Range Of Photodetectors Research Articles

Tunable electronic and optoelectronic characteristics of two-dimensional β-AsP monolayer: a first-principles study.

Two-dimensional (2D) semiconductors have attracted a great deal of interest from the electrical engineering community due to their intriguing electronic properties. In this study, we have systematically investigated the electronic and optoelectronic properties of β-AsP monolayers by first-principles calculations combined with strain engineering. The results show that the β-AsP monolayer has a suitable indirect bandgap and a strain-tunable electronic structure. On this basis, the designed two-electrode photodetector based on β-AsP monolayer exhibits a strong photoelectric response in the near-ultraviolet region, and the maximum photocurrent can reach 74a02 per phonon under the applied bias voltage of 1 V. In particular, the strain engineering not only improves the photoelectric performance of the β-AsP-based photodetector, but also adjusts its photodetection range. These findings suggest that β-AsP monolayers are ideal candidates for the development of near-ultraviolet photodetectors and optoelectronic devices.

Development of a novel fibre optic beam profile and dose monitor for very high energy electron radiotherapy at ultrahigh dose rates

Objective. Very high energy electrons (VHEE) in the range of 50–250 MeV are of interest for treating deep-seated tumours with FLASH radiotherapy (RT). This approach offers favourable dose distributions and the ability to deliver ultra-high dose rates (UHDR) efficiently. To make VHEE-based FLASH treatment clinically viable, a novel beam monitoring technology is explored as an alternative to transmission ionisation monitor chambers, which have non-linear responses at UHDR. This study introduces the fibre optic flash monitor (FOFM), which consists of an array of silica optical fibre-based Cherenkov sensors with a photodetector for signal readout. Approach. Experiments were conducted at the CLEAR facility at CERN using 200 MeV and 160 MeV electrons to assess the FOFM’s response linearity to UHDR (characterised with radiochromic films) required for FLASH radiotherapy. Beam profile measurements made on the FOFM were compared to those using radiochromic film and scintillating yttrium aluminium garnet (YAG) screens. Main results. A range of photodetectors were evaluated, with a complementary-metal-oxide-semiconductor (CMOS) camera being the most suitable choice for this monitor. The FOFM demonstrated excellent response linearity from 0.9 Gy/pulse to 57.4 Gy/pulse (R 2 = 0.999). Furthermore, it did not exhibit any significant dependence on the energy between 160 MeV and 200 MeV nor the instantaneous dose rate. Gaussian fits applied to vertical beam profile measurements indicated that the FOFM could accurately provide pulse-by-pulse beam size measurements, agreeing within the error range of radiochromic film and YAG screen measurements, respectively. Significance. The FOFM proves to be a promising solution for real-time beam profile and dose monitoring for UHDR VHEE beams, with a linear response in the UHDR regime. Additionally it can perform pulse-by-pulse beam size measurements, a feature currently lacking in transmission ionisation monitor chambers, which may become crucial for implementing FLASH radiotherapy and its associated quality assurance requirements.

High-responsivity photodetectors made of indium selenide with visible to near-infrared photodetection

This study demonstrates indium selenide (InSe) photodetectors (PDs) with a broadband photodetection range from the visible to the near-infrared (NIR) region (400–1000 nm). The InSe flakes exfoliated from bulk material are transferred to a sapphire substrate, followed by the deposition of Ni/Au bi-layer metal contact to fabricate the metal-semiconductor–metal (M-S-M) PDs. In addition to an absorption edge at around 1000 nm, a strong absorption edge at around 516 nm is observed from the typical spectral response taken from the fabricated InSe M-S-M PDs. Under a bias voltage of -1 V, the typical responsivity at 400 nm is as high as 1130 A W-1, corresponding to a photoconductive gain of approximately 3500. Thus, InSe has potential application in broadband photodetection from the NIR to the visible region.

Room-Temperature Self-Powered Infrared Spectrometer Based on a Single Black Phosphorus Heterojunction Diode.

