Showing papers on "Responsivity published in 2017"
TL;DR: In this article, a self-powered solar-blind photodetector with a sharp cutoff wavelength at 266 nm was constructed by a simple one-step chemical vapor deposition method, and showed an ultrahigh responsivity (9.7 mA W−1) at 251 nm with a high UV/visible rejection ratio (R251 nm/R400 nm) of 6.9 × 102 under zero bias.
Abstract: Highly crystallized ZnO–Ga2O3 core–shell heterostructure microwire is synthesized by a simple one-step chemical vapor deposition method, and constructed into a self-powered solar-blind (200–280 nm) photodetector with a sharp cutoff wavelength at 266 nm. The device shows an ultrahigh responsivity (9.7 mA W−1) at 251 nm with a high UV/visible rejection ratio (R251 nm/R400 nm) of 6.9 × 102 under zero bias. The self-powered device has a fast response speed with rise time shorter than 100 µs and decay time of 900 µs, respectively. The ultrahigh responsivity, high UV/visible rejection ratio, and fast response speed make it highly suitable in practical self-powered solar-blind detection. Additinoally, this microstructure heterojunction design method would provide a new approach to realize the high-performance self-powered photodetectors.
576 citations
TL;DR: A general strategy to enhance the perovskite film conductivity that carbon nanotubes (CNTs) conductive nanonets are constructed from to provide fast carrier tracks and indicates the promising potentials of the perOVskite/CNT composites for solution and ambient condition processed flexible devices.
Abstract: Intrinsically high mobility and large absorption coefficient endow inorganic halide perovskites (IHPs) with great promise for high-performance photodetectors (PDs), which, however, are being hindered by the low carrier extraction and transport efficiency of the solution assembled films. Here, we report on a general strategy to enhance the perovskite film conductivity that carbon nanotubes (CNTs) conductive nanonets are constructed from to provide fast carrier tracks. Resultantly, the CsPbBr3 nanosheet/CNT composite films exhibit both high light harvesting and high conductivity, such advantages are demonstrated by the high performances of corresponding planar PDs. Specifically, the highest external quantum efficiency (EQE) of 7488% and the highest responsivity of 31.1 A W–1 under a bias of 10 V among IHP PDs with planar structure are achieved, which are almost 125-fold over the previous best results. Besides, the efficient charge extraction and transport also remarkably contribute to the fast response spee...
252 citations
TL;DR: This work demonstrates for the first time the potential of the hybrid 2D/QD detector technology in reaching out to wavelengths beyond 2 µm with compelling sensitivity.
Abstract: Mercury telluride (HgTe) colloidal quantum dots (CQDs) have been developed as promising materials for the short and mid-wave infrared photodetection applications because of their low cost, solution processing, and size tunable absorption in the short wave and mid-infrared spectrum. However, the low mobility and poor photogain have limited the responsivity of HgTe CQD-based photodetectors to only tens of mA W-1 . Here, HgTe CQDs are integrated on a TiO2 encapsulated MoS2 transistor channel to form hybrid phototransistors with high responsivity of ≈106 A W-1 , the highest reported to date for HgTe QDs. By operating the phototransistor in the depletion regime enabled by the gate modulated current of MoS2 , the noise current is significantly suppressed, leading to an experimentally measured specific detectivity D* of ≈1012 Jones at a wavelength of 2 µm. This work demonstrates for the first time the potential of the hybrid 2D/QD detector technology in reaching out to wavelengths beyond 2 µm with compelling sensitivity.
247 citations
TL;DR: A simple solution growth method is demonstrated to prepare CsPbBr3 microcrystals (MCs) with low trap-state density and photodetectors with high charge carriers' collection efficiency that exhibit fast carrier diffusion with carrier mobility.
Abstract: Low trap-state density, high carrier mobility, and efficient charge carrier collection are key parameters for photodetectors with high sensitivity and fast response time. This study demonstrates a simple solution growth method to prepare CsPbBr3 microcrystals (MCs) with low trap-state density. Time-dependent photoluminescence study with one-photon excitation (OPE) and two-photon excitation (TPE) indicates that CsPbBr3 MCs exhibit fast carrier diffusion with carrier mobility over 100 cm2 V-1 S-1 . Furthermore, CsPbBr3 MC-based photodetectors with high charge carriers' collection efficiency are fabricated. Such photodetectors show ultrahigh responsivity (R) up to 6 × 104 A W-1 with OPE and high R up to 6 A W-1 with TPE. The R for OPE is over one order of magnitude higher (the R for TPE is three orders of magnitude higher) than that of previously reported all-inorganic perovskite-based photodetectors. Moreover, the photodetectors exhibit fast response time of ≈1 ms, which corresponds to a gain ≈105 and a gain- bandwidth product of 108 Hz for OPE (a gain ≈103 and a gain-bandwidth product of 106 Hz for TPE).
