High Performance Van der Waals Graphene-WS2-Si Heterostructure Photodetector

2D materials have become a major focus in material science due to their exotic properties originated from quantum confinement effects. Van der Waals heterostructures composed of 2D materials and conventional semiconductors always show enhanced optoelectronic performance and have attracted much attention in recent years. Here, high performance photodetectors based on graphene-WS2-Si van der Waals heterostructure is reported. The photodetector shows wide spectrum response from visible to near infrared with a maximum photoresponsivity of 54.5 A W-1 at 800 nm. Furthermore, the photodetector has a fast response speed with rise time of 45 mu s and decay time of 210 mu s. Photocurrent mapping shows that not only the graphene-WS2-Si area, but also the graphene-WS2-SiO2-Si area contributes to the photocurrent. With the increase of lateral size of the junction area, the photoresponsivity is reduced due to increased recombination. The response speed decreases with the increase of lateral size of the junction area, which is due to increased junction capacitance. The results indicate that this kind of van der Waals heterostructure has excellent photodetection performance and is suitable for application in high performance broadband photodetectors. Also, the simple fabrication method has a great potential for large scale device integration.