Spectral Measurement and Analysis of Silicon CMOS Light Sources

The emission spectra of pn-junction and punch-through (PT) carrier injection silicon (Si) CMOS light sources were measured at various current densities and temperatures. In contrast to the narrow-band forward-biased junction spectrum, that peaks around 1.1 μm (1.1 eV), the reverse-bias spectrum was found to extend from about 350 nm (3.4 eV) to about 1.7 μm (0.7 eV) covering the UV, Vis and NIR regions. Since the photon energy decreases with increasing wavelength, the significant NIR radiation implies that the quantum conversion efficiency of Si avalanche light sources is appreciably higher than previously reported. Calculating the photon flux at the emission source within the Si against photon energy allowed the deduction and quantification of the physical light emission processes with respect to silicon's electronic band structure. Intra-conduction-band (c-c) electron (e⁻) transitions seem to be the dominant physical mechanism responsible for the wide avalanche spectrum.