Polarized Light-Emitting Diodes Based on Anisotropic Excitons in Few-Layer ReS2

An on-chip polarized light source is desirable in signal processing, optical communication, and display applications. Layered semiconductors with reduced in-plane symmetry have inherent anisotropic excitons that are attractive candidates as polarized dipole emitters. Herein, the demonstration of polarized light-emitting diode based on anisotropic excitons in few-layer ReS₂, a 2D semiconductor with excitonic transition energy of 1.5–1.6 eV, is reported. The light-emitting device is based on minority carrier (hole) injection into n-type ReS₂ through a hexagonal boron nitride (hBN) tunnel barrier in a metal–insulator–semiconductor (MIS) van der Waals heterostack. Two distinct emission peaks from excitons are observed at near-infrared wavelength regime from few-layer ReS₂. The emissions exhibit a degree of polarization of 80% reflecting the nearly 1D nature of excitons in ReS₂.