AlAs/AlGaAs X-valley quantum-well normal-incidence infrared detectors on Si substrates

AlAs/AlGaAs X-valley multiquantum-well detectors grown on Si substrate are reported. Normal-incidence infrared-absorption measurements were performed on [113]- and [115]-oriented samples grown on Si substrate at a wavelength range of 5-20 μm. An absorption peak was observed in the [113]-oriented quantum wells with an infrared-absorption coefficient of α=1400 cm^-1 (quantum efficiency η=13%); similar results were attained with the [115] sample. The experimental results indicate the potential of these novel structures as normal-incidence infrared photodetectors. The results point to the possibility of integrating photodetectors and signal processing circuits on the same Si substrate.