Low-operating-voltage integrated silicon light-emitting devices

A solution is presented for the fabrication of low-voltage, low-power (<4.25 V and <5 mW) silicon light-emitting devices (Si-LEDs), utilizing standard very large scale integration technology without any adaptation. Accordingly, they can be integrated with their signal processing CMOS and BiCMOS circuits on the same chip. This enables the fabrication of much needed all-silicon monolithic optoelectronic systems operated by a single supply. The structural details of two distinctly different line-patterned Si-LEDs are presented, composed of heavily doped n⁺p⁺ junctions, made by BiCMOS n⁺ sinker and PMOS p⁺ source/drain doped regions, respectively. Using this approach, other Si-LED structures can be designed to yield low- or high-voltage Si-LED operation as well. Light is emitted at low reverse bias as a result of quantum transitions of carriers, generated by field emission, as indicated by the low reverse breakdown voltage V_B, the soft "knee" I-V characteristics and the negative temperature coefficient of V_B. The optical performance data show that, at low reverse operating current I_R, the overall emitted light intensity L is a nonlinear function of I_R and becomes linear at higher I_R. A bell-shaped light spectrum is obtained, with an enhanced short wavelength and attenuated long-wavelength radiation, relative to that of avalanche Si-LEDs.