244 citations
TL;DR: In this article, a broadband photodetector using a vertical photogate heterostructure of BP-on-WSe 2 (black phosphoruson-tungsten diselenide) was demonstrated.
233 citations
TL;DR: In this article, amorphous gallium oxide thin films were deposited by radio frequency (RF) magnetron sputtering, and the metal-semiconductor-metal (MSM) PD was fabricated and compared with a β-Ga2O3 film prepared side-by-side as the control sample.
Abstract: Recently, Ga2O3-based, solar-blind photodetectors (PDs) have been extensively studied for various commercial and military applications. However, to date, studies have focused only on the crystalline phases, especially β-Ga2O3, and the crystalline quality must be carefully controlled because of its strong impact on device characteristics. Based on previous reports, amorphous-semiconductor-based PDs can also be expected to exhibit excellent photodetection characteristics. In this work, amorphous gallium oxide thin films were deposited by radio frequency (RF) magnetron sputtering, and the metal–semiconductor–metal (MSM) PD was fabricated and compared with a β-Ga2O3 film prepared side-by-side as the control sample. The as-sputtered film possessed a high density of defects, including structural disorders, oxygen vacancies, and likely, dangling bonds, resulting in record-high responsivity (70.26 A/W) for a thin-film-type gallium oxide PD due to a high internal gain and the contribution of extrinsic transitions ...
219 citations
TL;DR: In this paper, a paper-based flexible broadband photodetector with ZnS and MoS2 hybrid active sensing material was fabricated using a simple, cost effective two-step hydrothermal method.
Abstract: Flexible broadband photodetectors based on 2D MoS2 have gained significant attention due to their superior light absorption and increased light sensitivity. However, pristine MoS2 has absorption only in visible and near IR spectrum. This paper reports a paper-based broadband photodetector having ZnS–MoS2 hybrids as active sensing material fabricated using a simple, cost effective two-step hydrothermal method wherein trilayer MoS2 is grown on cellulose paper followed by the growth of ZnS on MoS2. Optimization in terms of process parameters is done to yield uniform trilayer MoS2 on cellulose paper. UV sensing property of ZnS and broadband absorption of MoS2 in visible and IR, broadens the range from UV to near IR. ZnS plays the dual role for absorption in UV and in the generation of local electric fields, thereby increasing the sensitivity of the sensor. The fabricated photodetector exhibits a higher responsivity toward the visible light when compared to UV and IR light. Detailed studies in terms of energy band diagram are presented to understand the charge transport mechanism. This represents the first demonstration of a paper-based flexible broadband photodetector with excellent photoresponsivity and high bending capability that can be used for wearable electronics, flexible security, and surveillance systems, etc.
219 citations
TL;DR: In this paper, an all-layered 2D Bi2Te3-SnSe-Bi2Te-3 photodetector is presented, and the broadband photoresponse of the device from ultraviolet (370 nm) to near-infrared (808 nm) is demonstrated.
Abstract: Nanoelectronics is in urgent demand of exceptional device architecture with ultrathin thickness below 10 nm and dangling-bond-free surface to break through current physical bottleneck and achieve new record of integration level. The advance in 2D van der Waals materials endows scientists with new accessibility. This study reports an all-layered 2D Bi2Te3-SnSe-Bi2Te3 photodetector, and the broadband photoresponse of the device from ultraviolet (370 nm) to near-infrared (808 nm) is demonstrated. In addition, the optimized responsivity reaches 5.5 A W−1, with the corresponding eternal quantum efficiency of 1833% and detectivity of 6 × 1010 cm Hz1/2 W−1. These figures-of-merits are among the best values of the reported all-layered 2D photodetectors, which are several orders of magnitude higher than those of the previous SnSe photodetectors. The superior device performance is attributed to the synergy of highly conductive surface state of Bi2Te3 topological insulator, perfect band alignment between Bi2Te3 and SnSe as well as small interface potential fluctuation. Meanwhile, the all-layered 2D device is further constructed onto flexible mica substrate and its photoresponse is maintained roughly unchanged upon 60 bending cycles. The findings represent a fundamental scenario for advancement of the next generation high performance and high integration level flexible optoelectronics.
