Semiconductor channel-mediated photodoping in h-BN encapsulated monolayer MoSe 2 phototransistors
Jorge Quereda (Rijksuniversiteit Groningen)
Talieh S. Ghiasi (Rijksuniversiteit Groningen)
Caspar H. van der Wal (Rijksuniversiteit Groningen)
Bart J. van Wees (Rijksuniversiteit Groningen)
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Abstract
In optically excited 2D phototransistors, charge transport is often affected by photodoping effects. Recently, it was shown that such effects are especially strong and persistent for graphene/h-BN heterostructures, and that they can be used to controllably tune the charge neutrality point of graphene. In this work we investigate how this technique can be extended to h-BN encapsulated monolayer MoSe
2 phototransistors at room temperature. By exposing the sample to 785 nm laser excitation we can controllably increase the charge carrier density of the MoSe
2 channel by Δn ≈ 4.45 ×10
12 cm
-2, equivalent to applying a back gate voltage of ∼60 V. We also evaluate the efficiency of photodoping at different illumination wavelengths, finding that it is strongly correlated with the light absorption by the MoSe
2 layer, and maximizes for excitation on-resonance with the A exciton absorption. This indicates that the photodoping process involves optical absorption by the MoSe
2 channel, in contrast with the mechanism earlier described for graphene/h-BN heterostroctures.