Lateral photoconductivity of GeSn alloys

We report a study of the photoconductivity mechanism and transport paths of photoexcited charge carriers in the GeSn/Ge/Si heterostructures. The dark conductivity was studied as a function of temperature, which allowed to identify of the presence of deep levels at E_V+(100÷130) meV. We have established that point defects are the source of a band of electronic states and determine the photoconductivity response. The photocurrent dependencies on excitation intensity demonstrate that the main conduction occurs mainly through the Ge layer under low pumping and through the Si substrate under high one, since the GeSn top layer is much thinner has a much higher conductivity. This detailed understanding of the recombination processes is of critical importance for developing GeSn/Ge-based optoelectronic devices.