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Structure and transport properties of Ge quantum dots in a SiO2 matrix

Germanium (Ge) nanoparticles or quantum dots(QDs) embedded in a transparent dielectric matrix have properties radically different from the bulk semiconductor and present a great potential for application in electronic and optoelectronic devices. Due to quantum confinement properties, the optical bandgap of QD-based materials can be tuned by varying the nanoparticle size. These properties may be exploited for the fabrication of nanoscale electronic devices or advanced solar cells. In this work we explored structural and transport properties of QD based superstructures for advanced solar cells. Magnetron cosputtering was used for deposition and upon suitable thermal treatment a superstructure of QDs was formed. Transport properties were explored by I–V measurement in the dark together with a C–V characterization. The obtained results were modeled with the known transport mechanisms for QDs containing materials. A special emphasis is given to trap controlled space charge limited current and hopping conductivity mechanism. We have shown that in our samples a significant charge is stored in the SiO2 layers with embedded Ge QDs. That charge is predominantly stored into traps at or close to the Ge(QDs)/ SiO2 interface.

Ge quantum dots; solar cells; small angle x-ray scattering; transport properties

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