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Schematic excitation processes for direct - radiative recombination (Her ) in (a) photoluminescence (PL) and (b) electroluminescence (EL). Near-resonance interband photoexcitation of direct Γ-valleys contributes to PL. In EL, LC - intervalley scattering (Hep ) pumps electrons into the direct Γ-valley from the lower-lying indirect L-valleys that take up electrons thermally released from donors. Inset illustrates intervalley scattering between the relevant valleys. Closed and open circles represent electrons and holes, respectively. and indicate ionized donor and acceptor states, respectively. Note that indirect LC - emission should coexist.
Time-integrated EL spectrum of bulk Ge at room temperature. The lower energy edge rolls off due to detector's cutoff. Two modified Gaussians (broken lines) provide the best fit (solid line) to data. Left inset illustrates the device structure. Right inset shows current-voltage characteristics.
Transient EL decay of bulk Ge. Upper trace is the captured voltage waveform. Solid line laid on EL trace is a theoretical fit. Inset shows a wider view.
(a) EL decay traces as a function of energy. Solid lines are a double-exponential fit. (b) Energy dispersion of time constant of fast component. (c) Fraction of fast component as a function of energy.
Snapshot EL spectra of bulk Ge. Figures indicate the time span for each snapshot.
(a) Fourier spectra of EL output for a double pulse input of different frequencies, 1, 2, 5, 10 MHz. (b) Corresponding transient EL traces.
Fitting parameters of transient EL traces.
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