The diffusion of self-atoms and n-type dopants such as phosphorus, arsenic, and antimony in germanium was studied by means of isotopically controlled multilayer structures doped with carbon. The diffusion profiles reveal an aggregation of the dopants within the carbon-doped layers and a retarded penetration depth compared to dopant diffusion in high-purity natural Ge. Dopant aggregation and diffusion retardation are strongest for Sb and similar for P and As. In addition, the shape of the dopant profiles changes for dopant concentrations in the range of 10 20 cm −3 mainly due to the formation of dopant-vacancy complexes, which is more significant at high concentrations. Accurate modeling of the simultaneous self-diffusion and dopant diffusion is achieved on the basis of the vacancy mechanism and additional reactions that take into account the formation of neutral carbon-vacancy-dopant and neutral dopant-vacancy complexes. The stability of these complexes is compared to theoretical calculations published recently and to additional calculations presented in Part II. The overall consistency between the experimental and theoretical results supports the stabilization of donor-vacancy complexes in Ge by the presence of carbon and the dopant deactivation via the formation of dopant-vacancy and carbon-vacancy-dopant complexes.

We have investigated the gettering of transition metals in multicrystalline silicon wafers during a phosphorus emitter diffusion for solar cell processing. The results show that mainly regions of high initial recombination lifetime exhibit a significant lifetime enhancement upon phosphorus diffusion gettering. Nevertheless, transition metal profiles extracted by secondary ion mass spectrometry in a region of low initial lifetime reveal significant gradients in Cr, Fe, and Cu concentrations towards the surface after the emitter diffusion, without exhibiting a significant enhancement in the lifetime. In a region of higher initial lifetime, however, diminutive concentration gradients of the transition metal impurities are revealed, indicating a significantly lower initial concentration in these regions. From spatial maps of the dislocation density in the wafers, we find that lifetime enhancements mainly occur in regions of low dislocation density. Thus, it is believed that a generally higher concentration of transition metals combined with an impurity decoration of dislocations in regions of high dislocation density limit the initial lifetime and the lifetime after the phosphorus diffusion, in spite of the notable gettering of transition metal impurities towards the surface in these regions. Furthermore, after a hydrogen release from overlying silicon nitride layers, we observe that only regions of low dislocation density experience a significant lifetime enhancement. This is attributed to impurity decoration of the dislocations in the regions of both high dislocation density and high transition metal impurity concentration, reducing the ability of hydrogen to passivate dislocations in these regions.

The role of vacancy clustering and acceptor activation on resistivity evolution in N ion-implanted n-type hydrothermally grown bulk ZnO has been investigated by positron annihilation spectroscopy, resistivity measurements, and chemical profiling. Room temperature 220 keV N implantation using doses in the low 10 15 cm −2 range induces small and big vacancy clusters containing at least 2 and 3-4 Zn vacancies, respectively. The small clusters are present already in as-implanted samples and remain stable up to 1000°C with no significant effect on the resistivity evolution. In contrast, formation of the big clusters at 600°C is associated with a significant increase in the free electron concentration attributed to gettering of amphoteric Li impurities by these clusters. Further annealing at 800°C results in a dramatic decrease in the free electron concentration correlated with activation of 10 16 -10 17 cm −3 acceptors likely to be N and/or Li related. The samples remain n type, however, and further annealing at 1000°C results in passivation of the acceptor states while the big clusters dissociate.

High concentration in-diffusion of phosphorus in both Czochralski grown and solar grade multicrystalline Si from a spray-on liquid source has been studied by secondary ion mass spectrometry and electrochemical capacitance-voltage profiling. By extraction of the concentration dependent effective diffusivity employing the Boltzmann-Matano analysis, we adapt an integrated diffusion model based on a previous work by Uematsu [J. Appl. Phys. 82, 2228 (1997)], in order to gain insight into the mechanisms governing such in-diffusions. We find that in the tail region of the profiles, diffusion is mediated by interaction with Si self-interstitials, whereas a vacancy mechanism via doubly negative vacancies dominates in the higher concentration region towards the surface, in correspondence with a previous analysis by Fair and Tsai [J. Electrochem. Soc. 124, 1107 (1977)]. Moreover, we find that both the vacancy and interstitial mechanisms can be described by an Arrhenius behavior, exhibiting apparent activation energies of 5.2±0.3 and 2.1±0.1eV, respectively. The results form the basis for a simplified diffusion simulation, allowing simulation and subsequent optimization of phosphorus diffused emitters commonly employed in Si solar cells.

