Ultra-broadband Photodetectors Research Articles

Wavelength-modulated polarity switch self-powered Bi2Se3/GaN heterostructure photodetector

Van der Waals and wide-bandgap materials-based heterostructures have garnered substantial attention in developing self-powered broadband photodetectors owing to their exceptional photovoltaic capabilities. These materials also hold great potential for breakthroughs in optoelectronics. However, limitations to low selectivity constrain the potential of heterostructures-based broadband detectors. Here, we design wavelength-selective polarity switching in a heterostructure photodetector consisting of bismuth selenide (Bi2Se3) and gallium nitride (GaN). The analysis revealed a positive photocurrent under ultraviolet-C illumination to visible wavelength, whereas a negative photocurrent under infrared wavelengths at zero applied bias. The exposure to distinct optical wavelengths leads to an inversion in the electric field polarity across the junction, resulting in polarity switching. The fabricated Bi2Se3/GaN self-powered ultra-broadband photonic device demonstrates a peak photoresponsivity of 584 mAW−1 (−297 mAW−1) at 355 nm (1405 nm) wavelength illumination and can detect weak signals up to 650 femto-watt. Our strategy revealed alternative avenues for developing polarity-switchable, self-powered ultra-broadband photodetectors, offering a first step towards creating wavelength-adaptable sensors for future applications.

Recent Advances in Broadband Photodetectors from Infrared to Terahertz.

The growing need for the multiband photodetection of a single scene has promoted the development of both multispectral coupling and broadband detection technologies. Photodetectors operating across the infrared (IR) to terahertz (THz) regions have many applications such as in optical communications, sensing imaging, material identification, and biomedical detection. In this review, we present a comprehensive overview of the latest advances in broadband photodetectors operating in the infrared to terahertz range, highlighting their classification, operating principles, and performance characteristics. We discuss the challenges faced in achieving broadband detection and summarize various strategies employed to extend the spectral response of photodetectors. Lastly, we conclude by outlining future research directions in the field of broadband photodetection, including the utilization of novel materials, artificial microstructure, and integration schemes to overcome current limitations. These innovative methodologies have the potential to achieve high-performance, ultra-broadband photodetectors.

High-performance, ultra-broadband Sb2Te3 photodetector assisted by multimechanism

Ultra-broadband spectral detection is critical for the application of several technologies, such as imaging, sensing, spectroscopy, and communication. However, the development of high-performance photodetectors with a wide spectral response remains a significant challenge. In this study, we present an ultra-broadband, responsive, dual-mechanism fusion photodetector based on the topological insulator Sb2Te3. By employing methods such as applying bias voltages, energy band structures, and photocurrent imaging, we have confirmed that the operating mechanism in the visible to the infrared light region is the photoconductive effect, exhibiting a room-temperature responsivity of 114.6 mA/W and a specific detectivity of 1.78 × 108 cm2 Hz1/2 W−1, especially under the working condition of 520 nm. Moreover, extending the spectral detection capability from infrared to terahertz is critically important. In the terahertz range, where photon energies are significantly lower than those in the visible to infrared spectrum, the detector achieves a room-temperature responsivity of 38.5 mA/W at 0.12 THz and a specific detectivity of 3.44 × 1010 cm2 Hz1/2 W−1, with a response time of 20 µs, primarily attributed to the asymmetric scattering behavior of the topological surface states. Notably, we have successfully demonstrated high-resolution imaging in the visible to infrared and terahertz spectral ranges at room temperature, providing strong evidence of practical applications for our photodetector. In conclusion, Sb2Te3, as an emerging broadband photodetection material, exhibits significant potential and lays a robust foundation for further research in the field of ultra-broadband photodetectors.

Negative Photoconductivity of Fe3GeTe2 Crystal with Native Heterostructure for Ultraviolet to Terahertz Ultra-Broadband Photodetection.

