Optical Properties and Light-Emission Device Applications of 2-D Layered Semiconductors

Two-dimensional layered semiconductors have attracted a great deal of attention recently from many fields of science and technology. This article overviews the major progress from the perspective of light-emission properties and related device applications of such 2-D materials. We begin with the overview of basic optical properties, including emission features of various excitonic complexes, many-body effects, light-emission enhancement due to plasmonic coupling, and mechanisms of optical gain. This is followed by discussions of coupling of 2-D materials with an optical cavity, including cavity-enhanced emission due to the Purcell effect, strong and weak coupling, as well as lasing behavior. We then discuss the design and the fabrication of various heterostructures by stacking layers of different 2-D materials for the purpose of confining and injecting charge carriers. Such structures are indispensable for light-emitting devices under electrical injection, the ultimate goal of any semiconductor-based light-emitting diode (LED) or lasers. The progress in electrical injection devices is reviewed next, where LEDs under lateral and vertical electrical injection schemes are discussed. The review is concluded with an outlook and future perspectives.