Influence of doping on the optical properties of silicon nanocrystals embedded in SiO₂

Abstract

Co‐implantation, with overlapping implantation projected ranges, of Si and doping species (P, As, B) followed by a thermal annealing step is a viable route to form doped Si nanocrystals (NCs) embedded in SiO2. This presentation deals with optical characterizations of both doped and undoped Si‐NC prepared by this method. The NC effective presence in the oxide layer and their crystallinity is verified by Raman spectrometry. Photoluminescence (PL) and PL excitation measurements reveal quantum confinement effects and a gradual PL quenching with increasing dopant concentrations. The measured Stokes shift remains constant and its value ∼ 0.2 eV is almost twice the Si–O vibration energy. This suggests that a possible radiative recombination path is a fundamental transition assisted by a local phonon. Lifetime investigations show that PL time‐decays follow a stretched exponential. Atomic probe tomography analyses demonstrate that n‐type dopants (P, As) are efficiently introduced in the NC core, whereas p‐type dopant (B) are located at the NC/SiO2 interface. All together these experimental observations question on possible different carrier recombination paths in P or As doped NC compared to B one's. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Doped and codoped silicon nanocrystals: The role of surfaces and interfaces

“…Combining the results obtained by APT, Raman, PL and PLE analysis, the authors concluded that P impurities tend to be efficiently incorporated in the Si-NC core whereas B atoms are mainly localized at the Si-NC/SiO 2 interface (see Fig. 14, top left panel) [213,214,215].…”

“…Indeed it has been demonstrated that ion beam synthesis, which is a well known approach to grow undoped Si-NCs embedded in SiO 2 , is also an efficient technique to grow doped Si-NCs with diameters of few nanometers, if the dopants are co-implanted with Si [213,214,215]. Combining the results obtained by APT, Raman, PL and PLE analysis, the authors concluded that P impurities tend to be efficiently incorporated in the Si-NC core whereas B atoms are mainly localized at the Si-NC/SiO 2 interface (see Fig.…”