Thin film pc-Si by aluminium induced crystallization on metallic substrate

Abstract

Thin film polycrystalline silicon (pc-Si) on flexible metallic substrates is promising for low cost production of photovoltaic solar cells. One of the attractive methods to produce pc-Si solar cells consists in thickening a large-grained seed layer by epitaxy. In this work, the deposited seed layer is made by aluminium induced crystallization (AIC) of an amorphous silicon (a-Si) thin film on metallic substrates (Ni/Fe alloy) initially coated with a tantalum nitride (TaN) conductive diffusion barrier layer. Effect of the thermal budget on the AIC grown pc-Si seed layer was investigated in order to optimize the process (i.e. the quality of the pc-Si thin film). Structural and optical characterizations were carried out using optical microscopy, μ-Raman and Electron Backscatter Diffraction (EBSD). At optimal thermal annealing conditions, the continuous AIC grown pc-Si thin film showed an average grain size around 15 μm. The grains were preferably (001) oriented which is favorable for its epitaxial thickening. This work proves the feasibility of the AIC method to grow large grains pc-Si seed layer on TaN coated metal substrates. These results are, in terms of grains size, the finest obtained by AIC on metallic substrates.

Metal-induced layer exchange of group IV materials

“…Common to all metal species, the guideline for increasing grain size is to suppress nucleation, as with SPC without metal catalysts [116,117]. Lowering the growth temperature [118][119][120][121][122][123] or preparing an interlayer between semiconductor/metal are effective for this [124][125][126][127][128][129]. Thin film preparation also contributes to large grain growth because the thinner metal layer requires greater lattice diffusion of semiconductor atoms in addition to grain boundary diffusion, which delays nucleation [96].…”

Fabrication of Si(111) crystalline thin film on graphene by aluminum-induced crystallization

“…Using Al as the metal (AIC), this process is known to give a high quality Si film with a large grain size. 8 By combining this with transparent and flexible graphene, it can be highly beneficial for low cost production of Si photovoltaic cells 9,10 and photodetectors 11 as well as for the epitaxial growth of III-V nanowire devices on graphene. 12 The latter requires an (111)-orientation of the Si film, and the growth of vertical GaAs nanowires on a 10 nm thick crystallized Si(111) layer on SiO 2 has been demonstrated.…”