Two- and multi-terminal CMOS/BiCMOS Si LED's

Silicon is an indirect bandgap material, but light emission is observed from reverse biased pn junctions. Even though the quantum efficiency is low, it may still be advantageous to use these devices in all-silicon optoelectronic integrated circuits (OICs). In this paper new research results with regard to low-voltage field emission BiCMOS and CMOS two- and multi-terminal Si LEDs are presented. The differences observed between avalanche and low-voltage field emission LED performance are presented. It is shown that the low-voltage devices exhibit a square-law light intensity vs. reverse current non-linearity at low-current levels, but a linear dependency at higher currents, compared to the linear behaviour of avalanche devices at all current levels. The detail spectral characteristics of the field emission devices are investigated, showing that in the non-linear region of operation, the shape of the emitted spectrum changes, with reduced short wavelength generation at lower current levels. Bipolar junction transistor (BJT) multi-terminal devices are also discussed, and the square-law behaviour of these devices is presented.