Gaining insight into the photoelectric behavior of ferromagnetic materials is significant for comprehensively grasping their intrinsic properties and broadening future application fields. Here, through a specially designed Fe3GeTe2/O-Fe3GeTe2 heterostructure, first, the broad-spectrum negative photoconductivity phenomenon of ferromagnetic nodal line semimetal Fe3GeTe2 is reported that covers UV-vis-infrared-terahertz bands (355nm to 3000µm), promising to compensate for the inadequacies of traditional optoelectronic devices. The significant suppression of photoexcitation conductivity is revealed to arise from the semimetal/oxidation (sMO) interface-assisted dual-response mechanism, in which the electron excitation origins from the semiconductor photoconductivity effect in high-energy photon region, and semimetal topological band-transition in low-energy photon region. High responsivities ranging from 103 to 100mA W-1 are acquired within ultraviolet-terahertz bands under ±0.1V bias voltage at room temperature. Notably, the responsivity of 2.572 A W-1 at 3000µm (0.1 THz) and the low noise equivalent power of 26 pW Hz-1/2 surpass most state-of-the-art mainstream terahertz detectors. This research provides a new perspective for revealing the photoelectric conversion properties of Fe3GeTe2 crystal and paves the way for the development of spin-optoelectronic devices.

Experimental and theoretical study on the role of 2D Ti3C2Tx MXenes on superior charge transport and ultra-broadband photodetection in MXene/Bi2S3 nanorod composite through local Schottky junctions

2D MXenes have garnered widespread attention in the fields of photocatalysis, energy conversion etc. because of their unique properties. Integration of semiconductor nanostructures with 2D MXene can be a promising approach for high-performance photodetection. Herein, we adopted an in-situ hydrothermal approach for in-situ anchoring of Ti3C2Tx MXene nanosheets on 1D Bi2S3 nanorods and fabricated a Bi2S3/Ti3C2Tx (1D/2D) Schottky junction broadband photodetector (PD) with outstanding performance. The mechanism behind the excellent performance and formation of the local Schottky junction was investigated through density functional theory (DFT) calculations and validated through various microscopic and spectroscopic tools. In particular, the DFT analysis reveals that the partial density of states of Bi2S3 is altered with additional electronic states in the band-gap region due to attachment of Ti3C2O2, which helps in the efficient charge transport and charge separation across the local junctions. Ultraviolet photoelectron spectroscopy elucidates the nature of band alignment and interfacial charge transfer across the Bi2S3/Ti3C2Tx MXene junction locally. The low-cost PD exhibits an excellent broadband responsivity spanning from ultraviolet to near-infrared region (300–1550 nm) with a peak responsivity of 36.7 A/W and 26.2 A/W at 300 nm and 780 nm, respectively. Further, the device exhibited an external quantum efficiency of ∼3.9 × 103 %, and a fast response of ∼300 μs under 3 V bias, which are remarkable. Finally, the fabricated PD demonstrates a very high long-term storage stability in ambient condition. This work provides a deeper insight into the superior charge transport and ultra-broadband photodetection in MXenes based composites for high-performance optoelectronic applications.

Facile Vertical Structure Broadband Photodetectors Enabled by Polyvinylpyrrolidone-Regulated Perovskite and Near-Infrared-Sensitive Lead Phthalocyanine.

Broadband photodetectors have drawn tremendous attention in many application areas such as imaging, optical communication, and biochemical sensing. Perovskite is a star material with broad spectral absorption, but it is challenging to develop ultraviolet-visible-near-infrared (UV-Vis-NIR) ultra-broadband photodetectors due to the insufficient absorption in the near-infrared region. Moreover, it is difficult to construct a diode-type photodetector with a simple vertical structure based only on perovskite materials. Here, facile vertical structure broadband photodetectors were fabricated based on heterojunctions that were composed of perovskite MAPbI3 films with UV-Vis absorption spectrum and small organic molecule lead phthalocyanine (PbPc) with strong NIR optical absorption, resulting in UV-Vis-NIR ultra-broadband photodetection. The quality of MAPbI3 films was improved by introducing polyvinylpyrrolidone (PVP) modification, and subsequently, the corresponding MAPbI3/PbPc heterojunction-based photodetectors exhibited rectification characteristics and reduced reverse dark currents. When the PVP mass ratio is 1 wt%, the photodetector achieved the best performance that the spectral response uniformity factor was as high as 0.77, the photoresponsivity exceeded 10 A/W, and the photoresponse time was less than 0.5 ms under a light intensity of 0.013 mW/cm2 in the UV-Vis to NIR spectral range. These results are comparable or superior to those of some inorganic, organic, and perovskite photodetectors reported previously. This study would provide an effective strategy to construct high-performance perovskite photodetectors based on a simple vertical structure, paving the way to the realization of UV-Vis-NIR broadband photodetection.

