Fabrication of PdSe2/GaAs heterojunction for sensitive near-infrared photovoltaic detector and image sensor application

High-Speed Self-Powered PdSe2/Si 2D-3D PIN-like Photodetector with Broadband Response Based on PdSe2 Quantum Island Structure

As a two-dimensional (2D) material, palladium diselenide (PdSe2) has attracted extensive research attention due to its unique asymmetric crystal structure and extraordinary optoelectronic properties, showing great potential in electronic, optoelectronic, and other application fields. Thinner PdSe2 exhibits semiconductor properties, while the photoresponse of the photodetectors based on this film is weaker. Although increasing the thickness of the PdSe2 film can improve the photoresponse, thicker PdSe2 exhibits metallic-like properties, which is not conducive to the formation of the heterojunction. In this work, a PdSe2 2D material with a quantum island structure is prepared by a simple thermal-assisted conversion method. A new type of photodetector with a PdSe2/n--Si/n+-Si vertical PIN-like structure is innovatively proposed. Broad spectral absorption from 532 to 2200 nm and a high rectification ratio (106) of the device are achieved. The introduced n--Si layer concentrates the electric field in the depletion region, thereby shortening the transit time and accelerating the separation and collection of the carriers, resulting in the enhancement of the responsivity and 3 dB frequency compared to the traditional device with a PN structure. A recorded highest 3 dB frequency of ∼25 kHz is achieved for the PdSe2 2D-3D PIN-like device.

Wafer-Scale Patterning Synthesis of Two-Dimensional WSe2 Layers by Direct Selenization for Highly Sensitive van der Waals Heterojunction Broadband Photodetectors

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit promising potential in fabricating highly sensitive photodetectors due to their unique electrical and optoelectrical characteristics. However, micron-sized 2D materials produced by conventional chemical vapor deposition (CVD) and mechanical exfoliation methods fail to satisfy the demands for applications in integrated optoelectronics and systems given their poor controllability and repeatability. Here, we propose a simple selenization approach to grow wafer-scale (2 in.) 2D p-WSe₂ layers with high uniformity and customized patterns. Furthermore, a self-driven broadband photodetector with a p-WSe₂/n-Si van der Waals heterojunction has been in situ fabricated with a satisfactory responsivity of 689.8 mA/W and a large specific detectivity of 1.59 × 10¹³ Jones covering from ultraviolet to short-wave infrared. In addition, a remarkable nanosecond response speed has been recorded under 0.5% duty cycle of the input light. The proposed selenization approach on the growth of 2D WSe₂ layers demonstrates an effective route to fabricate highly sensitive broadband photodetectors used for integrated optoelectronic systems.

Fabrication of 2D PdSe2/3D CdTe Mixed-Dimensional van der Waals Heterojunction for Broadband Infrared Detection

Room-temperature infrared photodetectors are in great demand because of their vitally important applications in the military and civilian fields, which has inspired intensive studies in recent decades. Here, we present the fabrication of a large-size PdSe₂/CdTe mixed-dimensional van der Waals (vdW) heterojunction for room-temperature infrared detection. Taking advantage of the wide light absorption of the multilayer PdSe₂, high-quality vdW interface, and unique mixed-dimensional device geometry, the present device is capable of detecting an ultrawide light up to long-wave infrared (LWIR) of 10.6 μm at room temperature. In addition, our photodetector exhibits a good capability to follow short pulse infrared signals with a quick response rate of 70 ns, a large responsivity of 324.7 mA/W, and a reasonable specific detectivity of 3.3 × 10¹² Jones. Significantly, the assembled photodetector is highly sensitive to a polarized infrared light signal with a decent polarization sensitivity of 4.4. More importantly, an outstanding LWIR imaging capability based on the PdSe₂/CdTe vdW heterojunction at nonrefrigeration condition is demonstrated. Our work paves a novel route for the design of highly polarization-sensitive, room-temperature infrared photodetectors.

Technology CAD (TCAD) Simulations of Mg2Si/Si Heterojunction Photodetector Based on the Thickness Effect

Research on infrared detectors has been widely reported in the literature. For infrared detectors, PbS, InGaAs, PbSe, InSb, and HgxCd1-xTe materials are the most widely used and have been explored for photodetection applications. However, these are toxic and harmful substances which are not conducive to the sustainable development of infrared detectors and are not eco-friendly. Mg2Si is a green, healthy, and sustainable semiconductor material that has the potential to replace these toxic and damaging photoelectric materials, making photoelectric detectors (PDs) green, healthy, and sustainable. In this work, we report on the results of our simulation studies on the PN junction Mg2Si/Si heterojunction PD. A model structure of Mg2Si/Si heterojunction PD has been built. The effects of Mg2Si and Si layer thickness on the optical and electrical performance of Mg2Si/Si heterojunction PD are discussed. For the purpose of this analysis, we consider electrical performance parameters such as I-V curve, external quantum efficiency (EQE), responsivity, noise equivalent power (NEP), detectivity, on-off ratio, response time, and recovery time. The simulation results show that the Mg2Si/Si heterojunction PD shows optimum performance when the thickness of Si and Mg2Si layers are 300 nm and 280 nm, respectively. For the optimized structure, the reverse breakdown voltage was found to be -23.61 V, the forward conduction voltage was 0.51 V, the dark current was 5.58 × 10-13 A, and the EQE was 88.98%. The responsivity was found to be 0.437 A/W, the NEP was 6.38 × 10-12 WHz1/2, and the detectivity was 1.567 × 1011 Jones. With the on-off ratio of 1566, the response time was found to be 0.76 ns and the recovery time was 5.75 ns. The EQE and responsivity peak wavelength of PD show a redshift as the thickness of Mg2Si increases. The Mg2Si heterojunction PD can effectively detect infrared light in the wavelength range of 400 to 1400 nm. The simulation results can be utilized to drive the development of green Mg2Si/Si heterojunction PD in the future.