Optical properties of p-i-n structures based on amorphous hydrogenated silicon with silicon nanocrystals formed via nanosecond laser annealing

摘要

Silicon nanocrystals are formed in the i layers of p-i-n structures based on a-Si:H using pulsed laser annealing. An excimer XeCl laser with a wavelength of 308 nm and a pulse duration of 15 ns is used. The laser fluence is varied from 100 (below the melting threshold) to 250 mJ/cm(2) (above the threshold). The nanocrystal sizes are estimated by analyzing Raman spectra using the phonon confinement model. The average is from 2.5 to 3.5 nm, depending on the laser-annealing parameters. Current-voltage measurements show that the fabricated p-i-n structures possess diode characteristics. An electroluminescence signal in the infrared (IR) range is detected for the p-i-n structures with Si nanocrystals; the peak position (0.9-1 eV) varies with the laser-annealing parameters. Radiative transitions are presumably related to the nanocrystal-amorphous-matrix interface states. The proposed approach can be used to produce light-emitting diodes on non-refractory substrates.