Solid phase epitaxial thickening of boron and phosphorus doped polycrystalline silicon thin films formed by aluminium induced crystallization technique on glass substrate

Abstract

Aluminium induced crystallization (AIC) technique can be used to form the high-quality and large-grained polycrystalline silicon (poly-Si) thin films, which are with the thickness of ~200nm and used as a seed layer, on silicon nitride coated glass substrate. Thanks to aluminium metal in AIC process, the natural doping of AIC thin films is p + type (~2×10 18 cm -3 ). On the other hand, recombination of carriers can be controlled by partial doping through the defects that may have advantages to improve the thin film quality by the overdoping induced passivation. In this study, boron (B) and phosphorus (P) doped AIC seed layers were thicken to ~2μm by solid phase epitaxy (SPE) technique at 800°C for 3 hours under nitrogen flow in a tube furnace. During the crystallization annealing, exodiffusion of dopants was formed through the SPE film from the AIC seed layer. Optical microscope and electron back scattering diffraction technique (EBSD) were used to analyse the structural quality of the Si films. The poly-Si layer with an average grain size value of ~32µm was formed by AIC+SPE technique for P doped samples while EBSD analysis gave no results for B doped samples due to the quite deterioration on the surface of the films. AIC+SPE films were analysed in terms of structural properties by using micro-Raman Spectroscopy and X-ray diffraction systems. The results showed that the crystallinity of compressive stress formed AIC+SPE films reached up to 98.55%. Additionally, the Raman analysis pointed out that no temperature-induced stress were generated in the AIC+SPE films while compressive stress was induced by increasing the annealing duration for doped AIC film. For all samples, the preferred orientation was <100>, and the crystallite size up to 44.4nm was formed by phosphorus doping of AIC films. The doping efficiency was determined by time-of-flight secondary ion mass spectroscopy for doped samples. A graded n + n doping profile was obtained by exo-diffusion of phosphorus from the overdoped seed layer during the epitaxial thickening while boron doping of SPE film has failed with exo-diffusion of boron from AIC seed layer into SPE film. Finally, high-quality n + n type poly-Si films were fabricated on glass substrate by using AIC+SPE technique.

Metal-induced layer exchange of group IV materials

“…The seed layer approach, that is, the epitaxial growth of Si on large-grained p-type Si formed by Al-induced LE, has been studied (figure 10(a)) [162,172,173]. In line with this, epitaxial thickening of Si on the seed layer has been performed in various techniques, such as ion-assisted deposition [174,175], CVD [176][177][178][179][180][181] and solid-phase epitaxy [182][183][184]. However, the conversion efficiency remains low (8.5%) compared with other Si thin-film solar cell technologies (figure 10(b)) [171].…”

An updated review on boron removal from water through adsorption processes

“…The safe range for B intake in human falls in the range 1 to 13 mg/ day, which is mostly covered by a proper diet including nuts, dry fruits, and wine. Boron is also a very significant component in various industries including glass, semiconductors, cosmetics, nuclear reactors, and radiation treatment [13,14].…”

Boron Adsorption Using NMDG-Modified Polypropylene Melt-Blown Fibers Induced by Ultraviolet Grafting

“…Dietary boron has an important role in embryonic development, bone metabolism, and immunological development in cattle and poultry breeding [ 1 , 2 ], and boron is a unique essential element of higher plants, among others. Boron is in high demand in industry, where it is used in glass, semiconductors, cosmetics, nuclear reactors, and radiation therapy [ 3 , 4 ]. China is a large industrial user of boron, importing large amounts of it every year due to limited mineral deposits and manufacturing capacity.…”

“…The borate anion group can bind with molecules having cis-ortho and inter-hydroxyl functional groups, resulting in a family of materials with boron affinity. Because boric acid and borate exist as B(OH) 4 − in aqueous solutions, they may form stable chelation with neighboring hydroxyl groups [14].…”