2019年8月21日星期三

Determination of the free carrier concentration in atomic-layer doped germanium thin films by infrared spectroscopy

Novel silicon photonics applications requiring heavy n-type doping have recently driven a great deal of interest towards the phosphorous doping of germanium. In this work we report on infrared reflectance spectroscopy measurements of the electron density in heavily n-type doped germanium layers obtained by stacking multiple phosphorous δ-layers. Here, we demonstrate that the conventional Drude model of the electrodynamic response of free carriers in metals can be adapted to describe heavily doped semiconductor thin films. Consequently, the effect of the electron density on the plasma frequency, scattering rate and complex permittivity can be investigated.


Source:IOPscience

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

2019年8月16日星期五

Heat capacity of germanium crystals with various isotopic composition

The heat capacity of three pure (n, p2×1016 cm-3) germanium crystals with different isotopic compositions was measured in the temperature range from 2.8 K to 100 K. These samples, one made of enriched 70Ge (95.6%), Ge of natural isotopic composition and n, p < 1014 cm-3, and one of the largest possible isotopic mass variance 70/76Ge (43%/48%) with n, p<1014 cm-3, show a change of the molar heat capacity (and corresponding Debye temperature, θD) as expected from the average mass variation, corresponding to θDM-0.5 (M = molar mass) at low temperatures. The mass effect is best visible around 21.5 K, at the minimum of the corresponding Debye temperatures θD, and amounts to ΔθD = 5.3 K for the difference between the Debye temperatures of 70Ge and 70/76Ge. The specific heat capacity of the natural Ge crystal agrees within 2% with the best data available in the literature taken on much larger masses of Ge.


Source:IOPscience

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

2019年8月9日星期五

Thin germanium–carbon layers deposited directly on silicon for metal–oxide–semiconductor devices

We report the growth process and materials characterization of germanium–carbon alloys (Ge1−xCx) deposited directly on Si (1 0 0) substrates by ultra-high-vacuum chemical vapour deposition. The Ge1−xCx films are characterized by transmission electron microscopy, etch-pit density, x-ray diffraction, secondary ion mass spectrometry and electron energy loss spectroscopy. The results show that the films exhibit low threading dislocation densities despite significant strain relaxation. We also present evidence for carbon segregation in the Ge1−xCx and interpret these results as a strain relaxation mechanism.


Source:IOPscience

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

2019年8月1日星期四

New concept of planar germanium MOSFET with stacked germanide layers at source/drain

In this paper, we have proposed and simulated one novel Schottky barrier germanium-based MOSFET structure. Herein, the source/drain region of the device is consisted with two stacked layers of germanide materials. Different barrier heights of the top and bottom contact are hence formed with channel respectively. The top barrier height is designed lower enough to enlarge drive current, and the bottom barrier height is higher (nearly mid-gap) to diminish the leakage current. The working mechanism and the performance of n- and p-type devices is studied. Comparisons between dual barrier structure and single barrier structure are also carried out. The results show that the characteristics have been significantly enhanced with the proposed dual barrier structure. Besides, the devices' performance is nearly insensitive to germanium thickness, which leads to the relax of the requirement of germanium-on-insulator (GeOI) structures for leakage immunization.



Source:IOPscience

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

2019年7月23日星期二

Characteristics of Germanium-on-Insulators Fabricated by Wafer Bonding and Hydrogen-Induced Layer Splitting

There is considerable interest in germanium-on-insulator (GeOI) because of its advantages in terms of device performance and compatibility with silicon processing. In this paper, fabricating GeOI by hydrogen-induced layer splitting and wafer bonding is discussed. Hydrogen in germanium exists in molecular form and is prone to outdiffusion, resulting in a storage-time dependence of blistering. In contrast to the case of silicon, little effect of substrate doping on blistering is observed in germanium. Hydrogen implantation in germanium creates both {100}- and {111}-type microcracks. These two types of platelets are located in the same region for (111)-oriented wafers, but in different zones for (100) samples. This variation in distribution explains the smoother splitting of (111) surfaces than that of (100) surfaces. Hydrogen implantation also introduces a significant concentration of charged vacancies, which affect dopant diffusion in the transferred germanium film. Boron, with a negligible Fermi-level dependence, shows an identical diffusion profile to that of bulk germanium. In contrast, phosphorus diffusion is enhanced in the fabricated GeOI layers. These results also shed light on the understanding of dopant diffusion mechanisms in germanium.


Source:IOPscience

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

2019年7月17日星期三

Investigation of amorphous germanium contact properties with planar detectors made from USD-grown germanium crystals

The characterization of detectors fabricated from home-grown crystals is the most direct way to study crystal properties. We fabricated planar detectors from high-purity germanium (HPGe) crystals grown at the University of South Dakota (USD). In the fabrication process, a HPGe crystal slice cut from a USD-grown crystal was coated with a high resistivity thin film of amorphous Ge (a-Ge) followed by depositing a thin layer of aluminum on top of the a-Ge film to define the physical area of the contacts. We investigated the detector performance including the I-V characteristics, C-V characteristics and spectroscopy measurements for a few detectors. The results document the good quality of the USD-grown crystals and electrical contacts.



Source:IOPscience

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

2019年7月9日星期二

Infrared 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

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com