Constructing a High‐Quality t‐Se/Si Interface Via In Situ Light Annealing of a‐Se for a Self‐Powered Image Sensor

Abstract

The traditional methods for preparing high-quality interfaces on Si include magnetron sputtering, [12] pulsed laser deposition, [13] chemical vapor deposition, [14] and metalorganic chemical vapor deposition, [15] in which the growth rates of the materials are low. Because these methods require not only strict lattice matching between the deposit and the substrate, stringent conditions, including an appropriate temperature and O 2 pressure, are needed. In recent years, laser-annealing technology has been widely used for the large-scale production of semiconductor devices. [16,17] Using the heat generated by infrared light, materials under irradiation were crystallized in situ and underwent phase transitions, and high-quality interfaces were constructed. For example, organic-inorganic hybrid perovskite materials prepared via light annealing have advantages over those prepared via traditional thermal annealing, including a higher crystallinity and better compatibility with the substrate. [18] More importantly, the illumination can be easily manipulated. In addition to the irradiation of large-area samples, regional irradiation can be performed, allowing the fabrication of large-area or array photodetectors.In this study, a high-quality Se/Si interface was constructed via in situ transformation of amorphous Se (a-Se) into crystalline Se (t-Se) on a Si substrate surface via light annealing. Under infrared irradiation, an upward decreasing heat field was formed on the Si surface, and then a-Se began to crystallize along the c-axis direction from the interface. Eventually, a high crystallinity t-Se film was obtained on a Si substrate with an excellent Si-Se interface. Benefitting from the high-quality interface and appropriate energy band between Si and Se, the Se/Si device exhibited an extremely high sensitivity and ultrafast response under both visible and infrared light. In addition, through precise regional light annealing, an image sensor was prepared with the ability to recognize the designed patterns. Results and DiscussionFigure 1a shows a schematic of the t-Se/Si photodetector, and the fabrication process is described in the Experimental Section. X-ray diffraction (XRD) characterisation was performed to identify the crystal structure and phase composition of the synthesised composite, as shown in Figure 1b. Before deposition, only one peak at 69.5° was observed, corresponding to the Si (4 0 0) plane (JCPDS 78-2500). After a-Se was deposited onThe quality of the interface, e.g., the semiconductor-semiconductor or metalsemiconductor interface, is the main factor restricting the photodetection performance of a heterojunction. In this study, a high-quality Se/Si interface is constructed via in situ directional transformation of amorphous Se (a-Se) into crystalline Se (t-Se) on a Si substrate via light annealing. Benefitting from the high-quality interface and appropriate energy band between Si and Se, the t-Se/Si heterojunction exhibits an extremely high responsivity and detectivity of 583.33 mA W −1 and 8.52 × 10...

A fast-response self-powered UV–Vis–NIR broadband photodetector based on a AgIn5Se8/t-Se heterojunction

“…The n = 2 was used to calculate the optical bandgap of t-Se because it is a direct bandgap semiconductor. [49] The corresponding transformed reflectance spectra are shown in the inset of Fig. 2(e), where the intersection of the horizontal axis and the tangent line is the bandgap energy.…”