Direct-gap gain up to 850 cm-1 at 0.74 eV is measured and modeled in optically pumped Ge-on-Si layers for photoexcited carrier densities of 2.0×1020 cm-3. The gain spectra are correlated to carrier density via plasma-frequency determinations from reflection spectra. Despite significant gain, optical amplification cannot take place, because the carriers also generate pump-induced absorption of ≈7000 cm-1. Parallel studies of III–V direct-gap InGaAs layers validate our spectroscopy and modeling. Our self-consistent results contradict current explanations of lasing in Ge-on-Si cavities.
Direct-Gap Gain and Optical Absorption in Germanium Correlated to the Density of Photoexcited Carriers, Doping, and Strain
CECCHI, STEFANO CARLO;ISA, FABIO;CHRASTINA, DANIEL;ISELLA, GIOVANNI;
2012-01-01
Abstract
Direct-gap gain up to 850 cm-1 at 0.74 eV is measured and modeled in optically pumped Ge-on-Si layers for photoexcited carrier densities of 2.0×1020 cm-3. The gain spectra are correlated to carrier density via plasma-frequency determinations from reflection spectra. Despite significant gain, optical amplification cannot take place, because the carriers also generate pump-induced absorption of ≈7000 cm-1. Parallel studies of III–V direct-gap InGaAs layers validate our spectroscopy and modeling. Our self-consistent results contradict current explanations of lasing in Ge-on-Si cavities.File in questo prodotto:
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