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CPPL and DCP spectra of MQW (upper), Ge-on-Si (middle), and bulk Ge (lower). DCP values at E < 0.95 eV are relevant, whereas the feature near 1.03 eV is presumably due to hot luminescence. Inset: 8-K photoreflectance spectrum of Ge MQW. Vertical arrow indicates the transition due to the electron and heavy-hole ground-states.
Selection rules for angular-momentum-conserving dipole-allowed interband transitions. Figures indicate relative magnitudes of the oscillator strength. Inset figure illustrates intervalley scattering processes of electron. Upward arrow indicates near-resonant photoexcitation.
Temperature dependence of PL spectra from Ge MQW (thick solid line), Ge-on-Si (broken line), and bulk Ge (thin solid line). Vertical line indicates the cutoff energy of detector.
(a) PL decays of Ge MQW (thick solid line), Ge-on-Si (broken line), and bulk Ge (thin solid line). 2D energy (wavelength)-delay maps for PL decays of (b) bulk Ge and (c) Ge-on-Si.
Snapshot spectra of CPPL and DCP for (a) Ge-on-Si and (b) bulk Ge. Time evolution of DCP for bulk Ge (c) and Ge-on-Si ((d) and (e)). Figures indicate delays. Gate width is 0.2 ns. Apparent loss of indirect-gap PL for bulk Ge occurs due to its slow rise time, ns. The detection energies are given in parentheses. Note that the time origin is not necessarily at zero delay.
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