts provide devices and related methods for fabricating these devices that have a "thin film" encapsulation layer located directly on the surface of a colloidal quantum dot photodetector. The "thin film" encapsulation layer, in some embodiments, can be formed on the surface of a colloidal quantum dot photodetector using, for example, atomic layer deposition (ALD). While embodiments of the inventive concepts describe the use of ALD, it will be understood that embodiments of the inventive concepts are not limited thereto. As used herein, "thin film" refers to a film having a thickness of about 0.5 to about several hundred nanometers. In some embodiments, the encapsulation layer can comprise a variety of materials, including, for example, Al2O3, Zr2O3, ZnO, InO, SiO2, Si3N4, Hf2O3, TiO2, Ti3N4, SiO, Al2N3, and TaO2. These materials are provided by way of example only, and thus, embodiments of the inventive concepts are not limited thereto.

[0046]

[0058] In embodiments of the inventive concepts utilizing deposition to form the encapsulation layer, the atom-by-atom nature of the deposition process, e.g., ALD, provides a well-controlled, low-defect-density film on the surface of the colloidal quantum dot photodetector, which allows for low leakage rates (i.e., very airtight, sealed, and watertight) even at film thicknesses of tens to hundreds of nanometers, reducing deposition time and costs. Furthermore, many ALD films can be deposited at colloidal quantum dot-compatible temperatures, e.g., from about 25°C to about 150°C. Unlike many of the existing packaging methods described above, the ALD films provided on the surface of the colloidal quantum dot film described herein can be deposited and patterned at the wafer level, thus leveraging the capabilities of parallel processing. In other words, the ALD film can be deposited on the entire wafer and not necessarily at the individual photodetector level. A wide variety of materials can be deposited by ALD. These materials can include, for example, Al2O3, Zr2O3, ZnO, InO, SiO2, Si3N4, Hf2O3, TiO2, Ti3N4, SiO, Al2N3, and TaO2. This wide variety of films available allows for tailoring not only hermeticity but also optical properties such as anti-reflective coatings.

[0047]

[0059] 1A, a cross section of a sensor die 120 including a plurality of colloidal quantum dot photodiodes 100 according to some embodiments of the inventive concepts is illustrated. It will be understood that the sensor die 120 may be a single die or a wafer including an array of sensor dies without departing from the scope of the inventive concepts. In some embodiments, the wafer may be a partial wafer, e.g., a quarter wafer, including an array.

[0048]

[0060] As illustrated in FIG. 1A , the device includes a sensor die 120 having a plurality of colloidal quantum dot diodes 100 on its surface and an encapsulation layer / structure 110 over the plurality of colloidal quantum dot photodiodes 100. The sensor die 120 may be an integrated circuit 120, such as a silicon readout integrated circuit (IC). As further illustrated, the device of FIG. 1A also includes a plurality of wire bond pads 130. It will be understood that the cross section of FIG. 1A is a simplified diagram illustrating a “thin film” encapsulation layer as described in accordance with various embodiments of the inventive concepts, and that embodiments of the inventive concepts are not limited by FIG. 1A . In some embodiments, the colloidal quantum dot photodiodes 100 may be provided on the surface of an ROIC die (or wafer) to fabricate a plurality of image sensors.

[0049]

[0061] As mentioned above, one advantage provided by the methods according to embodiments described herein is that the encapsulation layer 110 can be deposited on the entire die 120 (wafer) at once, rather than being formed individually on each photodetector. Thus, the methods described herein provide a more efficient process by encapsulating multiple colloidal quantum dot photodiodes 100 at the wafer level, i.e., encapsulating the individual photodetectors all at once before separating them from the wafer.

[0050]

[0062] The encapsulation layer / structure 110 may include materials such as Al2O3, Zr2O3, ZnO, InO, SiO2, Si3N4, Hf2O3, TiO2, Ti3N4, SiO, Al2N3, or TaO2 and may be deposited on the surface of the die 120 and colloidal quantum dot detector 100. The encapsulation layer / structure 110 may be deposited using an ALD method, although embodiments of the inventive concept are not limited thereto. The encapsulation layer may be deposited at a temperature of about 25°C to about 150°C. These temperatures may therefore be compatible with colloidal quantum dot photodiode materials. The encapsulation layer / structure 110 may have a thickness T of about 0.5 nm to about 500 nm. The encapsulation layer / structure 110 may be a single material type or a combination of multiple material types. For example, alternating layers of 1.0 nm thick Al2O3 and 1.0 nm thick Zr2O3 can be used to build up a total thickness of 100 nm by repeating the combination of the two layers 10 times.

[0051]

[0063] Referring to FIG. 1B, a cross section of a device is illustrated that includes an ALD encapsulation layer 135. As used herein, "ALD layer" refers to an encapsulation layer formed using an ALD process. As illustrated in FIG. 1B, an array of colloidal quantum dot diodes / detectors 125 is provided on a silicon readout IC 121, with an ALD layer / structure 135 provided thereon. According to some embodiments, wire bond pads 130 are also provided. FIG. 1B is provided by way of example only, and embodiments of the inventive concepts are not limited thereto.

