Crystallographic Control in Thin-Layer Silicon Depositions by Atmospheric-Pressure Iodine Vapor Transport

Silicon thin layers that are either highly textured polycrystalline, randomly oriented polycrystalline, or epitaxial have been deposited by the technique of atmospheric-pressure iodine vapor transport on silicon or non-silicon substrates. Strongly [1 1 0]-textured polycrystalline silicon films are obtained by starting with a relatively low starting substrate temperature of 700°C, to increase nucleation density, then ramping up to 900°C at the end to increase growth rate. Alternatively, if a higher constant temperature of 900°C is used, we obtain polycrystalline silicon layers with randomly oriented large grains of ∼ 20μm in average size. When a still higher initial substrate temperature of 1000°C is used to eliminate condensation of silicon iodides at the interface, high-quality epitaxial silicon layers are grown on silicon substrates.