High-performance broadband Si/ZnO heterojunction photodetector based on pyro-phototronic effect

ZnO-based photodetectors are of great significance to military early warning and medical health. However, it is challenging to detect weak signals in a broad spectral range due to the nature of wide band gap and high background carriers, seriously limiting further practical application. In this work, large-area of uniform C-axis oriented ZnO films were grown on Si substrates via sputtering technique, and Si/ZnO heterojunction photodetectors were fabricated. Because of the compact ZnO thin films structure, built-in electrical field and the enhanced pyro-phototronic coupling effect at the heterojunction interface, the fabricated Si/ZnO photodetectors exhibited excellent broadband photoresponse behaviors in the vast range from the ultraviolet to the near-infrared (355-1550 nm) under zero external bias. Especially, the device shows a significant enhancement ability to ultralow laser power (-500 nW/cm2) with a high responsivity value of 550.6 mA/W and the great optical detectivity of 7.7 x 1012 cm Hz1/2 W-1, which is -1-2 orders of magnitude larger than others. These results supply an innovative strategy to develop high-performance ZnO-based photoelectric devices for weak light signal detection.