Jan 20, 2020

Hydrogen Implantation in Germanium

Hydrogen implantation of germanium is a promising technique for layer transfer. However, both the implantation process, and subsequent heat treatment can create defects in the transferred layer, which detrimentally effect the performance of devices fabricated on these transferred layers. In this study, implanted Germanium wafers were given various anneals and analysed optically and by spreading resistance, to gain insight on the nature of such defects. GeOI layers were produced by thermal splitting of implanted germanium wafers bonded to sapphire handle substrates.

Source:IOPscience

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Jan 13, 2020

The Study on Defects of Germanium-on-Insulator Fabricated by a Low Temperature Smart-Cut Process

Germanium-on-insulator (GeOI) was manufactured by a low temperature Smart-cut process. The blistering of H-implanted Ge wafer was first studied and the kinetics of blistering onset (time) as a function of annealing temperature was described to determine the subsequent splitting. Germanium layer transfer was achieved by a 2700C annealing after the atomic level Ge/SiO2 wafer bonding was formed by a 1500C annealing. The defects on the transferred Ge layer were mitigated thanks to the extended annealing and mainly distributed at the rim of GeOI wafer.

Source:IOPscience

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Jan 7, 2020

Gaseous Diffusion of Arsenic and Phosphorus into Germanium

Presence of germanium arsenide was found at the germanium surface, particularly at arsenic surface concentrations exceeding 1019 at./cc, using electron diffraction techniques. Thermal conversion of the interior of the germanium wafers (which were 15 ohm‐cm N‐type) to P‐type could be suppressed by arsenic surface concentrations exceeding 5.1018 at./cc. This elimination of thermal conversion depends on the surface to volume ratio of the wafer. It is proposed that the thermal conversion level in the bulk of the indiffused material depends on the electric field which arises during diffusion if the impurity concentration exceeds the intrinsic carrier concentration.

Source:IOPscience
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Jan 2, 2020

Germanium Back‐Side Gettering of Gold in Silicon

A novel back‐side gettering technique was developed. The technique consists of applying germanium to the back side of a silicon wafer and then annealing in either a nitrogen or an oxygen ambient. The concentration profiles for gold before and after anneals were established to better than the part per million (ppm) level by using atomic absorption spectroscopy. The minority carrier lifetime of control and gettered samples was determined. The technique was found to be effective for the removal of gold from the active device region of a silicon wafer. The difference in activity coefficients for gold in silicon and gold in germanium is the theoretical basis for the gettering of gold from the silicon to the germanium on the back side. In addition to gettering gold from the front surface of the wafer, comparison was made of a germanium‐gettered wafer with a control wafer, showing that the application of germanium to the back side of a silicon wafer, followed by thermal annealing, is effective in preventing the formation of oxidation‐induced stacking faults (OISF) during high temperature oxidation.

Source:IOPscience
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Dec 25, 2019

The Stabilization of Germanium Surfaces by Ethylation: II . Chemical Analysis

Radiotracer techniques and mass spectrometry have been employed in analyzing ethylated germanium surfaces; the results from these two analytical techniques are in good agreement. The number of ethyl fragments on a treated (111) germanium surface is the same as the number of surface germanium atoms, within experimental error. The surfaces are stable at temperatures below 200°C in vacuum and in air, but begin evolving C1 and C2 fragments above 200°C. At higher temperatures, additional hydrocarbon fragments are seen mass spectrometrically. Using wafers having labelled ethyl groups, it has been found that the treated surfaces are stable to immersion in common chemical solvents.

Source:IOPscience
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Dec 17, 2019

Heterostructures of germanium nanowires and germanium–silicon oxide nanotubes and growth mechanisms

We report on a method to fabricate one-dimensional heterostructures of germanium nanowires (GeNWs) and germaniumsilicon oxide nanotubes (GeSiOxNTs). The synthesis of the wire–tube heterostructures is carried out using a simple furnace set-up with germanium tetraiodide and germanium powders as growth precursors, gold-dotted silicon wafers as substrates and by controlling the temperature ramp rate/sequence of the growth precursors. Two types of wire–tube heterostructures resulting from distinct growth mechanisms are obtained. The type-1 heterostructure consists of a GeNW, grown via a gold-catalyzed vapour–liquid–solid process, at the lower end and a GeSiOxNT at the upper end. In contrast, the type-2 heterostructure is made up of a solid wire at the upper end and a hollow tube at the lower end. The solid wire portion of the type-2 heterostructure is formed through an oxide-assisted growth process.

Source:IOPscience
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Dec 11, 2019

Silicon and germanium nanostructures formed by spark discharge plasma

Formation of semiconductor nanostructures on the surface of single crystalline silicon and germanium wafers by spark discharge plasma in air was investigated. The prepared nanostructures were analyzed by means of the scanning and transmission electron microscopy and optical spectroscopy of the photoluminescence and Raman scattering. The formed nanostructures exhibit a fractal-like morphology with interconnected nanocrystals of 2-200 nm sizes that is explained by repeated processes of spark ablation and subsequent condensation. While the size and morphology of the nanostructure depend on power sources of the spark discharge, short interaction times of spark discharge plasma and target determine a relatively low efficiency of the chemical oxidation of germanium and silicon, as well as low ionic temperatures of the plasma.

Source:IOPscience
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