WO2016130582A1 - Filtres diélectriques en métal intégrés à des capteurs pour détecteurs d'ultraviolets en silicium pour stores solaires - Google Patents

Filtres diélectriques en métal intégrés à des capteurs pour détecteurs d'ultraviolets en silicium pour stores solaires Download PDF

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WO2016130582A1
WO2016130582A1 PCT/US2016/017200 US2016017200W WO2016130582A1 WO 2016130582 A1 WO2016130582 A1 WO 2016130582A1 US 2016017200 W US2016017200 W US 2016017200W WO 2016130582 A1 WO2016130582 A1 WO 2016130582A1
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dielectric
filters
layers
semiconductor substrate
filter
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PCT/US2016/017200
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Michael E. Hoenk
John J. Hennessy
Shouleh Nikzad
April D. JEWELL
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California Institute Of Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/208—Filters for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/28—Interference filters
    • G02B5/283—Interference filters designed for the ultraviolet
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02162—Coatings for devices characterised by at least one potential jump barrier or surface barrier for filtering or shielding light, e.g. multicolour filters for photodetectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0232—Optical elements or arrangements associated with the device
    • H01L31/02322—Optical elements or arrangements associated with the device comprising luminescent members, e.g. fluorescent sheets upon the device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
    • H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
    • H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
    • H01L31/107—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier working in avalanche mode, e.g. avalanche photodiodes

Definitions

  • This invention relates to filters for detectors (e.g., semiconductor device detectors). 2. Description of the Related Art.
  • UV light has applications in planetary imaging and spectroscopy, astronomy, communications, and medical imaging/diagnostics.
  • One major challenge facing UV detection is visible or solar rejection, as UV photons in bands of interest are often greatly outnumbered by visible photons, effectively reducing the signal- to-noise ratio.
  • One approach to selective UV detection is the use of wide bandgap semiconductors. These materials are inherently insensitive to lower-energy photons, but device performance is typically limited by material quality issues that degrade quantum efficiency in the ultraviolet.
  • Si sensors can be modified, through a technique invented at the Jet Propulsion Laboratory (JPL) called delta-doping, to have 100% internal quantum efficiency throughout the ultraviolet [1], but this high efficiency is maintained throughout the visible as well.
  • JPL Jet Propulsion Laboratory
  • One or more embodiments of the invention disclose the fabrication of metal– dielectric thin film stacks deposited directly onto semiconductor (e.g., silicon) substrates for use as ultraviolet bandpass filters. Integration of these filters onto semiconductor (e.g., silicon) improves the admittance matching of the structure when compared to similar designs fabricated on transparent substrates, leading to higher peak transmission or improved out-of-band rejection if used with a semiconductor based (e.g., Si-based) sensor platform.
  • semiconductor e.g., silicon
  • one or more embodiments of the invention disclose one or more filters for electromagnetic radiation, each of the filters comprising one or more dielectric spacer regions and one or more reflective regions integrated (e.g., grown) on a semiconductor substrate, the semiconductor substrate including a semiconductor photodetector, such that each of the filters transmit ultraviolet radiation to the semiconductor photodetector, the ultraviolet radiation having a range of wavelengths, and each of the filters suppress transmission of out-of-band electromagnetic radiation, having wavelengths outside the range of wavelengths, to the semiconductor photodetector.
  • the range of wavelengths can be 100 nm -300 nm and the wavelengths outside the range of wavelengths can include wavelengths corresponding to visible light and infrared radiation.
  • the filters can include a portion of the semiconductor substrate, forming photodetector integrated filters each comprising a Fabry-Perot cavity.
  • the dielectric spacers can be transparent to the ultraviolet radiation and the reflective regions can be reflective for the out-of-band electromagnetic radiation.
  • Each of the reflective regions can separate two of the dielectric spacer regions, and the reflective regions and the dielectric spacer regions can be structured to:
  • the one or more dielectric spacer regions can comprise one or more dielectric layers with the first dielectric layer deposited directly on the semiconductor substrate or on an oxide of the semiconductor substrate.
  • the one or more reflective regions can comprise one or more metal layers, each of the metal layers separating two of the dielectric layers.
  • Transparency of the dielectric layers to the ultraviolet radiation, a number of the dielectric layers, one or more thicknesses of the dielectric layers, a number of the metal layers, reflectivity of the metal layers, a refractive index of the semiconductor substrate, and an extinction coefficient of the semiconductor substrate can be controlled to achieve a desired transmittance:
  • Thicknesses of the dielectric and/or metal layers can be adjusted to account for oxidation of one or more of the metal layers.
