Electrical properties of thermal donors formed in silicon under elastic tensile stress

The electrical properties of thermal donors formed in the bulk and near-surface regions in silicon samples with (3–9) × 10¹⁷ cm⁻³ oxygen concentrations under elastic tensile stress σ of about 1 GPa have been studied. The original method allowing us to control an introduced elastic tensile stress during the thermal donor’s formation at T = 450°C by a double-crystal X-ray diffractometer has been used. The formation of thermal donors in silicon with a high oxygen concentration of 9.3 × 10¹⁷ cm⁻³ under tensile stress has been found to be less effective than in silicon with a low oxygen concentration of (3–5) × 10¹⁷ cm⁻³. Single-charged donors are formed in silicon with a low oxygen concentration under tensile stress while double-charged donors are formed in silicon with a high oxygen concentration.     

On the core concentration and the formation kinetics of thermal donors in silicon

Abstract

In this work the anomalous formation kinetics of old thermal donors (TD) observed in the initial stage of formation in pre-heat-treated carbon-rich samples are studied. Computer simulations applying a reaction scheme where the TD-complexes are subsequently formed by single oxygen diffusion reveal that the experimental results can only be acounted for if the pre-existing TD-core involves three oxygen atoms and has a concentration in the range 10¹³-10¹⁴ cm^?3. Carbon is found to have a major influence on the production rate of pre-existing cores.     

Structures of thermal double donors in silicon

Accurate total-energy calculations are used to study the structures and formation energies of oxygen chains as models for thermal double donors (TDD's) in Si. We find that the first three TDD's (TDD0-TDD2) consist of one four-member ring, with one or two adjacent interstitial O atoms. These metastable TDD's form bistable negative-U systems with the corresponding stable, electrically inactive staggered structures. The TDD3-TDD7 structures are found to consist of four-member rings with adjacent interstitial O atoms at both ends. The TDD's with a central "di-Y-lid" core are found to become energetically competitive with the four-member ring TDD's only for clusters larger than ten O atoms.     

Aggregation kinetics of thermal double donors in silicon

A general kinetic model based on accurate density-functional-theoretic total-energy calculations is introduced to describe the aggregation kinetics of oxygen-related thermal double donors (TDD's) in silicon. The calculated kinetics, which incorporates the reactions of associations, dissociations, and isomerizations of all relevant oxygen complexes, is in agreement with experimental annealing studies. The aggregation of TDD's takes place through parallel-consecutive reactions where both mobile oxygen dimers and fast migrating chainlike TDD's capture interstitial oxygen atoms.     

Shallow thermal donors in nitrogen-doped silicon single crystals

Czochralski-grown nitrogen-doped silicon crystals contain shallow thermal donors (STD) which are not present in reference crystals. In the course of annealing at 600 or 650°C, the STD concentration reaches saturation and this concentration scales with nitrogen content N as N^1/2. This implies that an STD includes only one nitrogen atom and that the most likely model of the STD defect is the NO_m complex of an interstitial nitrogen atom with m oxygen atoms. The number m is estimated as, on the average, m=3 from data on the temperature dependence of the equilibrium constant for the complex formation reaction     

Generation of thermal donors in silicon: Effect of self-interstitials

The generation of low-temperature thermal donors (TD) in silicon is sensitive to the sample cooling rate (from the anneal to room temperature) and the ambient (air or vacuum). This effect is most clearly pronounced in the case of annealing at 500°C, is noticeable at 480°C, and is practically undetectable at 450°C. The results are interpreted satisfactorily as being due to the TD generation becoming enhanced in the presence of silicon self-interstitial (Si_I) atoms. These atoms are emitted by thermal donors, to be subsequently absorbed by sinks, particularly the sample surface and grown-in microdefects (vacancy voids). When annealing in a vacuum, the surface acts as the main sink. If the anneal is done in air, this sink is passivated as a result of oxidation and/or contamination, with voids becoming the main sinks; as a result, the concentration of Si_I atoms increases substantially and the generation rate is enhanced. Rapid cooling brings about a partial passivation of the voids (as a result of their becoming decorated by rapidly diffusing impurities) and an additional enhancement of the generation rate. The calculated rate curves obtained within this model are well fitted to the experiment.     

