Optical properties of Er and Er+Yb doped hydrogenated amorphous silicon films

Abstract

Hydrogenated amorphous silicon (a-Si:H) films were prepared by sputtering a Si target in an atmosphere of Ar+H2. The Er (and Er+Yb) doping of the films was achieved by partially covering the Si target with small pieces of Er (Er+Yb) metal. After deposition the films were annealed up to 700 °C in an inert atmosphere. Ion beam analyses, Raman spectroscopy, optical transmission and photoluminescence measurements were employed for characterization purposes. According to the experimental results, thermal treatments up to ∼300 °C do not significantly alter the composition, atomic structure or optical bandgap of the present a-Si:H films. On the contrary, the Er-related photoluminescence intensity at 1540 nm increases and reaches its maximum at about 400 °C. Treatments at temperatures higher than ∼400 °C reduce both the Er-related light emission and the optical bandgap of the films due to the out-diffusion of hydrogen atoms. Furthermore, the relatively small optical bandgap and the presence of tail states prevent any optical activity of Yb3+ ions in the measured a-Si:H films. At the present doping levels and sample characteristics, ytterbium only increases the incidence of non-radiative processes.

Red–green–blue light emission and energy transfer processes in amorphous SiN films doped with Sm and Tb

“…It is evident that thermal annealing treatments induced either the diffusion of light atomic species or some structural reordering (not necessarily crystallization) in the a-SiN films. Actually, it is well established that both atomic diffusion and structural reordering have great influence on the electronic states of amorphous semiconductors; the former passivating dangling or broken bonds, and the latter promoting atomic rearrangements [11,12]. As a result of these changes, a decrease in the density of deep and/or tail defects takes place (figure 2) and, as a consequence, a substantial suppression of the nonradiative processes is expected [11].…”

Effect of thermal annealing treatments on the optical properties of rare-earth-doped AlN films

“…The changes experienced by both E 04 and I PL are attributed to the decrease in tail-states present in the AlN samples. In the case of the E 04 optical bandgap the suppression of tail-states induces a reduction in defect-related absorption processes and are at the origin of the observed bandgap widening [14,15,30]. Likewise, the improvement in I PL occurs because of a decrease in the number of non-radiative transitions and/or in the probability of re-absorption or backtransfer processes [2].…”

Filmes semicondutores amorfos à base de Si.

“…A partir da realização deste estudo ficou estabelecido que, ainda que interessante, a matriz do aSi:H não é apropriada para a extração de radiação devida a íons Yb 3+ e/ou para investigar o processo de sensitização envolvendo os íons Er 3+ e Yb 3+ . Dentre vários fatores, isto deve-se ao caráter amorfo dos filmes e, principalmente, à coincidência entre os estados de cauda do a-Si:H e os níveis eletrônicos dos íons Yb 3+ [56,57]. (2000)].…”

“…Como diferencial deste trabalho, e a fim de verificar o fenômeno de sensitização, vale mencionar a investigação de filmes simultaneamente dopados com Er e Yb. Os principais resultados deste estudo foram objeto de uma publicação [57] − ver quadro a seguir, e estão resumidos nas Figuras 8 e 9. After deposition the films were annealed up to 700 °C in an inert atmosphere.…”