219 citations
TL;DR: Based on the easy manipulation, low cost, large scale, and broadband photoresponse, this present detector has significant potential for the applications in optoelectronics and electronics in the future.
Abstract: Photodetectors with excellent detecting properties over a broad spectral range have advantages for the application in many optoelectronic devices. Introducing imperfections to the atomic lattices in semiconductors is a significant way for tuning the bandgap and achieving broadband response, but the imperfection may renovate their intrinsic properties far from the desire. Here, by controlling the deviation from the perfection of the atomic lattice, ultrabroadband multilayer MoS2 photodetectors are originally designed and realized with the detection range over 2000 nm from 445 nm (blue) to 2717 nm (mid-infrared). Associated with the narrow but nonzero bandgap and large photoresponsivity, the optimized deviation from the perfection of MoS2 samples is theoretically found and experimentally achieved aiming at the ultrabroadband photoresponse. By the photodetection characterization, the responsivity and detectivity of the present photodetectors are investigated in the wavelength range from 445 to 2717 nm with the maximum values of 50.7 mA W-1 and 1.55 × 109 Jones, respectively, which represent the most broadband MoS2 photodetectors. Based on the easy manipulation, low cost, large scale, and broadband photoresponse, this present detector has significant potential for the applications in optoelectronics and electronics in the future.
218 citations
TL;DR: In this paper, a solution to the fabrication of amorphous Ga2O3 solar-blind photodetectors on rigid and flexible substrates at room temperature is reported.
Abstract: A solution to the fabrication of amorphous Ga2O3 solar-blind photodetectors on rigid and flexible substrates at room temperature is reported. A robust improvement in the response speed is achieved by delicately controlling the oxygen flux in the reactive radio frequency magnetron sputtering process. Temporal response measurements show that the detector on quartz has a fast decay time of 19.1 µs and a responsivity of 0.19 A W−1 as well, which are even better than those single crystal Ga2O3 counterparts prepared at high temperatures. X-ray photoelectron spectroscopy and current–voltage tests suggest that the reduced oxygen vacancy concentration and the increased Schottky barrier height jointly contribute to the faster response speed. Amorphous Ga2O3 solar-blind photodetector is further constructed on polyethylene naphthalate substrate. The flexible devices demonstrate similar photoresponse behavior as the rigid ones, and no significant degradation of the device performance is observed in bending states and fatigue tests. The results reveal the importance of finely tuned oxygen processing gas in promoting the device performance and the applicability of room-temperature synthesized amorphous Ga2O3 in fabrication of flexible solar-blind photodetectors.
213 citations
TL;DR: In this article, a self-powered ultraviolet photodetector was constructed with GaN/Ga2O3 p-n junction by depositing n-type Ga 2O3 thin film on Al2O 3 single crystals substrate covered by p-type GAN thin film, which exhibits a typical rectification behavior in dark and excellent photovoltaic characteristics under 365 nm and 254 nm light illumination.
Abstract: A self-powered ultraviolet photodetector was constructed with GaN/Ga2O3 p–n junction by depositing n-type Ga2O3 thin film on Al2O3 single crystals substrate covered by p-type GaN thin film. The fabricated device exhibits a typical rectification behavior in dark and excellent photovoltaic characteristics under 365 nm and 254 nm light illumination. The device shows an extremely high responsivity of 54.43 mA W−1, a fast decay time of 0.08 s, a high Ilight/Idark ratio of 152 and a high detectivity of 1.23 × 1011 cm Hz1/2 W−1 under 365 nm light with a light intensity of 1.7 mW cm−2 under zero bias. Such excellent performances under zero bias are attributed to the rapid separation of photogenerated electron–hole pairs driven by built-in electric field in the interface depletion region of GaN/Ga2O3 p–n junction. The results strongly suggest that the GaN/Ga2O3 p–n junction based photodetectors are suitable for applications in secure ultraviolet communication and space detection which require high responsivity and self-sufficient functionality.
TL;DR: A facile fluid-guided antisolvent vapor-assisted crystallization (FGAVC) method for large-scale fabrication of high-quality single-crystalline MAPb(I1-xBrx)3 NW arrays that exhibited outstanding performance in respect of ultrahigh responsivity, broad linear dynamic rang (LDR) of 150 dB, and robust stability.
