Self-assembled nc-Si/a-SiNx: H quantum dots thin films: An alternative solid-state light emitting material

Nanocrystalline silicon quantum dots (QDs) of varying size from ~5.4 to 2.2 nm embedded in amorphous silicon-nitride matrix (nc-Si-QDs/a-SiNx:H) were prepared via ICP-CVD (13.56 MHz), using a mixture of silane (SiH4), ammonia (NH3) gases in H2-diluted plasma, by changing the low deposition pressure in a narrow range, 10-50 mTorr at low substrate temperature (250 °C). Strong visible photoluminescence (PL) tunable over a significantly wide range (1.67-3.02 eV) has been observed. The origin of the PL is mostly attributed to band-to-band recombination due to the quantum confinement effect (QCE) in the nanocrystalline silicon QDs. A large amount of atomic hydrogen flux that originates due to the high degree dissociation of the gas molecules in high-density inductively coupled plasma (ICP) passivates well the nonradiative dangling bonds and helps in growing plenty of ultra-nanocrystallites that demonstrate intense visible photoluminescence. The red-shift of Raman peak and the corresponding line broadening have been associated to the confinement of optical phonons within the nc-Si QDs. The widening of band gap and tune-ability of visible photoluminescence over a notably wide range along with significantly high electrical conductivity of the material demonstrates enormous promise for its utilization in the fabrication of effective solid-state light emitting devices.