[0052]

[0064] It will be understood that in embodiments of the inventive concepts described at the wafer / die level, multiple colloidal quantum dot photodetectors can be separated into individual colloidal quantum dot photodetectors after formation of the encapsulation layer and completion of the device. Furthermore, while embodiments of the inventive concepts describe deposition at the die level, embodiments of the inventive concepts are not so limited. Deposition of the encapsulation layer can occur at the wafer level, partial wafer level, or device level without departing from the scope of the inventive concepts.

[0053]

[0065] Referring now to FIG. 2 , a cross-section illustrating an embodiment of an ALD-sealed colloidal quantum dot sensor is described. As illustrated, the device of FIG. 2 includes an IC 121 having a colloidal quantum dot diode array 126 thereon. As further illustrated, a layer of epoxy 140 is on the diode array 126, a layer of glass 145 is on the epoxy layer 140, and an ALD layer 135 is on the array, epoxy, and glass structure. Thus, FIG. 2 illustrates an ALD-sealed colloidal quantum dot sensor with an ALD layer / structure deposited on a glass and epoxy structure. The embodiment illustrated in FIG. 2 differs from the embodiment illustrated in FIGS. 1A and 1B in that the ALD encapsulation primarily serves to reduce or potentially prevent atmospheric ingress through the edges of the epoxy. In the structure illustrated in FIG. 2 , the optical properties of the glass layer can provide performance advantages for certain sensing applications. For example, the embodiment illustrated in FIG. 2 can be used in sensors constructed using glass with optical filtering properties.

[0054]

[0066] As used herein, an "epoxy" layer may be provided by any of a class of adhesives, plastics, or other materials that are epoxide polymers. The epoxy layer 140 in FIG. 2 may have a thickness of about 0.1 μm to about 150 μm. Similarly, the glass layer 145 may have a thickness of about 0.1 mm to about 10 mm. As used herein, a "glass" layer may be provided by any of a class of inorganic materials that have non-zero optical transmission for the wavelengths of light utilized by the CQD detector for a particular application. Examples of these window materials include soda-lime glass, borosilicate glass, sapphire, and Si.

[0055]

[0067] Referring now to FIG. 3 , a microscopy image of a fabricated ALD encapsulation structure 300 is described. The microscopy image of FIG. 3 illustrates an optical microscopy image of a colloidal quantum dot image sensor fabricated using the ALD encapsulation layer illustrated in FIG. 2 . As illustrated, the microscopy image of the ALD encapsulated colloidal quantum dot device array in FIG. 3 illustrates the readout integrated circuit (ROIC) die edge 360, the ROIC wire bond pads 365, the ROIC surface 370, the edge of the ALD thin film encapsulant 375, the epoxy edge 380, and the glass edge 385. This ALD encapsulated sensor 300 was thermally stress tested in (ambient) air for hundreds of hours and did not exhibit any of the performance degradation exhibited by sensors stress tested without the thin film encapsulation layer described in accordance with some embodiments of the inventive concepts.

[0056]

[0068] Referring now to FIG. 4, a cross-section illustrating an embodiment of an ALD-sealed colloidal quantum dot sensor 400 is described. As illustrated in FIG. 4, the ALD-sealed colloidal quantum dot sensor 400 includes an ALD layer / structure 135 deposited directly on a colloidal quantum dot sensor structure / array 126, a coating of epoxy or other organic material 140, followed by an (optional) glass layer 145. The embodiment illustrated in FIG. 4 differs in the arrangement of layers from the embodiments illustrated in FIGS. 1A and 1B and 2 described above. The structure illustrated in FIG. 4 can be used, for example, when sensors fabricated using this structure offer manufacturing or performance advantages; for example, it can provide the mechanical robustness of glass with the flexibility of ALD, among other things.

[0057]

[0069] 4 may have a thickness of about 0.1 μm to about 150 μm. Similarly, the glass layer 145 may have a thickness of about 0.1 mm to about 10 mm.

[0058]

[0070] Referring now to FIG. 5, a photographic image 500 is shown of a colloidal quantum dot image sensor fabricated using an ALD structure similar to that illustrated in FIG. 4. As illustrated, at the center of the image is visible a rectangular 1920×1080 format 2.1 megapixel image sensor 590 fabricated using a colloidal quantum dot photodiode, ALD layers, epoxy layers, and glass layers in accordance with some embodiments of the inventive concepts. The colloidal quantum dot image sensor is shown with wire bonds 530 connecting the sensor bond pads to a circuit board. It will be understood that the sensor in FIG. 5 is provided by way of example only, and that embodiments of the inventive concepts are not limited thereby. For example, sensors in accordance with embodiments of the inventive concepts need not be rectangular.

