Abstract
Semiconductors are the basis of many vital technologies such as
electronics, computing, communications, optoelectronics, and sensing.
Modern semiconductor technology can trace its origins to the invention
of the point contact transistor in 1947. This demonstration paved the
way for the development of discrete and integrated semiconductor devices
and circuits that has helped to build a modern society where
semiconductors are ubiquitous components of everyday life. A key
property that determines the semiconductor electrical and optical
properties is the bandgap. Beyond graphene, recently discovered
two-dimensional (2D) materials possess semiconducting bandgaps ranging
from the terahertz and mid-infrared in bilayer graphene and black
phosphorus, visible in transition metal dichalcogenides, to the
ultraviolet in hexagonal boron nitride. In particular, these 2D
materials were demonstrated to exhibit highly tunable bandgaps, achieved
via the control of layers number, heterostructuring, strain engineering,
chemical doping, alloying, intercalation, substrate engineering, as well
as an external electric field. We provide a review of the basic physical
principles of these various techniques on the engineering of
quasi-particle and optical bandgaps, their bandgap tunability,
potentials and limitations in practical realization in future 2D device
technologies.
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