Electronic transport properties of polycrystalline silicon films deposited on ceramic substrates

Chemical Vapor Deposition

2015

Atmospheric pressure (AP) thermal CVD is used to deposit thin poly-Si films on glass substrates. Also produced are heterojunction solar cells carrying out the deposition on c-Si wafers. A batch-type hot-wall reactor, employing SiHCl 3 as a precursor, H 2 as a carrier and reaction gas, BBr 3 as a p-type doping agent, and PCl 3 as a n-type doping agent, is used. The films obtained are homogeneous and well-adhered to the substrate. Samples are structurally characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), reflectance spectroscopy in the UV-vis region, X-ray diffraction (XRD), and Raman spectroscopy (RS). The electrical characterization includes conductivity measurements as a function of temperature, and Hall effect measurements. For the p-doped samples, XRD reveals a strong (220) preferential orientation of the films, while the n-doped samples lack columnar structure or preferential orientation. RS and UV-reflectance confirm a high crystalline fraction. Dark conductivity measurements as a function of temperature show that the films can be grown intrinsic, p-type or n-type. Activation energies between 0.61 and $0 eV are obtained, with reasonable values for the carrier mobilities. For the solar cells, relatively high values of V OC ($507 mV) and J SC ($29.6 mA cm À2 ) are measured. In conclusion, these results demonstrate the feasibility of directly depositing doped poly-Si thin films on glass and c-Si substrates at intermediate temperatures, with interesting characteristics for photovoltaic applications.

show abstract

Section: Resultssupporting

confidence: 62%

Doped Polycrystalline Silicon Thin Films Deposited on Glass from Trichlorosilane**

Chemical Vapor Deposition

2015

show abstract

“…Those requirements are fulfilled by an aluminosilicate float glass, such as the AF37 of Schott GmbH, which has a thermal expansion coefficient of 3.77 × 10 −6 K −1 and a softening point of 942 • C [15]. To use this glass as a substrate for the deposition of poly-Si, it remains to be tested if AP-CVD can produce films of acceptable quality at temperatures lower than 900 • C. It is well known that the grain size of poly-Si deposited by AP-CVD decreases when the deposition temperature is decreased [16]. However, it has also been shown that solar cells produced from poly-Si having a grain size lower than 0.2 μm can lead to open-circuit voltages larger than 530 mV [17].…”

Section: Introductionmentioning

confidence: 99%

Polycrystalline silicon thin films on glass deposited from chlorosilane at intermediate temperatures

Eur. Phys. J. Appl. Phys.

2012

We show that commercial float glass can be used as a substrate to deposit polycrystalline silicon (poly-Si) by chemical vapor deposition from trichlorosilane at temperatures between 740 and 870 • C. By using scanning electron microscopy an average grain size lower than 0.4 μm was observed, with a columnar structure suitable for the electrical conduction in photovoltaic cells. X-ray diffraction reveals a strong (2 2 0) preferential orientation of the films, which is indicative of a low density of intra-grain defects. Atomic force microscope images reveal a conical structure, with a root mean square roughness of ∼65 nm for samples of around 3 μm in thickness. This natural texture is a positive characteristic from the point of view of light trapping. By using boron tribromide as a doping agent, degrees of doping ranging from intrinsic to clearly p-doped were obtained, as shown by dark conductivity measurements as a function of temperature. The process, the reactants and the substrate used are of low cost and proved to be adequate for direct poly-Si deposition.

show abstract

“…3, se tiene un crecimiento suave con la temperatura y una dispersión relativamente grande. Esta tendencia creciente con la temperatura está de acuerdo con resultados publicados en trabajos anteriores (10) ; como también lo está la amplia variación de tamaño entre granos de una misma película (11,12) . Sin embargo, según se informa en estos trabajos, el tamaño de grano promedio es relativamente grande, entre 1 y más de 10 mayores a los presentados aquí.…”

Section: Resultados Y Discusiónunclassified

“…Esto se debe a que esta estructura posee baja cantidad de bordes de grano horizontales que los portadores de carga deban atravesar circulando verticalmente a través de las capas que forman la celda (9) . Este tipo de estructura se presenta también en películas depositadas a mayores temperaturas y sobre diferentes sustratos, según se informa en referencias (10)(11)(12)(13) .…”

Section: Resultados Y Discusiónunclassified

“…Por su parte, el 111 311 aumentan para menores temperaturas. La orientación preferencial (2 2 0) se menciona en numerosos trabajos de crecimiento de silicio policristalino sobre diferentes sustratos (9)(10)(11) . Usualmente, esta orientación se asocia con el crecimiento columnar de granos, y con una baja actividad de recombinación en los bordes de grano.…”

Section: Figura 4 Imagen Sem De Una Vista De Perfil (Corte) De Una Punclassified

See 1 more Smart Citation

Obtention of Thin Polycrystalline Silicon Films From Chlorosilanes in CVD Reactors

2012

AnAFA