The velocities of screw and 60° dislocations in silicon are measured for temperatures ranging from 520 to 800 °C and stresses ranging from 4 to 30 MNm−2 and for various concentrations of phosphorous or boron atoms. n-doping results in an increase of the velocities of screw and 60° dislocations. In moderately p-doped Si, no clear effect is observed for screw dislocations while the velocities of 60° dislocations are slightly lower than in intrinsic Si. The effect of doping on the dislocation velocity is discussed mainly in terms of Haasen's calculation of the influence of the electrical charge carried by the dislocation on the formation of a double kink. In the case of 60° dislocations, the model fairly describes the measurements in heavily doped Si (≈ 1019 atoms cm−3) but underestimates the effect observed at moderate levels of doping.



Les vitesses des dislocations vis et a 60° dans le silicium ont ete mesurees en fonction de la temperature de 520 a 800 °C et de la contrainte de 4 a 30 MNm−2, pour differentes concentrations en phosphore ou en bore. Le dopage n provoque une augmentation des vitesses aussi bien pour les dislocations vis que pour les dislocations a 60°. Dans le silicium de type p, pour des dopages pas trop eleves, aucun effet n'a ete clairement observe pour les dislocations vis, mais les vitesses des dislocations a 60° sont legerement inferieures a celles mesurees dans le silicium intrinseque. L'influence du dopage sur la vitesse des dislocations est discutee principalement a l'aide du modele de Haasen, qui calcule l'influence de la charge electrique portee par la dislocation sur la formation des doubles decrochements. Dans le cas des dislocations a 60°, le modele rend bien compte des mesures effectuees dans du silicium fortement dope (≈ 1019 atomes cm−3) et sous estime l'effet observe pour des dopages plus faibles.

Velocities of screw and 60° dislocations in n- and p-type silicon

The elucidation of the effects of structurally extended defects on electronic properties of materials is especially important in view of the current advances in electronic device development that involve defect control and engineering at the nanometer level. This book surveys the properties, effects, roles and characterization of extended defects in semiconductors. The basic properties of extended defects (dislocations, stacking faults, grain boundaries, and precipitates) are outlined, and their effect on the electronic properties of semiconductors, their role in semiconductor devices, and techniques for their characterization are discussed. These topics are among the central issues in the investigation and applications of semiconductors and in the operation of semiconductor devices. The authors preface their treatment with an introduction to semiconductor materials and conclude with a chapter on point defect maldistributions. This text is suitable for advanced undergraduate and graduate students in materials science and engineering, and for those studying semiconductor physics.

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Extended Defects in Semiconductors: Electronic Properties, Device Effects and Structures

A new method to investigate directly the dynamical properties of dislocations was developed by means of HVEM. The motions of edge and screw dislocations were observed in thick foil specimens of Fe-Si being stretched in a HVEM operated at 500 kV. The dislocation motions were recorded continuously on a video tape recorder (VTR) with the aid of an image intensifier and the corresponding stress-strain curve was also recorded simultaneously. Edge dislocations moved well below the yield stress and the frequency of their motions increased with increasing applied stress. Luders band nucleated at upper yield point and propagated in transition from upper to lower yield points. The motions of screws were observed immediately after upper yield point, accompanying dislocation multiplication. Edge dislocations had much higher mobility than screws but both of them moved much faster in comparison with the observation by etch-pitting technique.

Direct Measurement of Mobility of Edge and Screw Dislocations in 3% Silicon-Iron by High Voltage Transmission Electron Microscopy

The tensile creep behavior of a siliconized silicon carbide was investigated in air, under applied stresses of 103 to 172 MPa for the temperature range of 1100° to 1200°C. At 1100°C, the steady-state stress exponent for creep was approximately 4 under applied stresses less than the threshold for creep damage (132 MPa). At applied stresses greater than the threshold stress for creep damage, the stress exponent increased to approximately 10. The activation energy for steady-state creep at 103 MPa was approximately 175 kJ/mol for the temperature range of 1100° to 1200°C. Under applied stresses of 137 and 172 MPa, the activation energy for creep increased to 210 and 350 kJ/mol, respectively, for the same temperature range. Creep deformation in the siliconized silicon carbide below the threshold stress for creep damage was determined to be controlled by dislocation processes in the silicon phase. At applied stresses above the threshold stress for creep damage, creep damage enhanced the rate of deformation, resulting in an increased stress exponent and activation energy for creep. The contribution of creep damage to the deformation process was shown to increase the stress exponent from 4 to 10.

Effect of Creep Damage on the Tensile Creep Behavior of a Siliconized Silicon Carbide

The introduction of dislocations during the growth of floating-zone silicon crystals as a result of point defect condensation

Glide velocity measurements were made on isolated screw and 60° dislocations in silicon for the temperature range 775°–925°C. The x‐ray topographs which were used to reveal dislocation displacements also gave qualitative information concerning the early stages of dislocation multiplication in highly perfect silicon crystals. Freshly generated dislocations were more mobile than aged dislocations. Pinning points which were tentatively attributed to thermal jogs developed along the lines. The pinning point spacing decreased with increasing temperature as would be expected for a jog formation energy of 1.2 eV. Heating to above 1000°C effectively immobilized all the dislocations present in the crystal. On subsequent loading at 825°C, no motion took place until the stress was high enough to cause catastrophic multiplication when a segment of dislocation did break away. This resulted in the formation of heavy bands of slip. For fresh dislocations the temperature dependence of velocity was analyzed on the basis of a kink pair nucleation and kink propagation model. The measured activation energy for motion of both 60° and screw dislocations was 1.8±0.3 eV.

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J. Washburn

Papers

Direct dislocation velocity measurement in silicon by x-ray topography