A Centimeter-Scale Type-II Weyl Semimetal for Flexible and Fast Ultra-Broadband Photodetection from Ultraviolet to Sub-Millimeter Wave Regime.

Flexible photodetectors with ultra-broadband sensitivities, fast response, and high responsivity are crucial for wearable applications. Recently, van der Waals (vdW) Weyl semimetals have gained much attention due to their unique electronic band structure, making them an ideal material platform for developing broadband photodetectors from ultraviolet (UV) to the terahertz (THz) regime. However, large-area synthesis of vdW semimetals on a flexible substrate is still a challenge, limiting their application in flexible devices. In this study, centimeter-scale type-II vdW Weyl semimetal, Td -MoTe2 films, are grown on a flexible mica substrate by molecular beam epitaxy. A self-powered and flexible photodetector without an antenna demonstrated an outstanding ability to detect electromagnetic radiation from UV to sub-millimeter (SMM) wave at room temperature, with a fast response time of ≈20 µs, a responsivity of 0.53mA W-1 (at 2.52 THz), and a noise-equivalent power (NEP) of 2.65 nW Hz-0.5 (at 2.52 THz). The flexible photodetectors are also used to image shielded items with high resolution at 2.52 THz. These results can pave the way for developing flexible and wearable optoelectronic devices using direct-grown large-area vdW semimetals.

Femtosecond laser upgrading the quality of bismuth films to enhance ultra-broadband photodetection.

Topological insulator bismuth has attracted considerable attention for the fabrication of room-temperature, wide bandwidth, and high-performance photodetectors due to the gapless edge state and insulating bulk state properties. However, both the photoelectric conversion and carrier transportation of the bismuth films are extremely affected by the surface morphology and grain boundaries to limit optoelectronic properties further. Here, we demonstrate a strategy of femtosecond laser treatment for upgrading the quality of bismuth films. After the treatment with proper laser parameters, the measurement of average surface roughness can be reduced from Ra = 44 nm to 6.9 nm, especially with accompany of the evident grain boundary elimination. Consequently, the photoresponsivity of the bismuth films increases approximately 2 times within an ultra-broad spectrum range from the visible to mid-infrared. This investigation suggests that the femtosecond laser treatment can help to benefit the performance of topological insulator ultra-broadband photodetectors.

Self-powered, ultra-broadband, and polarization-sensitive photodetectors based on 1D van der Waals layered material Nb2Pd3Se8

A Nb2Pd3Se8 photodetector based on the photothermoelectric effect exhibits a broadband detection capability (365 nm–10.6 μm) without external bias and polarization-sensitive detection capability with an anisotropic ratio of 1.42.

Ultra-broadband, self-powered and high performance vertical WSe2/AlOx/Ge heterojunction photodetector with MXene electrode

Two-dimensional materials/bulk semiconductor vertical van der Waals heterojunction are of great importance for high performance photodetector. However, their actualization are still impeded by their relatively narrow response range and large amounts of interfacial defects. Herein, in light of the excellent optoelectronic properties of WSe2 and Ge, we design a kind of self-powered vertical WSe2/AlOx/Ge heterojunction photodetector with MXene top electrode by simply stacking Ti3C2Tx MXene and WSe2 thin film on the AlOx/Ge substrate. The device enables an ultra-broadband spectral response from 405 nm to 3800 nm (mid-wave infrared light) because of the plasmon-induced hot electrons in the Ti3C2Tx MXene film. Also, the device proves the distinguished photodetection performance in terms of a large responsivity of ∼ 1088 mA/W, a high specific detectivity of ∼ 1.17 × 1012 Jones at 980 nm, and a fast response time of 43/63 μs. The vertical stacking structure, the introduction of passivation layer and MXene electrode are considered to be new strategies of designing heterojunction for ultra-broadband, low-power consumption and high performance next-generation photodetector.

High-Performance Ultrabroadband Photodetector Based on Photothermoelectric Effect.

