engleski

Quantum dot lattices of Ge/Si core/shell quantum dots in alumina glass matrix for application in solar cells

Materials consisting of semiconductor core-shell nanostructures, like nanowires or quantum dots, attract special attention due to their highly adjustable electronic structure and optical properties. Especially interesting for the application of such materials in solar cells is the fact that Ge/Si core/shell quantum dots have a type II band alignment, leading to the separation of charge carriers. We have recently developed a method for the growth of self-assembled core/shell Ge/Si quantum dots in an amorphous alumina matrix. The method is very simple and consists of magnetron sputtering deposition process of Al2O3/Ge/Si multilayer. The formed dots are spontaneously ordered in a three-dimensional body centered tetragonal quantum dot lattice. The light absorption properties of these complex materials are significantly different compared to the films that form quantum dot lattices of the pure Ge, Si or a solid solution of GeSi prepared by the same method. The core/shell-based materials show a strong narrow absorption peak, while others show only broad, low-intensity bands. The properties of the absorption observed for the core/shell quantum dots is in accordance with the theoretical predictions from Ref. [1], and it is characteristic for type II confinement. Tuning the radius of the Ge core and thickness of the Si shell we are able to tune the position of the absorption peak in a broad range of energies. To demonstrate that effect several sets of Ge/Si/Al2O3 - films differing by deposition conditions are compared.

QD ; core/shell ; sputtering

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