Ab-Initio Studies of Exciton Modulation by Polarization Mismatch at Wurtzite/Zinc-Blende CdS Heterostructures

Spatial modulation from stacking can introduce a new electrostatic potential that can significantly alter excited state properties. For example, in two-dimensional transition metal dichalcogenides, charge-transfer excitons emerge with specific moire stacking. In bulk II-VI or III-V semiconductors stacking between competing polar wurtzite and nonpolar zinc-blende phases can also lead to variations in electrostatic modulation. The polarization mismatch between these two phases can generate an internal electric field that provides an unexplored knob for tuning exciton properties. Here, we explore the consequences of these stacking-induced internal fields by performing ab initio Bethe-Salpeter equation calculations on periodic wurtzite/zinc-blende CdS heterostructures, a system which has been explored in the past for photocatalysis [1]. We demonstrate strong modifications of excitons in the heterostructures relative to either bulk crystalline phase, and illustrate the sensitivity of excitonic properties to the polarization-mismatched interfaces, with implications for other related naturally-occurring and artificial heterostructures in bulk crystals and thin films.

[1] Liu, M., Jing, D., Zhou, Z. et al. Twin-induced one-dimensional homojunctions yield high quantum efficiency for solar hydrogen generation. Nat Commun 4, 2278 (2013). https://doi.org/10.1038/ncomms3278