HYDROGEN-INDUCED PLATELETS IN DISORDERED SILICON

It is demonstrated that hydrogen passivation of polycrystalline silico n(poly-Si) causes the formation of hydrogen stabilized platelets. Thes e extended defects appear within 1000 Angstrom of the sample surface a nd are predominantly oriented along (111) crystallographic planes. Nom inally undoped and phosphorous doped poly-Si ([P]=10(17) cm(-3)) show platelet concentrations of approximate to 5x10(15) cm(-3) and 1.5x10(1 6) cm(-3), respectively. An estimate of the number of H atoms accommod ated in platelets by forming Si-H bonds is consistent with the hydroge n concentration in the surface layer measured by SIMS. Platelets were not observed in the grain boundary regions. This is due to two effects : (I) The presence of a depletion layer at grain boundaries causing hy drogen to migrate in the positive charge state which is unfavorable fo r the platelet formation; (ii) Platelet nucleation is surpressed due t o the presence of a high concentration of hydrogen trapping sites at g rain boundaries. Copyright (C) 1996 Published by Elsevier Science Ltd