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Schematic drawing of the infrared photodetector. The active region is the phosphorus -doped Ge dots embedded in the intrinsic Si layer, which is sandwiched by the two heavily -type doped Si layers.
Dark curves at 15, 25, 50, and 77 K for a device.
(a) Photoresponse spectrum in the mid-IR range at 1.5 V bias taken with a 2–5 μm band pass filter. (b) Spectra in the far-IR range at various biases taken with an 8–25 μm band pass filter. Note that in this plot, the axis is in logarithmic scale. Light is incident normally for both (a) and (b).
The band diagrams of Ge quantum dot in the Si matrix with phosphorus -doping (a) and without doping (b). QW is formed in the conduction band due to the -doping, while the band offset is mainly in the valence band without doping. Excitation of electrons takes place in the well from the low-energy levels to high-energy levels and the conduction-band edge by absorbing photons.
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