Electronic properties of silicon epitaxial layers deposited by ion-assisted deposition at low temperatures

Ion-assisted deposition enables epitaxial growth of high-quality Si films with high deposition rates at low growth temperatures. The present study investigates structural and electronic properties of monocrystalline Si epitaxial layers deposited at temperatures between 470 and 800 °C and deposition rates between 0.07 and 0.18 μm/min. The density of extended defects decreases with increasing deposition rate and saturates at values around 2×104 cm−2 for deposition rates above 0.16 μm/min. We apply methods of design of experiment to systematically investigate the influence of deposition parameters on the electronic properties of epitaxial layers. The majority carrier mobility in p- and n-type layers reaches values comparable to those in Czochralski Si and does not depend on deposition rate, deposition temperature, and sample pretreatment prior to epitaxy in the investigated parameter range. The minority carrier diffusion length strongly increases with rising deposition temperature and reaches about 22 μm in a 7 μm thick epitaxial layer deposited at 710 °C. Extended structural defects limit the minority carrier diffusion length at deposition temperatures below 500 °C, while point defects limit the minority carrier diffusion length at deposition temperatures between 540 and 800 °C.