Epitaxial GeSn obtained by high power impulse magnetron sputtering and the heterojunction with embedded GeSn nanocrystals for SWIR detection.

GeSn alloys have the potential of extending the Si photonics functionality in short-wave infrared (SWIR) light emission and detection. Epitaxial GeSn layers were deposited on a relaxed Ge buffer on Si(100) wafer by using high power impulse magnetron sputtering (HiPI-MS). Detailed X-ray reciprocal space mapping and HRTEM investigations indicate higher crystalline quality of GeSn epitaxial layers deposited by Ge HiPI-MS in respect to commonly used radio frequency magnetron sputtering (RF-MS). To obtain a rectifying heterostructure for SWIR light detection, a layer of GeSn nanocrystals (NCs) embedded in oxide was deposited on the epitaxial GeSn one. Embedded GeSn NCs are obtained by co-sputtering deposition of (Ge1-xSnx)1-y(SiO2)y layers and subsequent rapid thermal annealing at a low temperature of 400oC. Intrinsic GeSn structural defects give p-type behaviour, while the oxygen presence leads to the n-character of the embedded GeSn NCs. Such embedded NCs/epitaxial GeSn p-n heterostructure shows superior photoelectrical response up to three orders of magnitude increase in the 1.2-2.5 µm range, as compared to performances of diode based only on embedded NCs.