Single photon detection by means of SiGe-quantum dot arrays

The fabrication process of single-photon detectors (SPD) based on high-density arrays of Ge quantum dots (QD) is proposed. The design of the SPD exploits the phenomenon that the contribution of an individual QD to the hopping transport through this high-density Ge QDs array crucially depends on the occupation of the dot with carriers. A change in the conductance of the array can be induced by changing the charge state of one QD by illumination. For sub-micron sized devices step-like variations of the conductance due to the absorption of single photons are expected to be noticeable. The fabrication process combines molecular beam epitaxy (MBE) with means of semiconductor technology as E-Beam lithography and reactive ion etching. The process flow developed is described and measurement results are shown, confirming the suitability of the device design for single photon detection.