Ultrabroadband photodetectors (PDs) working in the frequency range from the UV to THz regions of the spectrum play a crucial role in integrated multifunction photoelectric detection. Even so, a shortage of high-performance PDs has seriously restricted the overall development of this field. The present work demonstrates a high-performance, ultrabroadband PD with a composite nanostructure comprising a suspended carbon nanotube (CNT) film on which titanium and palladium are deposited. The application of titanium and palladium to the CNT film in this device provides n-doping and p-doping, respectively, and the deposited metal nanoparticles also ensure enhanced thermal localization. This device exhibits short response time, high responsivity, large linear dynamic range, and small noise equivalent power over the ultrabroadband spectrum based on a strong photothermoelectric effect. Numerical simulation results also confirm the effective doping and enhanced thermal localization in this PD resulting from the deposited metals. A theoretical analysis shows that the thermal conductivity of the composite film is no longer independent of the temperature over a wide temperature range. This work provides a simple but novel strategy for the design of high-performance ultrabroadband PDs.

High-performance broadband photodetector based on PdSe2/black phosphorus heterodiode

Uncooled long-wavelength infrared photodetectors based on two-dimensional materials have wide applications, such as remote sensing, missile guide, imaging, and night vision. However, realizing high-performance photodetectors based on 2D materials with high photoresponsivity and fast response speed is still a challenge. Here, we report an ultra-broadband photodetector based on the PdSe2/BP van der Waals heterodiode with a fast response speed. The detection range of the PdSe2/BP heterodiode is covered from visible to long-wave infrared (0.4–10.6 μm). A high photoresponsivity of 116.0 A/W and a low noise equivalence power of 8.4 × 10−16 W/Hz1/2 and D* of 2.05 × 109 cm Hz1/2/W were demonstrated. Notably, the heterodiode exhibits a very fast response speed with τr = 2.9 and τd = 4.0 μs. Our results introduced a promising application in broadband and fast photoresponse at weak light intensity.

High-Performance, Polarization-Sensitive, Long-Wave Infrared Photodetection via Photothermoelectric Effect with Asymmetric van der Waals Contacts.

Long-wavelength infrared (LWIR) photodetection is important for heat-seeking technologies, such as thermal imaging, all-weather surveillance, and missile guidance. Among various detection techniques, photothermoelectric (PTE) detectors are promising in that they can realize ultra-broadband photodetection at room temperature without an external power supply. However, their performance in terms of speed, responsivity, and noise level in the LWIR regime still needs further improvement. Here, we demonstrated a high-performance PTE photodetector based on low-symmetry palladium selenide (PdSe2) with asymmetric van der Waals contacts. The temperature gradient induced by asymmetric van der Waals contacts even under global illumination drives carrier diffusion to produce a photovoltage via the PTE effect. A responsivity of over 13 V/W, a response time of ∼50 μs, and a noise equivalent power of less than 7 nW/Hz1/2 are obtained in the 4.6-10.5 μm regime at room temperature. Furthermore, due to the anisotropic absorption of PdSe2, the detector exhibits a linear polarization angle sensitive response with an anisotropy ratio of 2.06 at 4.6 μm and 1.21 at 10.5 μm, respectively. Our proposed device architecture provides an alternative strategy to design high-performance photodetectors in the LWIR regime by utilizing van der Waals layered materials.

Ultrabroadband Tellurium Photoelectric Detector from Visible to Millimeter Wave.

Ultrabroadband photodetection is of great significance in numerous cutting‐edge technologies including imaging, communications, and medicine. However, since photon detectors are selective in wavelength and thermal detectors are slow in response, developing high performance and ultrabroadband photodetectors is extremely difficult. Herein, one demonstrates an ultrabroadband photoelectric detector covering visible, infrared, terahertz, and millimeter wave simultaneously based on single metal–Te–metal structure. Through the two kinds of photoelectric effect synergy of photoexcited electron–hole pairs and electromagnetic induced well effect, the detector achieves the responsivities of 0.793 A W−1 at 635 nm, 9.38 A W−1 at 1550 nm, 9.83 A W−1 at 0.305 THz, 24.8 A W−1 at 0.250 THz, 87.8 A W−1 at 0.172 THz, and 986 A W−1 at 0.022 THz, respectively. It also exhibits excellent polarization detection with a dichroic ratio of 468. The excellent performance of the detector is further verified by high‐resolution imaging experiments. Finally, the high stability of the detector is tested by long‐term deposition in air and high‐temperature aging. The strategy provides a recipe to achieve ultrabroadband photodetection with high sensitivity and fast response utilizing full photoelectric effect.

