Bi2Se3 van der Waals Virtual Substrates for II-VI Heterostructures.

We report on the growth and characterization of optical quality multiple quantum well structures of Zn _x Cd_1-x Se/Zn _x Cd _y Mg_1-x-y Se on an ultra-thin Bi₂Se₃/CdTe virtual substrate on c-plane Al₂O₃ (sapphire). Excellent quality highly oriented films grown along the (111) direction were achieved as evidenced by reflection high energy electron diffraction and X-ray diffraction studies. We also observed room temperature and 77 K photoluminescence emission with peak energies at 77 K of 2.407 eV and linewidths of 56 meV comparable to those achieved on structures grown on InP. Exfoliation of the structures is also possible due to the van der Waals bonding of Bi₂Se₃. Exfoliated (substrate free) films exhibit photoluminescence emission nearly identical to that of the supported film. Additionally, contactless electroreflectance measurements show good agreement with simulations of the multiple quantum well structure as well as evidence of excited state levels. These results open new avenues of research for substrate independent epitaxy and the possibility of ultra-thin electronics.