In this work, we have fabricated a single layer graphene spin transistor on SiO₂/Si with a semiconducting tri-layer MoS₂ as the tunneling barrier between the ferromagnetic electrodes and the graphene channel. The spin transport in this parallel heterostructure were investigated in detail. The spin switch signal was controlled by tuning the conductivity of MoS₂ with different gate voltages. When MoS₂ was turned off under negative back gate voltage, the spin switch signal was clearly obtained, whereas it disappeared when MoS₂ was conductive under positive back gate bias. This spin transistor showed on, subthreshold and off states when back gate voltage changed from negative to positive. This work exploited a new possibility of semiconducting 2D materials as the tunneling barrier of spin valves.

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.

A novel infrared light emitting diode (LED) based on an ordered p-n heterojunction built of a p-Si_1–xGe_x alloy and n-ZnO nanowires has been developed. The electroluminescence (EL) emission of this LED is in the infrared range, which is dominated by the band gap of Si_1–xGe_x alloy. The EL wavelength variation of the LED shows a red shift, which increases with increasing mole fraction of Ge. With Ge mole fractions of 0.18, 0.23 and 0.29, the average EL wavelengths are around 1, 144, 1, 162 and 1, 185 nm, respectively. The observed magnitudes of the red shifts are consistent with theoretical calculations. Therefore, by modulating the mole fraction of Ge in the Si_1–xGe_x alloy, we can adjust the band gap of the SiGe film and tune the emission wavelength of the fabricated LED. Such an IR LED device may have great potential applications in optical communication, environmental monitoring and biological and medical analyses.