Ge quantum dot infrared photo-detector

In our experiments, vertical aligned superlattices of multiple self-assembled Ge island layers separated by Si spacer layers on Si(100) substrates have been grown by ultra high vacuum chemical vapor deposition system (UHV/CVD). The photoluminescence of material was excited with 500nm laser and measured at 10 K, the PL peaks representing Ge islands and Si wetting layers were observed at 825 and 1010 mev respectively. Based on this material, samples of quantum dot infrared photo-detectors (QDIP), with p-i-n junctions, were fabricated. The responsivity of the detectors was measured with various semiconductor light-emitting diodes and semiconductor lasers. At room temperature and at -3V applied bias, for samples with 245 × 245 μm² large window and dark current I_d∼10^-9A, the maximum photocurrent responsivity of 0.52 A/W at 774 nm was found, and 0.043mA/W at 1.31 μm. Higher responsivities can be obtained with a waveguide geometry and optimization of the whole structure, such as thickness of layers and type of doping.