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(Color online) (a) Schematic view showing a cross section of the Ge/SiGe MQW waveguide emitting diode. The p- and n-type regions were doped to ∼1 × 1018 cm−3. (b) Optical microscope view of the device; the waveguide length is 80 μm. (c) The I–V characteristic of the diode.
(Color online) RT EL spectra of the 80 μm long Ge/SiGe MQW diode as a function of injection currents. In the inset, the band diagram of the Ge/SiGe MQWs (energies not to scale): c1 and cL1 are the energies of the lowest confined QW states in the conduction band at and L valleys, respectively, and HH1 and LH1 are the lowest confined QW states in the valence bands, associated with the heavy and light holes, respectively. A clear peak in the EL is seen at around 1420 nm corresponding to the excitonic HH1-cΓ1 transition.
(Color online) (a) EL peak wavelength and (b) EL peak intensity (excitonic HH1-c1 transition) as a function of current density.
(Color online) EL spectra at different temperatures and constant current density of 1.3 kA/cm2 from a 300 μm long waveguide.
EL spectra from 80 μm long diode for different injection currents obtained with and without an optical polarizer between the output facet of the waveguide and the detector. EL spectra in TE polarization are consistent with the EL spectra obtained with no optical polarizer. No EL is observed in TM polarization.
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