Highly Efficient, Ultrabroad PdSe2 Phototransistors from Visible to Terahertz Driven by Mutiphysical Mechanism.

The noble transition metal dichalcogenide palladium diselenide (PdSe2) is an ideal candidate material for broad-spectrum photodetection owing to the large bandgap tunability, high mobility, low thermal conductivity, and large Seebeck coefficient. In this study, self-powered ultrabroadband PdSe2 photodetectors from the visible-infrared to terahertz (THz) region driven by a mutiphysical mechanism are reported. In the visible-infrared region, the photogenerated electron-hole pairs in the PdSe2 body are quickly separated by the built-in electric field at the metal-semiconductor interface and achieve a photoresponsivity of 28 A·W-1 at 405 nm and 0.4 A·W-1 at 1850 nm. In the THz region, PdSe2 photodetectors display a room-temperature responsivity of 20 mA·W-1 at 0.10 THz and 5 mA·W-1 at 0.24 THz based on efficient production of hot carriers in an antenna-assisted structure. Owing to the fast response speed of ∼7.5 μs and low noise equivalent power of ∼900 pW·Hz-1/2, high-resolution transmission THz imaging is demonstrated under an ambient environment at room temperature. Our research validates the great potential of PdSe2 for broadband photodetection and provides a possibility for future optoelectronic applications.

Ultra-broadband photodetection based on two-dimensional layered Ta2NiSe5 with strong anisotropy and high responsivity

Broadband photodetectors have attracted substantial attention in recent years. The ternary chalcogenide Ta2NiSe5 is a layered material with a direct narrow-band gap (Eg ~ 0.33 eV) which possesses greatly potential to broadband photodetectors. Here, high-quality bulk Ta2NiSe5 was synthesized by Chemical Vapor Transport (CVT) method. We demonstrate a photodetector based on exfoliated Ta2NiSe5 nanoflake, which exhibits a broadband photo-response from 405 nm to 4300 nm. Meanwhile, its main characteristics are superior to other typical 2D materials: high responsivity ~198.1 A W−1 at 1350 nm and ultrafast response time of ~27.4 µs. Long-time photocurrent reproducibility shows that the photodetector has excellent stability under atmosphere. Furthermore, the scanning photocurrent mapping reveals the photoconductive mechanism of Ta2NiSe5 photodetector. In addition, the anisotropic ratio of the photocurrent is ~1.46. The broadband photodetection, high responsivity, anisotropic and environmental stability achieved simultaneously in Ta2NiSe5 photodetector, which are promising for neotype electronics and optoelectronics field.

Ultrabroadband and High-Detectivity Photodetector Based on WS2/Ge Heterojunction through Defect Engineering and Interface Passivation.

Broadband photodetectors are of great importance for numerous optoelectronic applications. Two-dimensional (2D) tungsten disulfide (WS2), an important family member of transition-metal dichalcogenides (TMDs), has shown great potential for high-sensitivity photodetection due to its extraordinary properties. However, the inherent large bandgap of WS2 and the strong interface recombination impede the actualization of high-sensitivity broadband photodetectors. Here, we demonstrate the fabrication of an ultrabroadband WS2/Ge heterojunction photodetector through defect engineering and interface passivation. Thanks to the narrowed bandgap of WS2 induced by the vacancy defects, the effective surface modification with an ultrathin AlOx layer, and the well-designed vertical n-n heterojunction structure, the WS2/AlOx/Ge photodetector exhibits an excellent device performance in terms of a high responsivity of 634.5 mA/W, a large specific detectivity up to 4.3 × 1011 Jones, and an ultrafast response speed. Significantly, the device possesses an ultrawide spectral response spanning from deep ultraviolet (200 nm) to mid-wave infrared (MWIR) of 4.6 μm, along with a superior MWIR imaging capability at room temperature. The detection range has surpassed the WS2-based photodetectors in previous reports and is among the broadest for TMD-based photodetectors. Our work provides a strategy for the fabrication of high-performance ultrabroadband photodetectors based on 2D TMD materials.

