In situ synthesis of Te/Si heterojunction photodetectors enabling ultra-broadband UV-vis-IR photoelectric conversion

Over the past decade, 2D elemental semiconductors have risen to prominence within the 2D material family, thanks to their simple crystal structures and compositions coupled with a wealth of physical properties. Among these, 2D tellurium (Te) stands out as a highly promising candidate for ultra-broadband photoelectric technologies, owing to its relatively small bandgap, exceptional carrier mobility, high air-stability, and strong light interactions. In this study, high-quality centimeter-scale Te nanofilms have been successfully produced by exploiting pulsed-laser deposition (PLD). By performing the deposition on pre-patterned SiO2/Si substrates, Te/Si 2D/3D heterojunction array is in-situ formed. Inspiringly, taking advantages of the relatively small bandgap of Te, the Te/Si photodetectors demonstrate ultra-broadband photoresponse from ultraviolet to near-infrared (370.6 nm to 2240 nm), enabling them to serve as important complements to conventional 2D materials such as MoS2. In addition, an outstanding on/off ratio of ~108 and a fast response rate (a response/recovery time of 3.7 ms/4.4 ms) are achieved, which is associated with the large band offset and strong interfacial built-in electric field that contributes to suppressing the dark current and separating photocarriers. Beyond these, a 35×35 matrix array has been successfully constructed, where the devices exhibit comparable properties, with a production yield of 100% for the random 100 tested devices. The average responsivity, external quantum efficiency and detectivity reach 249 A/W, 76350% and 1.15 1011 Jones, respectively, making the Te/Si devices among the best-performing 2D/3D heterojunction photodetectors. On the whole, this study have established that PLD is a promising technique for producing high-quality Te nanofilms in a well scalable manner, and Te/Si 2D/3D heterojunction provides a promising platform for implementing high-performance ultra-broadband photoelectronic technologies.