2D semiconductor structures as a basis for new high-tech devices (Review)

Abstract

In this article, we present a short overview of the Ukrainian contribution to the physics of 2D semiconductor structures as a basis for high-tech devices of modern nanoelectronics, together with some new results in this field. The possibility of creating “low-threshold” 2D lasers in Si₃N₄-GaAs and AlxGa₁₋ₓAs-GaAs layered heterostructures, in which a two-dimensional electron-hole plasma (EHP) is formed, has been analyzed. The investigations of optical amplification spectra in heterostructures with a two-dimensional quantum well have been performed in detail. It has been demonstrated that under the conditions of simultaneous co-existence of 3D-EHP and 2D-EHP, stimulated radiation is formed predominantly in 2D-EHP, with the laser excitation threshold at which optical amplification occurs in 2D-EHP by two orders of magnitude lower than in 3D-EHP, and the corresponding value of the coefficient of optical amplification is 2.5 times greater. A simple theoretical model of electron heating in a system with two valleys is applied to describe 2D semiconductor monolayers of the MoS₂ and WS₂ types. The model is demonstrated to describe sufficiently well the available experimental data on the negative differential conductance effect in a WS₂ monolayer. It confirms the possibility of fabricating Gunn diodes of a new and advanced EMW generation based on the structures concerned. These diodes are capable of generating frequencies of the order of 10 GHz and higher, which makes them attractive for HF practical applications.