nanolayers*

Ga₂O₃ is a wide-band-gap semiconductor with promising applications in transparent electronics and in power devices. It is not a layered material in bulk, but nevertheless nanolayers can be produced by exfoliation [1]. First-principles calculations based on hybrid functionals show that there is seemingly an absence of quantum confinement in the Ga₂O₃ nanolayers: the calculated nanolayer band gap, independent of thickness, is equal to the bulk band gap.
This lack of quantum confinement is due to the presence of a compensating effect: the interaction between surface states on both sides of the nanolayer. The lowest two conduction bands have surface character, and these states interact through the nanolayer, inducing a splitting that almost exactly compensates the quantum confinement. The midpoint between these bands does show the effect of quantum confinement, as do the higher conduction-band states. Further validation is obtained by embedding the nanolayer in a larger-band-gap material: this removes the surface states and results in also the lowest conduction band showing quantum confinement [2].

[1] W. S. Hwang et al., Appl. Phys. Lett. 104, 203111 (2014).
[2] H. Peelaers and C.G. Van de Walle, Phys. Rev. B 96, 081409(R) (2017).