Aluminum-induced iso-epitaxy of silicon for low-temperature fabrication of centimeter-large p+n junctions

Aluminum-induced crystallization of Si is achieved on crystalline Si substrates in a manner that produces near-ideal p⁺n diodes for centimeter large sizes. A layer-stack of physical-vapor-deposited materials, amorphous Si on aluminum, is inverted at an anneal temperature of 400 °C to form a monocrystalline p-doped Si layer by solid-phase epitaxy (SPE). The stages of the crystallization process are been reviewed here and studied with respect to the filling of the large-area SPE Si layers. It is shown that a complete isoepitaxy coverage of large areas is possible if the starting c-Si substrate is free of nucleation centers. This can be achieved by appropriate wet-etching of the oxide to the Si followed by diluted HF dip-etching and Marangoni drying before deposition of the Al mediator layer and α-Si layer. Near-ideal p⁺n diodes have been fabricated at 400 °C with areas up to 1 × 1 cm², having ideality factors down to 1.02 and low leakage currents of a few nA/cm². From temperature-dependent measurements it can be concluded that the dominant origin of the leakage current is from ideal diffusion over the depletion regions and not from defectrelated generation-recombination currents. The full coverage by p⁺ SPE-Si is confirmed by material analysis.