Phosphorus ion implantation in silicon nanocrystals embedded in SiO2

Abstract

We have investigated phosphorus ion ͑P + ͒ implantation in Si nanocrystals ͑SiNCs͒ embedded in SiO 2 , in order to clarify the P donor doping effects for photoluminescence ͑PL͒ of SiNCs in wide P concentrations ranging in three orders. Some types of defects such as P b centers were found to remain significantly at the interfaces between SiNCs and the surrounding SiO 2 even by high-temperature ͑1000°C͒ annealing of all the samples. Hydrogen atom treatment ͑HAT͒ method can efficiently passivate remaining interface defects, leading to significant increase in the intensity of PL arising from the recombination of electron-hole pairs confined in SiNCs, in addition to significant decrease in interface defects with dangling bonds detected by electron spin resonance. From both the results of the P dose dependence before and after HAT, it is found that the amount of remaining defects is higher for samples with SiNCs damaged by implantation with relatively lower P + doses and then annealed, and that through HAT the observed PL intensity increases surely as the P concentration increases up to a critical concentration. Then it begins to decrease due to Auger nonradiative recombination above the critical concentration which depends on the size of SiNCs. These results suggest an effect of relatively low concentration of P atoms for the enhancement of PL intensity of SiNCs and we present an unconventional idea for explaining it.

Influence of surface chemistry on photoluminescence from deuterium-passivated silicon nanocrystals

“…9-11 Electron spin resonance measurements have shown that hydrogen annealing removes nonradiatve defects at the Si/ SiO 2 interface, which results in an increase in PL. 9, 10 Cho et al 12 showed that hydrogen passivated Si nanocrystals embedded in silicon nitride have enhanced charge retention characteristics as compared to unpassivated nanocrystals. This was attributed to reduction in charge loss pathways because of hydrogen passivation of the defects at the Si nanocrystal/silicon nitride interface.…”

Doping efficiency of phosphorus doped silicon nanocrystals embedded in a SiO2 matrix

“…8,9 Therefore, usually very high dopant concentrations are employed. 10,11 Up to now, the main processes used for phosphorus (P) doping of SiNCs in a SiO 2 matrix are the co-sputtering technique [10][11][12] which normally results in a continuous doping of the whole layer, or ion implantation [13][14][15] resulting in a non-uniform dopant depth profile. However, a selected doping of ultra thin layers (either the barrier or the SiNCs containing active layer) during the deposition process is not possible with these methods.…”

Anomalous B diffusion profiles in nanocrystalline Si

“…This is the reason why this type of process is currently widely used in solar cell production. However, despite its potential application for nanostructure doping such as nano-grains in nc-Si [1,2,4], nanowires [5] or nanocrystals [6,7], atomic transport in nanometric phases is still poorly known. In the case of nc-Si, it has been shown that atomic transport kinetics could be enhanced in nanograins and that triple junction diffusion is several orders of magnitude faster than grain boundary (GB) diffusion [8,9].…”