Blue-violet photoluminescence from amorphous Si-in-SiN_x thin films with external quantum efficiency in percentages

摘要

Bright blue-violet photoluminescence centered at 428 nm was obtained in amorphous Si-in-SiN_x thin films prepared in a cyclic growth mode on cool substrates by plasma-enhanced chemical vapor deposition, in which the typical size of the silicon particles has been brought down to ～1.80 nm and the number density amounts to 1.07 x 10~(13) cm~2. A maximum external quantum efficiency over 3.0% was measured in the as-deposited samples. Time-resolved photoluminescence spectra revealed decay times within nanosecond even at room temperature, disclosing a fast recombination dynamics in this amorphous system. The excellent efficiency can be attributed to a better passivation of the silicon particles—hence, the conventional rapid thermal annealing has a negligible effect on the photoluminescence intensity—and also to an improved transparency of the film by cyclic growth. The high-efficiency, tunable wavelength and nanosecond decay time at room temperature, achieved via a low-temperature process without invoking any posttreatment, combine to make the Si-in-SiN_x system a promising candidate for light-emitting nanostructures in photonic and optoelectronic applications.