Crystalline silicon on glass by steady-state solution growth using indium as solvent

Abstract

In order to grow crystalline silicon on glass at low temperatures for photovoltaic applications, a two-step process has been developed. In the first step, amorphous Si films are crystallized at temperatures around 300 °C by metal-induced crystallization, whereby liquid indium serves as a solvent for silicon. Due to the difference of chemical potentials between the amorphous and the crystalline state, an in-plane movement of the liquid metal droplets on the formerly amorphous Si film is accompanied by precipitation of crystalline Si along the droplets’ traces, a process we call amorphous–liquid–crystalline (ALC) transition. In the second step, the ALC seed layers serve as templates for the growth of crystalline silicon by steady-state solution growth. In contrast to common liquid-phase epitaxy, the supersaturation in front of the seed layer is established by a stationary temperature difference between a silicon source and the substrate. Si crystallites in the range of 20–50 µm with low impurity concentrations are grown by this technique. Essential features of steady-state solution growth are compatible with the float glass process in large-scale industrial glass production, which raises hopes for a successive production of glass and thin Si films for solar cells in a continuous production line.