Abstract: Compared with polycrystalline films, single-crystalline methylammonium lead halide (MAPbX3, X = halogen) perovskite nanowires (NWs) with well-defined structure possess superior optoelectronic properties for optoelectronic applications. However, most of the prepared perovskite NWs exhibit properties below expectations due to poor crystalline quality and rough surfaces. It also remains a challenge to achieve aligned growth of single-crystalline perovskite NWs for integrated device applications. Here, we report a facile fluid-guided antisolvent vapor-assisted crystallization (FGAVC) method for large-scale fabrication of high-quality single-crystalline MAPb(I1–xBrx)3 (x = 0, 0.1, 0.2, 0.3, 0.4) NW arrays. The resultant perovskite NWs showed smooth surfaces due to slow crystallization process and moisture-isolated growth environment. Significantly, photodetectors made from the NW arrays exhibited outstanding performance in respect of ultrahigh responsivity of 12 500 A W–1, broad linear dynamic rang (LDR) of 15...
TL;DR: A feasible strategy for hybrid photodetector by integrating an array of self-ordered TiO2 nanotubes (NTs) and selenium is demonstrated to break the compromise between the responsivity and response speed.
Abstract: A feasible strategy for hybrid photodetector by integrating an array of self-ordered TiO2 nanotubes (NTs) and selenium is demonstrated to break the compromise between the responsivity and response speed. Novel heterojunction between the TiO2 NTs and Se in combination with the surface trap states at TiO2 help regulate the electron transport and facilitate the separation of photogenerated electron–hole pairs under photovoltaic mode (at zero bias), leading to a high responsivity of ≈100 mA W−1 at 620 nm light illumination and the ultrashort rise/decay time (1.4/7.8 ms). The implanting of intrinsic p-type Se into TiO2 NTs broadens the detection range to UV–visible (280–700 nm) with a large detectivity of over 1012 Jones and a high linear dynamic range of over 80 dB. In addition, a maximum photocurrent of ≈107 A is achieved at 450 nm light illumination and an ultrahigh photosensitivity (on/off ratio up to 104) under zero bias upon UV and visible light illumination is readily achieved. The concept of employing novel heterojunction geometry holds great potential to pave a new way to realize high performance and energy-efficient optoelectronic devices for practical applications.
TL;DR: Flexible devices based on the MoTe2 /graphene heterostructure on flexible substrate also retains a good photodetection ability after thousands of times bending test, which provides a promising platform for highly efficient, flexible, and low cost broadband NIR Photodetectors.
Abstract: 2D transition metal dichalcogenides (TMDCs) have attracted considerable attention due to their impressively high performance in optoelectronic devices. However, efficient infrared (IR) photodetection has been significantly hampered because the absorption wavelength range of most TMDCs lies in the visible spectrum. In this regard, semiconducting 2D MoTe2 can be an alternative choice owing to its smaller band gap ≈1 eV from bulk to monolayer and high carrier mobility. Here, a MoTe2/graphene heterostructure photodetector is demonstrated for efficient near-infrared (NIR) light detection. The devices achieve a high responsivity of ≈970.82 A W−1 (at 1064 nm) and broadband photodetection (visible-1064 nm). Because of the effective photogating effect induced by electrons trapped in the localized states of MoTe2, the devices demonstrate an extremely high photoconductive gain of 4.69 × 108 and detectivity of 1.55 × 1011 cm Hz1/2 W−1. Moreover, flexible devices based on the MoTe2/graphene heterostructure on flexible substrate also retains a good photodetection ability after thousands of times bending test (1.2% tensile strain), with a high responsivity of ≈60 A W−1 at 1064 nm at VDS = 1 V, which provides a promising platform for highly efficient, flexible, and low cost broadband NIR photodetectors.
TL;DR: In this paper, the authors demonstrate high spectral responsivity (SR) in MBE-grown epitaxial beta-Ga2O3-based solar blind photodetectors.
Abstract: In this report, we demonstrate high spectral responsivity (SR) in MBE grown epitaxial beta-Ga2O3-based solar blind metal-semiconductor-metal (MSM) photodetectors (PD). The (-201)-oriented beta-Ga2O3 thin film was grown using plasma-assisted MBE on c-plane sapphire substrates. MSM devices fabricated with Ni/Au contacts in an interdigitated geometry were found to exhibit peak SR > 1.5 A/W at 236-240 nm at a bias of 4V with a UV to visible rejection ratio > 10(5). The devices exhibited very low dark current 10(3). These results represent the state-of-art performance for the MBE-grown beta-Ga2O3 MSM solar blind detector. Published by AIP Publishing.
