Si quantum dots in silicon nitride: Quantum confinement and defects

Abstract

Luminescence of amorphous Si quantum dots (Si QDs) in a hydrogenated silicon nitride (SiNx:H) matrix was examined over a broad range of stoichiometries from Si3N2.08 to Si3N4.14, to optimize light emission. Plasma-enhanced chemical vapor deposition was used to deposit hydrogenated SiNx films with excess Si on Si (001) substrates, with stoichiometry controlled by variation of the gas flow rates of SiH4 and NH3 gases. The compositional and optical properties were analyzed by Rutherford backscattering spectroscopy, elastic recoil detection, spectroscopic ellipsometry, photoluminescence (PL), time-resolved PL, and energy-filtered transmission electron microscopy. Ultraviolet-laser-excited PL spectra show multiple emission bands from 400 nm (3.1 eV) to 850 nm (1.45 eV) for different Si3Nx compositions. There is a red-shift of the measured peaks from ∼2.3 eV to ∼1.45 eV as Si content increases, which provides evidence for quantum confinement. Higher N content samples show additional peaks in their PL spectra at higher energies, which we attribute to defects. We observed three different ranges of composition where Tauc band gaps, PL, and PL lifetimes change systematically. There is an interesting interplay of defect luminescence and, possibly, small Si QD luminescence observed in the intermediate range of compositions (∼Si3N3.15) in which the maximum of light emission is observed.

Room-temperature single-photon emitters in silicon nitride

“…The origin of luminescence in SiN systems has been extensively studied in the past for their applications in Si-based optoelectronic devices. PL emission from SiN films in the visible range has been previously attributed to both the quantum confinement effect of carriers inside Si QDs embedded in the SiN and radiative defect–related states in SiN or at Si-QD/SiN interface structures ( 40 , 41 ). PL peaks exhibiting spectral shifts with annealing temperature and SiN composition were typically associated with the Si QDs.…”

Systematic Study of the SiOx Film with Different Stoichiometry by Plasma-Enhanced Atomic Layer Deposition and Its Application in SiOx/SiO2 Super-Lattice

“…A large number of studies have been reported on Si-NCs embedded in silicon dioxide (SiO 2 ) [12,13,14]. Based on the quantum confinement theory [15,16,17], the correlation between the photoluminescence (PL) properties and the size of the nanocrystals has been established. Control over all three parameters (size, density, spherical shape) can be reached by depositing thin alternating layers of stoichiometric and Si rich dielectrics in the form of a superlattice (SL).…”

A Review: Preparation, Performance, and Applications of Silicon Oxynitride Film

“…Therefore, it is of great significance to study the luminescence characteristics of SiN x O y film. Some reported results showed that the luminescence mechanism of SiN x O y film is generally divided into three types: defect-state radiation composite luminescence [46], band-tail (BT) radiation composite luminescence [47] and quantum dot radiation composite luminescence [48].…”