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.

半导体是许多重要技术的基础，例如电子，计算，通信，光电和传感。现代半导体技术的起源可以追溯到1947年点接触晶体管的发明。该演示为分立和集成半导体器件和电路的开发铺平了道路，这有助于建立一个现代社会，其中半导体是日常生活中无处不在的组件。决定半导体电学和光学特性的关键特性是带隙。除石墨烯外，最近发现的二维（2D）材料还具有半导体带隙，范围从双层石墨烯中的太赫兹和中红外到过渡金属二卤化物中可见的黑磷，到六方氮化硼中的紫外。尤其是，这些2D材料通过控制层数，异质结构，应变工程，化学掺杂，合金化，插层，衬底工程以及外部电场，实现了高度可调的带隙。我们对准粒子和光学带隙的工程设计中的各种技术的基本物理原理，它们的带隙可调性，在未来2D器件技术中实际实现的潜力和局限性进行了综述。