Deep level transient spectroscopy (DLTS) is the best technique for monitoring and characterizing deep levels introduced intentionally or occurring naturally in semiconductor materials and complete devices. DLTS has the advantage over all the techniques used to-date in that it fulfils almost all the requirements for a complete characterization of a deep centre and their correlation with the device properties.In particular the method can determine the activation energy of a deep level, its capture cross-section and concentration and can distinguish between traps and recombination centers.

In this invited paper we provide an overview of the extensive R & D work that has been carrier out by the authors on the identification of the recombination and compensator centers in Si and III-V compound materials for space solar cells. In addition, we present an overview of key problems that remain in the understanding of the role of the point defects and their correlation with the solar cell parameters.

We show that low-energy (20 eV–20 keV) electron or photon irradiation extinguishes the characteristic physical and chemical properties of single-walled carbon nanotubes, indicating that the irradiation damages the nanotubes. The irradiation-induced defects convert the electric properties of metallic SWNTs to semiconducting, and the nominal bandgap can be tuned simply by the irradiation dose. The defects also have the following interesting properties. The damage and recovery are reversible, indicating that the number of carbon atoms is preserved. The damage and recovery strongly depend on the diameter, suggesting that the damage is prominent in a rolled up graphene sheet, but not in a planar one. The activation energy of the defect healing is so small, depending on the diameter, that the defects can be healed even at room temperature or below.

We studied stress effects on As activation in silicon using density functional theory. Based on lattice expansion coefficient, we calculated formation energy change due to applied stress and plotted the stress dependence of AsmV concentration. We found that biaxial stress results in minimal impact on As activation, which is consistent with experimental observation by Sugii et al. [J. Appl. Phys. 96, 261 (2004)], who found no significant change in As activation under tensile stress.

Examination of dislocations in the as-grown and annealed SiGe/Si heterostructures by DLTS indicates the three strong DLTS bands from 70 to 270K in the as-grown sample are likely related to intrinsic point defects or dislocation trails. A small amount of Fe at dislocations dramatically increases their electrical activity, and the trap concentration due to Fe-decorated dislocations can well exceed the total Fe impurities presented along dislocations. Through examining the competitive trapping of Fe at boron and dislocations, it is suggested that Fe trapping only happens at disordered sites along dislocations, such as kinks.

Copper is one of the most concerned contaminants for silicon process, due to its detrimental effects on device performance if present in active regions. Gettering of Cu by changing the surface conditions at the wafer surface is commonly used. Acceleration of Cu out-diffusion and surface precipitation was observed with changes of the surface potential, which could be altered by both existing Cu precipitates and organics at the surface.In this work, physically based models are developed to describe the Cu evolution at the wafer surface including the dependence of surface potential. These models are verified by comparison to the experiment measurements from Ohkubo et al. [Jpn. J.Appl. Phys. 1 44, 3793 (2005)].

In this work, we present a comparative study of vibrational and luminescent properties of Ge nanocrystals (NCs) prepared by ion implantation (Process I) and radio frequency (RF) sputter deposition techniques (Process II). Optical Raman studies reveal presence of strain in the Ge NCs embedded in SiO2 in both cases. Polarization dependent Raman scattering studies show that process I yields NCs with surface symmetrical Raman modes only, whereas process II yields additional surface quadrupolar Raman modes. Photoluminescence studies using 488 nm excitation show broad PL emissions peaked at ∼2.3 in all the samples with varying intensities. PL studies on Ar implanted and similarly annealed SiO2 layers confirm that 2.3 eV emission is originated from oxygen deficient defects in the SiO2 matrix. PL studies with 325 nm excitation show additional strong peaks at higher energies, which are believed to be due to Ge/O interface defects. It is concluded that room temperature visible light emission from embedded Ge NCs is primarily dominated by the oxygen deficient defects in SiOx matrix and non-bridging oxygen surrounding the Ge NCs, while light emission due to quantum confined carriers in the NCs are quenched perhaps due to inherent strain in the embedded NCs.

It is well known that Au indiffusion in Si is dominated by the Kick-Out mechanism governed by Si self-interstitials, with negligible contribution from the Frank-Turnbull mechanism governed by vacancies. In this paper we present modeling and simulation results to show that the Frank-Turnbull mechanism actually dominates Au outdiffusion in Si.

A new carbon-interstitial clustering model has been developed. The model has been implemented into the process simulator Sentaurus Process. Model parameters have been calibrated using fundamental marker layer experiments. B diffusion retardation in the C doped layer as well as Sb diffusion enhancement in the region close to a layer with high C concentration are successfully simulated. The calibrated model has been applied to simulations of ultra-shallow junction formation by high dose P-C and B-C co-implantation. It is assumed that, in regions which are amorphized by ion implantation and recrystallized by solid phase epitaxy, C is in the substitutional state right after the recrystallization. In contrast, in non-amorphized regions, C is assumed to be in clusters at the beginning of thermal annealing. A good agreement between simulation and experimental results has been achieved. The dependence of dopant diffusion on implanted C dose and spike annealing temperature has been reproduced.

The segregation of As atoms at the Si/SiO2 interface during annealing was investigated by grazing incidence X-ray fluorescence spectroscopy in combination with successive removal of silicon layers by etching with thicknesses on the order of a nanometer. With this method it is possible to clearly distinguish between the segregated atoms and the As atoms in the bulk over a large range of implantation doses from 3·12 cm−2 to 1·16 cm−2. The samples were annealed at 900 °C and 1000 °C, respectively, for times sufficiently long to ensure that the segregation reflects an equilibrium effect. The results were confirmed by medium energy ion scattering, Z-contrast measurements and electron energy loss spectroscopy.

Two cast multi-crystalline silicon (mc-Si) sister wafers before and after solar cell processing were investigated to explore the gettering effect in low and high density structural defect regions.For the processed wafer, the minority carrier recombination lifetime was correlated to the structural defect distribution.For the low density region of as-grown wafer, Cr impurities were 3.28x1013cm-3 and they were reduced to 1.74×1012cm−3 for the processed wafer.The isolated Cr impurities dissolved from the precipitates at 900°C which is the typical gettering temperature in the solar cell processing are getterd effectively in the low density regions.Our current understanding for the gettering effect in the high density regions is that the segregated Cr impurities at defect sites are not released to the silicon matrix at 900°C resulting in the poor gettering effect.

The simulation of deep-submicron silicon-device manufacturing processes relies on predictive models for extended defect clusters. For submicroscopic interstitial clusters and {311} defects, an efficient and highly accurate model for process simulation has been developed and calibrated recently [1]. This model combines equations for three small interstitial clusters and two moments for {311} defects. In this work, we extend this model to include dislocation loops and to reproduce a greatly increased range of experimental data, including thermal annealing of end-of-range defects after amorphizing implants.

A novel scheme for the fabrication of SiGe-on-insulator (SGOI) substrates comprising a thin and relaxed silicon-germanium (SiGe) layer with high Ge mole fraction is reported.A cyclical thermal oxidation and annealing (CTOA) process is introduced to alleviate issues associated with surface roughening and non-uniformity in Ge content.A systematic study of the stress developed in the SiGe layer as condensation takes place is presented.A clear understanding of the strain evolution enables the SGOI substrate fabrication to be tailored according to the requirements of strain engineering in high mobility MOSFETs.