Mechanism for erbium luminescence in silicon at 1.54 um

摘要

Origin of erbium luminescence at 1.54 $mu@m, a prospective optical source in silicon based optoelectronics has been analyzed. Erbium atoms in silicon have been considered as recombination centers with specific values of capture and emission coefficients. Electron-hole recombination through these levels has been considered to be the origin of erbium excitation. At steady state of excitation, a certain fraction of erbium sites were found to remain occupied by electrons. Trapped electrons, which eventually recombine with holes in the valence band, provide the energy for $+4$/I$-15/2 $YLD $+4$/I$-13/2$/ transition of erbium atoms. It was however found that, even with 100 percent quantum efficiency of this energy transmission, not every electron- hole recombination corresponds to the excitation of an erbium atom. This wastage of recombination energy was attributed to the rather long lifetime of erbium decay. Capture and emission processes of photo generated excess carriers in the erbium related level have been equated for non-steady conditions. It has been shown that the steady state erbium luminescence actually follows a transient rise, typically of the order of few hundred microseconds. The anomalous behavior of continuous rise of erbium luminescence after termination of short excitation pulses of 30 $mu@s has been explained mathematically for the first time.