Hanka Przybylinska

On the local structure of optically active Er centers in Si

We report high resolution (<0.05 cm−1) photoluminescence (PL) spectra of erbium implanted float‐zone (FZ) and Czochralski grown (CZ) silicon. We show that the PL spectrum of cubic Er centers observed in CZ‐Si annealed at 900°C is the dominant emission in FZ‐Si for the same annealing conditions. We assign it to isolated, interstitial erbium. We observe also two other kinds of optically active Er centers with lower than cubic site symmetry: (i) O‐related (found only in CZ Si) and (ii) those related to radiation defects. We conclude that coimplantation with light elements does not lead to the formation of Er‐codopant complexes, but rather to Er forming complexes with implantation induced lattice defects.

Site selective excitation of Er-implanted GaN

The photoluminescence (PL), and PL excitation studies of Er-implanted GaN reveal a variety of Er centers with different excitation mechanisms. The PL of the centers dominating under above band-gap illumination is mediated primarily by donor-acceptor pair recombination, and subject to temperature quenching. Evidence is found for significant energy migration among Er centers dominating under direct excitation into the 4f-shell, which leads to a stronger quenching. The PL intensity of centers excited by a broad, below-gap absorption band, associated with deep traps is temperature independent.

Optimisation of Er centers in Si for reverse biased light emitting diodes

Abstract Depending on the doping and annealing conditions, as well as the oxygen content, erbium produces a big variety of different centres in silicon. These centres can be distinguished by their fine structure patterns seen both in luminescence and in excitation spectroscopy. Centres with a well-defined geometry of their constituents exhibit very sharp line spectra. Such centres can be excited via recombination of electron-hole pairs, produced in a forward biased diode, with surprisingly high quantum efficiency below 100 K — but they are strongly quenched at higher temperatures. Another type of spectrum — with a much higher line width (∼20 nm) and weak thermal quenching up to 370 K is obtained after annealing at temperatures above 950°C. This type of spectrum is identified as being due to Er in SiO 2− δ precipitates. Such centres have much smaller quantum efficiencies for forward bias excitation than for reverse bias. We discuss properties that are important for the realisation of LED structures based on this type of centres for room temperature (RT) operation.

Erbium in SiOx environment: ways to improve the 1.54 μm emission

Abstract The only way to obtain room temperature electroluminescence at 1.54xa0μm from Si diodes due to intra-atomic transitions of erbium is the excitation of SiO 2 xa0:xa0Er clusters by hot electron injected in a reverse biased diode. Impact excitation of erbium and thus electroluminescence can be achieved in tunnelling diodes, although at very small excitation volume, which would cover only a small fraction of a wave guide. Making use of an avalanche process allows one to increase the excitation volume considerably. This requires accurate control of doping gradients and thus knowledge of the electrical activity and the distribution of the implanted dopants. We present data from SIMS and Hall effect investigations, which demonstrate significant deviations from TRIM simulations of the implantation profiles and the hitherto assumed electrical activity of Er in such environment. We present optimum parameters for design and realisation of diodes working at room temperature.