Exciton-dynamics of molybdenum disulfide on gallium nitride

Layered transition metal dichalcogenides (TMD) have generated significant research interest because of interesting optical properties that are strongly dependent on the substrate. The integration of two dimensional (2D) materials with the bulk semiconductors provides an attractive platform to enhance the device functionality. Of all the 2D/3D heterostructures, MoS₂/GaN structures are at the top because of strong lattice matching and direct gap structures of both semiconductors. The properties of the heterostructures are governed by excitons, which are weakly bound in nitrides but are strongly bound in MoS₂. Here we present the exciton dynamics of single layer MoS₂ on GaN substrate. We studied the non-equilibrium exciton-dynamics with the pump-probe spectroscopy using a tunable laser as a pump and a supercontinuum white light probe. The transient absorption spectrum shows different excitonic states. We will discuss the evolution of these states at different delay times starting as early as 200 fs and the corresponding decay kinetics. Our study will be useful to understand the energy transfer as well as the charge transport across the junction in the heterostructure which is crucial to enhance the performance of the device.