III-Te-graphene van der Waals heterostructures for optoelectronic devices

JIMENA A. OLMOS ASAR; CEDRIC ROCHA LEÃO; ADALBERTO FAZZIO

Buzios

Encuentro; Encontro Nacional de Física da Matéria Condensada; 2017

Optimal optoelectronic devices are made of materials which (i) interact strongly with photons and (ii) sustain the photoexcited carrier long enough to form an electric signal at the metallic contacts. For semiconductors, adirect band gap no greater than the energy of the incoming radiation and high mobility free carriers are needed to fulfill those requirements. With a direct band gap of 1.7 eV,[1] Gallium telluride presents an intense excitonicabsorption.[2] In addition to solar cells and thermoelectric devices, GaTe has also been considered for radiation detection. These applications of GaTe, however, have been hampered by very low carrier mobilities as well as significant trap centers. Graphene, on the other hand, is a material with ballistic electron transfer.[3] However, the absence of an intrinsic band gap has prevented its application replacing traditional semiconductors. Inrecent years, important experimental developments have turned a reality the synthesis of heterostructures by the stacking of 2D materials.[4] This engineering could be used to combine the properties of graphene withother materials, circumventing the limitations of the isolated components. In this work we study, using DFT calculations, 2D heterostructures composed of a graphene sheet stacked on III-Te layers: GaTe, and hypothetical InTe and TlTe monolayers with the same structure than GaTe. We propose that these heterojunctions could highly improve the performance of optoelectronic devices. Additionally, as the III-Te monolayers interact with graphene in a slighlty different way, it results in different alignment of the band edges with graphenes dirac cone,opening new possibilities for technological applications and could also boost massive fabrication of commercially viable structures.[1] F. Liu et al., ACS Nano 8, 752 (2014)[2] J. F. Sanchez-Royo et al., Phys. Rev. B 65, 115201 (2002)[3] K. S. Novoselov et al., Nature 490, 192 (2012)[4] A. K. Geim and I. V. Grigorieva, Nature 499, 419 (2013)