Stability in Electroluminescence From Ag-NSi Schottky Junction LED: Role of Ambient Oxidation

This work explores the electroluminescence performance and long-term stability of silver contact nanostructured silicon Schottky junction LEDs under prolonged DC bias. Si-based LEDs are increasingly sought for all-silicon integrated photonic circuits due to their compatibility with monolithic CMOS integration technology. Although their external quantum efficiency remains lower than that of commercial LEDs, NSi-based LEDs show promise for applications in quantum optics, including quantum random number generation and high-speed on-chip optical communication systems. While numerous studies have addressed factors influencing electroluminescence in nanostructured silicon devices, such as work function and transparency of the contact, injection, radiative recombination, and light extraction efficiencies, long-term spectral stability remains largely unexplored. A key factor is the non-stoichiometric native oxide layer that forms on nanostructured silicon and gets modified due to Joule heating under prolonged electrical bias. This alteration influences charge injection dynamics and affects overall device performance over time. In this study, we systematically investigate how this oxide layer governs injection efficiency and temporal stability of EL emission, including peak energy and intensity. A simple equivalent circuit is employed to account for current components associated with injection and heating. Our results indicate that the oxide layer modulates carrier injection as well as plays a stabilizing role in the output spectrum over extended operation. The calculated luminescence characteristics of the LEDs qualitatively align with experimental findings that offer valuable insights into mechanisms affecting the performance and reliability of silicon nanodevices.