Large Scale MoS 2 /Si Photodiodes with Graphene Transparent Electrodes

Photodiodes comprising n+-silicon / molybdenum disulfide (MoS2) / graphene heterojunctions configured in a vertical architecture are investigated. The silicon substrates have been fabricated in a silicon pilot line using standard silicon process technology. The two-dimensional MoS2 has been grown from thin, pre-patterned molybdenum films in a sulfur environment through thermally assisted conversion (TAC). Graphene has been grown through chemical vapor deposition and transferred onto the MoS2 / Si diodes as a transparent conductor. Under reverse DC-bias, the heterojunction photodiodes exhibit a spectral responsivity that is a fingerprint of the combined materials and their direct and indirect band transitions. In addition, the diodes show finite responsivity in the infrared, below the band gaps of MoS2 and Si, which is attributed to the broadband absorption in the graphene electrodes and/or defect states in the MoS2. The work demonstrates the feasibility of scalable integration of two-dimensional materials with conventional silicon processes technology, and provide a substantial contribution towards the realization of scalable next generation optoelectronic devices based on 2D materials.