Defects as a factor limiting carrier mobility in WSe2: a spectroscopic investigation

TL;DR

This study links structural defects in WSe2 to reduced electrical performance, using optical spectroscopy to identify defect-related emissions and demonstrating a method to improve mobility by reducing defects.

Contribution

It introduces a spectroscopic approach to quantify defects in WSe2 and shows how defect reduction enhances carrier mobility in devices.

Findings

Defect-related photoluminescence correlates with electrical degradation.

E-beam-free transfer reduces defects and improves mobility.

Achieved record hole mobility of 200 cm2/Vs in WSe2 devices.

Abstract

The electrical performance of two dimensional transitional metal dichalcogenides (TMDs) is strongly influenced by the amount of structural defects inside. In this work, we provide an optical spectroscopic characterization approach to correlate the amount of structural defects and the electrical performance of WSe2 devices. Low temperature photoluminescence (PL) spectra of electron beam lithography (EBL) processed WSe2 presents a clear defect-induced PL emission due to excitons bound to defects, which would strongly degrade the electrical performance. By adopting an e-beam-free transfer-electrode technique, we are able to prepare backgated WSe2 device with limited amount of defects. A maximum hole-mobility of about 200 cm2/Vs was achieved due to reduced scattering sources, which is the highest reported value among its type. This work would not only provide a versatile and nondestructive method to monitor the defects in TMDs, but also a new route to approach the room temperature phonon-limited mobility in high performance TMDs devices.