[0059]

[0071] Referring now to FIGS. 6A and 6B, graphs illustrating performance characteristics of devices without a thin film encapsulation layer according to some embodiments of the inventive concepts are described. In particular, FIG. 6A illustrates the change in sensor dark signal as a function of thermal stress time for a sensor fabricated without a thin film encapsulation structure. FIG. 6B illustrates the change in sensor optical response signal as a function of thermal stress time for a sensor fabricated without a thin film encapsulation layer. Accordingly, FIGS. 6A and 6B illustrate plots of sensor dark signal and irradiated signal as a function of thermal and humidity stress chamber exposure time. FIGS. 6A and 6B illustrate data from four different sensors, labeled 1, 2, 3, and 4. The plotted data in FIG. 6A shows the average dark signal of the pixel array on the y-axis versus the time the sensor is exposed to 75°C and 85% relative humidity conditions in the thermal stress chamber. This dark signal is normalized to the time 0 data point, collected after sensor fabrication was completed. The measured dark signal over subsequent periodic time periods is then shown.

[0060]

[0072] Similarly, the plotted data in Figure 6B shows the average optical response of the pixel array to spatially flat 1550 nm wavelength illumination for the same sensors 1, 2, 3, and 4 shown in Figure 6A. The instability of the sensor output over time illustrates the need for improvement to produce long-life sensors with stable performance.

[0061]

[0073] Referring now to FIGS. 7A and 7B, graphs illustrating performance characteristics of devices including thin film encapsulation layers according to some embodiments of the inventive concepts are described. In particular, FIG. 7A illustrates the change in sensor dark signal as a function of thermal stress time for sensors fabricated using the thin film encapsulation structure. FIG. 7B illustrates the change in sensor optical response signal as a function of thermal stress time for sensors fabricated using the thin film encapsulation layer. FIGS. 7A and 7B illustrate the thermal stability of six different 2.1-megapixel image sensors 1, 2, 3, 4, 5, and 6 in a 1920 x 1080 format fabricated using thin film encapsulation structures according to embodiments described herein. In particular, the plotted data in FIG. 7A illustrates the average dark signal of each pixel array normalized to the time 0 data point. This represents measurement data collected at different times when sensors 1, 2, 3, 4, 5, and 6 were exposed to 75°C and 85% relative humidity conditions in a stress test chamber. FIG. 7B illustrates the average optical response for the same sensors 1, 2, 3, 4, 5, and 6 as a function of stress test chamber exposure time. These plots illustrate the thermal stability advantages of colloidal quantum dot sensors fabricated using encapsulation structures according to embodiments described herein.

[0062]

[0074] Referring now to the cross-sectional views of Figures 8A-8C, processing steps in the fabrication of a colloidal quantum dot device, according to some embodiments, are described. Referring initially to Figure 8A, a sensor die 120 including a plurality of colloidal quantum dot photodiodes 100 according to some embodiments of the inventive concepts is described and provided. It will be understood that the sensor die 120 may be a single die or a wafer including an array of sensor dies without departing from the scope of the inventive concepts. In some embodiments, the wafer may be a partial wafer, e.g., a quarter wafer, including an array of sensor dies. The sensor die 120 may, in some embodiments, be an integrated circuit 120, e.g., a silicon readout integrated circuit (IC).

[0063]

[0075] As illustrated in FIG. 8B, a mask 895 is formed on the surface of the device of FIG. 8A to define the encapsulation layer / structure. The mask can be any typical mask material, such as, for example, SiO 2 , Si 3 N 4 , gold (Au), chromium (Cr), and boron. The encapsulation layer / structure 110 is formed according to the mask 895. In some embodiments, the encapsulation layer / structure is deposited using ALD to form an ALD layer on the colloidal quantum dot device 100 according to the mask. The atom-by-atom nature of the ALD deposition process provides a well-controlled, low-defect-density film on the surface of the colloidal quantum dot photodetector 100, which allows for a low leakage rate (i.e., very airtight, sealed, and watertight) even at film thicknesses of tens to hundreds of nanometers, reducing deposition time and cost.

[0064]

[0076] ALD layers can be deposited at temperatures between about 25°C and about 150°C, which is compatible with the colloidal quantum dot material. The ALD films provided on the surfaces of the colloidal quantum dot films described herein can be deposited and patterned at the wafer level, thus leveraging parallel processing capabilities. In other words, ALD films can be deposited over the entire wafer and not necessarily at the individual photodetector level. A wide variety of materials can be deposited by ALD. These materials can include, for example, Al2O3, Zr2O3, ZnO, InO, SiO2, Si3N4, Hf2O3, TiO2, Ti3N4, SiO, Al2N3, and TaO2. This wide variety of films available allows for tailoring of optical properties, such as hermeticity and anti-reflective coatings.

