Ultrafast Exciton Dynamics in p- and n-Type MoTe ₂ Thin Films

Transition metal dichalcogenides (TMDCs) can be utilized to fabricate next-generation logic circuits, including field-effect transistors (FETs) and complementary metal-oxide-semiconductor (CMOS) inverters. Top gates fabricated via electron-beam evaporation (EBE) can introduce defects that induce strong n-doping in molybdenum telluride (MoTe2), converting it from p-type to n-type. Using ultrafast spectroscopy, we investigated the exciton dynamics in multilayer 2H-MoTe2 films before and after the electron-beam evaporation coating. The processes of defect-assisted nonradiative recombination and intervalley scattering of thermalized excitons were observed. The n-type film exhibits enhanced defect-assisted nonradiative recombination, suppressing thermalized exciton scattering from the K valley to the Λ valley. These findings provide fundamental insights into exciton behavior in p- and n-type TMDCs, enabling improved device design and optimization.