Emerging van der Waals junctions based on TMDs materials for advanced gas sensors

Fast Photothermoelectric Response in CVD-Grown PdSe2 Photodetectors with In-Plane Anisotropy

A photodetector based on 2D non-layered materials can easily utilize the photogating effect to achieve considerable photogain, but at the cost of response speed. Here, a rationally designed tunneling heterojunction fabricated by vertical stacking of non-layered In2 S3 and Te flakes is studied systematically. The Te/In2 S3 heterojunctions possess type-II band alignment and can transfer to type-I or type-III depending on the electric field applied, allowing for tunable tunneling of the photoinduced carriers. The Te/In2 S3 tunneling heterojunction exhibits a reverse rectification ratio exceeding 104 , an ultralow forward current of 10-12 A, and a current on/off ratio over 105 . A photodetector based on the heterojunctions shows an ultrahigh photoresponsivity of 146 A W-1 in the visible range. Furthermore, the devices exhibit a response time of 5 ms, which is two and four orders of magnitude faster than that of its constituent In2 S3 and Te. The simultaneously improved photocurrent and response speed are attributed to the direct tunneling of the photoinduced carriers, as well as a combined mechanism of photoconductive and photogating effects. In addition, the photodetector exhibits a clear photovoltaic effect, which can work in a self-powered mode.

Non-Layered Te/In2 S3 Tunneling Heterojunctions with Ultrahigh Photoresponsivity and Fast Photoresponse.

2D material (2DM) based photodetectors with broadband photoresponse are of great value for a vast number of applications such as multiwavelength photodetection, imaging, and night vision. However, compared with traditional photodetectors based on bulk material, the relatively slow speed performance of 2DM based photodetectors hinders their practical applications. Herein, a submicrosecond-response photodetector based on ternary telluride InSiTe3 with trigonal symmetry and layered structure was demonstrated in this study. The InSiTe3 based photodetectors exhibit an ultrafast photoresponse (545-576 ns) and broadband detection capabilities from the ultraviolet (UV) to the near-infrared (NIR) optical communication region (365-1310 nm). Besides, the photodetector presents an outstanding reversible and stable photoresponse in which the response performance remains consistent within 200 000 cycles of switch operation. These significant findings suggest that InSiTe3 can be a promising candidate for constructing fast response broadband 2DM based optoelectronic devices.

A Submicrosecond-Response Ultraviolet-Visible-Near-Infrared Broadband Photodetector Based on 2D Tellurosilicate InSiTe3.

Emerging two-dimensional semiconductors, particularly black phosphorus, have attracted great interest for their potential use in room-temperature and low-cost infrared photodetectors. Nevertheless, widespread application with black phosphorus has been substantially delayed by its lack of scalability and low environmental stability. Herein we report the hydrothermal synthesis of air-stable 2D tellurium with tunable thickness ranging from tens of nanometers down to 2.6 nm as well as the fabrication of a Te/MoS2 van der Waals heterojunction for a high-performance short-wave infrared (SWIR) photodetector. The heterostructure exhibits well-behaved field-effect transistor properties with a high ON/OFF ratio of over 107 and a steep subthreshold swing of 150 mV dec−1. Due to the narrow bandgap of Te, the photodetector's response spectrum covers the whole SWIR band with a peak responsivity of 28.4 A W−1, 4.0 A W−1, and 0.87 A W−1 under 980 nm, 1.55 μm, and 3.0 μm illumination, respectively. Accordingly, detectivity up to 2.7 × 1010 and 3.4 × 109 Jones is obtained at 980 nm and 1.55 μm wavelengths, respectively. These findings demonstrate the potential of 2D Te as a new platform for realizing room-temperature SWIR photodetectors. Besides, our study can serve as a reference for other vdW structure designs, thus expanding the research scope for 2D Te-based optoelectronics.

A high-performance short-wave infrared phototransistor based on a 2D tellurium/MoS2 van der Waals heterojunction

Broken-gap van der Waals (vdW) heterojunctions based on 2D materials are promising structures to fabricate high-speed switching and low-power multifunctional devices thanks to its charge transport versus quantum tunneling mechanism. However, the tunneling current is usually generated under both positive and negative bias voltage, resulting in small rectification and photocurrent on/off ratio. In this paper, we report a broken-gap vdW heterojunction PtS2/WSe2 with a bilateral accumulation region design and a big band offset by utilizing thick PtS2 as an effective carrier-selective contact, which exhibits an ultrahigh reverser rectification ratio approaching 108 and on/off ratio over 108 at room temperature. We also find excellent photodetection properties in such a heterodiode with a large photocurrent on/off ratio over 105 due to its ultralow forward current and a comparable photodetectivity of 3.8 × 1010 Jones. In addition, the response time of such a photodetector reaches 8 μs owing to the photoinduced tunneling mechanism and reduced interface trapping effect. The proposed heterojunction not only demonstrates the high-performance broken-gap heterodiode but also provides in-depth understanding of the tunneling mechanism in the development of future electronic and optoelectronic applications.