[0065]

[0077] The encapsulation layer / structure 110 may be deposited to a thickness T of about 0.5 nm to about 500 nm. The encapsulation layer / structure 110 may be a single material type or a combination of multiple material types. For example, as illustrated in FIG. 9 of the present application, in some embodiments, the encapsulation layer / structure 998 may include multiple alternating layers 1 through N, where N may be any reasonable integer. For example, the encapsulation structure 998 may include alternating layers of 1.0 nm thick Al2O3 and 1.0 nm thick Zr2O3, which may be used to build up a total thickness T of, for example, 100 nm by repeating the combination of the two layers 10 times. Thus, in this embodiment, N is 10. This is provided by way of example only, and embodiments of the inventive concepts are not limited thereby.

[0066]

[0078] Once the encapsulation layer / structure is complete, mask 895 may be removed, and the device illustrated in FIG. 8C may be completed, including, for example, wire bond pad 130. It will be understood that FIGS. 8A-8C are provided as an example of an embodiment including only ALD layers similar to FIG. 1B. However, as noted above, embodiments may also include epoxy and glass layers, as shown in FIGS. 2 and 4 above, without departing from the scope of the inventive concept.

[0067]

[0079] Embodiments of the inventive concepts are described herein in the context of one or more "colloidal quantum dot devices" on an integrated circuit, wafer, or die. These devices may be any colloidal quantum dot device, optoelectronic device, photodetector, sensor, or the like. However, in some embodiments, the colloidal quantum dot device is provided by, for example, devices described in U.S. Pat. No. 8,729,528, entitled "Quantum Dot-Fullerene Junction Optoelectronic Devices," and U.S. Pat. No. 8,742,398, entitled "Quantum Dot-Fullerene Junction Based Photodetectors," the contents of which are incorporated herein by reference above.

[0068]

[0080] A cross-section of an exemplary colloidal quantum dot device 1000 for use in accordance with some embodiments of the inventive concepts will now be described with reference to Figure 10. As illustrated in Figure 10, the device includes a substrate 1028, an electrode 1020 on the substrate 1028, an optional electron-blocking layer 1044, a first quantum dot (QD) layer 1008, a second QD layer 1012 or fullerene layer 1012, an optional hole-blocking layer 1042, and at least one electrode 1024. It will be understood that the cross-section of device 1000 illustrated in Figure 10 is provided by way of example only, and that embodiments of the inventive concepts are not limited thereto. As noted above, both the electron-blocking layer and the hole-blocking layer may be omitted without departing from the scope of the inventive concepts.

[0069]

[0081] In some embodiments, device 1000 is an optoelectronic device that operates as an image sensor, although one skilled in the art will understand that optoelectronic device 1000 may be adapted to function as another type of optoelectronic device without departing from the scope of the inventive concept. In embodiments in which layer 1012 is a fullerene layer, optoelectronic device 1000 may be any optoelectronic device based on an electronic heterojunction 1004 formed by a quantum dot (QD) layer 1008 directly coupled to fullerene layer 1012. QD layer 1008 is photosensitive, forming excitons in response to absorption of light. Fullerene layer 1012 is also photosensitive, forming excitons in response to absorption of light. In the case of a PV device or other type of light-absorbing device, the QD layer 1008 may be disposed on an electrode 1020 (acting as an anode), the fullerene layer 1012 may be disposed directly on the QD layer 1008, and the electrode 1024 (acting as a cathode) may be disposed on the fullerene layer 1012. In typical implementations, the electrode 1024 is intended to transmit incident light and is therefore made of a transparent material. In these embodiments, the electrode 1024 may be referred to as the front electrode (which receives the incident light), and the other electrode 1020 may be referred to as the back electrode.

[0070]

[0082] It will be understood that in some embodiments, layer 1012 may be a second quantum dot layer, and in some embodiments, layer 1012 may be a fullerene layer distinct from the quantum dot layer. As used herein, QD layer 1008 / 1012 includes a plurality of quantum dots (QDs). QD layer 1008 / 1012 may have a thickness ranging from about 5.0 nm to about 5.0 μm. In this context, thickness is defined vertically from the perspective of FIG. 10 , with the understanding that no restrictions are imposed on a particular orientation of optoelectronic device 1000 relative to any particular frame of reference. In exemplary implementations of the present teachings, the QDs are comprised of inorganic semiconductor materials. In one particularly advantageous, but non-limiting, example, the QDs are lead sulfide (PbS) crystals or particles. More generally, the QDs may be selected from a variety of II-VI, I-III-VI, III-V, IV, IV-VI, and V-VI materials. Examples include, but are not limited to, II-VI materials such as ZnS, ZnSe, ZnTe, ZnO, CdS, CdSe, CdTe, CdO, HgS, HgSe, HgTe, HgO, MgS, MgSe, MgTe, MgO, CaS, CaSe, CaTe, CaO, SrS, SrSe, SrTe, SrO, BaS, BaSe, BaTe, and BaO, CuInS2, Cu(In,Ga)S2, CuInSe2, and Cu(In,Ga) Examples of QDs include I-III-VI materials such as Se2, III-V materials such as AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb, IV materials such as Si, Ge, and C, IV-VI materials such as GeSe, PbS, PbSe, PbTe, PbO, SnSe, SnTe, and SnS, and V-VI materials such as Sb2Te3, Bi2Te3, and Bi2Se3. Transition metal compounds such as oxides, sulfides, and phosphides of Fe, Ni, and Cu may also be applicable. Examples of QDs further include binary, ternary, quaternary, and other alloys or compounds containing the aforementioned species (e.g., SiGe, InGaAs, InGaN, InGaAsP, AlInGaP, etc.). Other QDs may include other types of semiconductor materials (e.g., certain organic and polymeric materials).In the case of QDs with a core-shell structure, the shell may consist of one of the aforementioned species or other species, and the respective compositions of the core and shell may be different, for example, the core-shell composition may be CdSe-ZnS.

