photodetectors*

Scalable fabrication of high quality photodetectors derived from synthetically grown monolayer transition metal dichalcogenides is highly desired and important for a wide range of nanophotonic applications. We present here scalable fabrication of monolayer MoS2 photodetectors on sapphire substrates through an efficient process, which includes growing large scale monolayer MoS2 via chemical vapor deposition (CVD) and multi-step optical lithography for device patterning and high quality metal electrode fabrication. In every measured device, we observed the following universal features: (i) negligible dark current (Idark≤10 fA), (ii) sharp peaks in photocurrent at ∼1.9 eV and ∼2.1 eV attributable to the optical transitions due to band edge excitons, and (iii) a rapid onset of photocurrent above ∼2.5 eV peaked at ∼2.9 eV due to an excitonic absorption originating from the van Hove singularity of MoS2. We observe a low (≤300%) device-to-device variation of photoresponsivity. Furthermore, we observe a fast DC time response of ∼0.5 ms, which is two orders of magnitude faster than other reported CVD grown 1L-MoS2 based photodetectors. The combination of scalable device fabrication, high sensitivity, and high speed offers great potential for applications in photonics.