Solid State Phenomena Vols. 156-158

Abstract: PL spectra of SOI wafers with buried oxide (BOX) layer were measured after dissolution annealing at 1200°. Depending on mutual orientation of starting base and top wafers different patterns of luminescence bands were observed after annealing. While the small fraction of luminescence clearly originated from dislocation related centers, another intensive band appeared in the range 0.8 – 0.95eV with certain dependence of maximum position on the twist misorientation. TEM investigation confirmed the existence of dislocation net at the interface. On the other hand some peculiarities of PL spectra did not support their relation to dislocations. Though a stepped chemical etch of surface layer confirmed the origin of new band being at the interface too. Therefore a nature of possible defects generated due to dissolution of BOX layer is discussed.

Abstract: We have characterized optical property of small-angle (SA) grain-boundaries (GBs) in high-pure multicrystalline Si by using cathodoluminescence (CL). Prior to CL measurement, the electrical activity of GBs were evaluated by using electron-beam-induced current (EBIC). The SA-GBs are categorized into two groups with room temperature (RT-) EBIC contrast. The SA-GBs with misorientation angle about 1º give weak RT-EBIC contrast and yield D3 and D4. The SA-GBs with 2.5º show strong EBIC contrast and yield D1 and D2. These correspondences reflect the dislocation density at the SA-GBs. We also found the curious distribution of D1 emission in some special GBs, which is now difficult to explain. It is noticed that large-angle GBs do not show any D-line emissions at all.

Abstract: The investigation of regular dislocation networks (DN) formed by direct wafer bonding suggests that the D1 and D2 peaks of dislocation-related luminescence (DRL) in silicon is linked to screw dislocations, whereas edge dislocations are responsible for D3 and D4 DRL peaks. Non-radiative recombination activity in DN could be attributed to edge dislocations and could be related to enhanced ability of these dislocations to getter impurity atoms. Obtained relation of DRL intensity with the density of screw dislocations suggests existence of the optimum twist angle for the wafer-bonding geometry for which the DRL intensity has a maximum. The dependence of DRL intensity on the spacing between screw dislocations has the maximum at about 7 nm. Reported radiative and non-radiative recombination properties of DN present substantial interest not only for possible LED applications in all-Si photonics but also for photovoltaics, since DNs represent a model system for grain boundaries controlling carrier lifetime in microcrystalline-Si material.

Abstract: Structural and luminescence properties have been studied in silicon layers with dislocation-related luminescence. Multiple room temperature implantation of oxygen ions with doses low than the amorphization threshold was carried out. Silicon ions with a dose exceeding the amorphization threshold by two orders of magnitude were implanted at a higher temperature (≥ 80°C). Both the implantations were not followed by the amorphization of the implanted layers. Annealing in a chlorine-containing atmosphere resulted in formation of extended structural defects and luminescence centers. Some regularities and peculiarities in the properties of the extended defects and dislocation-related luminescence lines were revealed in dependence on the implantation and annealing conditions.

Abstract: Incorporation of optical components into microelectronic devices will significantly improve their performance. Absence of effective Si-based light emitter hampers such integration. In the present work light emitting Si diodes, fabricated by dopant (boron or phosphorous) implantation and annealing are investigated. Different implantation doses and annealing temperatures were employed. The efficiency of the electroluminescence (EL), obtained from such structures was measured and correlated with the fabrication process parameters. As previously reported, the EL of band-to-band radiative transition in Si is strongly influenced, by the dopant implantation dose, i.e. higher doses usually enhance EL. Our results suggest that the effect is mainly related to the increase of minority carrier lifetime in the substrate. Distinct measurements showed that the higher implantation doses lead longer carrier lifetimes in the samples. The correlation between lifetime and the EL efficiency could be satisfactory explained in the frame of a classical model, considering the carrier-injection dependence of the rates of the three main recombination mechanisms in silicon, i.e. multi-phonon, radiative and Auger recombination. We suppose that the increase in the implantation dose improves minority carrier lifetime due to the gettering of impurity atoms from the substrate material to the highly doped emitter region.