Normal incidence infrared detector using p-type SiGe/Si multiple quantum wells

The photoresponse of p-type SiGe/Si multiple quantum well infrared detectors is measured as a function of incidence beam polarization. With the infrared (IR) beam polarized in the growth direction, a photoresponse peak is observed at near 8.6 μm with a full width at half maximum (FWHM) of about 80 meV. On the other hand, with the beam polarized parallel to the growth plane (normal incidence), a peak is observed at near 7.2 μm with nearly the same FWHM. The photoresponse at peak positions is about 0.3 A/W for both cases. With an unpolarized beam, the peak photoresponse of about 0.6 A/W is observed for the present unoptimized structure. The results of the detection of normal incidence IR suggest possible applications of SiGe/Si multiple quantum wells for normal incidence IR detection.