TL;DR: In this article, the first exploration of optoelectronic application based on few-layered PtS2 using h-BN as substrate is presented, where the phototransistor exhibits high responsivity up to 1.56 × 103 A W−1 and detectivity of 2.9 × 1011 Jones.
Abstract: The very recently rediscovered group-10 transition metal dichalcogenides (TMDs) such as PtS2 and PtSe2, have joined the 2D material family as potentially promising candidates for electronic and optoeletronic applications due to their theoretically high carrier mobility, widely tunable bandgap, and ultrastability. Here, the first exploration of optoelectronic application based on few-layered PtS2 using h-BN as substrate is presented. The phototransistor exhibits high responsivity up to 1.56 × 103 A W−1 and detectivity of 2.9 × 1011 Jones. Additionally, an ultrahigh photogain ≈2 × 106 is obtained at a gate voltage Vg = 30 V, one of the highest gain among 2D photodetectors, which is attributed to the existence of trap states. More interestingly, the few-layered PtS2 phototransistor shows a back gate modulated photocurrent generation mechanism, that is, from the photoconductive effect dominant to photogating effect dominant via tuning the gate voltage from the OFF state to the ON state. Such good properties combined with gate-controlled photoresponse of PtS2 make it a competitive candidate for future 2D optoelectronic applications.
TL;DR: A photovoltage field-effect transistor that uses silicon for charge transport, but is also sensitive to infrared light owing to the use of a quantum dot light absorber, and shows that colloidal quantum dots can be used as an efficient platform for silicon-based infrared detection, competitive with state-of-the-art epitaxial semiconductors.
Abstract: The detection of infrared radiation enables night vision, health monitoring, optical communications and three-dimensional object recognition. Silicon is widely used in modern electronics, but its electronic bandgap prevents the detection of light at wavelengths longer than about 1,100 nanometres. It is therefore of interest to extend the performance of silicon photodetectors into the infrared spectrum, beyond the bandgap of silicon. Here we demonstrate a photovoltage field-effect transistor that uses silicon for charge transport, but is also sensitive to infrared light owing to the use of a quantum dot light absorber. The photovoltage generated at the interface between the silicon and the quantum dot, combined with the high transconductance provided by the silicon device, leads to high gain (more than 104 electrons per photon at 1,500 nanometres), fast time response (less than 10 microseconds) and a widely tunable spectral response. Our photovoltage field-effect transistor has a responsivity that is five orders of magnitude higher at a wavelength of 1,500 nanometres than that of previous infrared-sensitized silicon detectors. The sensitization is achieved using a room-temperature solution process and does not rely on traditional high-temperature epitaxial growth of semiconductors (such as is used for germanium and III-V semiconductors). Our results show that colloidal quantum dots can be used as an efficient platform for silicon-based infrared detection, competitive with state-of-the-art epitaxial semiconductors.
TL;DR: A ferroelectric BaTiO3 film-based photodetector is demonstrated that can be operated without using any external power source and a fast sensing of 405 nm light illumination is enabled.
Abstract: Ferroelectric materials have demonstrated novel photovoltaic effect to scavenge solar energy. However, most of the ferroelectric materials with wide bandgaps (2.7–4 eV) suffer from low power conversion efficiency of less than 0.5% due to absorbing only 8–20% of solar spectrum. Instead of harvesting solar energy, these ferroelectric materials can be well suited for photodetector applications, especially for sensing near-UV irradiations. Here, a ferroelectric BaTiO3 film-based photodetector is demonstrated that can be operated without using any external power source and a fast sensing of 405 nm light illumination is enabled. As compared with photovoltaic effect, both the responsivity and the specific detectivity of the photodetector can be dramatically enhanced by larger than 260% due to the light-induced photovoltaic–pyroelectric coupled effect. A self-powered photodetector array system can be utilized to achieve spatially resolved light intensity detection by recording the output voltage signals as a mapping figure.
TL;DR: The results show that the collection of charge carriers is strongly dependent on the electronic properties of the 2D MoS2 with metallicMoS2 showing high responsivity and the semiconducting phase exhibiting high on/off ratios.
Abstract: Integration of organic/inorganic hybrid perovskites with metallic or semiconducting phases of 2D MoS2 nanosheets via solution processing is demonstrated. The results show that the collection of charge carriers is strongly dependent on the electronic properties of the 2D MoS2 with metallic MoS2 showing high responsivity and the semiconducting phase exhibiting high on/off ratios.
