Electrical Characterization of SiGeSn/Ge/GeSn-pin-Heterodiodes at Low Temperatures

The combination of the ternary alloy Si x Ge l-x-y Sn y with Gel -y Sn y is very promising for electrooptical applications in the near infrared regime up to 2.5 µm wavelength. With the tunable bandgap at a non-varying lattice constant SixGe l-x-y Sny is predestined for the lattice matched growth on a Ge virtual substrate and the integration of pseudomorphic Gel-ySny layers with high Sn content (> 10 %). The main challenge of the growth of such alloys is to achieve a low density of defects. However, in the last few years there was a major progress in growing highly doped SixGe l-x-y Sny layers with good crystal quality. In this work we investigate the electrical characteristics of a SixGe l-x-y Sny/Ge/Ge l-y Sny -pin-heterodiode in a temperature range from 300 K to 8 K. This temperature depended measurement provides the opportunity for a more precise characterization of such diodes. A linear relation between reciprocal temperature and the ideality factor is found. With the extrapolation of this relation up to room temperature the ideality factor of the diode is calculated (n = 1.22). From the temperature dependent reverse current the activation energy is determined ( EA=0.178 eV). We discuss the possibility to utilize such diodes for near infrared electrooptical applications.