Amorphous Silicon Carbide for Photovoltaic Applications

Dissertation zur Erlangung des akademischen Grades Doktor der Naturwissenschaften Introduction Figure 1.1: One possible amorphous silicon (white) and carbon (black) network with incorporated hydrogen (small black dots) a-SiC:H. 20 Figure 1.2: Fourier transformed infrared (FTIR) absorption spectra for a typical stoichiometric SiC layer as deposited at 350°C. 21 Figure 1.3: Auger electron spectroscopy (AES) spectra for a typical stoichiometric SiC layer as deposited at 350°C. 23 Figure 1.4: Scheme of the dominating processes in the plasma during deposition and etching. 24 Figure 1.5: Schematic picture of one microwave antenna used in the AK400M reactor from Roth&Rau and graphs of plasma density (n e) and plasma temperature (T e). These graphs have been provided by Roth&Rau. 27 Figure 1.6: Scheme of the AK400M reactor from Roth&Rau company with the reaction chamber (left) and the load lock (right). 28 Figure 1.7: Optical Emission Spectroscopy graphs of two deposition processes with different CH 4 /SiH 4 gas flow ratios. 32 Figure 1.8: SiC deposition rate in dependence of CH 4 /SiH 4 gas flow ratio in the regime for diffusion barrier layers (SiC). 34 Figure 1.9: C/Si ratio in dependence of the CH 4 /SiH 4 ratio for the regime for diffusion barrier layers (SiC). 35 Figure 1.10: SiC deposition rate in dependence of the microwave power in the regime of low defect generation (Si x C 1-x). 36 Figure 2.1: Etching rate on stoichiometric SiC layers in dependence of the NF 3 /Ar gas flow ratio. 41 Figure 2.2: Etching rate on stoichiometric SiC layers in dependence of the bias voltage of the RF plasma source. 42 Figure 3.1: Refractive index n in the SiC layers in dependence of C/Si ratio (diffusion barrier regime). 52 Figure 3.2: Refractive index n of Si x C 1-x layers in dependence of microwave power (low defect regime). 53 Figure 3.3: Bandgap determination from transmission measurement data of a SiC layer after the theory of Tauc et al..