TL;DR: A graphene-based SWIR photodetector with high responsivity and fast photoresponse is demonstrated and is promising for the development of mid/far-infrared optoelectronic applications.
Abstract: Graphene’s unique electronic and optical properties have made it an attractive material for developing ultrafast short-wave infrared (SWIR) photodetectors. However, the performance of graphene SWIR photodetectors has been limited by the low optical absorption of graphene as well as the ultrashort lifetime of photoinduced carriers. Here, we present two mechanisms to overcome these two shortages and demonstrate a graphene-based SWIR photodetector with high responsivity and fast photoresponse. In particular, a vertical built-in field is employed in the graphene channel for trapping the photoinduced electrons and leaving holes in graphene, which results in prolonged photoinduced carrier lifetime. On the other hand, plasmonic effects were employed to realize photon trapping and enhance the light absorption of graphene. Thanks to the above two mechanisms, the responsivity of this proposed SWIR photodetector is up to a record of 83 A/W at a wavelength of 1.55 μm with a fast rising time of less than 600 ns. This ...
17 Mar 2017
TL;DR: In this article, the authors constructed SnSe2/MoS2 based van der Waals heterostructures using MoS2 as templates, which may enrich the family of 2D van derWaals HetNets.
Abstract: Van der Waals heterostructures from atomically thin 2D materials have opened up new realms in modern semiconductor industry. Recently, 2D layered semiconductors such as MoS2 and SnSe2 have already demonstrated excellent electronic and optoelectronic properties due to their high electron mobility and unique band structures. Such combination of SnSe2 with MoS2 may provide a novel platform for the applications in electronics and optoelectronics. Thus, we constructed SnSe2/MoS2 based van der Waals heterostructures using MoS2 as templates, which may enrich the family of 2D van der Waals heterostructures. We demonstrate that the vdW heterostructures with high symmetry crystallographic directions show efficient interlayer charge transfer due to the strong coupling. This strong coupling is confirmed by theory calculations, low-temperature photoluminescence (PL) spectra, and electrical transport properties. High performance photodetector based on the vdW heterostructure has been demonstrated with a high responsivity of up to 9.1 × 103 A W−1 which is higher by two orders of magnitude than those MoS2-only devices. The improved performance can be attributed to the efficient charge transfer from MoS2 to SnSe2 at the interface.
TL;DR: The fabrication of high-performance ultraviolet photodetectors based on a heterojunction device structure in which ZnO quantum dots were used to decorate Zn2SnO4 nanowire suggest that the band alignment engineering on nanowires can be rationally achieved using compound semiconductor quantum dots.
Abstract: Here we report the fabrication of high-performance ultraviolet photodetectors based on a heterojunction device structure in which ZnO quantum dots were used to decorate Zn2SnO4 nanowires. Systematic investigations have shown their ultrahigh light-to-dark current ratio (up to 6.8 × 104), specific detectivity (up to 9.0 × 1017 Jones), photoconductive gain (up to 1.1 × 107), fast response, and excellent stability. Compared with a pristine Zn2SnO4 nanowire, a quantum dot decorated nanowire demonstrated about 10 times higher photocurrent and responsivity. Device physics modeling showed that their high performance originates from the rational energy band engineering, which allows efficient separation of electron–hole pairs at the interfaces between ZnO quantum dots and a Zn2SnO4 nanowire. As a result of band engineering, holes migrate to ZnO quantum dots, which increases electron concentration and lifetime in the nanowire conduction channel, leading to significantly improved photoresponse. The enhancement mecha...
TL;DR: Considering the thickness-dependent band gap in BP, this material represents a powerful photodetection platform that is able to sustain high performance in the IR wavelength regime with potential applications in remote sensing, biological imaging, and environmental monitoring.
Abstract: The presence of a direct band gap and high carrier mobility in few-layer black phosphorus (BP) offers opportunities for using this material for infrared (IR) light detection. However, the poor air stability of BP and its large contact resistance with metals pose significant challenges to the fabrication of highly efficient IR photodetectors with long lifetimes. In this work, we demonstrate a graphene–BP heterostructure photodetector with ultrahigh responsivity and long-term stability at IR wavelengths. In our device architecture, the top layer of graphene functions not only as an encapsulation layer but also as a highly efficient transport layer. Under illumination, photoexcited electron–hole pairs generated in BP are separated and injected into graphene, significantly reducing the Schottky barrier between BP and the metal electrodes and leading to efficient photocurrent extraction. The graphene–BP heterostructure phototransistor exhibits a long-term photoresponse at near-infrared wavelength (1550 nm) wit...