Infrared spectrometers with the ability to resolve the spectral intensity and wavelength simultaneously are widely used in industry and the laboratory. However, their huge volume, high price, and cryogenic operating temperature limit their applications in the rapidly developing field of portable devices. Here, we demonstrate a room-temperature self-powered infrared spectrometer based on a single black phosphorus (BP) heterojunction diode. The nonlinearly gate-tunable photocurrent spectrum involving quantum-confined Franz-Keldysh and Burstein-Moss effects in a single BP/MoS2 diode instead of using space-consuming detector arrays provides a new dimension for resolving the intensity and wavelength information of spectra simultaneously. The active area for spectral sensing is only 1500 μm2, and the photodetection range is from 1.7 to 3.6 μm. Room-temperature operation, micrometer-scale size, and silicon-compatible technology make the BP/MoS2 heterojunction a promising configuration for portable spectrometer applications.

Tuning the optoelectronic properties of reduced graphene Oxide@MoS2 nanocomposite for room temperature photodetection application

Due to the precise manipulation of its optical and electrical characteristics, MoS2 has been described as the most novel two-dimensional material for photodetectors, gas sensing, and temperature sensing applications. Monolayer MoS2 is considered an emerging optoelectronic material because its direct bandgap allows a high absorption coefficient and efficient generation of electron–hole pair under photoexcitation. But it lacks sufficient carrier density and carrier mobility as well, which in turn, mars its prospect to be competitive with its peers in terms of characteristic parameters required for an efficient optical detector. Hence, reduced graphene oxide (RGO) is chosen to compensate those factors where the right stoichiometry of the RGO@MoS2 composite is employed to improve the sensing characteristics of the MoS2 mono-to-few layers-based optical detector. It resulted in a widened photodetection range (Vis-NIR) and fast detection response because of – (i) RGO’s passible role to inject free carriers to MoS2 to improve its free carrier density, and (ii) MoS2′s direct role to demonstrate its sensing performance. The experimental study reveals that the sensor shows a responsivity of ∼1.17 mA W−1 with a good detectivity of ∼1.84 × 1011 Jones and response and recovery time of 3.52 and 3.48 s, respectively. The fabricated RGO@MoS2 nanocomposite sensor shows a fast-sensing response, and enhancement of photo-sensing parameters such as photoresponsivity, and detectivity, sensor response, and recovery time. These results are encouraging due to the fast sensor response and extended range of detection from visible to NIR range.

Enhanced photoresponsivity in Bi2Se3 decorated GaN nanowall network-based photodetectors

Recently, highly responsive photodetectors which are capable of photodetection in a wide range of wavelength spectra are in great demand. To fulfil this, photodetectors formed using heterojunctions of multiple semiconducting materials gain a lot of interest as they cover a broad range of photodetection, and the built-in electric field developed at their interface helps to enhance photoresponse. Here, we have demonstrated a fascinating broadband metal-semiconductor-metal type photodetector (PD) by integrating sputtered Bi2Se3 with the laser molecular beam epitaxy (LMBE) grown GaN film and porous nanowall network on sapphire (0001) substrates. The fabricated photodetectors using a hybrid Bi2Se3/LMBE-GaN nanowall structure exhibit broadband characteristics with a high responsivity of 51.4 and 1.46 A/W when illuminating with the laser of wavelength 355 nm (UV) and 1064 nm (NIR), respectively. The enhanced UV responsivity and good response in the NIR region using Bi2Se3/GaN heterojunction nanostructures suggest futuristic application in dual-wavelength detector devices.

Coupling between Pyroelectricity and Built-In Electric Field Enabled Highly Sensitive Infrared Phototransistor Based on InSe/WSe2/P(VDF-TrFE) Heterostructure

The assorted utilization of infrared detectors induces the demand for more comprehensive and high-performance electronic devices that work at room temperature. The intricacy of the fabrication process with bulk material limits the exploration in this field. However, two-dimensional (2D) materials with a narrow band gap opening aid in infrared (IR) detection relatively, but the photodetection range is narrowed due to the inherent band gap. In this study, we report an unprecedented attempt at the coordinated use of both 2D heterostructure (InSe/WSe2) and the dielectric polymer (poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE)) for both visible and IR photodetection in a single device. The remnant polarization due to the ferroelectric effect of the polymer dielectric enhances the photocarrier separation in the visible range, resulting in high photoresponsivity. On the other hand, the pyroelectric effect of the polymer dielectric causes a change in the device current due to the increased temperature induced by the localized heating effect of the IR irradiation, which results in the change of ferroelectric polarization and induces the redistribution of charge carriers. In turn, it changes the built-in electric field, the depletion width, and the band alignment across the p-n heterojunction interface. Consequently, the charge carrier separation and the photosensitivity are therefore enhanced. Through the coupling between pyroelectricity and built-in electric field across the heterojunction, the specific detectivity for the photon energy below the band gap of the constituent 2D materials can reach up to 1011 Jones, which is better than all reported pyroelectric IR detectors. The proposed approach combining the ferroelectric and pyroelectric effects of the dielectric as well as exceptional properties of the 2D heterostructures can spark the design of advanced and not-yet realized optoelectronic devices.