Interfacial Gated Graphene Photodetector with Broadband Response.

A much stronger interfacial gating effect was observed in the graphene/HfO2/Si photodetector when compared with that in the graphene/SiO2/Si photodetector. We found that this improvement was due to the higher interface state density at the HfO2/Si interface and the higher dielectric constant of the HfO2 layer. The photoresponsivity of the graphene/HfO2/Si photodetector is as high as 45.8 A W-1. Germanium and amorphous MoS2 (a-MoS2) were used to prepare graphene/HfO2/Ge and graphene/HfO2/a-MoS2 photodetectors, further demonstrating the high efficiency of the interfacial gating mechanism for photodetection. Because of the 0.196 eV bandgap of a-MoS2, which was verified in our previous report, the graphene/HfO2/a-MoS2 photodetector realized ultrabroadband photodetection over the range from 473 nm (visible) to 2712 nm (mid-infrared) at room temperature with photoresponsivity as high as 5.36 A W-1 and response time as fast as 68 μs, which represent significant improvements from the corresponding properties of the pure a-MoS2 photodetectors in our previous report and are comparable with those of state-of-the-art broadband photodetectors. By taking full advantage of the interfacial gating mechanism, a fast response, high photoresponsivity and ultrabroadband photodetection were achieved simultaneously. These interfacial gated graphene photodetectors also offer simple fabrication and full semiconductor process compatibility. The advantages described here indicate that the proposed photodetectors have significant potential for use in electronic and optoelectronic applications and offer a new path toward the development of ultrabroadband photodetectors.

Self-powered, flexible, and ultrabroadband ultraviolet-terahertz photodetector based on a laser-reduced graphene oxide/CsPbBr3 composite

Self-powered and flexible ultrabroadband photodetectors (PDs) are desirable in a wide range of applications. The current PDs based on the photothermoelectric (PTE) effect have realized broadband photodetection. However, most of them express low photoresponse and lack of flexibility. In this work, high-performance, self-powered, and flexible PTE PDs based on laser-scribed reduced graphene oxide ( LSG ) / CsPbBr 3 are developed. The comparison experiment with LSG PD and fundamental electric properties show that the LSG / CsPbBr 3 device exhibits enhanced ultrabroadband photodetection performance covering ultraviolet to terahertz range with high photoresponsivity of 100 mA/W for 405 nm and 10 mA/W for 118 μm at zero bias voltage, respectively. A response time of 18 ms and flexible experiment are also acquired at room temperature. Moreover, the PTE effect is fully discussed in the LSG / CsPbBr 3 device. This work demonstrates that LSG / CsPbBr 3 is a promising candidate for the construction of high-performance, flexible, and self-powered ultrabroadband PDs at room temperature.

Flexible SnSe Photodetectors with Ultrabroad Spectral Response up to 10.6 μm Enabled by Photobolometric Effect.

A broad spectral response is highly desirable for radiation detection in modern optoelectronics; however, it still remains a great challenge. Herein, we report a novel ultrabroadband photodetector based on a high-quality tin monoselenide (SnSe) thin film, which is even capable of detecting photons with energies far below its optical band gap. The wafer-size SnSe ultrathin films are epitaxially grown on sodium chloride via the 45° in-plane rotation by employing a sputtering method. The photodetector delivers sensitive detection to ultraviolet-visible-near infrared (UV-Vis-NIR) lights in the photoconductive mode and shows an anomalous response to long-wavelength infrared at room temperature. Under the mid-infrared light of 10.6 μm, the fabricated photodetector exhibits a large photoresponsivity of 0.16 A W-1 with a fast response rate, which is ∼3 orders of magnitude higher than other results. The thermally induced carriers from the photobolometric effect are responsible for the sub-bandgap response. This mechanism is confirmed by a temperature coefficient of resistance of -2.3 to 4.4% K-1 in the film, which is comparable to that of the commercial bolometric detectors. Additionally, the flexible device transferred onto polymer templates further displays high mechanical durability and stability over 200 bending cycles, indicating great potential toward developing wearable optoelectronic devices.