  • the dielectric layers can each have a thickness in a range of 20-100 nm and the metal layers can each have a thickness in a range of 5-50 nm.
  • the dielectric spacer regions can consist of two dielectric layers and the reflective region can consist of a metal layer between the dielectric layers.
  • the dielectric spacer regions can consist of three dielectric layers, the reflective regions can consist of two metal layers, and each of the metal layers can separate two of the dielectric layers.
  • the dielectric spacer regions can consist of four dielectric layers, the reflective regions can consist of three metal layers, and each of the metal layers can separate two of the dielectric layers.
  • Test structures fabricated with metallic Al and atomic layer deposited Al2O3 were characterized with spectroscopic ellipsometry and agree well with optical models. These models predict transmission as high as 90% in the spectral range of 200–300 nanometers (nm) for simple three-layer coatings.
  • the dielectric spacer regions can comprise at least one dielectric selected from aluminum oxide, silicon dioxide, and magnesium fluoride, and the reflective regions comprise aluminum or a dielectric that reflects the electromagnetic radiation having wavelengths outside said range of wavelengths.
  • the semiconductor photodetector (e.g., avalanche photodiode) can include the MDF and a passivation layer comprising multiple doped layers configured to provide the semiconductor photodetector having a peak quantum efficiency (QE) greater than 40% for the ultraviolet radiation (e.g., at a wavelength of 225 nm).
  • QE peak quantum efficiency
  • a scintillator can be electromagnetically coupled to each of the filters, wherein the scintillators each emit scintillation comprising the ultraviolet radiation in response to interactions with energetic photons or particles.
  • One or more embodiments of the invention further disclose a system for performing Positron Emission Tomography (PET) comprising:
  • the first scintillator positioned to receive a first gamma photon and emit a first scintillation in response thereto
  • the second scintillator positioned to receive a second gamma photon and emit a second scintillation in response thereto
  • the first and second gamma photons emitted as a pair from an electron-positron annihilation, and the positron emitted by a radionuclide tracer introduced into a biological cell
  • pairs of the filters comprising a first filter and a second filter, the first filter positioned to receive the first scintillation and the second filter positioned to receive the second scintillation.
  • Fig.1 is a comparison of the UV bandpass filter F255W in the Hubble Space Telescope’s Wide-Field Planetary Camera 2 with the calculated performance of a nine- layer Al ⁇ MgF 2 filter structure on Si designed to match the out-of-band rejection performance according to one or more embodiments of the invention (inset shows transmission in the passband on a linear scale).
  • Fig.2 is calculated performance of a five-layer MDF filter structures described in Table 1 demonstrating the relative performance of structures with similar out-of-band rejection fabricated on silicon (Si) substrates (according to one or more embodiments) or quartz substrates;
  • Fig.3 is contours of constant transmission for MDF structures composed of two 10 nm Al layers and dielectric spacers of variable thickness assumed to be aluminum oxide for (a) peak transmission at 250 nm and (b) out-of-band transmission at 500 nm.
  • Fig.4 is measured SE parameters for three-layer MDF filter structures at incident angles of 45° and 65° for samples (a)–(c), as described in Table 2.
  • Fig.5(a)-(b) illustrates an optical model and layer structure for experimental MDF structures and the original target model at 45° incidence in comparison with the ellipsometrically predicted transmission at the same angle of incidence (AOI), according to one or more embodiments of the invention.
  • AOI angle of incidence
  • Fig.6 illustrates a method of fabricating a detector for electromagnetic (EM) radiation, according to one or more embodiments of the invention.
  • Fig.7 is a cross-sectional schematic of a detector according to one or more embodiments of the invention.
  • Fig.8 shows the measured quantum efficiency of superlattice-doped APDs having a 9 mm by 9 mm surface area (area A in Fig.7) for receiving electromagnetic radiation, for 3 and 5 layer metal-dielectric filters, as a function of wavelength of incident EM radiation in nanometers, fabricated according to one or more embodiments of the invention.
  • Fig.9 is comparison of the response times (amplitude of response in arbitrary units versus time in nanoseconds) of a superlattice doped avalanche photodiode (SL- APD) and a conventional, state-of-the-art APD, showing faster response for the SL-APD fabricated according to one or more embodiments of the invention.