[0071]

[0083] As will be appreciated by those skilled in the art, the composition selected for the QDs can be based on desired properties such as bandgap energy or wavelength sensitivity. For example, QDs such as PbS, PbSe, PbTe, HgTe, InAs, InP, InSb, InGaAsP, Si, Ge, or SiGe can be selected for IR sensitivity, QDs such as CdS, CdSe, or CdTe can be selected for visible light sensitivity, and QDs such as ZnS or ZnSe can be selected for UV sensitivity. Because the majority of solar energy available for conversion by optoelectronic devices is in the IR region, PbS and other IR-sensitive QDs are particularly useful in photovoltaic devices. Blue-absorbing, UV-absorbing, and near-IR-absorbing (or emitting) QDs can also be selected. Furthermore, the size of the QDs can be selected to absorb or emit electromagnetic radiation in a desired range. Generally, for a given species of QD below a critical size, smaller sizes are more sensitive to shorter (bluer) wavelengths, and larger sizes are more sensitive to longer (redder) wavelengths. Furthermore, the optoelectronic behavior of the QDs can be customized depending on their shape or their size distribution in the QD layer 1008. Furthermore, the QD layer 1008 / 1012 can include two or more different species (compositions) and / or two or more different specific sizes of QDs. This is useful when it is desirable to expand the range of properties, behavior, or performance of the QD layer 1008 / 1012. For example, the mixture of QDs in the QD layer 1008 / 1012 can be selected so that the QD layer 1008 / 1012 has enhanced response to different bands of the electromagnetic spectrum (e.g., visible light and IR radiation, visible light and UV radiation, etc.). Alternatively or additionally, two or more separate QD layers 1008 / 1012 can be provided, each with a different QD composition or size. The two or more QD layers can form part of a corresponding number of separate QD-fullerene junctions within the optoelectronic device 1000 having a fullerene layer therein.

[0072]

[0084] QDs can be formed by various known techniques, such as colloidal synthesis, plasma synthesis, vapor deposition, epitaxial growth, and nanolithography. The size, size distribution, shape, surface chemistry, or other attributes of the QDs can be designed or tailored to have desired properties (e.g., photon absorption and / or emission) by any suitable technique, now known or later developed. The QD layer 1008 / 1012 can be formed on an underlayer (e.g., electrode 1020 or an intervening layer) by any suitable method, particularly solution-based methods such as various known coating and printing methods or doctor blading. In some embodiments, the QDs are provided in a solution of an organic carrier solvent, such as anisole, octane, hexane, toluene, butylamine, or water, with or without a matrix or host material, and deposited to a desired thickness by spin coating. Excess solvent can then be removed by evaporation, vacuum, or heat treatment. After formation, the QD layer 1008 / 1012 may or may not contain residual solvent. The as-deposited QD layer 1008 / 1012 can be characterized as containing a plurality of QDs or aggregates or arrays thereof. The QDs may be densely packed or more or less free-standing without a matrix material. In the absence of a matrix material, the QD layer 1008 / 1012 may be stabilized by London or van der Waals forces. Alternatively, the QDs may be dispersed at a desired density or concentration in a matrix material, which may consist of a polymer, sol-gel, or other material that can easily form a film on the intended underlying surface. Generally, the matrix material selected is chosen to improve the optical-to-electrical or electrical-to-optical conversion or other performance parameters of the QDs and the intended optoelectronic device 1000 as a whole. One example of such a matrix material is a semiconducting polymer such as poly-3-hexylthiophene. Alternatively, the QDs may be stabilized by treatment, as described below, to reduce the solubility of the film.

