Nanostructured si-alloys for silicon solar cells

amorphous SiO2 phase after annealing), the SiC revealed several drawbacks that limit the usability of the SiC/SiOx HSL as a Si-QD absorber: (i) The Si-QDs extended into adjacent SiC layers especially with smaller SiOx sublayer thickness or higher silicon excess, which suggests that SiC is an insucient Si diusion barrier. (ii) The hydrogen release from SiC sublayers gave rise to the decrease of the optical band gap, the increase of the defect density and the increase of the sub-band gap absorption in HSL. (iii) The defects in the carbide layers seem to open non-radiative recombination paths for carriers generated in Si-QDs. (iv) The annealing-induced doping character of SiC is expected to increase recombination in these layers during carrier transport. The systematic analysis of HSL and single layers of SiC and SiOx annealed at various temperatures and passivated by various techniques using a number of characterization methods yielded a consistent picture of the fundamental dierences between SiC and SiOx. The hydrogen eusion mechanisms during annealing and the hydrogen reincorporation mechanisms during passivation in HSL are well understood. The stronger increase of spin density upon annealing in SiC as compared to SiOx is ascribed to the eusion of a higher amount of hydrogen and the less ecient atomic diusion. The much lower optical band gap and the significantly higher sub-band gap absorption of SiC in the annealed state as compared to SiOx can be traced back to the lower exibility of its relatively dense 4-fold coordinated atomic structure. The less ecient stress relaxation in SiC increases the probability of creating strained bonds that additionally contributes to the sub-band gap absorption.