Abstract: Two-dimensional (2D) transition-metal dichalcogenide (TMD) monolayers, which reveal remarkable semiconductor properties, are the subject of active experimental research. It should be noted that, unlike bulk TMDs, which are indirect-band semiconductors, 2D TMD monolayers have the extreme points of the conduction and valence bands at the same K and K′ points of the Brillouin zone. Therefore, they are direct-band semiconductors and can claim to be widely used in optoelectronics devices. Recently, it has been shown experimentally that quantum yield in MoS2 and WSe2 monoatomic layers can reach values close to unity when electrostatic doping makes them intrinsic semiconductors. However, the available theoretical description does not provide an understanding of the physical mechanisms underlying the gate voltage control of quantum yield. This work is an attempt to propose a consistent semi-phenomenological theory of photoinduced charge-carrier relaxation in 2D TMDs, which allows an analytical dependence of the quantum yield on the voltage applied to the field effect transistor gate to be obtained. We consider a standard experimental situation, when the 2D TMD monolayer and the metal gate are plates of a flat capacitor, and the capacitor charge is proportional to the gate voltage. Owing to very strong electron-hole interaction in TMD monolayers, quantum yield on the gate voltage and the carrier generation rate have been calculated for the cases of the prevailing recombination of excitons (radiative and Auger recombination). Analytical expressions are derived for the dependence of quantum yield on the gate voltage and photoinduced carriers generation rate at a fixed gate voltage. Quantitative agreement with experiment allows us to draw conclusions about the relevance of the proposed theoretical model for the description of carrier photogeneration and recombination in 2D TMD monolayers. The obtained results demonstrate the possibilities of 2D TMD quantum yield control by the gate voltage and indicate that 2D TMDs are promising candidates for modern optoelectronics devices.
Title: Gate-Voltage Control of Quantum Yield in Monolayer Transition-Metal Dichalcogenide
DOI: https://doi.org/10.1103/PhysRevApplied.13.014040 Physical Review Applied (2020) 13, 014040
Preprint deposited in the repository: https://arxiv.org/abs/1909.10099