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

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.