Integration of electrically isolated porous silicon leds for applications in cmos technology

摘要

Previously we reported on integrated porous silicon (PSi) based LEDs with local bipolar drivers that would have possible applications in an active-matrix configuration for display or optical signal transmission[1]. We now report further progress in device engineering and integration that has enabled the fabrication of improved light-emitting silicon devices based on oxide-passivated nanocrystalline silicon (OPNSi) that can be integrated with standard CMOS technology. Design of experiments methodology was used to direct device engineering experiments, providing a better understanding of how process parameters influence the resulting device performance. It was discovered that the formation of stacking fault defects in the LED region prior to anodization has a predominant effect on both carrier transport and electroluminescence (EL) capabilities of the devices. Process development work has resulted in the fabrication of OPNSi LEDs that offer many of the required attributes of a useful silicon light-emitter. The devices exhibit EL at a bias <5V, diode-like rectifying I-V characteristics, good stability under DC bias, and uniform emission over the LED contact area. These LEDs have been combined with a new fabrication technique which enables the formation of electrically isolated integrated LEDs in the single-crystal substrate. Each diode structure is formed in its own individual well, enabling junction-isolated devices without a common substrate electrode. Such a process is required to realize integrated LEDs which can be individually addressed in an X-Y array configuration using full-rail voltage modulation. Details of the LED characteristics and device integration will be discussed.