High-MobilityInSe Transistors: The Nature of Charge Transport
2019
InSe
is a high-mobility layered semiconductor with mobility being highly
sensitive to any surrounding media that could act as a source of extrinsic
scattering. However, little effort has been made to understand electronic
transport in thin InSe layers with native surface oxide formed spontaneously
upon exposure to an ambient environment. Here, we explore the influence
of InOx/InSe interfacial trap states on
electronic transport in thin InSe layers. We show that wet oxidation
(processed in an ambient environment) causes massive deep-lying band-tail
states, through which electrons conduct via 2D variable-range hopping
with a short localization length of 1–3 nm. In contrast, a
high-quality InOx/InSe interface can be
formed in dry oxidation (processed in pure oxygen), with a low trap
density of 1012 eV–1 cm–2. Metal–insulator transition can be thus observed in the gate
sweep of the field-effect transistors (FETs), indicative of band transport
predominated by extended states above the mobility edge. A room-temperature
band mobility of 103 cm2/V s is obtained. The
profound difference in the transport behavior between the wet and
dry InSe FETs suggests that fluctuating Coulomb potential arising
from trapped charges at the InOx/InSe
interface is the dominant source of disorders in thin InSe channels.
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