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Li is present in hydrothermally grown ZnO at high concentrations and is known to compensate both n-and p-type doping due to its amphoteric nature. However, Li can be manipulated by annealing and ion implantation in ZnO. Fast, 20 ms flash anneals in the 900-1400°C range result in vacancy cluster formation and, simultaneously, a low-resistive layer in the implanted part of the He-and Li-implanted ZnO. The vacancy clusters, involving 3-4 Zn vacancies, trap and deactivate Li, leaving other in-grown donors to determine the electrical properties. Such clusters are not present in sufficient concentrations after longer ͑1 h͒ anneals because of a relatively low dissociation barrier ϳ2.6± 0.3 eV, so ZnO remains compensated until Li diffuses out after 1250°C anneals.ZnO has great potential as a material for optoelectronic applications. 1,2 Hydrothermally ͑HT͒ grown ZnO material is of particular interest, as this growth method is scalable. 3 However, electronic doping issues in ZnO in general, and in HT ZnO in particular, are not fully controlled or understood. For example, the role of lithium needs to be addressed. HT ZnO is synthesized in a solution containing LiOH and is therefore abundant with Li. Lithium's lattice position decides whether it exhibits donor-or acceptorlike character in ZnO; occupying zinc sites ͑Li Zn ͒ it is an acceptor, occupying interstitial sites ͑Li i ͒ it is a donor. 4-6 This amphoteric behavior 7 explains why Li doping produces highly resistive or even semi-insulating 8 material. Interestingly, it has recently been reported that in sputtered thin ZnO films Li may act as a dominating p-type dopant. 9 However, the atomistic doping mechanism is not well understood, and the doping efficiency depends strongly on the sputtering and annealing conditions. 9 It is thus important to investigate if and how Li can be ͑i͒ stabilized as Li Zn or Li i , ͑ii͒ deactivated or gettered, or ͑iii͒ removed from the HT ZnO material. Either scenario would facilitate electronic doping, minimizing compensation by amphoteric Li.Ion implantation introduces intrinsic defects, and in some cases electronic states associated with the implanted impurity. However, activation of the implanted impurities by annealing results in limited modifications in the conductivity of the highly resistive HT ZnO, 10 presumably because of the amphoteric role of Li. The measurements in Ref. 10 were performed on highly Li-contaminated samples employing conventional anneals at temperatures Շ1000°C; these conditions were probably insufficient to remove Li from the samples, but sufficient to promote Li amphoteric behavior. In this work we report on how an extremely fast heat treatment ͑ϳ20 ms͒, so called flash annealing, influences the interaction between Li and the implantation-induced defects and how it affects the electrical properties of the ion-implanted ZnO. We have used two types of ions, He + and Li + . The former generates intrinsic defects only, whereas the latter, in addition, alters the Li concentration in the sample. Thus, we are able to ...

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The impurity diffusion of Pr(3+) in dense polycrystalline LaMnO(3), LaCoO(3) and LaFeO(3) was studied at 1373-1673 K in air in order to investigate cation diffusion in these materials. Cation distribution profiles were measured by secondary-ion mass spectrometry and it was found that penetration profiles of Pr(3+) had two distinct regions with different slopes. The first, shallow region was used to evaluate the bulk diffusion coefficients. The activation energies for bulk diffusion of Pr(3+) in LaMnO(3), LaCoO(3) and LaFeO(3) were 126 +/- 6, 334 +/- 68 and 258 +/- 75 kJ mol(-1), respectively, which are significantly lower than previously predicted by atomistic simulations. The bulk diffusion of Pr(3+) in LaMnO(3) was enhanced compared to LaCoO(3) and LaFeO(3) due to higher concentrations of intrinsic point defects in LaMnO(3), especially La site vacancies. Grain-boundary diffusion coefficients of Pr(3+) in LaCoO(3) and LaFeO(3) materials were evaluated according to the Whipple-Le Claire equation. Activation energies for grain-boundary diffusion of Pr(3+) in LaCoO(3) and LaFeO(3) materials were 264 +/- 41 kJ mol(-1) and 290 +/- 36 kJ mol(-1) respectively. Finally, a correlation between activation energies for cation diffusion in bulk and along grain boundaries in pure and substituted LaBO(3) materials (B = Cr, Fe, Co) is discussed.