[0073]

[0085] The electrode 1024 can be any material that is electrically conductive and optically transparent when the electrode 1024 is intended to receive incident light. In some embodiments, an electrically conductive material is generally a material that is considered acceptable for use as an electrode or contact for passing electrical current in commercial or industrial-grade circuits, i.e., a material that has an acceptably low level of resistive losses. An optically transparent material is generally a material that allows a sufficient amount of incident light to pass through its thickness to illuminate the QDs in the QD layer 1008 / 1012, i.e., there is no significant reflection or absorption of photons. As one non-limiting example, a transparent material can be a material that allows at least 50% of incident electromagnetic radiation (of a desired wavelength or range of wavelengths) to transmit through its thickness. Furthermore, the material of the electrode 1020 should be a material that provides a suitable surface for QD deposition and generally facilitates fabrication of the optoelectronic device 1000 in a reliable and low-cost manner.

[0074]

[0086] Examples of electrode 1024 include, but are not limited to, transparent conductive oxides (TCOs), transparent metals, and transparent conductive polymers. TCOs may include, for example, tin oxide (TO), indium tin oxide (ITO), zinc oxide (ZnO), zinc indium oxide (ZIO), zinc indium tin oxide (ZITO), gallium indium oxide (GIO), and further alloys or derivatives of the foregoing. Tin oxide may also be doped with fluorine (F). ZnO may be doped with Group III elements such as gallium (Ga) and / or aluminum (Al), and thus more generally stoichiometrically doped with Zn. x Al y Ga z0, where x+y+z=1, 0≦x≦1, 0≦y≦1, and 0≦z≦1. Other metal oxides may be suitable, as well as non-oxide thin-film semiconductors. In the case of metals, various metals (e.g., silver, gold, platinum, titanium, lithium, aluminum, magnesium, copper, nickel, etc.), metal-containing alloys (including multiple layers or two or more different metals, with or without an adhesion-promoting layer such as tungsten), or metal-containing compounds may be used as electrode 1024, as long as the metal electrode 1024 is thin enough to be transparent, i.e., has a "transparent thickness." If optoelectronic device 1000 is desired to be sensitive in the IR range, electrode 1024 should be sufficiently transparent to IR wavelengths. The electrode 1024 is typically fabricated by a vacuum deposition technique, such as chemical vapor deposition (CVD), metalorganic CVD (MOCVD), radio frequency (RF) or magnetron sputtering, molecular beam epitaxy (MBE), ion beam epitaxy, laser MBE, or pulsed laser deposition (PLD). Depending on the composition, other deposition techniques, such as thermal evaporation or sublimation, may be suitable. Conducting polymers, if sufficiently transparent, may alternatively be used as the electrode 1024 and may be deposited by solution-based processes, spin coating, dip coating, spray coating, etc. One non-limiting example of a transparent conductive polymer is poly(3,4-ethylenedioxythiophene):polystyrenesulfonate) (PEDOT:PSS) and its chemical analogs and derivatives. A layer of conductive carbon nanotubes (CNTs) or nanosheets (e.g., graphene) may be used as electrode 1024, with or without a matrix material surrounding the CNTs or nanosheets. Electrode materials may be combined to form a composite electrode 1024. One example is the use of a TCO such as ITO in combination with a conductive polymer such as PEDOT:PSS to improve interface quality. In another embodiment, conductor 1024 need not be transparent and may be selected from a metal, a metal-containing alloy, or a metal-containing compound. One or both of electrodes 1020 or 1024 should be transparent.

[0075]

[0087] Electrode(s) 1020 may also be provided according to the above description for electrode 1024. In typical implementations of optoelectronic devices, electrode 1020 need not be transparent, and therefore its composition is typically selected from a metal, a metal-containing alloy, or a metal-containing compound. Electrode 1020 may be selected based on its work function or its usefulness as an ohmic contact.

[0076]

[0088] As mentioned above, in some embodiments, it may be advantageous to provide an electron blocking layer 1044 on the electrode 1020. In some embodiments, the electron blocking layer may be fabricated to only partially cover the electrode 1020. An electron blocking layer 1044 that provides partial coverage may be referred to as a discontinuous layer or film. The discontinuous electron blocking layer 1044 may provide the best combination of exciton and / or electron blocking capabilities while allowing efficient hole transport to the electrode 1020. This partial coverage may be formed by known patterning techniques or by depositing a film under appropriate conditions to result in only partial coverage. Examples of patterning techniques include, but are not limited to, the use of a mask, deposition by inkjet printing, and the like. In some implementations, the discontinuous electron blocking layer 1044 has a configuration in which islands or regions of electron blocking material are separated or surrounded by areas that do not include the electron blocking material (i.e., there is no electron blocking material at the plane level of the electron blocking layer 1044). In some embodiments, the discontinuous electron blocking layer 1044 has a configuration in which areas that do not contain electron blocking material are surrounded by electron blocking material. Thus, in the discontinuous electron blocking layer 1044, the electron blocking material may or may not occupy the majority of the planar area of ​​the electron blocking layer 1044. When the discontinuous electron blocking layer 1044 is provided in a pattern, the pattern may be regular or irregular. Examples of patterns include, but are not limited to, a series of stripes, an array of polygons, an array of circles or dots, etc.

