Interface roughness and interface roughness scattering in amorphous oxide thin-film transistors

Abstract

In amorphous oxide semiconductors, rough interfaces influence transport in two main ways: changing the trap distributions and interface roughness scattering. Interface roughness scattering is expected to become important in high-mobility semiconductors in which charge transport takes place through a combination of trapping and band transport. Interface roughness scattering is quantitatively analyzed for amorphous oxide thin-film transistors (TFTs) within the framework of the Boltzmann transport equation. It is shown to be the main mobility limiting mechanism at room temperature under the conditions when carrier concentration is high and the interface is rough. The use of the precise extent of wavefunction overlap with the interface is important and the use of a finite potential barrier height at the insulator-semiconductor interface leads to more accurate calculations. The specific semiconductors considered are zinc tin oxide and indium gallium zinc oxide. It is shown that the consideration of interface roughness scattering can become important in evaluating transport in high-mobility TFTs.