Point Defects In Germanium Research Articles

On the solubility and diffusivity of the intrinsic point defects in germanium

There is a strong interest to use germanium as an active device layer in deep sub-micron devices. This imposes similar stringent material and process requirements for germanium as for silicon. Lattice defect formation during crystal growth and device processing as well as dopant diffusion and activation are to a large extent controlled by the intrinsic point defects in the semiconductor. The properties of the vacancy and the self-interstitial in germanium are, however, not well known. The scarce available experimental data are combined with ab initio and molecular-dynamics calculations and other published simulation results. Based on this a best estimate is made for the formation and migration energies of the vacancy and the self-interstitial in germanium.

Molecular dynamics simulation of intrinsic point defects in germanium

Results are presented of the calculations of thermodynamic properties of intrinsic point defects in germanium. The results are based on molecular dynamics calculations using the Stillinger and Weber potential and on the Einstein diffusion equation. The obtained formation and migration energies of the neutral vacancy, as well as the formation energy of the self-interstitial, are in good agreement with other recent calculations results. It is also shown that the calculated formation energy of the neutral vacancy is in good agreement with the experimental values obtained from quenching experiments, taking into account the equilibrium theory in pure elemental crystals. Finally, molecular dynamics simulations of the relaxation of a spherical vacancy cluster in germanium predicted a truncated octahedral equilibrium shape, similar to the observed surface pit shape on polished germanium wafers.

Simulation of intrinsic point defect properties and vacancy clustering during Czochralski germanium crystal growth

Results are presented of the simulation of vacancy agglomeration in Czochralski-grown germanium crystals. Molecular dynamics (MD) calculations using a Stillinger and Weber potential are used to determine the thermodynamic properties of intrinsic point defects in germanium. It is shown that the vacancy diffusivity derived from Stillinger and Weber MD calculations does not lead to realistic vacancy cluster distributions. Using a corrected value of the vacancy diffusivity, taking into account experimental data for the self-diffusion coefficient, leads to the correct vacancy cluster size distributions. The good agreement with respect to size between calculated vacancy cluster distributions and observed pits on germanium wafer surfaces strongly suggests that these pits originate from voids formed by vacancy clustering and vacancy diffusion controlled cluster growth during the cooling of the crystal.

Point defects in germanium: Reliable and questionable data in radiation experiments

This review paper outlines some important findings in the field of radiation-produced defects in Ge. Because of poor identification of point defects in this semiconductor the interpretation of electrical and optical data, especially those obtained in low-temperature radiation experiments, has been given by a common analogy with the known defects in Si. However, there are many examples of striking dissimilarities between defect production and annealing processes in both materials. First of all, this is true for the Frenkel pairs as primary defects in irradiated materials. Their properties and behavior in n- and p-Ge are a major focus of discussion in this review. All important data concerning the annealing stages of defects taking place below room temperature are scrutinized to accumulate reliable information on the native defects in Ge. Together with this, the data obtained with the help of such nuclear physics techniques as the Huang diffuse scattering of X-rays, γ– γ perturbed angular correlation, etc., are also briefly discussed.

Studies of the interaction of dislocations with point defects in germanium by means of irradiation in a high-voltage electron microscope

The interaction of point defects with dislocations and interstitial type dislocation loops is studied, generated by electron irradiation of Ge crystals in a high-voltage electron microscope. The investigation of the dislocation climb kinetics as a function of the irradiation conditions indicates that at temperatures between 290 and 470 K the interaction is limited by the insertion of point defects into lattice sites in the dislocation core. In the temperature range of 470 to 670 K the peculiarities of climb of a perfect dislocation are due to the interaction of point defects with partial dislocations in a core of perfect ones. Interaction conditions for dislocations with vacancies and the contribution of self-diffusion processes with increasing irradiation temperature are under discussion. [Russian Text Ignored].

Deformation-induced point defects in germanium

Abstract Using a transient capacitive method (deep-level transient spectroscopy), we have studied defects introduced into n-type germanium by plastic deformation at temperatures below 0·6T m (where T m is the melting temperature). From the annealing behaviour of a defect with a level at E c - 0·29 eV, we conclude that point-defect clouds surround the dislocation formed during plastic deformation, and that these anneal out at high temperatures.

In-Diffusion and Annealing of Copper in Germanium

The in-diffusion and anealing of copper in germanium are examined experimentally over the temperature range 600 to 805°C, and using the experimental results, discussions are made as to whether the dissociative mechanism or the kick-out mechanism is at work in these processes. The experimental results support the theory that copper in germanium diffuses by the dissociative mechanism and the dominant point defects in germanium are vacancies.