[0077]

[0089] Depending on its composition and the properties of the semiconductor layer to which it is coupled, hole-blocking layer 1042 and / or electron-blocking layer 1044, such as those described above, may also act as exciton-blocking layers, confining photogenerated excitons to the region of the heterojunction where they need to dissociate and keeping them away from the electrode / semiconductor interface. In addition to hole-blocking layer 1042 and / or electron-blocking layer 1044, anode-side and / or cathode-side exciton-blocking layers may also be provided. As will be understood by those skilled in the art, the composition of the exciton-blocking layer may be dictated by whether it is positioned adjacent to the anode (e.g., electrode 1020) or the cathode (e.g., electrode 1024), so that the exciton-blocking layer does not impair hole transport or electron transport in the relevant direction. It will also be understood that hole-blocking layer, electron-blocking layer, and exciton-blocking layer may be doped with other compounds as needed for various purposes, such as improving mobility or stabilizing their structure. Additionally, these types of layers may also be desirable as protective layers to protect the as-deposited underlying layers during the fabrication process. Those skilled in the art will recognize the applicability of chemical derivatives or analogs of the aforementioned exemplary materials that may be utilized as hole-blocking, electron-blocking, and exciton-blocking layers, as well as alternatives to such materials that behave similarly.

[0078]

[0090] As briefly described above, some embodiments of the inventive concept provide colloidal quantum dot-based photodetectors that are hermetically sealed with a thin-film encapsulation layer, e.g., an ALD thin film(s). Due to the availability of a variety of materials for the encapsulation layer, as discussed above, the hermetically sealed ALD film(s) can be tailored to serve as an anti-reflection (AR) coating. The thin-film encapsulation methods for colloidal quantum dot photodetectors described herein offer advantages over conventional methods, such as infrared sensor packaging techniques, including reduced packaging cost, size, and weight. The low-cost, low-size, and low-weight encapsulation methods for colloidal quantum dot photodetectors can be used for industrial, mobile, and automotive sensing applications.

[0079]

[0091] Embodiments of the inventive concepts are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments of the inventive concepts. As such, variations from the shapes of the illustrations are to be expected as a result, for example, of manufacturing techniques and / or tolerances. Thus, embodiments of the inventive concepts should not be construed as limited to the particular shapes of regions illustrated herein and are intended to include deviations in shape that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle typically has rounded or curved features and / or has a gradient of implant concentration at its edges rather than a binary transition from implanted to non-implanted region. Similarly, a buried region formed by implantation may result in some implantation into the region between the implanted region and the surface where the implantation occurs. Thus, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the exact shape of a region of a device, nor are they intended to limit the scope of the inventive concepts.

[0080]

[0092] Additionally, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another element illustrated in the figures. It will be understood that the relative terms are intended to encompass different orientations of the device in addition to the orientation depicted. For example, if the device in the figures were inverted, elements described as being "lower" of other elements would then be oriented "upper" of the other elements. Thus, the exemplary term "lower" can encompass both an orientation of "lower" and "upper," depending on the particular orientation of the figure. Similarly, if the device in a figure were inverted, elements described as "below" or "below" other elements would then be oriented "above" the other elements. Thus, the exemplary terms "lower" or "bottom" can encompass both an orientation of top and bottom.

[0081]

[0093] Additionally, although various layers, portions, and regions of a photodetector may be described as being p-type and / or n-type, it will be understood by those skilled in the art that in many devices, these conductivity types may be interchanged without affecting the function of the device. When an element, region, or layer is referred to as "n-type," this means that the element, layer, or region is doped with an n-type dopant, e.g., Si, germanium (Ge), or oxygen, to a particular concentration. When an element, region, or layer is referred to as "p-type," this means that the element, region, or layer is doped with a p-type dopant, e.g., magnesium (Mg), beryllium (Be), zinc (Zn), calcium (Ca), or carbon (C). In some embodiments, an element, region, or layer may be referred to as "p-type." + " or "n + ", which refers to a p-type or n-type element, region, or layer that has a higher doping concentration than other p-type or n-type elements, regions, or layers in the device. Finally, regions may be described as epitaxial regions, implanted regions, etc. Although these regions may contain the same material, layers resulting from various formation methods may result in regions with different properties. In other words, epitaxially grown regions may have different properties than implanted or deposited regions of the same material.

[0082]

[0094] In the drawings and specification, illustrative embodiments of the inventive concepts are disclosed. However, many variations and modifications can be made to these embodiments without substantially departing from the principles of the inventive concepts. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the inventive concepts being defined by the following claims.

