Ji-Hong Jhe

The characteristic carrier–Er interaction distance in Er-doped a-Si/SiO2 superlattices formed by ion sputtering

The characteristic interaction distance between Er3+ ions and carriers that excite them in Er-doped a-Si/SiO2 superlattices is investigated. Superlattice thin films consisting of 12 periods of a-Si/SiO2:Er/SiO2/SiO2:Er layers were deposited by ion sputtering and subsequent annealing at 950 °C. The dependence of the Er3+ photoluminescence intensity on the thickness of the Er-doped SiO2 layers is well-described by an exponentially decreasing Er-carrier interaction with a characteristic interaction distance of 0.5±0.1 nm.

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.

Er–carrier interaction and its effects on the Er3+ luminescence of erbium-doped Si/SiO2 superlattices

The Er–carrier interaction and its effects on the Er3+ photoluminescence properties of erbium-doped Si/SiO2 superlattices are investigated. The interaction between the erbium atoms and the electronic carriers was controlled by doping erbium into the SiO2 layers only and by depositing buffer layers of pure SiO2 between the erbium-doped SiO2 layers and the Si layers. We demonstrate that by controlling the erbium-carrier interaction, a three orders of the magnitude enhancement of the Er3+ luminescence intensity and a nearly complete suppression of the temperature-induced quenching of Er3+ luminescence can be achieved while still allowing the Er3+ ions to be excited by the carriers. We identify the asymmetry between the dominant carrier-mediated excitation and the de-excitation paths of Er3+ ions as the possible cause for the observed effects.

Si nanocluster sensitization of Er-doped silica for optical amplet using top-pumping visible LEDs

A review is presented of Si nanocluster sensitization of Er-doped silica for planar optical amplifiers using top-pumping 470-nm light-emitting diodes (LEDs). The motivation and basic physical principles underlying the nanocluster sensitization are first reviewed. The material structures necessary for optimum performances are presented, with emphasis on the need for nanoscale engineering of the composition and structure. Evidence of optical gain using commercial GaN-visible LEDs are presented, and the simulation results of possible device performances described. Finally, some possible future directions for research are discussed

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.

Er3+ photoluminescence properties of erbium-doped Si/SiO2 superlattices with subnanometer thin Si layers

The effect of the Si layer thickness on the Er3+ photoluminescence properties of the Er-doped Si/SiO2 superlattice is investigated. We find that the Er3+ luminescence intensity increases by over an order of magnitude as the Si layer thickness is reduced from 3.6 nm down to a monolayer of Si. Temperature dependence of the Er3+ luminescence intensity and time-resolved measurement of Er3+ luminescence intensity identify the increase in the excitation rate as the likely cause for such an increase, and underscore the importance of the Si/SiO2 interface in determining the Er3+ luminescence properties.

Controlling the quantum effects and erbium-carrier interaction using Si/SiO2 superlattices

The Er3+ luminescent properties of Er-doped Si/SiO2 superlattices are investigated. The superlattices were deposited either by electron cyclotron resonance plasma enhanced chemical vapor deposition or by ultra-high vacuum ion beam sputter deposition method and subsequently annealed at 950 degrees C. The thickness of the layers was varied 0.6 to 4.8 nm, and location of Er controlled within sub-nm. The structure and the composition of the films were confirmed using transmissions electron microscopy and medium energy ion spectroscopy. By carefully controlling the Si and SiO2 layer thickness and the locations of Er, we demonstrate several orders of magnitude enhancement of Er3+ luminescence and suppression of de-excitation mechanisms. We also demonstrate fabrication of waveguides using Er-doped Si/SiO2 superlattices, and discuss implications for possible applications.

Er3+ photoluminescence properties of erbium-doped Si/SiO2 superlattices with sub-nm thin Si layers

This work was supported in part by Advanced Photonics Project, the University Research Program supported by Ministry of Information and Communications in South Korea, the National Research Laboratory Program by the MOST of Korea, and the Brain Korea 21 Project.