Highly Sensitive Hybrid Oxide Phototransistors with Photoresponsive Zeolitic‐Imidazolate‐Frameworks for Real‐Time Light Detection

AbstractConventional oxide‐based thin‐film phototransistors (Ph‐TRs) with a hybrid structure with additional photoabsorbers show limitations in real‐time on/off operations without additional input bias. Here, hybrid InGaZnO (IGZO) Ph‐TRs utilizing zeolitic‐imidazolate‐framework‐67 (ZIF‐67), an electrically insulating material with a unique metal‐to‐metal charge transfer (MMCT) pathway enabling charge migration, are presented. A wide photodetection range and fast response/recovery speed without additional gate bias are achieved. In particular, ZIF‐67 used as a photoabsorber exhibits absorption of visible light over a wide range of wavelengths. Photoexcited electrons migrate through the MMCT pathway between Co ions and migrate to the IGZO conduction band, causing a significant change in the photocurrent (Iph) of the hybrid ZIF‐67/IGZO Ph‐TR. In the dark, ZIF‐67 immediately returns to the insulating state, resulting in a fast rise/fall time under dynamic photo‐stimulus. In addition, it exhibits repeatable photo‐sensing performance without persistent photocurrent behavior under pulsed light‐on/off cycles. A high photosensitivity of 108 for red light (592 nm, 0.1 mW cm–2) is obtained as it suppresses the dark current and amplifies photocurrent generation in the subthreshold gate voltage region. This combination of fast response time, high photosensitivity, and high stability is promising for ideal Ph‐TRs, enabling real‐time detection even for high‐frequency operations.

High-performance one-dimensional MOSFET array photodetectors in the 0.8-µm standard CMOS process.

This paper reports a series of novel photodetectors based on one-dimensional array of metal-oxide-semiconductor field-effect transistors (MOSFETs), which were fabricated using the standard 0.8-µm complementary metal oxide semiconductor (CMOS) process. Normally, the metal fingers of MOSFET must be manufactured above active region in standard CMOS process, causing MOSFET insensitive to light. The proposed photodetectors use the metal fingers of MOSFETs in a one-dimensional array to form periodical slit structures, which make the transmittance of incident light higher, due to the surface plasmons (SPs) resonance effect. The number of parallel MOSFETs in one-dimensional array is 3, 5, 7, 9 and 11. The experimental results show that all responsivities (Rv) are greater than 103 A/W within visible and near-infrared spectra under room temperature and a maximum value of 1.40 × 105 A/W is achieved, which is at least one order of magnitude larger than those of published photodetectors. Furthermore, a minimum noise equivalent power (NEP) of 5.86 fW/Hz0.5 at 30 Hz and a maximum detectivity (D*) of 2.21 × 1013 Jones are obtained. The photodetectors still have good signal-to-noise ratio when the bandwidth is 1 GHz. At the same time, the optical scanning imaging was completed by utilizing the photodetectors. This combination of high Rv, excellent NEP, high speed and broad spectrum range photodetectors will be widely used in imaging systems.