  • SL- APD superlattice doped avalanche photodiode
  • Fig.10 illustrates a system for performing Positron Emission Tomography (PET) and that can include the detector of Fig.7. DETAILED DESCRIPTION OF THE INVENTION
  • One or more embodiments of the present invention show that the concept of metal–dielectric bandpass filters can be extended for use directly on a semiconductor (e.g., silicon (Si)) photodetector, and can achieve superior transmission/rejection performance when compared to similar structures fabricated on transparent substrates as stand-alone filter elements.
  • a semiconductor e.g., silicon (Si)
  • visible band rejection can be extended to a semiconductor (e.g., silicon) sensor platform for use in a narrow- to medium-band UV imager, or implemented with a stepped or wedged thickness structure for use in spectroscopy applications.
  • simple three-layer dielectric–metal–dielectric (DMD) structures are capable of a peak narrow-band transmittance of greater than 90% over the entire range of 100 to 300 nm, a significant improvement over the performance of simple dielectric-based antireflection (AR) coatings in the 100-300 nm spectral range. Due to the small and rapidly changing refractive index of Si in this wavelength range, single-layer dielectric AR coatings are only capable of providing transmittance in the range of 50%–60% [2]. Multilayer high–low dielectric stacks are required to produce peak transmittances greater than 80% [3].
  • the metal–dielectric filters (MDFs) implemented according to one or more embodiments of the invention also known as Fabry–Perot filters or photonic bandgaps, have a long history of use as bandpass filters for spectral ranges from the ultraviolet to the infrared [4–7].
  • the basic concept consists of matched parallel reflecting plates separated by a transparent spacer layer in order to destructively phase-match the reflection off of one metal layer at a particular wavelength and maximize transmission through the structure. Out-of-band light is not subjected to the same interference and is rejected by the high natural reflectance of the stack.
  • Fig.1 shows a comparison between the F255W bandpass filter on the Hubble Space Telescope’s Wide-Field Planetary Camera 2 (WFPC2) [16] and a simulation of a nine-layer Al/MgF2 MDF on silicon that matches the rejection
  • Optical simulations utilizing the transfer matrix method [19] were performed in order to compare the theoretical performance of Si-integrated MDFs with more traditional transparent MDFs on quartz substrates.
  • Three (DMD), five (DMDMD), and seven (DMDMDMD) layer structures were considered, consisting of alternating layers of Al2O3 dielectric and Al metal.
  • the optical constants of Al2O3 were determined experimentally via spectroscopic ellipsometry (SE) of standalone layers deposited via atomic layer deposition (ALD) on HF-cleaned Si substrates [20].
  • SE spectroscopic ellipsometry
  • Al atomic layer deposition
  • the optical constants of Al were taken from Rakic et al. [21], and the optical constants of Si and quartz (assumed to be equal to SiO2) were taken from Palik [22].
  • filter designs were generated in order to yield a peak transmittance at 250 nm, while yielding an average out-of-band transmittance as specified in Table
  • Layer optimization was performed by considering only first order dielectric thicknesses while allowing variable Al layer thicknesses in order to match the desired rejection value. Increased Al layer thickness will increase out-of-band rejection at the cost of reduced peak transmission.
  • the individual Al layers in the filter were defined as equal to one another in order to simplify the optimization space. Generally, mismatched cavities may be useful to make slight alterations to the shape and width of the passband and the stopband.
  • performance improvement is the result of better admittance matching with the metal– dielectric assembly as well as the improved out-of-band reflectivity of Si compared to transparent materials in the visible wavelength range.
  • Fig.3 shows the results of the calculated performance of MDFs composed of two 10 nm Al thin films separated by transparent dielectric (Al 2 O 3 ) spacers.
  • the impact of the substrate’s refractive index and extinction coefficient was evaluated by calculating the transmission of this filter stack in-band at 250 nm and out-of-band at 500 nm.
  • the thicknesses of the dielectric spacer layers were optimized via a simplex algorithm in order to result in maximum possible transmittance at 250 nm.
  • the indices of Si, Al, and the transparent alumina spacer layer are indicated on each plot for the respective target wavelength.
  • Fig.3(a) It can be seen in Fig.3(a) that there exists a range of real and imaginary refractive indices that yield maximum front-surface transmission for the given structure. Because only front-surface effects were considered in these calculations, the values may vary from the final transmission of a completed element. For example, the calculated transmission on a photosensitive material such as silicon is accurate because the increase in absorption does not imply an additional loss if it is part of the detection process. Likewise, the calculation for transparent materials is accurate because there are no additional losses through the substrate (except for those at the back surface, which can be mitigated).
