Photo- and electroluminescence of oxide-nitride-oxide-silicon structures for silicon-based optoelectronics

Abstract

Oxide-nitride-oxide-silicon (SiO2/SiN0.9/SiO2/Si) structures have been fabricated by chemical vapor deposition. The elemental composition and light emission properties of “SiO2/SiN0.9/SiO2/Si” structures have been studied using Rutherford backscattering spectroscopy (RBS), photo- and electroluminescence (Pl, El). The RBS measurements has shown the presence of an intermediate silicon oxynitride layers at the SiO2–SiN0.9 interfaces.It has been shown that the photoluminescence of the SiO2/SiN0.9/SiO2/Si structure is due to the emission of a SiN0.9 layer, and the electroluminescence is attributed to the emission of silicon oxide and oxynitride layers. A broad intense band with a maximum at 1.9 eV dominates the Pl spectrum. This band attributed to the radiative recombination of excited carriers between the band tail states of the SiN0.9 layer. The origin of the less intense Pl band at 2.8 eV is associated with the presence  of nitrogen defects in the silicon nitride.El was excited in the electrolyte-dielectric-semiconductor system. The electric field strength in the SiO2 layers reached 7–8 MV/cm and exceeded this parameter in nitride layer nearly four times. The electrons accelerating in electric field of 7–8 MV/cm could heat up to energies more than 5 eV. It is sufficient for the excitation of luminescence centres in the silicon oxide and oxynitride layers. The SiO2/SiN0.9/SiO2/Si composition El bands with quantum energies of 1.9 and 2.3 eV are related to the presence of silanol groups (Si–OH) and three-coordinated silicon atoms (≡Si•) in the silicon oxide layers. The El band with an energy of 2.7 eV is attributed to the radiative relaxation of silylene (O2=Si:) centers in the silicon oxynitride regions. It is observed the least reduction of this band intensity under the influence of strong electric fields after a charge flow  of 1–3 C/cm2.