Effect of Erbium Incorporation on SiN_xO_y/c-Si Interface in Silicon-Based Optoelectronic Devices

During the fabrication process of erbium (Er) doped Si-based light-emitting devices (LEDs), it is well known that high-temperature annealing is necessary for the activation of Er3+ ions and its diffusion in the dielectric layer is inevitable in this process. However, whether Er3+ ions will contaminate the interface and deteriorate the device during postanneal remains unclear. This work sheds light on the detailed electrical properties of interface between silicon oxynitride (SiNxOy) and crystal silicon (c-Si) before and after Er doping. We found that the activated Er3+ ions will bring about higher positive fixed charge density, which may aggravate the bending of the energy band and form deeper depletion region for majority carriers near the surface of silicon. Furthermore, higher density of interface states and wider energy distribution have been found via deep-level transient spectroscopy (DLTS) method in the Er-doped samples. These results enable us to reasonably propose that the Er3+ impurities may interact with the intrinsic defects at the SiNxOy/c-Si interface. Such a viewpoint is well supported by the energy dispersive X-Ray spectroscopy (EDX) analysis of Er in the fabricated SiNxOy:Er film. The obtained results show us a clear microscopic picture of Er contamination influencing the SiNxOy/c-Si interface.