Space-charge-limited current passivation of the self-powered and ultraviolet-to-visible range bilayer p-Si/n-Bi2S3 heterojunction photodetector by Ag coating

In this research, effect of the Ag coating on the physical properties of the mesostructured bismuth sulfide (Bi2S3) films for optoelectronic applications was studied. Bi2S3 films were deposited using the chemical vapor deposition (CVD) method in an atmosphere-controlled tube furnace. X-ray diffraction (XRD) results showed the formation of polycrystalline orthorhombic Bi2S3 films. Scanning electron microscopy (SEM) images indicated that the Ag coating decreased the morphology size on the surface of the Bi2S3 film. The optical energy band gap of the Bi2S3 film was reduced when Ag coating was used (from 1.67 to 1.62 eV). Electrical results indicated that the Ag coating increased the carrier concentration (from 1.89 ×10+18 to 35.30 ×10+18 cm−3) and flat band potential (from 0.02 to 0.65 V). Moreover, the charge transport mechanism study of Bi2S3-based devices with Ag/p-Si/n-free or Ag-coated Bi2S3/Ag configuration indicated the existence of the space-charge-limited current behavior in the free-coated device, which used the Ag coating to passivate it due to the changes in the electronic band structure. The Bi2S3 films were characterized as a photodetector; it was observed that adding the Ag coating enhanced the quality parameters (QPs). Furthermore, the response of the Bi2S3-based photodetectors increased when longer wavelengths were applied. Therefore, more studies on improving the responsivity demonstrated the mesostructured Bi2S3 films can be a potential candidate to be used as self-powered and ultraviolet-to-visible range photodetectors.

Germanium-Tin (GeSn) Metal-Semiconductor-Metal (MSM) Near-Infrared Photodetectors.

Narrow-bandgap germanium–tin (GeSn) is employed to fabricate metal–semiconductor–metal (MSM) near-infrared photodetectors with low-dark currents and high responsivity. To reduce the dark current, the SiO2 layer is inserted in between the metal and semiconductor to increase the barrier height, albeit at the expense of photocurrent reduction. To couple more incident light into the absorption layer to enhance the responsivity, the distributed Bragg reflectors (DBRs) are deposited at the bottom of the GeSn substrate while placing the anti-reflection layer on the surface of the absorption layer. With the interdigital electrode spacing and width, both set at 5 µm and with 1 V bias applied, it is found the responsivities of the generic MSM control sample detector, the MSM with DBR, and the MSM with AR layer are 0.644 A/W, 0.716 A/W, and 1.30 A/W, respectively. The corresponding specific detectivities are 8.77 × 1010, 1.11 × 1011, and 1.77 × 1011 cm·Hz1/2/W, respectively. The measurement data show that these designs effectively enhance the photocurrent and responsivity. At 1 V bias voltage, normalized responsivity evinces that the photodetection range has been extended from 1550 nm to over 2000 nm, covering the entire telecommunication band. Incorporating GeSn as a sensing layer offers one of the new alternative avenues for IR photodetection.

Enhanced Photodetection Range from Visible to Shortwave Infrared Light by ReSe2/MoTe2 van der Waals Heterostructure.

Type II vertical heterojunction is a good solution for long-wavelength light detection. Here, we report a rhenium selenide/molybdenum telluride (n-ReSe2/p-MoTe2) photodetector for high-performance photodetection in the broadband spectral range of 405–2000 nm. Due to the low Schottky barrier contact of the ReSe2/MoTe2 heterojunction, the rectification ratio (RR) of ~102 at ±5 V is realized. Besides, the photodetector can obtain maximum responsivity (R = 1.05 A/W) and specific detectivity (D* = 6.66 × 1011 Jones) under the illumination of 655 nm incident light. When the incident wavelength is 1550–2000 nm, a photocurrent is generated due to the interlayer transition of carriers. This compact system can provide an opportunity to realize broadband infrared photodetection.

Photoresponse of porous silicon for potential optical sensing

In this work, porous silicon (P-Si) structures were fabricated by anodizing n-type monocrystalline Si into an ethanoic-HF solution. Anisotropic electrochemical etching with constant time and current density was carried out to fabricate pores and their average diameter was found to be . Raman spectra exhibited widened peaks for red, blue, and green wavelengths. The widened photoluminescence (PL) spectrum was blue-shifted owing to the quantum confinement effect. The P-Si exhibited an energy gap of 1.80 eV and manifested a direct bandgap. The photoresponse of the fabricated P-Si based device was studied at different laser irradiation wavelengthsin the range of 400–1100 nm. The best photoresponse was observed for 785 nm wavelength and the corresponding sensitivity was determined to be 9.4%. Hence, the P-Si can potentially be used for visible range photodetectors.

