High-speed heterojunction photodiodes made of single- or multiple-layer MoS2 directly-grown on Si quantum dots
2019 Elsevier B.V. Recently, chemical vapor deposition-grown molybdenum disulfide (MoS2) has been actively employed for MoS2/Si-wafer heterojunction (HJT) photodetectors due to the attractive optoelectronic properties. However, the MoS2/Si HJT is not so advantageous in that it exhibits low photoresponse due to the low light absorption despite the simple device structure. In addition, there is a limitation in achieving high-quality MoS2 films due to the defects at the MoS2/Si interface developed during the transfer of the MoS2 films to the target substrate, resulting from the restriction of the direct growth on the Si wafer. Here, we first report successful direct growth of single- and multi-layer MoS2 films on Si quantum dots (SQDs) multilayers (MLs) embedded SiO2 (SQDs:SiO2 MLs) substrates. The multilayer MoS2/SQDs HTJ photodiodes show response speed of rise time: ∼60 ns/fall time: ∼756 ns, highest than ever achieved, and detectivity of 6.1 x 1013 cm Hz1/2 W−1. This excellent performance can be attributed to well formation of the HJT at the MoS2/SQDs:SiO2 interface by the direct growth, resulting in the reduction of the defects, thereby facilitating the carrier transport, and high light absorptivity of the SQDs:SiO2 MLs.