Line Array Heterojunction Devices Based On PtSe₂/Ge And Their Applications In Imaging And Optical Communications

Light detection in the short-wavelength infrared(SWIR,typically 700-3000 nm)spectrum region has long garnered enormous research enthusiasm due to its wide military and civil applications,e.g.,night vision,optical communication,target detection,environmental monitoring,surveillance,remote sensing imaging,and so on.High-performance SWIR photodetectors are pivotal components of many electronic and optoelectronic products such as laser rangefinder,night vision viewer,thermal imaging system,infrared digital camera and medical diagnostics apparatus.Currently,the majority of the commercially available SWIR photodetectors are made from traditional inorganic semiconductors including crystalline Si,Si/Ge heterostructures and ?-? semiconductor alloys(primarily In Ga As and its related heterostructures).Nevertheless,the fabrication of these SWIR photodetectors normally requires high-quality epitaxially grown photoactive materials,expensive high-vacuum instruments and complex multistep manufacturing procedures,which renders them uneconomical and also hampers their extensive applications.In recent years,there is a grand interest in exploring SWIR photodetectors based on novel functional materials with narrow bandgaps,e.g.,InAs nanowires(NWs),Pb S colloidal quantum dots(QDs)and narrow bandgap organic semiconductors(OSCs).These photodetectors are particularly suitable for some special uses requiring mechanical flexibility,large area or color adjustability.¹⁴ Although some achievements have already been attained,the difficulties in device assembly of NWs-based detectors and the slow response speed of QDs-and OSCs-based devices due to low charge carrier mobilities still limit their practical applications for many optoelectronic purposes.As an alternative solution to the above circumstances,study on SWIR photodetectors based on hybrid heterostructures combing graphene or other emerging two-dimensional(2D)layered materials with traditional narrow bandgap semiconductors,e.g.,Ga As and Ge,has recently attracted particular research interests.Very recently,Wu and colleagues reported the design of a SWIR photodetector based on a graphene/multilayered Pd Se₂/Ge heterostructure,which possessed an outstanding photoresponse to SWIR illumination with an ultrahigh polarization sensitivity of about 112.2,enabling the preliminary realization of polarization optical imaging.In this work,we present the construction of a multilayered PtSe₂/Ge heterostructure-based photodetectors array comprising 1×10 device units operating in the short-wavelength infrared(SWIR)spectrum region.The as-fabricated heterostructures show an obvious photovoltaic effect,providing the devices with the ability to work as self-driven photodetectors.Upon 1550 nm illumination,a typical photodetector exhibits prominent photoresponse performance with the current on/off ratio,responsivity,external quantum efficiency and specific detectivity reaching 1.08×10³,766 m AW^-1,61.3%and1.1×10¹¹ Jones,respectively.The device also has a fast response speed with rise/fall times of 54.9?s/56.6?s.Thanks to the respectable homogeneity in device performance,the photodetectors array can reliably record an image of a“diode symbol”produced by the SWIR irradiation.What is more,the photodetector is successfully integrated into a SWIR optical communication system serving as an optical receiver to transmit a text signal.The above results imply a huge possibility of the present heterostructure-based photodetectors array for some optoelectronic purposes such as SWIR image sensing and optical communication applications.