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.

Lateral homojunctions made of two-dimensional (2D) layered materials are promising for optoelectronic and electronic applications. Here, we report the lateral WSe 2 -WSe 2 homojunction photodiodes formed spontaneously by thickness modulation in which there are unique band structures of a unilateral depletion region. The electrically tunable junctions can be switched from n−n to p−p diodes, and the corresponding rectification ratio increases from about 1 to 1.2 × 10 4 . In addition, an obvious photovoltaic behavior is observed at zero gate voltage, which exhibits a large open voltage of 0.49 V and a short-circuit current of 0.125 nA under visible light irradiation. In addition, due to the unilateral depletion region, the diode can achieve a high detectivity of 4.4 × 10 10 Jones and a fast photoresponse speed of 0.18 ms at V g = 0 and V ds = 0. The studies not only demonstrated the great potential of the lateral homojunction photodiodes for a self-power photodetector but also allowed for the development of other functional devices, such as a nonvolatile programmable diode for logic rectifiers.

PdSe2, a star photosensitive functional material, has been successfully used in photodetectors based on sensing mechanisms of photogating, photoconductive, and photovoltaic effects. Here, a photothermoelectric (PTE) effect is observed in photodetectors based on PdSe2 flakes grown by chemical vapor deposition. The unique photoresponse arises from an electron temperature gradient instead of electron–hole separation. Direct evidence of the PTE effect is confirmed by a nonlocal photoresponse under zero bias. Moreover, the PdSe2 photodetector shows high performance in terms of ultrafast response speed (4 µs), high air‐stability, broadband spectrum photodetection, reasonable responsivity, and anisotropic optical response. This study paves a new way for developing high‐performance photodetectors based on PdSe2 layered materials.

2D materials have attracted extensively growing attention due to their novel electronic and optoelectronic properties. [1] Up to now, hundreds of transistors and photodetectors based on Silicon-based semiconductor materials dominate modern technology for more than half a century with extraordinary electrical-optical performance and mutual processing compatibility. Now, 2D materials have rapidly established themselves as prospective candidates for the next-generation semiconductor industry because of their novel properties. Considering chemical and processing compatibility, silicon-based 2D materials possess significant advantages in integrating with silicon. Here, a systematic study is reported on the structural, electrical, and optical performance of silicon telluride (Si 2 Te 3) 2D material, a IV−VI silicon-based semiconductor with a layered structure. The ultrawide photoluminescence (PL) spectra in the range of 550-1050 nm reveals the intrinsic defects in Si 2 Te 3. The Si 2 Te 3-based fieldeffect transistors (FETs) and photodetectors show a typical p-type behavior and a remarkable broadband spectral response in the range of 405-1064 nm. Notably, the photoresponsivity and detectivity of the photodetector device with 13.5 nm in thickness and upon 405 nm illumination can reach up to 65 A W −1 and 2.81 × 10 12 Jones, respectively, outperforming many traditional broadband photodetectors. It is believed this work will excite interests in further exploring the practical application of 2D silicon-based materials in the field of optoelectronics. 2D materials have been fabricated and studied, showing their great vitality and broad application prospect. [2] However, integrating with silicon technology to build the next-generation heterogeneous devices is of central interest considering the modern electronic industry. [3] From this point of view, silicon-based 2D materials are believed to have a bright future due to their chemical and processing compatibility with silicon technology. [3a,4] As a typical silicon-based material and 2D isomer of silicon with a great promise for a variety of novel applications, [5] silicene is expected to integrate with or revolutionize silicon technology. [4a,6] Nevertheless, due to the lack of intrinsic bandgap and suffering from the thermodynamic instability, research and application of silicene are severely impeded. [6a,7] Therefore, recent efforts have focused on siliconbased compound systems. [4c] 2D siliconbased chalcogenides, typical Group IV−VI compounds, hold many fascinating properties including good ambient environment stability, [8] strain-dependent bandgap, [9] and high Seebeck coefficient. [4c,10] Among them, Si 2 Te 3 seems to be a good candidate to introduce the exotic 2D material properties into the integrated electronic and optoelectronic applications. [4c,10b] Unlike 2D silicon-based monosulfide SiX (X = S, Se, and Te), [8,10a,c,d,11] Si 2 Te 3 has a special stoichiometric ratio (Si/Te = 2/3) and a very interesting trigonal layered crystal structure, in which a certain pr...