Claims

1. An integrated circuit; a colloidal quantum dot structure on the integrated circuit; a sealing layer on the colloidal quantum dot structure, the sealing layer having a thickness of about 0.5 nm to about 500 nm; A colloidal quantum dot device comprising:

2. The colloidal quantum dot device comprising an optoelectronic device, the optoelectronic device comprising: A first electrode; a first quantum dot layer on the first electrode, the first quantum dot layer including a plurality of quantum dots; a second quantum dot layer comprising a plurality of quantum dots and located directly on the first quantum dot layer; a second electrode on the second quantum dot layer; and 13. The colloidal quantum dot device of claim 1, comprising:

3. 3. The colloidal quantum dot device of claim 2 further comprising an electron blocking layer on said first electrode between said first electrode and said first quantum dot layer.

4. The colloidal quantum dot device comprising an optoelectronic device, the optoelectronic device comprising: A first electrode; a quantum dot layer on the first electrode, the quantum dot layer including a plurality of quantum dots; a fullerene layer located directly on the quantum dot layer; a second electrode on the fullerene layer; 10. The colloidal quantum dot device of claim 1 , wherein the quantum dot layer and the fullerene layer form an electronic heterojunction.

5. 10. The colloidal quantum dot device of claim 1 , wherein the encapsulation layer comprises an atomic layer deposition (ALD) layer.

6. The ALD layer is located directly on the colloidal quantum dot structure, and the colloidal quantum dot device comprises: an epoxy layer on the ALD layer; a glass layer on the epoxy layer; 6. The colloidal quantum dot device of claim 5, further comprising:

7. an epoxy layer on the colloidal quantum dot structure; a glass layer on the epoxy layer; 7. The colloidal quantum dot device of claim 6, further comprising: said ALD layer on said glass layer.

8. 10. The colloidal quantum dot device of claim 1 , wherein the colloidal quantum dot device comprises one of a photodiode device and a photodetector device.

9. 10. The colloidal quantum dot device of claim 1, wherein the colloidal quantum dot device detects light with sensitivity over a spectral range from about 250 nm to about 2400 nm.

10. 10. The colloidal quantum dot device of claim 1 , wherein the encapsulation layer comprises a plurality of alternating layers having a combined thickness of about 0.5 nm to about 500 nm.

11. An integrated circuit; a plurality of colloidal quantum dot devices on the integrated circuit; an encapsulation layer over the plurality of colloidal quantum dot devices, the encapsulation layer having a thickness of about 0.5 nm to about 500 nm; A die comprising:

12. The plurality of colloidal quantum dot devices comprises a plurality of optoelectronic devices, each of the optoelectronic devices comprising: A first electrode; a first quantum dot layer on the first electrode, the first quantum dot layer including a plurality of quantum dots; a second quantum dot layer comprising a plurality of quantum dots and located directly on the first quantum dot layer; a second electrode on the second quantum dot layer; and The die of claim 11 comprising:

13. The die of claim 11 , wherein the die is configured to be separated into a plurality of individual colloidal quantum dot devices.

14. The die of claim 11 , wherein the encapsulation layer is an ALD layer.

15. The ALD layer is located directly on the plurality of colloidal quantum dot devices, and the die comprises: an epoxy layer on the ALD layer; a glass layer on the epoxy layer; The die of claim 14 further comprising:

16. an epoxy layer on the plurality of colloidal quantum dot devices; a glass layer on the epoxy layer; 20. The die of claim 14, further comprising: the ALD layer on the glass layer.

17. 1. A method of making a colloidal quantum dot device, comprising: providing an integrated circuit including a plurality of colloidal quantum dot structures thereon; forming an encapsulation layer over the plurality of colloidal quantum dot structures, wherein the encapsulation layer has a thickness of about 0.5 nm to about 500 nm; separating the plurality of colloidal quantum dot structures into individual colloidal quantum dot devices; A method for providing the above.

18. 20. The method of claim 17, wherein the encapsulation layer comprises one or more of Al2O3, Zr2O3, ZnO, InO, SiO2, Si3N4, Hf2O3, TiO2, Ti3N4, SiO, Al2N3, and TaO2.

19. forming the encapsulation layer comprises depositing the encapsulation layer using ALD.

20. The method of claim 17.

20. The method of claim 19, wherein the encapsulation layer is deposited at a temperature of about 25°C to about 150°C.

21. The ALD layer is formed directly on the plurality of colloidal quantum dot structures, the method comprising: forming an epoxy layer on the ALD layer; forming a glass layer on the epoxy layer; 20. The method of claim 19 further comprising:

22. forming an epoxy layer over the plurality of colloidal quantum dot structures; forming a glass layer on the epoxy layer; 20. The method of claim 19, further comprising: wherein the ALD layer is formed on the glass layer.

23. 20. The method of claim 17, wherein each of the plurality of colloidal quantum dot structures comprises one of a photodiode device and a photodetector device.

24. The method of claim 17, wherein forming the encapsulation layer comprises forming a plurality of alternating layers having a combined thickness of about 0.5 nm to about 500 nm.

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