Electron distribution and scattering in InAs films on low-k flexible substrates

On low-k flexible substrates, we obtained InAs films with thickness ranging from several hundreds of nm to sub-10-nm, by epitaxial lift-off and van der Waals bonding. Using Hall measurements, we investigated the electron mobility and sheet concentration depending on the InAs film thickness L. In spite of the undoped InAs films, we do not observe electron depletion even for sub-10-nm thickness L, owing to the Fermi level pinning above the conduction band bottom. We observed three regimes of the behavior of the electron mobility μ with decrease in L: almost constant or slightly increasing μ with decrease in L for ≳150 nm, weakly decreasing μ for 150 nm≳L≳15 nm, and more rapidly decreasing μ proportional to L^γ with γ≃ 5–6 for L≲15 nm. By using Poisson-Schrödinger calculation, we examined the electron distribution in the film depending on L and the associated scattering mechanisms contributing to the behavior of μ, such as phonon, Coulomb, and thickness fluctuation scattering