Origin of preferential grain orientation in excimer laser-induced crystallization of silicon thin films

Abstract

The origin of the formation of {100} and {111} grain textures in polycrystalline silicon thin films prepared with multiple excimer laser shots at the super-lateral-growth crystallization regime is investigated in this study. Our results demonstrate that the type of texture formed is determined solely by the thickness of the silicon layer. At a critical value of 40 nm, a transition from {100} to {111} texture is observed with increasing layer thickness. It is therefore proposed that below this critical value, the texture formation is governed by surface energy anisotropy whereas above it, the kinetics of the solidification process predominate.

Photoluminescence study of polycrystalline silicon thin films prepared by liquid and solid phase crystallization

“…On the other hand, a too high fluence leads to complete melting of the seed layer which also suppresses the formation of preferential grain orientation. However, applying a laser fluence well adjusted to the films thickness SLG and a preferred texture is observable . Epitaxially thickened, these seed layers lead to the best results in V OC as well as in the former mentioned PL ratio.…”

“…However, conventionally solid phase crystallized silicon thin films are limited electronically by a high density of defects so the open circuit voltage ( V OC ) of the so far best cells based on this material still not exceed a 500 mV limit . A recently published and here investigated method of creating poly‐Si thin films was the seed layer approach in which poly‐Si seed layers were formed using pulsed laser beam crystallization (pLBC) and subsequent epitaxial thickening, leading to comparable grain sizes as the SPC approach. The integration of laser crystallized seed layers, however, offers the advantage of a preferential grain orientation when the laser fluence is well chosen (super lateral growth (SLG) regime ).…”

“…A recently published and here investigated method of creating poly‐Si thin films was the seed layer approach in which poly‐Si seed layers were formed using pulsed laser beam crystallization (pLBC) and subsequent epitaxial thickening, leading to comparable grain sizes as the SPC approach. The integration of laser crystallized seed layers, however, offers the advantage of a preferential grain orientation when the laser fluence is well chosen (super lateral growth (SLG) regime ). This preferred texture leads to a smaller distribution of growth angles and, hence, low‐angle grain boundaries which possess a lower concentration of localized defect states .…”

Laser processing for thin film crystalline silicon solar cells

“…For thin silicon film in particular laser beam was extensively used to produce polycrystalline silicon by crystallization of an amorphous silicon layer deposited on glass or metal foil. Most of the reported work on laser induced crystallization uses excimer laser beams [8][9][10] . However, such process results in very small grains 11 (<1µm) which might be appropriate for thin film transistors by not for solar cells as the density of grains boundaries is limiting the efficiency [12][13][14] .…”

Remarkable Improvement in Foldability of Poly‐Si Thin‐Film Transistor on Polyimide Substrate Using Blue Laser Crystallization of Amorphous Si and Comparison with Conventional Poly‐Si Thin‐Film Transistor Used for Foldable Displays

“…The crystallization of amorphous silicon (a‐Si) on glass substrate can be possible by using solid phase crystallization (SPC), metal‐induced crystallization (MIC), ELA, and continuous wave (CW) laser annealing. Because of no intradefects in the grains, the ELA poly‐Si is widely used for the manufacturing of AMOLED and active‐matrix liquid crystal display (AMLCD) .…”