Broken-Gap PtS2/WSe2 van der Waals Heterojunction with Ultrahigh Reverse Rectification and Fast Photoresponse.

Metal phosphorous tri‐chalcogenides are a category of new ternary 2D layered materials with a wide range of tuneable bandgaps (1.2–3.5 eV). These wide‐bandgap semiconductors exhibit great potential applications in solar‐blind ultraviolet (SBUV) photodetection. However, these 2D solar‐blind photodetectors suffer from low photoresponsivity, slow photoresponse speed, and narrow operation spectral region, thereby limiting their practical applications. Here, an ultra‐broadband photodetection based on a FePSe3/MoS2 heterostructure with coverage ranging from solar‐blind ultraviolet 265 nm to longwave infrared (LWIR) 10.6 µm is reported. Notably, the device exhibits excellent weak light detection capability. A high photoresponsivity of 33 600 A W−1 and an external quantum efficiency of 1.57 × 107% are demonstrated. A noise‐equivalent power as low as 5.7 × 10–16 W Hz−1/2 and a specific detectivity up to 1.51 × 1013 cm Hz1/2 W−1 are realized in the SBUV region. The room temperature LWIR photoresponsivity of 0.12 A W−1 is realized. This work opens a route to design high‐performance SBUV photodetectors and wide spectral photoresponse applications.

Ultrasensitive Solar‐Blind Ultraviolet Photodetector Based on FePSe3/MoS2 Heterostructure Response to 10.6 µm

Most of the studies focused on V2O5 have been devoted to obtaining specific morphology and microstructure for its intended applications. Two dimensional (2D) V2O5 has the most valuable structure because of its unique planar configuration that can offer more active sites. In this study, a bottom-up and low-cost method that is hydrothermal combined with spin-coating and subsequent annealing was developed to prepare 2D V2O5 nanosheets film on quartz substrate. First, VOOH nanosheets were prepared by the hydrothermal method using V2O5 powders and EG as raw materials. Further, V2O5 nanosheets with an average lateral size over 500 nm and thickness less than 10 nm can be prepared from the parent VOOH nanosheets by annealing at 350 °C for 15 min in air. The prepared V2O5 nanosheets film was assembled of multiple nanosheets. The structural, morphological, microstructural and optical properties of the films were respective investigated by XRD, SEM, TEM and UV-Vis. The photodetector based on V2O5 nanosheets film shows good photoresponse with a response time of 2.4 s and a recovery time of 4.7 s.

https://www.mdpi.com/1996-1944/15/23/8313/pdf?version=1669198440

Facile Synthesis of Two Dimensional (2D) V2O5 Nanosheets Film towards Photodetectors

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 broadband photodetector based on PdSe2/black phosphorus heterodiode

As a new type of detection technology, photodetector has played an extensive role in military and civilian fields, especially having multi-band detection capabilities. Therefore we have demonstrated a fast-speed ultraviolet-visible photodetector which based on the amorphous-Ga2O3/p-Si heterojunction with the comb-shaped Au electrode. At 10 V bias, the a-Ga2O3/p-Si photodetector shows two response peaks which are at 292 nm and 560 nm, with the responsivity for the UV and visible reaching as 6.39 A/W and 7.72 A/W, respectively, which shows that this detector has a good dual-band detection capability. And the fast response speed can also be clearly observed with 90%-10% decay times of less 80 ms, which is satisfiable to the needs of modern fast detection. Our findings provide new ideas for fabricating high-performance photodetectors.

Yuan Lu

Papers

Broken-Gap PtS2/WSe2 van der Waals Heterojunction with Ultrahigh Reverse Rectification and Fast Photoresponse.

Ultrasensitive Solar‐Blind Ultraviolet Photodetector Based on FePSe3/MoS2 Heterostructure Response to 10.6 µm

Facile Synthesis of Two Dimensional (2D) V2O5 Nanosheets Film towards Photodetectors

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

Design of the fast-speed ultraviolet-visible photodetector based on an amorphous-Ga2O3/p-Si heterojunction