Enhanced Photoresponse in MoTe2 Photodetectors with Asymmetric Graphene Contacts

Atomically thin 2D materials are promising candidates for miniaturized high-performance optoelectronic devices. This study reports on multilayer MoTe2 photodetectors contacted with asymmetric electrodes based on n- and p-type graphene layers. The asymmetry in the graphene contacts creates a large (E-bi similar to 100 kV cm(-1)) built-in electric field across the short (l = 15 nm) MoTe2 channel, causing a high and broad (lambda = 400-1400 nm) photoresponse even without any externally applied voltage. Spatially resolved photovoltage maps reveal an enhanced photoresponse and larger built-in electric field in regions of the MoTe2 layer between the two graphene contacts. Furthermore, a fast (similar to 10 mu s) photoresponse is achieved in both the photovoltaic and photoconductive operation modes of the junction. The findings can be extended to other 2D materials and offer prospects for the implementation of asymmetric graphene contacts in future low-power optoelectronic applications.