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

The electrical performance of two-dimensional transition metal dichalcogenides (TMDs) is strongly affected by the number of structural defects. In this work, we provide an optical spectroscopic characterization approach to correlate the number of structural defects and the electrical performance of WSe₂ devices. Low-temperature photoluminescence (PL) spectra of electron-beam-lithographyprocessed WSe₂ exhibit a clear defect-induced PL emission due to excitons bound to defects, which would strongly degrade the electrical performance. By adopting an electron-beam-free transfer-electrode technique, we successfully prepared a backgated WSe₂ device containing a limited amount of defects. A maximum hole mobility of approximately 200 cm²·V^-1·s^-1 was achieved because of the reduced scattering sources, which is the highest reported value for this type of device. This work provides not only 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 TMD devices.