Defects in hydrogenated microcrystalline silicon prepared by plasma-enhanced chemical vapour deposition

Defects in hydrogenated microcrystalline silicon (mu c-Si:H) prepared by plasma-enhanced chemical vapor deposition at 100 degrees C have been investigated as a function of crystalline volume fraction (X-c) from electron spin resonance (ESR) measurements. Magnetic centers responsible for ESR are suggested from g-value considerations to be dangling bonds on the surface of crystalline grains for X-c of less than 50% and positively charged single vacancies with positive correlation energy inside the crystalline grain for X-c of more than 50%. For the latter X-c range, it is suggested from correlation of these defects with photoluminescence (PL) and its light-induced effect and optically detected magnetic resonance that they are nonradiative centers. Further, the low-energy PL associated with the microcrystalline phase in mu c-Si:H is concluded to arise from radiative recombination between trapped electrons in the conduction-band tail and trapped holes in the valence-band tail arising from disordered potentials around the grain boundary.