Solid State Phenomena Vols. 108-109

Abstract: Electroluminescence of B and P implanted samples has been studied. P implantation is found to have a similar effect on light emission as B implant. The band-to-band (BB) luminescence of P implanted diodes is observed to increase by more than one order of magnitude upon rising the temperature and an internal efficiency of 2 % has been reached at 300 K. An efficiency larger than 5% seems to be reachable. The strong BB line emission at 1.1 &m is attributed to high bulk SRH lifetime. The BB line escapes from the substrate below the p-n junction. It is not due to the implantation-related defects/dislocations. The luminescence spectrum can be tailored to achieve dominance of the dislocation-related D1 line at about 1.5 &m. It is observed that a regular periodic dislocation network, formed by Si wafer direct bonding with a specific misorientation, exhibits even at 300 K only D1 photoluminescence. Such a dislocation network is believed to be a serious candidate to gain an efficient Si-based light emitter.

Abstract: Using ion implantation different rare earth luminescent centers (Gd3+, Tb3+, Eu3+, Ce3+, Tm3+, Er3+) were formed in the silicon dioxide layer of a purpose-designed Metal Oxide Silicon (MOS) capacitor with advanced electrical performance, further called a MOS-light emitting device (MOSLED). Efficient electroluminescence was obtained for the wavelength range from UV to infrared with a transparent top electrode made of indium-tin oxide. Top values of the efficiency of 0.3 % corresponding to external quantum efficiencies distinctly above the percent range were reached. The electrical properties of these devices such as current-voltage and charge trapping characteristics, were also evaluated. Finally, application aspects to the field of biosensing will be shown.

Abstract: Light-emitting diodes (LEDs) based on single crystal SiGe with the Ge content of 5.2% were fabricated using a planar technology. Their electroluminescence (EL) parameters were studied over a wide range of measured currents (up to 11 A) and temperatures (80 - 300) K. The integrated EL intensity at a fixed current increased approximately two times with temperature increasing from 80 to 200 K and changed insignificantly in the temperature range of 200 – 300 K. The analysis of the EL spectra shows that the recombination involving excitons is the dominant mechanism of radiative recombination at both no-phonon and phonon-assisted transitions in SiGe LEDs not only at low temperature but at room temperature, too. The linear dependence of the integrated EL intensity on the current and the exponential decay of the integrated EL intensity confirm this conclusion. The room temperature internal quantum efficiency of EL in the region of band-to-band transitions is estimated to be 0.5%. A sublinear current dependence of the integrated EL intensity and a fast decay of the integrated EL intensity after the diode turn-off were observed at room temperature and currents > 2.5 A. The effect is associated with the appearance of an additional (Auger) mechanism of non-radiative recombination parallel to Shockley-Read-Hall recombination.

Abstract: The samples of p- and n-doped Fz Si were deformed in 3-point bending mode in the temperature range 800-950°C. The fine structure of dislocation related luminescence in the region of D1 and D2 bands was most pronounced at lowest rate of deformation. The temperature variation of intensity of individual lines did not reveal any thermalization effects. It implies that centers responsible for different individual lines are situated in diverse places. The most narrow lines with maximum positions of 802 meV and 807 meV (D1 band) and 869 meV and 873 meV (D2 band) are rapidly quenched with increase in temperature, while the broader background lines survive at higher temperature. The new line with maximum position at about 882 meV appears in the D2 band with enhanced carbon doping. It was found that at higher P-doping the low energy fine structure lines 802 meV and 869 meV are absent. Besides, the Fz samples with different P doping level from 6×1014 cm-3 to 1.2×1016 cm-3 demonstrate quite a different temperature variation of broad background lines. At lowest level of P-doping they move to low energy side at temperature above 30K, while at P-doping above 1015 cm-3 these lines move to higher energy in the same temperature range. A possible explanation of this observation can be related to distribution of electrons in the cband. It implies that the corresponding electronic transitions occur between the edge of conduction band and deep states.

Abstract: The samples of Cz Si were subjected to multi-step annealing at different temperatures. After high temperature consequent steps the dislocation related spectra (DRL) were detected from the samples. The main feature of the DRL spectra was the very narrow low energy bands D1/D2, which are unusual for Cz Si. TEM analysis shown that the only candidates for DRL spectra are dislocation loops, punched out from precipitates. To explain the absence of influence of oxygen it was assumed that the distribution of interstitial oxygen is nonuniform in such samples and has some depletion regions in the vicinity of precipitates.

Abstract: Structural defects in Si:Er layers grown by molecular beam epitaxy have been studied by transmission electron microscopy. Two kinds of second phase precipitates are the main defects in the layers with Er concentration ≥ 2х1019 cm-3: ball-shaped precipitates (4-25 nm) of metallic Er localized at the layer-substrate interface and platelet precipitates of ErSi2 extending through the whole layer. We studied the effect of Er concentration (8х1018 - 4х1019 cm-3) and growth temperature (400 - 700°C) on the defect generation. The peculiarities of defect generation in MBE Si:Er layers implanted with B+ ions were also studied.

Abstract: There now a large variety of methods exists for the elaboration of nanoobjects and nanodevices. At the same time the reduction in size together with the improvement of theoretical techniques and computational power should allow efficient quantitative simulation of these objects. Such predictive simulation is highly needed since it can serve as a useful guide to build new nanostructures with the desired properties. The aim of this talk is than to give an overview of what has already been achieved in this rapidly evolving field, what can be done at present and what is expected for the future. The focus will be mostly on semiconductor nanostructures and especially silicon.

Abstract: Due to a number of advances in molecular biology, cell and tissue culture in combination with more sensitive methods to transduce biological signals, it has become increasingly feasible to detect unknown toxicity or pharmacological effects by using biological systems which are electrically coupled to micro- or nanoelectrodes or field-effect transistors (FETs). The coupling of biomolecules with electronic devices is demonstrated. In order to identify the contributions of the various cell signals we have investigated the coupling of cardiac myocytes with FETs. On the other side such systems can also be used to study the very basics of distributed information processing by interfacing cultured neuronal networks with microelectronic devices.

Abstract: Strain adjustment is obtained by virtual substrates which are composed of a silicon substrate and a strain relaxed buffer. The basics of strain relaxation are explained and applied to the covalent bonded Si/Ge system which shows a large regime of metastability. A solution to ultrathin strain relaxed buffers is given by the injection of point defects which nucleate to dislocation loops in the interface. Principle and injection mechanism are shown.