Spectral characteristics of Si light emitting diodes in a 0.8 μm BiCMOS technology

It is well known that silicon diodes biased in the avalanche breakdown region of operation emit visible light. Silicon light sources in monolithic optoelectronic systems will only be used on a large scale if the devices can be easily integrated with other circuits in the standard VLSI technology. This paper investigates the spectral properties of silicon diode light sources in a 0.8 μm BiCMOS technology. The light sources include both avalanche and field emission breakdown devices, and it Is shown that the breakdown mechanism has a significant effect on the spectral properties of the diodes. The emitted light patterns as defined by the layout also play a role, and evidence is provided that point sources have more long wavelength emission than line sources. The emission originating from bulk diodes, e.g. the buried layer, is also compared to the emission from surface-dominated junctions, and a definite shift in spectra towards longer wavelengths is observed