Hydrogenated amorphous SiC films ( a - Si 1-x C x: H ) were prepared by DC magnetron sputtering technique on p type Si (100) and corning 9075 substrates at low temperature, by using 32 sprigs of silicon carbide (6 H - SiC ). The deposited film a - Si 1-x C x: H was realized under a mixture of argon and hydrogen gases. The ( a - Si 1-x C x: H ) films have been investigated by scanning electronic microscopy equipped with EDS system (SEM-EDS), X-rays diffraction (XRD), secondary ions mass spectrometry (SIMS), Fourier transform infrared spectroscopy (FTIR), UV-visible-IR spectrophotometry, and photoluminescence (PL). XRD results showed that the deposited film was amorphous with a structure of a - Si 0.81 C 0.19: H corresponding to 19 at.% carbon. The photoluminescence response of the samples was observed in the visible range at room temperature with two peaks centered at 463 nm (2.68 eV) and 542 nm (2.29 eV). The structural properties and the origin of the luminescence were discussed.
The structural and photoelectrical properties of Al-doped ZnO (AZO)/SiC/p-Si and AZO/SiC/n-Si heterojunctions, fabricated at low temperature by pulsed laser deposition, were investigated by means of a number of techniques. Raman analysis indicates that SiC layers have the cubic 3C-SiC phase, whilst X-ray diffraction measurements show that AZO films exhibit a hexagonal wurtzite structure, highly textured along the c-axis, with average crystallites size of 35.1 nm and lattice parameter c of 0.518 nm. The homogeneous and dense surface morphology observed by scanning electron microscopy was confirmed by atomic force microscopy images. Moreover, UV–Vis-NIR spectra indicated a high transmittance of SiC films in the region 550–2500 nm, about 80% transmittance of AZO films in the 450–1000 nm region, and optical band gaps in good agreement with literature. These results prove that pulsed laser deposition is a low-cost technique suitable to grow SiC and AZO films with excellent material properties. The effect of the Si doping on the current transport mechanisms in the heterojunctions was investigated by current-voltage measurements under dark and white light illumination. Both heterojunctions exhibit a diode behaviour and relatively low leakage current, with a noticeable superiority for the AZO/SiC/n-Si device also under illumination, with an illumination/dark ratio of about 400. Our results indicate that the AZO/SiC/p-Si heterojunctions, with higher values of ideality factor, series resistance and lower rectifying ratio, have a complex current transport compared to the diodes grown on n-type Si. Additionally, capacitance-voltage measurements and Mott-Schottky plot allowed to determine a built-in potential of 0.51 V for the Al/AZO/SiC/p-Si/Al device.
The Photoelectrical properties of hydrogenated amorphous silicon thin films (a-Si:H) deposited on porous silicon (PSi) were investigated. Porous Si layers were formed by electrochemical etching of p+-type crystalline Si in a hydrofluoric solution, whereas a-Si:H films were deposited in a partially hydrogenated atmosphere using the DC-Magnetron sputtering method. Samples with a-Si:H films deposited at different H2 flow rates and with PSi layers of different porosities and thicknesses were characterized. The Dark and under illumination I-V characteristics as well as the photocurrent response of these samples, were recorded on Al/a-Si:H/PSi/Si structures using both sandwich and planar configurations. These measurements were compared to that obtained with a-Si:H directly in contact with c-Si substrate. The results of our investigation demonstrate that the PSi layer characteristics strongly affect the photoelectrical properties of a-Si:H thin films and their influence depends on the electrical properties of these films.
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