2019年5月28日星期二

nfrared and terahertz transmission properties of germanium single crystals

Experimental transmission spectra of samples fabricated of germanium single crystals doped with stibium were registered in the infrared 2.5-25 μm and terahertz 130 μm regions of spectrum. It is shown that doping concentration and treatment of the crystals surface have a noticeable influence on the samples absorption.

Source:IOPscience

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2019年5月23日星期四

Germanium layers grown by zone thermal crystallization from a discrete liquid source

It is proposed and investigated a method for growing thin uniform germanium layers onto large silicon substrates. The technique uses the hexagonally arranged local sources filled with liquid germanium. Germanium evaporates on very close substrate and in these conditions the residual gases vapor pressure highly reduces. It is shown that to achieve uniformity of the deposited layer better than 97% the critical thickness of the vacuum zone must be equal to l cr = 1.2 mm for a hexagonal arranged system of round local sources with the radius of r = 0.75 mm and the distance between the sources of h = 0.5 mm.

Source:IOPscience

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2019年5月16日星期四

Highly boron-doped germanium layers on Si(001) grown by carbon-mediated epitaxy

Smooth and fully relaxed highly boron-doped germanium layers were grown directly on Si(001) substrates using carbon-mediated epitaxy. A doping level of ${N}_{{\rm{A}}}\approx 1.1\times {10}^{20}\,{{\rm{cm}}}^{-3}$ was measured by several methods. Using high-resolution x-ray diffraction we observed different lattice parameters for intrinsic and highly boron-doped samples. A lattice parameter of a Ge:B = 5.653 Å was calculated using the results obtained by reciprocal space mapping around the (113) reflection and the model of tetragonal distortion. The observed lattice contraction was adapted and brought in accordance with a theoretical model developed for ultra-highly boron-doped silicon. Raman spectroscopy was performed on the intrinsic and doped samples. A shift in the first order phonon scattering peak was observed and attributed to the high doping level. A doping level of $(1.28\pm 0.19)\times {10}^{20}\,{{\rm{cm}}}^{-3}$ was calculated by comparison with literature. We also observed a difference between the intrinsic and doped sample in the range of second order phonon scattering. Here, an intense peak is visible at $544.8\,{{\rm{cm}}}^{-1}$ for the doped samples. This peak was attributed to the bond between germanium and the boron isotope 11B.

Source:IOPscience

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2019年5月9日星期四

The effect of germanium doping on oxygen donors in Czochralski-grown silicon

In this paper the effect of germanium doping on oxygen donors in Czochralski (CZ) silicon has been investigated. It is found that germanium suppresses the formation of thermal donors during annealing at 450 °C, as a result of the reaction of Ge with point defects in CZ silicon. Meanwhile, it is clarified that germanium enhances the formation of new donors in CZ silicon, which is proposed to be a process associated with the nucleation enhancement of oxygen precipitation by germanium doping.

Source:IOPscience

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