2D Nb-doped MoS$_2$: Tuning the Exciton Transitions and Application to p-type FETs

TL;DR

This study reports the synthesis of high-quality p-type 2D MoS$_2$ doped with Nb, investigates how Nb doping modulates exciton transitions, and demonstrates a Nb-doped MoS$_2$ FET with tunable performance for optoelectronic applications.

Contribution

It introduces a novel two-step synthesis method for wafer-scale p-type Nb-doped 2D MoS$_2$ and analyzes its optical and electronic properties, advancing 2D material doping techniques.

Findings

Nb doping modulates exciton peaks in 2D MoS$_2$

Broadening of peak B linked to impurity-induced transitions

Fabricated p-type FET with performance adjustable by Nb concentration

Abstract

Two-dimensional (2D) MoS$_2$ has been intensively investigated for its use in the fields of microelectronics, nanoelectronics, and optoelectronics. However, intrinsic 2D MoS$_2$ is usually used as the n-type semiconductor due to the unintentional sulphur vacancies and surface gas adsorption.The synthesis and characterization of 2D MoS$_2$ semiconductor of p-type are crucial for the development of relevant p-n junction devices, as well as the practical applications of 2D MoS$_2$ in the next-generation CMOS integrated circuit. Here, we synthesize high-quality, wafer-scale, 2D p-type MoS$_2$ (Mo$_{1-x}$Nb$_x$S$_2$) with various niobium (Nb) mole fractions from 0 to 7.6% by a creative two-step method. The dielectric functions of 2D Mo1-xNbxS2 are accurately determined by spectroscopic ellipsometry. We find that the increasing fraction of Nb dopant in 2D MoS$_2$ can modulate and promote the combination of A and B exciton peaks of 2D MoS$_2$. The direct causes of this impurity-tunable combination are interpreted as the joint influence of decreasing peak A and broadening peak B. We explain the broadening peak B as the multiple transitions from the impurity-induced valance bands to the conductive band minimum at K point of Brillouin zone by comparing and analyzing the simulated electronic structure of intrinsic and 2D Nb-doped MoS$_2$. A p-type FET based on the 2D Nb-doped MoS$_2$ was fabricated for characterization, and its working performance is expected to be adjustable as a function of concentration of Nb dopant according to our theoretical research. Our study is informative for comprehending optical and electronic properties of extrinsic 2D transitional metal dichalcogenides, which is important and imperative for the development and optimization of corresponding photonics and optoelectronics devices.