Ultrahigh sensitive near-infrared photodetectors based on MoTe2/germanium heterostructure

Abstract

The efficient near-infrared light detection of the MoTe2/germanium (Ge) heterojunction has been demonstrated. The fabricated MoTe2/Ge van der Waals heterojunction shows excellent photoresponse performances under the illumination of a 915 nm laser. The photoresponsivity and specific detectivity can reach to 12,460 A/W and 3.3 × 1012 Jones, respectively. And the photoresponse time is 5 ms. However, the MoTe2/Ge heterojunction suffers from a large reverse current at dark due to the low barrier between MoTe2 and Ge. Therefore, to reduce the reverse current, an ultrathin GeO2 layer deposited by ozone oxidation has been introduced to the MoTe2/Ge heterojunction. The reverse current of the MoTe2/GeO2/Ge heterojunction at dark was suppressed from 0.44 µA/µm2 to 0.03 nA/µm2, being reduced by more than four orders of magnitude. The MoTe2/Ge heterojunction with the GeO2 layer also exhibits good photoresponse performances, with a high responsivity of 15.6 A/W, short response time of 5 ms, and good specific detectivity of 4.86 × 1011 Jones. These properties suggest that MoTe2/Ge heterostructure is one of the promising structures for the development of high performance near-infrared photodetectors.