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

Abstract

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 Lγ 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.

An InAs/high-k/low-k structure: Electron transport and interface analysis

“…From room-temperature measurements of the Hall-bar devices, as shown in 15 The InAs/high-k/low-k exhibits similar µ attributed to Coulomb scattering, but slightly lower than that of the InAs/low-k. This suggests more Coulomb scattering centers near the interface for the InAs/high-k/low-k, as discussed later.…”

“…[14][15][16][17] Nomarski optical microscope images of the Hall-bar devices are shown in the bottom of Fig. 1, where the differential interference contrasts indicate same smooth surfaces for the InAs/high-k/low-k and the InAs/low-k.…”

“…18,19 The InAs/low-k (InAs/FS) exhibits high electron mobilities, where the FS with k ∼ 3, polyethylene terephthalate (PET) coated by bisaziderubber, has a merit for device applications because of a low parasitic capacitance. However, we found a serious problem of InAs/FS interface fluctuation affecting electron mobilities 15 and lowfrequency noise. 17 In addition, poor heat release capability due to a low thermal conductivity of PET, κ ∼ 0.3 W/m-K, is also problematic.…”

“…1. Using a heterostructure, InAs device layer (500 nm thickness)/ AlAs sacrificial layer (4 nm thickness)/ InAs buffer layer (2500 nm thickness)/ GaAs(001), we carried out ELO, [14][15][16][17] separation of the InAs device layer attached to an adhesive sheet. The InAs device layer was transferred onto an intermediate support, a sapphire(0001) coated by resists, followed by removal of the adhesive sheet and InAs surface cleaning using phosphoric acid.…”

“…8,9 In particular, heterogeneous integration of InAs devices on foreign host substrates is quite important. [10][11][12][13] We previously fabricated and investigated an InAs/low-k structure, where high-quality InAs thin films are bonded on host low-dielectric-constant (low-k) flexible substrates (FS), [14][15][16][17] by using epitaxial liftoff (ELO) and van der Waals bonding (VWB) method. 18,19 The InAs/low-k (InAs/FS) exhibits high electron mobilities, where the FS with k ∼ 3, polyethylene terephthalate (PET) coated by bisaziderubber, has a merit for device applications because of a low parasitic capacitance.…”