Oxygen diffusion and thermal donor formation in silicon

The information available on the diffusion of oxygen and on the formation of thermal donors in silicon is critically reviewed. In this context the effects of intrinsic point defects on the diffusion-controlled growth of oxygen precipitates is investigated in some detail. Seemingly contradictory experimental results on the diffusivity of oxygen in silicon at temperatures around 400° C are explained in terms offast-diffusing gas-like molecular oxygen in silicon. The concept of molecular oxygen is also invoked in a newly suggested model of thermal donor formation in silicon. The diffusivity of molecular oxygen in silicon is estimated to be around 10^–9cm²s^–1 at 450° C, almost nine orders of magnitude higher than the diffusivity of atomic oxygen in interstitial position.     

Use of electron irradiation in studying thermal donors in silicon by the EPR method

The bistable thermal donors in Czochralski-grown silicon crystals were investigated by EPR spectroscopy and IR-absorption techniques. It is shown that using heat treatment at a temperature ≤400°C and appropriate conductivity compensation by irradiation with 3.5 MeV electrons, one can select from the total signal the EPR-signal associated with only one type, namely TDD2, of the thermal donors. Based on the model of a two-center core structure of the given complexes, an explanation of the EPR-spectroscopy data on the oxygen thermal donors in silicon is suggested. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 188–191, March–April, 2000.     

Phosphorus-doped silicon under uniaxial tensile strain investigated by PAC

Half-metallic diluted antiferromagnetic semiconductors (HM-AF-DMSs) are magnetic materials that are half-metallic and yet do not exhibit magnetization. The remarkable features of these materials and the possible experimental verifications for determining whether or not a material is a HM-AF-DMS by the detection of hyperfine interactions are discussed on the basis of the first-principles calculations of the electronic structure.     

Influence of elastic stress fields on the diffusional redistribution of impurities in silicon

The redistribution of boron in silicon under the action of elastic stress fields created by the diffusion of various impurities is investigated experimentally. It is shown that the diffusion of boron slows down in the elastic compression interval. The slowing effect intensifies with increasing absolute stress values. A model is proposed to account qualitatively for the experimental results.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 124–127, June, 1977.     

Hole structure of gray tin under tensile stress

The energy band structure for holes in gray tin under uniaxial tensile stress is discussed. It is shown that there is a region in the Brillouin Zone where the hole effective mass along the stress direction becomes negative. The structure of the constant energy surfaces is studied, and the number of holes contained in the energy surface is shown to obey a E³ law for small energy E.     

拉伸应力下的高温超导带材临界电流特性研究

针对在低温、拉伸应力共同作用下,高温超导带材临界电流测量困难的问题,详细介绍了一种独立改造后的简便拉伸设备,利用四引线法对两种具有代表性的高温超导带材的临界电流进行了测量,并对结果进行了一系列的验证,证明了此设备能较好的完成测量任务。最后,结合带材的物理结构,简要分析了临界电流产生变化的原因。对今后的测量工作和超导磁体的设计与制备有一定的指导意义。     

Copper donors in silicon

The temperature dependences of the resistivity and of the Hall constant were measured for dislocation-free p-type silicon saturated with copper under different conditions at temperatures round 1000°C. The analysis of the results and their discussion led to the conclusion that the copper donors form complexes the dimension and physical characteristics of which depend on the way the sample is prepared.     

Effect of Cu addition on whisker formation in tin-rich solder alloys under thermal shock stress

This article focuses on the influence of thermal shocks and Cu addition on tin whiskers growth on the surface of tin-rich materials and alloys. The tests were carried out on real samples manufactured with classical PCB technology. Four Pb-free materials i.e. pure Sn, Sn99Cu1, Sn98Cu2 and Sn97Cu3 were tested from the point of view of susceptibility to whisker formation after thermal shocks. Results show that all tested materials were prone for whisker formation. Copper addition in coexistence with thermal shocks did not promote the growth of filament-like whiskers.     

Thermal double donors in silicon

A family of double donors with only slightly differing binding energies can be generated in silicon containing oxygen. In the 30 years since they were discovered the microscopic structure of these defects has not been unravelled in spite of being investigated with all the tools of solid state physics.