  • the final transmission may be improved over the calculated values by extending the structure with an additional cavity; however, this final transmission will be necessarily lower than the maximum value represented in Fig.3(a) due to finite losses in the metal layers, as well as the requirement to ultimately terminate the structure with either a transparent material or a photosensitive one as described here.
  • the out-of-band rejection of a MDF is determined by the reflectivity of the‘metal’ layers, which is supported by the calculations in Fig.3(b) that show a significant reduction in transmission at 500 nm for increasing values of k/n. Again, for reflective materials this amount of rejection can be achieved only if the structure is continued with an additional cavity. For transparent substrates the amount of achievable rejection is approximately 100 ⁇ less than a similar structure with one additional metal layer. This relative improvement is supported by calculated rejection values in Table 1. Although a material such as Si does not match this improvement, it is capable of improving rejection by more than 3 ⁇ depending on the target wavelengths and desired transmission. When combined with the in-band improvement in transmission, this represents a significant performance increase for the Si MDF over fully transparent implementations.
  • the Si MDF can then be viewed as a general MDF with one additional mismatched cavity.
  • This additional cavity does not require a metallic Al layer, whose interface stability represents a significant fabrication challenge, especially for target wavelengths in the far UV. This challenge is the result of the rapid oxidation of the Al surface, which has been observed to degrade the optical properties of Al thin films, even under ultrahigh-vacuum conditions. It is expected that the
  • Al-based MDFs performance of Al-based MDFs is ultimately limited by the total number of Al layers, each of which provides an interface that may be subject to this degradation.
  • Experimental results for Al/Al 2 O 3 filters according to one or more embodiments In order to verify the calculated performance of these filter systems, simple test structures were fabricated on bulk silicon substrates with three designs targeting peak transmission at 200, 250, and 300 nm.
  • the dielectric spacer was chosen to be Al2O3, which is transparent in this wavelength range and has an inherent chemical stability with the metallic Al reflector layer.
  • the Al layer thickness was fixed at 15 nm, and the thickness of the remaining dielectric layers was optimized to result in maximized transmission at the target wavelengths.
  • a fixed Al layer thickness was chosen so that the metal layer in each filter structure could be co-deposited. In this way, subsequent optical fitting could be corroborated with this fixed-thickness reference point.
  • Al2O3 was deposited via atomic layer deposition (ALD) using trimethylaluminum and oxygen plasma at a substrate temperature of 200°C.
  • ALD atomic layer deposition
  • QE detector quantum efficiency
  • ALD has been shown to be superior to other dielectric deposition techniques (such as sputtering) at maintaining UV QE [23], and may be effective at preventing additional surface damage during the evaporation or sputtering of subsequent metal layers.
  • the Al layer was evaporated by an electron beam and the thickness was monitored by a quartz crystal microbalance.
  • Al was evaporated at a rate of 2 ⁇ /s at a system base pressure of 2 ⁇ 10 ⁇ 9 Torr.
  • the chamber pressure was monitored by ion gauge and increased to a range of 8 ⁇ 10 ⁇ 9 to 1 ⁇ 10 ⁇ 8 Torr during evaporation.
  • Al 2 O 3 layer thicknesses were calibrated by previous depositions of single-layer thin films on silicon as measured by spectroscopic ellipsometry (SE). No particular precaution was taken to prevent ambient exposure of the evaporated Al films prior to ALD; samples were transferred ex situ.
  • sample (c) the largest ⁇ 2 difference occurs for sample (c), particularly at wavelengths approaching the expected absorption edge of Al2O3 (as well as any unintended AlOx interfacial components).
  • Sample (c) also has the highest projected peak transmission of approximately 90% at normal incidence. A small contribution from higher-order interference is evident in sample (a), which targets a wavelength of 300 nm. When using an Al2O3 spacer layer, this higher-order peak will continue to become more evident at longer target wavelengths.
  • MDFs with a single dielectric material are considered; however, other combinations or dielectric materials can be used. Suitable options include Al2O3 for target UV wavelengths down to its absorption edge at 190 nm, or metal fluorides, such as MgF2, AlF3, or LiF, for applications down to approximately 100 nm.
  • the transparency of the spacer layer is the primary requirement for the performance of the MDF structure; changes in refractive index can be offset by changing the physical thickness in order to create the same phase-matching condition. For example, similar theoretical performance can be predicted for SiO2, MgF2, or Al2O3, as long as the MDF is operated above the absorption cutoff of the chosen material.