GeSn Waveguide Photodetectors with Vertical p–i–n Heterostructure for Integrated Photonics in the 2 μm Wavelength Band

GeSn Waveguide Photodetectors In article number 2100330, Guo-En Chang and co-workers demonstrate new complementary metal-oxide-semiconductor compatible, integrable GeSn waveguide photodetectors for integrated photonics at 2 μm band. The devices show a wide photodetection range up to 2090 nm with outstanding responsivity and detectivity, opening up new routes toward high-performance integrated photonics for 2 μm band applications.

GeSn Waveguide Photodetectors with Vertical p–i–n Heterostructure for Integrated Photonics in the 2 μm Wavelength Band

The 2 μm wavelength band (1800–2100 nm) emerges as a promising candidate for next‐generation optical communication. As a result, silicon photonic platforms acquire great interest since they offer the ultimate minimization of photonic systems for 2 μm band applications. However, the large bandgap and indirectness of the band structure of the conventional SiGe alloy prevent their utilization for efficient photodetection in the 2 μm wavelength band. To overcome this drawback, complementary metal‐oxide semiconductor (CMOS)‐compatible GeSn waveguide photodetectors (WGPDs) with a vertical p–i–n heterojunction configuration that can operate in the 2 μm wavelength band is demonstrated. The proposed photodetector incorporates 5.28% Sn into the GeSn active layer, which redshifts the photodetection range to 2090 nm. In addition, the longer light–matter interaction length and good optical confinement of the proposed GeSn WGPD enhance the optical responses significantly. As a result, the proposed GeSn WGPD achieves a responsivity up to 0.52 A W−1 and a detectivity up to 7.9 × 108 cm Hz½ W−1 in the 2 μm wavelength band at room temperature. These promising results indicate that the developed GeSn WGPDs are promising candidates for integrated photonics in the 2 μm wavelength band.

Mono-crystalline Ge1-xSnxSe micro-sheets with hexagonal morphologies for Visible-NIR photodetectors: Increased carrier concentration, narrowed band gap and improved performances

GeSe is a narrow band gap semiconductor with feasible application as infrared photoelectric devices. However, challenges are still maintained to improve their carrier concentration and conductivity for broader scope of photodetector applications. Aiming at such scope, the Ge1-xSnxSe (0 ​< ​x ​< ​0.2) were synthesized via a facile “one-pot” wet chemical method and a lattice site substitution strategy. Compared to the pure GeSe micro-sheets the synthesized Ge1-xSnxSe micro-sheets possessed a smaller band gap (0.914 ​eV) and a better electrical conductivity (2.80 ​× ​10−5 ​Ω−1 cm−1), where the former exhibit greatly improved photo-current. The Ge1-xSnxSe micro-sheet was then assembled into a photodetector device to demonstrate its remarkable photo responsivities in visible to NIR spectral region (3614 A/W at 532 ​nm and 86 A/W at 1319 ​nm). The photo-detection range broadening and the responsivity enhancement can be attributed the carrier concentration increment as well as the band gap narrowing. Therefore, the Ge1-xSnxSe micro-sheets can be considered as an excellent candidate that can be applied as high performance photodetectors in the visible to near infrared region.

Lead Selenium Colloidal Quantum Dots for 400-2600 nm Broadband Photodetectors

By the photodetector manufactured using traditional semiconductor materials, such as HgCdTe and InGaAs, it is difficult to broaden the application range of such photodetectors due to their high cost and complex manufacturing process. PbSe colloidal quantum dots (CQDs) have the potential to shift the working range of photodetector from visible to infrared wavelength region, and it also has high photoresponsivity. Herein, we report the characterization of PbSe CQDs synthesized using a facile solution process, as well as the relationship between the size of nanocrystal and the reaction temperature. The films of PbSe CQDs are deposited using the layer-by-layer (LbL) spin-coating method, which is then used to fabricate the photoconductive device. The fabricated device is found to have an efficient response in a broad spectrum range of 400-2600 nm. The device maintains good responsivity of ~320 mA/W at room temperature. Its external quantum efficiency was quite high in the shorter wavelength infrared region, and it has approximately 14% external quantum efficiency (EQE) at 2520 nm. The device demonstrated excellent performance, confirming that PbSe colloidal quantum dots is a promising material for future broadband spectrum photodetectors.