TL;DR: In this article, the fabrication of ultraviolet photodetector on non-polar (11−20), nearly stress free, Gallium Nitride (GaN) film epitaxially grown on r-plane (1−102) sapphire substrate was reported.
Abstract: We report the fabrication of ultraviolet photodetector on non-polar (11–20), nearly stress free, Gallium Nitride (GaN) film epitaxially grown on r-plane (1–102) sapphire substrate. High crystalline film leads to the formation of two faceted triangular islands like structures on the surface. The fabricated GaN ultraviolet photodetector exhibited a high responsivity of 340 mA/W at 5 V bias at room temperature which is the best performance reported for a-GaN/r-sapphire films. A detectivity of 1.24 × 109 Jones and noise equivalent power of 2.4 × 10−11 WHz−1/2 were also attained. The rise time and decay time of 280 ms and 450 ms have been calculated, respectively, which were the fastest response times reported for non-polar GaN ultraviolet photodetector. Such high performance devices substantiate that non-polar GaN can serve as an excellent photoconductive material for ultraviolet photodetector based applications.
TL;DR: A systematic investigation of gated-photoconductors based on b-PAs alloys as a function of thickness over the composition range of 0-91% As finds that the specific detectivity (D*) can be optimized by adjusting the thickness of the b- P/b- PAs layer to maximize absorption and minimize dark current.
Abstract: Black phosphorus (b-P) and more recently black phosphorus-arsenic alloys (b-PAs) are candidate 2D materials for the detection of mid-wave and potentially long-wave infrared radiation. However, studies to date have utilized laser-based measurements to extract device performance and the responsivity of these detectors. As such, their performance under thermal radiation and spectral response has not been fully characterized. Here, we perform a systematic investigation of gated-photoconductors based on b-PAs alloys as a function of thickness over the composition range of 0-91% As. Infrared transmission and reflection measurements are performed to determine the bandgap of the various compositions. The spectrally resolved photoresponse for various compositions in this material system is investigated to confirm absorption measurements, and we find that the cutoff wavelength can be tuned from 3.9 to 4.6 μm over the studied compositional range. In addition, we investigated the temperature-dependent photoresponse and performed calibrated responsivity measurements using blackbody flood illumination. Notably, we find that the specific detectivity (D*) can be optimized by adjusting the thickness of the b-P/b-PAs layer to maximize absorption and minimize dark current. We obtain a peak D* of 6 × 1010 cm Hz1/2 W-1 and 2.4 × 1010 cm Hz1/2 W-1 for pure b-P and b-PAs (91% As), respectively, at room temperature, which is an order of magnitude higher than commercially available mid-wave infrared detectors operating at room temperature.
TL;DR: An ultrasensitive two-dimensional photodetector employing an in-plane phototransistor with an out-of-plane vertical MoS2 p–n junction as a sensitizing scheme yields a record sensitivity with specific detectivity combined with broadband response.
Abstract: Two-dimensional transition metal dichalcogenide-based photodetectors have demonstrated potential for the next generation of 2-dimensional optoelectronics. However, to date, their sensitivity has not been superior to that of other technologies. Here we report an ultrasensitive two-dimensional photodetector employing an in-plane phototransistor with an out-of-plane vertical MoS2 p–n junction as a sensitizing scheme. The vertical built-in field is introduced for the first time in the transport channel of MoS2 phototransistors by facile chemical surface doping, which separates the photo-excited carriers efficiently and produces a photoconductive gain of >105 electrons per photon, external quantum efficiency greater than 10%, responsivity of 7 × 104 A W−1, and a time response on the order of tens of ms. This taken together with a very low noise power density yields a record sensitivity with specific detectivity $$D^*$$
of 3.5 × 1014 Jones in the visible and a broadband response up to 1000 nm. Photodetectors based on 2D transition metal dichalcogenides exhibit ever increasingly competitive performance, yet not superior to that of alternative technologies. Here, the authors devise a MoS2-based phototransistor with an out-of-plane junction, yielding a record detectivity combined with broadband response.
TL;DR: Single crystalline α-Ga2O3 epilayers are achieved on nonpolar ZnO (112̅0) substrates for the first time and a high performance Au/α-Ga3/ZnO isotype heterostructure-based Schottky barrier avalanche diode is demonstrated, holding promise for developing high performance solar-blind photodetectors.
