A. S. Loshachenko

Electrical Characterization and Defect-Related Luminescence in Oxygen Implanted Silicon

Defect structure, electrical properties and defect-related luminescence (DRL) of light emitting diodes (LED) with the active defect-rich region produced by oxygen implantation and a subsequent multistep annealing of silicon wafers were investigated. It was found that defect-rich regions possess an embedded positive charge in both n-and p-type of the samples whose origin was ascribed to oxygen precipitates (OP). The presence of that charge in the implanted region of p-based LED gave rise to the apparent conductivity type conversion and to a significant increase of free electron concentration in n-based LEDs. A significant difference in the shape and in the excitation dependence of luminescence spectra as well as in the properties of DLTS signals was found between p-and n-type samples. From an analysis of the obtained data the DRL band centered at 0.79 eV was ascribed to small OPs segregated at dislocations whose filling with the holes hinders optical transitions via dislocation-related states at 0.805 eV and the broad DRL band at energies higher than 0.81 eV was ascribed to large OPs.

Atomic configuration and charge state of hydrogen at dislocations in silicon

The effect of the introduction of hydrogen upon the vibration spectra and electrical characteristics of samples with dislocation networks at the interface of bonded silicon wafers was studied. In order to improve the sensitivity of measurements and to distinguish the signal from dislocation networks in Raman spectra, thin foils conventionally prepared for transmission electron microscopy were used as the sample under investigation. In the samples with dislocation networks, a Raman peak at 2000 cm–1 was observed. This peak survived after annealing at a temperature of T = 500°C and was not observed in reference samples. Comparison of the experimental data with currently available theoretical calculations allowed one to attribute the observed peak to neutral hydrogen atoms H0 at the center of Si–Si bonds. The peak is metastable in the ideal lattice, but becomes stable in the vicinity of dislocations.

Formation of donor centers upon the annealing of silicon light-emitting structures implanted with oxygen ions

It is found that the implantation of silicon with oxygen ions and subsequent annealing at high temperatures are accompanied by the formation of electrically active donor centers and by the p-n conversion of the conductivity of silicon. The concentration and spatial distribution of these centers depend on the annealing temperature. The results are accounted for by the interaction of oxygen atoms with intrinsic point defects formed upon the annealing of implantation damages.

Structural and luminescent properties of electron-irradiated silicon

Structural defects induced by electron irradiation of p-Cz-Si wafers were identified. The influence of the annealing conditions in a chlorine-containing atmosphere on the structural and luminescent properties of the samples was examined. Light-emitting diodes based on electron-irradiated and high-temperature-annealed wafers were fabricated by a vapour-phase epitaxy technique and their luminescence properties were studied. A high-intensity dislocation-related D1 line was observed at 1.6 μm in the room-temperature electroluminescence spectrum.

Kinetics of Hydrogen Motion via Dislocation Network in Hydrophilically Direct Bonded Silicon Wafers

The kinetics of hydrogen penetration through dislocation networks produced by silicon wafer bonding are investigated by means of reverse bias annealing (RBA) procedure. By using the combination of capacitance-voltage (CV) profiling of net-acceptor concentration and deep level transient spectroscopy (DLTS) the total concentration of H introduced in the samples during wet–chemical etching at room temperature was defined. Two processes with the different time constants τ1 and τ2 was found for the bonded sample. The slow process τ1 with an activation energy of (1.25±0.13) eV was analogous to that in the reference sample and corresponded to the dissociation of boron-hydrogen pairs. The fast process τ2 was found to exhibit a lower activation energy of (0.87±0.25) eV and was identified as the release of hydrogen bound at screw dislocations by their elastic strains.

Fabrication of Light-Emitting Diodes with Dislocation-Related Luminescence by Annealing of Electron-Irradiated Silicon

Structural defects induced by electron irradiation of n-Cz-Si wafers were identified. The influence of the annealing conditions in a chlorine-containing atmosphere on the structural and luminescent properties of the samples was examined and the optimal annealing conditions were found. Light-emitting diodes based on electron-irradiated and high-temperature-annealed wafers were fabricated by a vapour-phase epitaxy technique and their luminescence properties were studied. A high-intensity dislocation-related D1 line was observed at 1.6 μm in the room-temperature electroluminescence spectrum.

The electrically active centers in oxygen-implanted silicon

Electrically active centers have been firstly studied by the capacitance transient spectroscopy technique in p-Cz-Si implanted with oxygen ions and annealed in a chlorine-containing atmosphere. The temperature dependences of the thermal emission rates of holes from the levels to the valence band were measured and the influence of the annealing conditions on the level concentrations were studied. The deep and shallow levels revealed in the samples with dislocation related luminescence are characterized by similar level parameters to those observed in samples containing extended defects and performed by different techniques (deformation, formation of oxygen precipitates and direct bonding of wafers). Some distinctions in the parameters are associated with the changes of the extended defect strain fields due to specific conditions of their preparing.