Voltage-tunable, two-band mid-infrared detection based on Si/SiGe quantum cascade injector structures

Photocurrent spectroscopy has been performed on doped Si/SiGe valence band cascade injector structures in the mid-infrared spectral region. A large tunability of the photoresponse peak wavelength (from 5.2 to 3.2 µm) by an externally applied electric field is observed. The tunability of the photoresponse is a consequence of an electric-field-induced transfer of holes from the deepest to the shallowest quantum well of the injector sequence. Depending on the bias voltage, dark-current-limited peak detectivities of D* = 1 x 10(exp 9) cm root of Hz/W (peak wavelength 5 µm at -4 V bias) and of D* = 1.3 x 10 (exp 9) cm root of Hz/W (peak wavelength 3.2 µm at 5 V bias) are obtained at a temperature of 77 K.