  • the MDF is combined with a photon-counting ultraviolet detector (having high quantum efficiency in the deep ultraviolet).
  • the combination can be used to fabricate an ultrafast scintillator for detecting high energy particles with subnanosecond temporal resolution.
  • the photon- counting detector can comprise an avalanche photodiode (APD) whose performance in the deep ultraviolet is upgraded using surface passivation technology (e.g., superlattice doping).
  • APD avalanche photodiode
  • Fig.6 illustrates a method of combining or integrating the detector with the MDF.
  • the method can comprise the following steps.
  • Block 600 represents obtaining a semiconductor photodetector (e.g., a wafer).
  • the semiconductor (e.g., silicon) photodetector can comprise a sensor such as a Charge Coupled Device (CCD), Complementary Metal–Oxide–Semiconductor (CMOS) sensor/imaging detector, and a photodiode (e.g., an avalanche photodiode, e.g., operated in a proportional mode, or a multi pixel photon counter module APD).
  • CMOS Complementary Metal–Oxide–Semiconductor
  • the photodetector can be a detector having built in gain through avalanche multiplication or avalanche gain (e.g., up to 1000 times gain), wherein charge generated in the semiconductor
  • photodetector in response to the ultraviolet radiation is amplified through impact ionization.
  • Block 602 represents thinning the photodetector, e.g., to optimize the depth of the pn junction (e.g., removing 100 micrometers from the p-doped side of the detector).
  • Fig. 7 illustrates the resulting detector 700 can comprise the semiconductor photodetector comprising a photosensitive p + type silicon epilayer 702 having a thickness of ⁇ 5 ⁇ m, p + regions and an n + region, and n contact 704.
  • Block 604 represents surface preparation of the thinned surface (e.g., cleaning the surface to be thinned using solutions of bases, acids and oxidizers to remove organic and metallic contamination).
  • Block 606 represents at least partially passivating the thinned surface area of the semiconductor photodetector, e.g., using surface doping methods to provide a peak quantum efficiency greater than 40% for light with wavelengths corresponding to the desired ultraviolet radiation.
  • the passivation (and thinning and preparation in Blocks 602-604) can use the method and conditions described in [25] (see, for example col.16 line 63- col.7 line 52 of [25]).
  • the passivation layer 706 can comprise a layer of semiconductor (e.g., silicon) that is doped with a sheet density of at least 10 14 cm -2
  • the passivation layer 706 can comprise a (e.g., silicon) layer with at one or more doped (e.g., delta-doped) layers 708 (e.g., at least two delta-doped layers, at least 4 delta doped layers).
  • the passivation layer can be deposited by Molecular Beam Epitaxy (MBE), for example.
  • MBE Molecular Beam Epitaxy
  • the passivation layer can passivate a density of interface traps (D it ) greater than 10 14 cm -2 eV -1 . In one or more embodiments, the passivation layer is typically less than 5 nm thick.
  • the passivation layer can be configured to be insensitive to radiation-induced surface damage, for example such that there is no change in Quantum Efficiency (QE), to within 5% or within 1%, after irradiation of the passivated surface area A with a billion pulses of the Electromagnetic radiation having an integrated intensity of greater than 2 kilojoules per centimeter square and a wavelength of 193 nanometers (see [27]).
  • QE Quantum Efficiency
  • Block 608 represents applying/integrating/forming/combining/depositing one or more dielectric regions/layers 712a, 712b and one or more reflective regions/layers 714 on the passivated surface area A, as illustrated in Fig.7, to form a photodetector integrated filter acting as a bandpass filter that transmits light/radiation within a range of wavelengths corresponding to ultraviolet radiation and suppresses transmission of light/radiation with wavelengths outside that range of wavelengths.
  • the dielectric regions can comprise transparent dielectric 712a-712b (e.g., sapphire, Al 2 O 3 ) and the reflective regions can comprise dielectric or metal 714 (e.g., Aluminum, Al) to form a Fabry-Perot cavity and/or a photonic bandgap (e.g., a one- dimensional photonic bandgap).
  • the bandpass filter can comprise reflective regions including metal (e.g., Al) embedded in dielectric (e.g., Al 2 O 3 , aluminum oxide) or a multilayer film fabricated from alternating thin films of transparent dielectric layers and reflective metallic layers.
  • the dielectric layers may be composed of any material that is optically transparent in the intended range which may include, for example, HfO 2 , Al 2 O 3 , SiO 2 , MgF 2 , or AlF 3 . Multilayer stacks of these materials (or others) may also be used to improve the index- matching of the composite dielectric layer.
