Proximity Gettering of Slow Diffuser Contaminants

In this paper, we test proximity gettering layers obtained by carbon or silicon implantation for their efficiency in molybdenum and tungsten gettering. DLTS was used to measure the impurity concentration in the solid solution and so to evaluate gettering efficiency. It was found that carbon implantation is effective in capturing these impurities, whereas silicon implantation is not. Extended defects seem not to play an important role in gettering these impurities. In addition, gettering was found to be most effective at high impurity concentration.

Resistivity Distribution Characteristics of Metallurgical Silicon Ingot after Directional Solidification

The distribution of resistivity, impurity and polarity in multicrystalline silicon ingot prepared by directional solidification method was detected. The effect of impurity distribution on resistivity was also researched. The results show that the shapes of equivalence line of resistivity in the cross section and vertical section of the silicon ingot depend on the solid-liquid interface. The resistivity in the vertical section increases with the increasing of solidified height at the beginning of solidification and reaches to maximum at the polarity transition point, then decreases rapidly with the increasing of solidified height and tends to zero on the top of the ingot because of the high impurity concentration. Study proves that the variation of resistivity in the vertical section is mainly relevant to the concentration distribution of the impurities such as Al, B and P in the growth direction.

Bridgman Growth of SrI2

ABSTRACTEu2+– activated strontium iodide is a promising material for x-ray and gamma ray detector. A lot of difficulties are though encountered growing strontium iodide crystals due to the high oxygen-sensitivity, hygroscopic property and high impurity concentration. Single crystals of SrI2:Eu were grown from zone refined starting materials in silica ampoules. The crystals showed good optical qualities. The light yield of two samples cut from the same ingot was determined to be 53 000 photons/MeV and 119±22 photons/keV for a 0.4 cm3 sample and a 360 μm sample respectively, indicating some level of light trapping in the bulk sample.

Fabrication and electrical characteristics of Ti/Al ohmic contact to Si+ implanted GaN

Ti/Al ohmic contact with an extremely low specific contact resistance has been formed by the deposition of Ti and Al films on Si+ lanted GaN. The ohmic contact formed by annealing at 600 o C of Ti film with a thickness of 50 nm and Al film with a thickness of 200 nm reveals the good smooth surface and uniform structure as compare to those of contacts formed above 700 °C, which is correlated to whether the Al-Ti alloy is melted during the annealing of ohmic contact or not. The specific contact resistance of 2 × 10-6Ω-cm2 is obtained for Si+ implanted GaN with a dose of 5 × 1013 cm-2. As Si ion dose increases to 5 × 1014 /cm2, the specific contact resistance is reduced to 2 × 10-8 Ω-cm2. It is revealed that the selective doping at high impurity concentration in the surface region by Si+ implantation is useful to reduce the contact resistance for Ti/Al contact to GaN.

Constituent Diffusion in a Deformable Thermoelastic Solid

Solid mixtures containing initially uniform dilute concentrations of impurity elements may, upon the application of mechanical and thermal loading, develop regions of high impurity concentration that could result in local degradation of material properties. To address these degradation processes, a fully coupled thermomechanical-diffusion theory has been developed to describe the mass transport of mobile constituents driven by gradients in concentration, strain dilatation and temperature in a solid deformable parent material. A finite element code has been assembled to solve plane transient thermomechanical-diffusion problems. The theory presented and the resulting code have been successfully used to model internal hydrogen redistribution in β-phase Ti alloys induced by elastic strain gradients during bending.