Abstract: The metastable α-phase Ga2O3 is an emerging material for developing solar-blind photodetectors and power electronic devices toward civil and military applications. Despite its superior physical properties, the high quality epitaxy of metastable phase α-Ga2O3 remains challenging. To this end, single crystalline α-Ga2O3 epilayers are achieved on nonpolar ZnO (1120) substrates for the first time and a high performance Au/α-Ga2O3/ZnO isotype heterostructure-based Schottky barrier avalanche diode is demonstrated. The device exhibits self-powered functions with a dark current lower than 1 pA, a UV/visible rejection ratio of 103 and a detectivity of 9.66 × 1012 cm Hz1/2 W–1. Dual responsivity bands with cutoff wavelengths at 255 and 375 nm are observed with their peak responsivities of 0.50 and 0.071 A W–1 at −5 V, respectively. High photoconductive gain at low bias is governed by a barrier lowing effect at the Au/Ga2O3 and Ga2O3/ZnO heterointerfaces. The device also allows avalanche multiplication processes in...
TL;DR: In this paper, the authors demonstrate high spectral responsivity (SR) in MBE grown epitaxial Ga2O3-based solar blind MSM photodetectors (PD).
Abstract: In this report, we demonstrate high spectral responsivity (SR) in MBE grown epitaxial \b{eta}-Ga2O3-based solar blind MSM photodetectors (PD). (-2 0 1)-oriented \b{eta}-Ga2O3 thin film was grown by plasma-assisted MBE on c-plane sapphire substrates. MSM devices fabricated with Ni/Au contacts in an interdigitated geometry were found to exhibit peak SR > 1.5 A/W at 236-240 nm at a bias of 4 V with a UV to visible rejection ratio > 105. The devices exhibited very low dark current 103. These results represent the state-of-art performance for MBE-grown \b{eta}-Ga2O3 MSM solar blind detector.
TL;DR: In this article, a simple spincoating process is successfully adopted to incorporate MAPbI3 quantum dots (QDs) onto the surface of TiO2 NTs to form a heterostructure, extending the response range from ultraviolet to visible.
Abstract: Broadband photodetectors based on TiO2 nanotubes (NTs) array have significant prospects in many fields such as environmental monitoring. Herein, a simple spin-coating process is successfully adopted to incorporate MAPbI3 quantum dots (QDs) onto the surface of TiO2 NTs to form a heterostructure, extending the response range of TiO2 NT from ultraviolet to visible. Compared with pure TiO2 NTs, the heterostructure demonstrates an improvement of responsivity in visible range by three orders of magnitude, and maintains its response performance in the UV range simultaneously. The TiO2 NTs based heterostructure photodetectors demonstrate a relative fast and stable response in the 300–800 nm range and even have a reponsivity of 0.2 A W−1 at 700 nm. The photoelectric performance of the hybrid photodetector based on TiO2 NTs maintains well when exposed to moist air for 72 h or heated from room temperature to 100 °C. Moreover, such a TiO2 NTs/MAPbI3 QDs heterostructure device demonstrates excellent flexibility and high transparency (85%) in the 400–800 nm range, their photodetecting performance is well retained after 200 cycles of repeated bending at 90°. The present strategy that combines facile electrospinning and solution-processed QDs may open a new avenue for wide range response and flexible devices construction.
TL;DR: In this article, the peak responsivity and external quantum efficiency of the GaN nanowire UV photodetector were increased from 773 to 6.39 × 104 A W−1 and from 2.71 × 105% to 2.24 × 107%, respectively.
Abstract: High performance ultraviolet (UV) photodetectors based on semiconducting nanowires are expected to have extensive applications in UV-ray detection, optical communication and environmental monitoring. In this work, GaN nanowire photodetectors have been fabricated and giant UV photoresponse has been achieved with Pt nanoparticle (NP) modification. The peak responsivity and external quantum efficiency (EQE) of the GaN nanowire UV photodetector were increased from 773 to 6.39 × 104 A W−1 and from 2.71 × 105% to 2.24 × 107%, respectively, and the response time and sensitivity were improved greatly after Pt NP decoration on the GaN nanowire surface. Moreover, the Pt–GaN nanowire photodetector still presents its spectrum selectivity in the UV region. Our results reveal that Pt nanoparticles play a key role in enhancing the photodetection performance of the nanodevice due to the strong absorption and scattering of incident light induced by localized surface plasmon resonance (LSPR) and the improvement of interfacial charge separation owing to the special device configuration. These findings offer an efficient avenue toward the performance enhancement of GaN nanowire and related optoelectronic devices or systems.