A prototypical near-infrared light-emitting diode from CdS/Si heterojunctions based on the defect emissions in the interface

Abstract Optimizing and tuning the interface to enhance the performance of heterojunctions is an important research topic in the optoelectronic fields. In the present work, a CdS layer of ∼5.0 nm in the thickness, which is prepared by the radio frequency magnetron sputtering method, has been incorporated in the interface of CdS/Si heterojunctions which is constructed through depositing nano CdS films on porous polysilicon by using the chemical bath deposition method. Through the annealed treatment at 500 oC in the Ar atmosphere, the CdS/Si heterojunctions show typical rectification characteristics with the improved turn-on voltage from ∼2.10 V to ∼0.83 V. At the forward voltage of ∼6.0 V, a green band can be observed. With increasing the applied voltage, the near-infrared emission band can be obtained, which is ascribed to the transition from the sulfur vacancies in the surface CdS layers to the cadmium interstitials in the interface. It is believed that understanding of near-infrared emission from CdS/Si heterojunction is crucial to the field of optoelectronic devices.