Enhanced visible to near-infrared photodetectors made from MoS2-based mixed-dimensional structures

Two-dimensional (2D) photodetectors based on semiconducting transitional metal chalcogenides (TMDs) have attracted much attention because of its unique mechanical and opto-electronic properties which can be integrated into nanoscale-sized opto-electronic devices and complex circuits. However, the photodetection range of 2D TMDs materials based detectors are generally limited within the visible range due to its intrinsic relatively large band-gap. In addition, 2D TMDs materials also suffers from weak light absorption inherited from their atomically thin layers, resulting in a photoresponsivity that can be further improved. Herein, by combining 2D MoS2 with zero-dimensional (0D) PbSe quantum dots (QDs) and Au nanocrystals (NCs), a novel 2D-0D photodetector (i.e., MoS2/PbSe@Au) is fabricated. Our MoS2/PbSe@Au photodetector exploits the 2D MoS2 as the conduction channels and PbSe@Au NCs as light sensitizer, which promote the absorption of the entire device and enable appreciable photodetection extending to the near-infrared (NIR). Prominently, the mixed-dimensional photodetector exhibits high responsivity of 1.22 A/W and detectivity of 1.56*109 Jones (cm·Hz1/2·W−1) at NIR (e.g., 1064 nm) compared with the MoS2 photodetector with PbSe QDs only, which are ascribed to the more efficient two-step charge transfer process between PbSe and MoS2 with the presence of Au NCs. We further identify the new carrier multiplication mechanism when comparing the photoresponse of our photodetectors at 405 nm and 635 nm. We found the extremely high EQE of MoS2/PbSe@Au photodetector at the wavelength of 405 nm (268.1%) could be ascribed to the synergism of carrier multiplication (CM) in PbSe QDs and the photo-gating effect induced by Au nanoparticles. Our study demonstrates that the novel mixed-dimensional photodetectors based on CVD-grown MoS2 may provide a new route for designing and realizing high-performance optoelectronic devices with harvesting merits of hybrid nanomaterials.

Engineering sensitivity and spectral range of photodetection in van der Waals materials and hybrids

Exploration of van der Waals heterostructures in the field of optoelectronics has produced photodetectors with very high bandwidth as well as ultra-high sensitivity. Appropriate engineering of these heterostructures allows us to exploit multiple light-to-electricity conversion mechanisms, ranging from photovoltaic, photoconductive to photogating processes. These mechanisms manifest in different sensitivity and speed of photoresponse. In addition, integrating graphene-based hybrid structures with photonic platforms provides a high gain-bandwidth product, with bandwidths ≫1 GHz. In this review, we discuss the progression in the field of photodetection in 2D hybrids. We emphasize the physical mechanisms at play in diverse architectures and discuss the origin of enhanced photoresponse in hybrids. Recent developments in 2D photodetectors based on room temperature detection, photon-counting ability, integration with Si and other pressing issues, that need to be addressed for these materials to be integrated with industrial standards have been discussed.

Engineering Surface Plasmons in Metal/Nonmetal Structures for Highly Desirable Plasmonic Photodetectors

Recently, small-size photodetectors have attracted considerable attention, because of their promising potential for superintegrated circuits in the photoelectric sensor system. However, the small size may disable the photodetectors or result in low photoelectric conversion efficiency, because of the optical diffraction limit and the inefficient light absorption. Encouragingly, plasmonic nanostructures take excellent advantage of light-confinement effect and electric fields enhancement at the nanoscale, providing huge opportunities to achieve small-size photodetectors while maintaining high device performance (broad photodetection range, high photoresponsivity, and fast response speed). This Review highlights the state-of-the art progress in the development of photodetectors based on various plasmonic structures. Since surface plasmons are well-controlled by the shape, size, and component of nanostructures, special emphasis will be put on the rational regulation of plasmonic nanostructures including metal nanostructures, doped semiconductors, and graphene to achieve high-performance photodetectors. In addition, the underlying enhanced mechanism is also discussed. Finally, we highlight the challenges that require deeper insights into the underlying plasmon enhanced mechanism, develop inexpensive plasmonic nanostructures for practical application, and need more research on plasmonic photodetectors based on nonmetal nanostructures and provide perspectives for future research. This Review may provide guidance for rational design of plasmonic nanostructures for small-size photodetectors with high performance.