Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 15: Quantum Dots and Wires: Fabrication and Devices

HL 15.6: Vortrag

Montag, 7. März 2016, 16:00–16:15, H16

Preparation of Silicon Nanocrystals in Silicon Carbide by a Multilayer Approach — •Charlotte Weiss, Andreas Reichert, and Stefan Janz — Fraunhofer Institut für Solare Energiesysteme ISE, Heidenhofstraße 2, 79110 Freiburg, Germany

The embedment of Si nanocrystals (NC) in a SiC matrix yields a promising semiconductor for tandem solar cell applications, due to its tunable bandgap by the variation of the Si NC size. The samples are prepared by plasma enhanced chemical vapour deposition (PECVD) of alternating stoichiometric SiC and Si-rich SiC (SRC) layers. During the subsequent annealing step at 1100°C phase separation into Si and SiC takes place in the SRC layers and NC form. The stochiometric SiC layer is intended to act as barrier layer for Si NC growth, which would mean that the thickness of the SRC layers define the Si NC size. It turns out that this so called multilayer (ML) approach does not control the Si NC size sufficiently, due to Si/SiC interdiffusion during annealing, accompanied with the loss of the ML structure.

Now we successfully preserved the multilayer structure by the incorporation of oxygen in the samples. This was achieved by providing CO2 during PECVD. The successful incorporation in the form of Si-O was confirmed by fourier transformed infrared spectroscopy while the preserved ML structure is observed in scanning electron micrographs. Raman measurements provide further evidence for lowered intermixing, as they show enhanced Si crystallinity in the ML with oxygen compared to samples without oxygen.