  • the metallic layer is ideally fabricated from a material with high natural reflectance in the band of interest, for UV applications at wavelengths below 300 nm the most optimal choice is pure aluminum.
  • the final filter structure is deposited directly on the passivated surface A of the detector with a suitable technique that may include atomic layer deposition (ALD) (e.g., using the process described in [26]), chemical vapor deposition, and evaporation among others.
  • ALD atomic layer deposition
  • the ALD deposition conditions can include using trimethylaluminum and oxygen plasma (or water vapor) at a substrate temperature of 200°C for the Al 2 O 3 , depositing the Al layers by electron beam evaporation, and monitoring the thickness of the layers using a quartz crystal microbalance.
  • Al 2 O 3 layer thicknesses can be calibrated by previous depositions of single layer thin films on silicon as measured by spectroscopic ellipsometry, for example.
  • ALD is used because it can achieve layer by layer growth of the coating/filter with Angstrom level/resolution control over arbitrarily large surface areas, a wide suite of materials can be deposited, such as metals, oxides, and nitrides, with excellent film properties, and the ALD layers can be directly integrated into existing detectors to vastly improve performance.
  • the ALD enables precise, repeatable targeting of desired frequency bands, e.g., using different thicknesses.
  • the MDF comprises a“3 layer” design (one metal layer embedded between two dielectric layers), although other designs are possible. Filter throughput, rejection ratio, bandwidth, and other performance parameters are a functions of the final design which may include multiple periods of the metal-dielectric assembly. Total throughput is ultimately limited by optical absorption losses in the metal layers which may limit the optimal number of periods that can be utilized.
  • the dielectric layers and metal layer can be dimensioned and structured to destructively phase-match reflection of the ultraviolet radiation off of the reflective regions so as to increase transmission of the ultraviolet radiation through the filter to the semiconductor photodetector, and increase reflection of radiation, having wavelengths outside said range of wavelengths, away from the semiconductor photodetector.
  • an extinction coefficient of the semiconductor substrate can be selected/controlled/effective to achieve a desired transmittance, e.g., achieving the filter having (for example):
  • a transmittance of more than 80%/90% for the ultraviolet radiation at a wavelength of 250 nm and a transmittance of at most 1% for electromagnetic radiation at a wavelength of 500 nm for example see e.g., Fig.5, however, filters with a different peak transmission (higher or lower) at one or more wavelengths different from 250 nm and having suppressed out of band transmittance for a range of wavelengths, can also be designed/provided
  • the thicknesses of the metal layers and/or the dielectric spacer layers can be adjusted to account for oxidation of one or more of the metal regions.
  • the dielectric layers can each have a thickness of 10’s nanometers (e.g., in a range of 20-100 nm) and the metal layers can each have a thickness in a range of 5-50 nm.
  • the dielectric layer could in some implementations comprise multiple layers, or in others it might have a non-homogeneous or graded composition. In some
  • a native oxide there might not be a native oxide, although a native oxide between the passivation layer and dielectric 712a is possible (note that a native oxide is an oxide that forms from exposure to air, as opposed to an oxide that is intentionally grown or deposited as part of the structure).
  • Block 610 represents further processing of the detector and providing electronics or circuitry for processing the detected signal.
  • Block 612 represents optionally positioning a scintillator 716 (e.g., coated or glued on the MDF, as illustrated in Fig.7, or positioned with a gap, such as an air gap, or remote from the photodetector) such that the semiconductor photodetector detects electromagnetic radiation comprising the scintillation 718a-b generated in response to energetic photons or particles 720 incident on the scintillator.
  • a scintillator 716 e.g., coated or glued on the MDF, as illustrated in Fig.7, or positioned with a gap, such as an air gap, or remote from the photodetector
  • the scintillator comprises a BaF 2 crystal and/or emits the scintillation including a fast component with a peak wavelength of or near 220 nanometers and a slow component including a wavelength of or near 300 nanometers.
  • Block 614 represents the end result, a detector useful for detecting ultraviolet radiation or scintillation emitted by a scintillator.
  • Fig.7 further illustrates the unwanted out of band component of the radiation (e.g., scintillation 718b, e.g., at 300 nm wavelength) is suppressed by the filter and the desired component of the ultraviolet radiation (e.g., scintillation 718a, e.g., at 220 nm wavelength) is absorbed in the p-type silicon epilayer 702 to photogenerate electrons e- .
