First-principles investigation on Schottky barrier modification of graphene/CdSe heterojunction by the interlayer distance

Based on the first-principles calculation method of quantum mechanics, we systematically studied the geometric structure and electronic properties of graphene/CdSe heterojunction, and considered the influence of vertical strain on its performance. The calculated results show that the model II has the smallest binding energy of −1.09 eV when the interlayer distance is 3.4 Å. Graphene opens a small band gap of 3 meV, which indicates that it has a good application prospect in future micro-nano devices. Differential charge density found that the electrons and holes at the interface gathered on the surface of CdSe and graphene, respectively. When the interlayer distance increases from 2.6 Å to 4.0 Å, the band gap decreases from 19 meV to 1 meV. In addition, the most stable heterojunction has n- and p-type Schottky barrier heights of 0.224 eV and 1.324 eV, respectively, thus the system forms n-type Schottky contact. As the interlayer distance increases, the n- and p-type Schottky barrier heights continuously decrease and increase, respectively. When the interlayer distance increases from 2.6 Å to 2.8 Å, the heterojunction changes from p-type Schottky contact to n-type Schottky contact, and when the interlayer distance reaches 4.2 Å, the heterojunction can realize the transformation from n-type Schottky contact to n-type Ohmic contact. These findings may have potential guiding significance for the design and preparation of graphene/CdSe heterojunction nanodevices.