Hydrogen Passivation Kinetics of Si Nanocrystals in SiO₂

Hydrogen passivation of non-radiative defects increases the luminescence intensity from silicon nanocrystals. In this study, photoluminescence (PL) and time-resolved PL were used to investigate the chemical kinetics of the hydrogen passivation process. Isochronal and isothermal annealing sequences were used to determine the reaction kinetics for the absorption and desorption of hydrogen, using the generalised consistent simple thermal (GST) model proposed by Stesmans for P_b defects at planar Si/SiO₂ interfaces. This included determination of the activation energies and rate constants for the forward and reverse reactions as well as the associated spread in activation energies. The reaction kinetics determined from such measurements were found to be in excellent agreement with those for the passivation of Pb defects at planar Si/SiO₂ interfaces, suggesting the nanocrystal emission process is also limited by such defects. These results provide useful model data as well as insight into the processing conditions needed to achieve optimum passivation in H₂. As an extension to the work, a preliminary study into passivation by atomic hydrogen was pursued via a post-metallization Al anneal (alneal). A considerable gain in luminescence efficiency was achieved over the previously optimised passivation in H ₂.