  • the electrons e- can be transported to the pn junction 722 by diffusion or drift (e.g., with a drift velocity of 10 micrometers per picosecond).
  • the detector When the detector is biased, the electrons e- generate further electrons e- via impact ionization, thereby causing avalanche gain (multiplication) in the pn junction 722.
  • the detected signal can be read out as is done typically for such devices (see e.g., [24]).
  • a plurality of the detector integrated filters can be fabricated in an array, wherein each detector integrated filter can comprise a pixel or detector element.
  • electromagnetic radiation receiving surface area A of the detector (and filter) can be at least 1 millimeter (mm) by 1 millimeter, or at least 9mm by 9mm, for example.
  • Fig.8 shows the measured quantum efficiency of superlattice-doped APDs with 3 and 5 layer metal-dielectric filters, demonstrating the performance of two different filters on actual devices.
  • Fig.9 is a comparison of the measured response times of a superlattice doped avalanche photodiode (SL-APD) with filter according to one or more
  • Fig.9 shows faster response (rise and decay times) for the superlattice doped avalanche photodiode with coating/MDF according to one or more embodiments of the present invention.
  • the underlying device was a Si APD (e.g., as illustrated in Fig.7) and the approximate layer thicknesses in the MDF were:
  • 3 layer MDF Si APD / 40 nm Al 2 O 3 / 20 nm Al / 20 nm Al 2 O 3 .
  • the top layer thickness (20 & 25 nm in the examples above) is less critical to obtaining the same QE.
  • the metal layer thicknesses can be changed in this range (10– 20 nm) to adjust the relative height of the QE peak to the out of band level, and the other Al 2 O 3 layers (first two in the 5 layer MDF, first one only in the 3 layer MDF) define the wavelength where the QE peak occurs.
  • the passivation layer comprises a silicon superlattice with 4 delta doped layers having a combined surface doping density of 8 x 10 14 cm -2 and a total thickness of less than 5nm (as illustrated in Figure 5 of U.S. Patent Application Serial No.14/670,365 filed on March 26, 2015, by Michael E. Hoenk, John Hennessy, and David Hitlin, entitled“SUBNANOSECOND SCINTILLATION DETECTOR, and cross-referenced above).
  • Fig.8 shows the peak quantum efficiency of a 5-layer MDF is about 33%, while the peak quantum efficiency for a 3-layer MDF is about 50%.
  • the inventors note that quantum efficiency and transmittance are not the same thing (transmittance is only one of the limiting factors in quantum efficiency). Another factor is recombination of electrons and holes in the semiconductor, which reduces the measured signal from photogenerated charge. Consequently, the quantum efficiency measured in Fig.8 is necessarily lower than the transmittance of the filter.
  • the quantum efficiency in Fig.8 was measured at low bias voltage so that there would be no gain in the device. Therefore, the data of Fig.8 really show a lower limit of quantum efficiency as measured under unity gain conditions (i.e., low bias voltage).
  • Fig.10 illustrates a PET system comprising pairs of scintillators each comprising a first scintillator 1000a and a second scintillator 1000b.
  • the first scintillator1000a is positioned to receive a first gamma photon ⁇ 1 and emit a first scintillation 1002a in response thereto
  • the second scintillator 1000b positioned to receive a second gamma photon ⁇ 2 and emit a second scintillation 1002b in response thereto.
  • the first and second gamma photons ⁇ 1, ⁇ 2 are emitted as a pair from an electron-positron annihilation 1004, wherein the positron is emitted by a radionuclide tracer 1006 introduced into a biological cell in a patient 1008.
  • the radionuclide tracer 1006 comprises a positron emitter such as 11 C, 13 N, 15 O, 18 F, or 82 Rb, for example, that undergoes positron emission decay (beta decay), emitting the positron which travels a distance in the patient’s 1008 tissue (e.g., less than 1 mm, but dependent on the isotope) before it annihilates 1004 with an electron, producing the pair of gamma photons ⁇ 1, ⁇ 2 each having 0.511 MeV energy and moving in approximately opposite directions (180 degrees to each other).
  • a positron emitter such as 11 C, 13 N, 15 O, 18 F, or 82 Rb, for example, that undergoes positron emission decay (beta decay), emitting the positron which travels a distance in the patient’s 1008 tissue (e.g., less than 1 mm, but dependent on the isotope) before it annihilates 1004 with an electron, producing the pair of gam
  • the scintillators 1000a-1000b are positioned in a ring around the patient 1008.
