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

Abstract

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.

Study on the fundamental factors of the property evolution of a 300 mm polycrystalline trap-rich layer

“…The annealing process can release poly-Si stress by increasing grain size and changing the polycrystalline orientation, but the effect is limited [10]. Adjusting the deposition temperature, reaction gas pressure, dopant concentration and other process parameters have been certified to control poly-Si film stress after deposition [11][12][13][14]. Poly-Si layers can generally be obtained by direct deposition of amorphous silicon by annealing or chemical vapor deposition (CVD) on a substrate with an oxide layer [15][16][17].…”

Flexible Solar Cells Using Doped Crystalline Si Film Prepared by Self-Biased Sputtering Solid Doping Source in SiCl4/H2 Microwave Plasma

“…Various doping sources for B include diborane (B 2 H 6 ), 5 trimethylboron (B(CH 3 ) 3 ), 7 and boron trifluoride (BF 3 ), 7 and sources for P include phosphane (PH 3 ) 6 and phosphorus trichloride (PCl 3 ). 8 However, the most commonly used gaseous doping sources for B or P are explosive, highly hazardous, and difficult to store. Moreover, added elements in the doping sources (e.g., H, C, F, and Cl) which may drastically degrade the structural and electrical properties of the doped Si films, may be incorporated into the synthesized films.…”

“…These methods include plasma-enhanced chemical vapor deposition (PECVD), hot-wire chemical vapor deposition (HWCVD), and photochemical vapor deposition (photo-CVD). − Dopants for acceptor impurities belong group III (B) and donor impurities belong group V (P) are extensively used to form p -type and n -type characters, respectively. Various doping sources for B include diborane (B 2 H 6 ), trimethylboron (B­(CH 3 ) 3 ), and boron trifluoride (BF 3 ), and sources for P include phosphane (PH 3 ) and phosphorus trichloride (PCl 3 ) . However, the most commonly used gaseous doping sources for B or P are explosive, highly hazardous, and difficult to store.…”