Moon-Seung Yang

Effect of nitride passivation on the visible photoluminescence from Si-nanocrystals

The effect of nitride passivation on the visible photoluminescence from nanocrystal Si (nc-Si) is investigated. Silicon-rich silicon nitride (SRSN) and silicon-rich silicon oxide (SRSO), which consist of nc-Si embedded in silicon nitride and silicon oxide, respectively, were prepared by reactive ultrahigh vacuum ion beam sputter deposition followed by a high temperature anneal. Both SRSN and SRSO display photoluminescence peaks after high temperature annealing, coincident with the formation of Si nanocrystals, and similar changes in the peak luminescence position with the excess Si content. However, the luminescence peak positions from SRSN are blueshifted by about 0.6 eV over that of comparable SRSO such that its luminescence peaks in the visible range. The results demonstrate that control of the surface passivation is critical in controlling the nc-Si luminescence, and indicate the possibility of using nitride-passivated nc-Si for visible luminescence applications including white luminescence.

Effects of silicon nanostructure evolution on Er3+ luminescence in silicon-rich silicon oxide/Er-doped silica multilayers

The effect of silicon nanostructure evolution on Er3+ luminescence is investigated by using multilayers of 2.5nm thin SiOx (x<2) and 10nm thin Er-doped silica (SiO2:Er). By separating excess Si and Er atoms into separate, nanometer-thin layers, the effect of silicon nanostructure evolution on np-Si sensitized Er3+ luminescence could be investigated while keeping the microscopic Er3+ environment the same. The authors find that while the presence of np-Si is necessary for efficient sensitization, the overall quality of np-Si layer has little effect on the Er3+ luminescence. On the other hand, intrusion of np-Si into Er-doped silica layers leads to deactivation of np-Si∕Er3+ interaction, suggesting that there is a limit to excess Si and Er contents that can be used.

Development and Application of Er-Doped Silicon-Rich Silicon Nitrides and Er Silicates for On-Chip Light Sources

On-chip light sources are a critical part for an integrated Si photonic technology, yet they lag other photonic components in their level of development. In this chapter, Er used as an optical dopant and utilizing its intra-4f transition at 1.54µm will be introduced as a viable means for on-chip light generation that has the advantage of being compatible with long-distance telecom as well. First, a general introduction to the topic of developing a Si-based/compatible light source will be presented, with emphasis on the need for a novel high-index material for Er-doping that can provide both a higher Er content and refractive index than has been reported so far. Second, Er-doped silicon-rich silicon nitride (SRSN) and Er silicates will be introduced as a promising host material for compact on-chip light sources. Finally, results of fabricating basic photonic components using Er-doped SRSN and Er-silicates will be presented.

ErxY2-xSiO5 nanocrystal and thin film for high gain per length material

We report on fabricating ErxY2-xSiO5 nanocrystals using ErCl3•6H2O and YCl3•6H2O solutions and Si nanowires grown by VSL method. Use of crystalline host allows incorporation of up to 25 at % Er without clustering and loss of optical activity, and use of Y enables continuous mixing of Er and Y for controlling cooperative upconversion. We obtain a cooperative upconversion coefficients of (2.2±1.1)×10-18 cm3/s and (5.4±2.7)×10-18 cm3/s at an Er concentration of 1.2×1021 cm-3 and 2.0×1021 cm-3, respectively. These values are up to 10 times lower at 10 times higher Er concentration than those reported for Er-doped silica, and shows that up to 69 dB/cm gain could be achieved for ultra-compact optical amplification. Also, we report on the deposition of ErxY2-xSiO5 thin film on Si substrate using ion beam sputter deposition. Rapid thermal annealing at 1100°C is enough to form crystal phase the film and activate most of Er3+ ions.

Suppression of Er optical de-activation using silicon-rich silicon nitride

The effect of nitride passivation on the Si nanocluster -Er coupling and Er optical activity is investigated. Based on a comparison with Er doped Si-rich Si oxide (SRSO), breaking of nc-Si/Er coupling and Er de-activation in Si-rich Si nitride (SRSN) are strongly reduced.

Effect of nitride passivation on the Si nanocluster-Er coupling and Er optical activity

We have investigated the Er3+ photoluminescence (PL) properties from Er doped Si-rich Si nitride (SRSN) films. Based on a comparison with Er doped Si-rich Si oxide (SRSO) films, breaking of nc-Si / Er coupling and Er deactivation in Er doped SRSN film are strongly reduced. We suggest that SRSN can be an effective alternative to SRSO for obtaining efficient Er activity.

Sensitization of Er by Si-nanoclusters in Erbium doped Si-rich Si nitride films

Er3+ luminescent properties from Erbium doped Si-rich Si nitride (SRSN) films were investigated through photoluminescence (PL) and photoluminescence excitation spectroscopy (PLE). These films grown by ultra-high vacuum ion beam sputtering are annealed at high temperature in order to form the Si-nanoclusters (nc-Si). We find that nc-Si can act as efficient sensitizers for Er3+, displaying the strong energy transfer form nc-Si to Er ions. Er3+ luminescence lifetimes were in the 1-3 msec range at room temperature with complete suppression of temperature quenching of Er3+ intensity, indicating high luminescence efficiency as well. The PLE spectrum in film with nc-Si shows efficient Er3+ PL intensity, compared with that of pure nitride. These results imply that Er doped SRSN is a promising alternative for compact, high-efficiency Si based light sources.