  • the PET system further comprises pairs of detector integrated filters 700 including one of the detector integrated filters 1010a positioned to detect the ultraviolet radiation 1012a comprising the first scintillation 1002a and one of the detector integrated filters 1010b positioned to detect the ultraviolet radiation 1012b comprising the second scintillation 1002b.
  • the PET system further comprises one or more computers 1014 for performing a (e.g., three dimensional) calculation of a location of the radionuclide tracer 1006.
  • a location of the radionuclide tracer 1006 From the gamma photons detected by the scintillators 1000a, 1000b, it is possible to localize their source along a straight line of response (LOR).
  • the first and second scintillations 1002a, 1002b define a line of response LOR and the intersections of the lines of response LOR are used to determine the location of the radionuclide tracer 1006 (e.g., in two dimensions) with, e.g., a first uncertainty ⁇ LOR.
  • ⁇ LOR can represent the uncertainty resulting from the emitted gamma photons not being exactly 180 degrees apart and/or the scintillators having a aperture that can receive photons from different directions.
  • MDF structure One drawback of the MDF structure is that the interference repeats at higher orders, allowing additional passbands at shorter wavelengths. This can be combatted by combining with a longpass filter structure when desired, or through the use of spacer layers that become absorbing at higher-energy wavelengths.
  • Another approach is the use of the so-called induced transmission filter, which combines the thin metallic reflectors with dielectrics assemblies as matching layers in order to provide more accurate admittance matching [18].
  • the metallic layers can also be replaced by dielectric mirrors for all-dielectric
  • Michailos “Color filters including infrared cut-off integrated on CMOS image sensor,” Opt. Express 19, 13073–13080 (2011).

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Abstract

L'invention concerne un filtre pour le rayonnement électromagnétique incluant une ou plusieurs zones d'entretoises diélectriques et une ou plusieurs zones réfléchissantes intégrées sur un substrat semi-conducteur, le substrat semi-conducteur incluant un photodétecteur semi-conducteur, de sorte que le filtre émet un rayonnement ultraviolet vers le photodétecteur semi-conducteur, le rayonnement ultraviolet présentant une plage de longueurs d'onde, et le filtre supprimant l'émission de rayonnement électromagnétique, dont la longueur d'onde est extérieure à la plage de longueurs d'onde, vers le photodétecteur semi-conducteur.
PCT/US2016/017200 2015-02-09 2016-02-09 Filtres diélectriques en métal intégrés à des capteurs pour détecteurs d'ultraviolets en silicium pour stores solaires WO2016130582A1 (fr)

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CN109425436A (zh) * 2017-08-25 2019-03-05 中国科学院西安光学精密机械研究所 一种日盲紫外单光子成像系统及方法
CN110412674A (zh) * 2019-08-19 2019-11-05 苏州微纳激光光子技术有限公司 一种全日盲紫外滤光片
CN115236783A (zh) * 2022-07-28 2022-10-25 中山吉联光电科技有限公司 紫外诱导透射带通滤光片及其制备方法
CN116110985A (zh) * 2023-04-12 2023-05-12 合肥工业大学 集成非对称F-P腔的InSe基日盲紫外光电探测器
CN109425436B (zh) * 2017-08-25 2024-05-31 中国科学院西安光学精密机械研究所 一种日盲紫外单光子成像系统及方法

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CN109425436A (zh) * 2017-08-25 2019-03-05 中国科学院西安光学精密机械研究所 一种日盲紫外单光子成像系统及方法
CN109425436B (zh) * 2017-08-25 2024-05-31 中国科学院西安光学精密机械研究所 一种日盲紫外单光子成像系统及方法
CN108387961A (zh) * 2018-05-16 2018-08-10 德州尧鼎光电科技有限公司 一种深紫外窄带滤光片
CN110412674A (zh) * 2019-08-19 2019-11-05 苏州微纳激光光子技术有限公司 一种全日盲紫外滤光片
CN110412674B (zh) * 2019-08-19 2024-02-27 苏州微纳激光光子技术有限公司 一种全日盲紫外滤光片
CN115236783A (zh) * 2022-07-28 2022-10-25 中山吉联光电科技有限公司 紫外诱导透射带通滤光片及其制备方法
CN116110985A (zh) * 2023-04-12 2023-05-12 合肥工业大学 集成非对称F-P腔的InSe基日盲紫外光电探测器
CN116110985B (zh) * 2023-04-12 2023-08-08 合肥工业大学 集成非对称F-P腔的InSe基日盲紫外光电探测器

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