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. The spectrum of PT light source constitutes a scaled combination of both the forwardand reverse-biased junction spectra. 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. The effect of current densities up to 10⁶ A/cm² and temperatures between 22 °C and 122 °C on the emission spectrum and consequently the physical light generation mechanism are investigated and quantified.

Date Published: 2 February 2012
PDF: 11 pages
Proc. SPIE 8266, Silicon Photonics VII, 82660S (2 February 2012); doi: 10.1117/12.907923

Published in SPIE Proceedings Vol. 8266:
Silicon Photonics VII
Joel Kubby; Graham Trevor Reed, Editor(s)