Photoluminescence from SiO₂/Si/SiO₂structures

Abstract

Si layers were developed on pre-oxidized Si wafers by decomposition of silane in a low pressure chemical vapour deposition reactor. By keeping the deposition time constant (2 min) three sets of samples were fabricated at deposition temperatures equal to 580, 610 and 625 °C. The deposited Si layers were thinned by high temperature dry oxidation thus forming SiO2/Si/SiO2 structures. Room temperature photoluminescence (PL) measurements showed that for those samples in which the thickness of the remaining Si layer was greater than ∼ 6 nm, the spectra exhibited a peak at ∼ 650 nm. Prolonged oxidations led to the formation of SiO2/nanocrystalline-Si/SiO2 structures in which the thickness of the remaining nanocrystalline Si (nc-Si) layer was smaller than 3 nm. The PL spectra obtained from these structures were at least ten times stronger compared to the previous ones. The PL peak wavelength exhibited a weak dependence on the nc-Si layer thickness shifting from 800 to 720 nm for nc-Si thickness decreasing from ∼ 3 to ∼ 0.5 nm. In this publication we present our experimental findings, which indicate that the intensity of the 720–800 nm PL band is influenced by the deposition temperature of the initial Si layer and by the thickness of the oxide layer between the nc-Si layer and the Si substrate.