Low-temperature transport properties of Si and Ge films with Ga-rich nanoprecipitates

Ga-rich (~ 10 at.%) Si and Ge films were fabricated by high-fluence Ga+ ion implantation through a SiO2 capping layer. The structure and the electrical transport properties of these films have been studied after flash-lamp [1-3] and rapid thermal annealing [4, 5]. Amorphous, Ga-rich nanoprecipitates are embedded in a heavily p-type doped semiconductor matrix [3, 4].
These nanoprecipitates become superconducting below critical temperatures up to 7 K. They can interact due to the proximity effect in the degenerately doped semiconductor matrix and form a random network of Josephson junctions. Small modifications of the junction properties, e.g. by annealing or current pulses, can dramatically change the electronic transport in the film. In particular, Ga-rich Si films show a wealth of low-temperature transport phenomena which have been known until now only from granular metals or high-temperature superconductors: superconductor-insulator transition, quasi-reentrant superconductivity and current-controlled sheet resistance [6, 7] .
The possibility to prepare and modify Ga-rich Si and Ge films with microelectronics-compatible technology makes them interesting for both fundamental research on transport phenomena in nanostructured, disordered superconductors as well as for the integration of superconducting circuits into Si devices.

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