Germanium

About: Germanium is a research topic. Over the lifetime, 22212 publications have been published within this topic receiving 382980 citations. The topic is also known as: Ge & element 32.

Nanometre-scale germanium photodetector enhanced by a near-infrared dipole antenna

Abstract: A critical challenge for the convergence of optics and electronics is that the micrometre scale of optics is significantly larger than the nanometre scale of modern electronic devices. In the conversion from photons to electrons by photodetectors, this size incompatibility often leads to substantial penalties in power dissipation, area, latency and noise1,2,3,4. A photodetector can be made smaller by using a subwavelength active region; however, this can result in very low responsivity because of the diffraction limit of the light. Here we exploit the idea of a half-wave Hertz dipole antenna (length ∼ 380 nm) from radio waves, but at near-infrared wavelengths (length ∼ 1.3 µm), to concentrate radiation into a nanometre-scale germanium photodetector. This gives a polarization contrast of a factor of 20 in the resulting photocurrent in the subwavelength germanium element, which has an active volume of 0.00072 µm3, a size that is two orders of magnitude smaller than previously demonstrated detectors at such wavelengths. By scaling down device size, the principles of radio antennas can be used in the optical regime. These optical antennas act as a bridge between optics and electronics, collecting and enhancing light to enable the creation of tiny semiconductor photodetectors.

Enhanced thermoelectric figure of merit in nanostructured n-type silicon germanium bulk alloy

Abstract: The dimensionless thermoelectric figure of merit (ZT) of the n-type silicon germanium (SiGe) bulk alloy at high temperature has remained at about one for a few decades. Here we report that by using a nanostructure approach, a peak ZT of about 1.3 at 900 °C in an n-type nanostructured SiGe bulk alloy has been achieved. The enhancement of ZT comes mainly from a significant reduction in the thermal conductivity caused by the enhanced phonon scattering off the increased density of nanograin boundaries. The enhanced ZT will make such materials attractive in many applications such as solar, thermal, and waste heat conversion into electricity.

Refractive index of silicon and germanium and its wavelength and temperature derivatives

Abstract: Refractive index data for silicon and germanium were searched, compiled, and analyzed. Recommended values of refractive index for the transparent spectral region were generated in the ranges 1.2 to 14 μm and 100–740 K for silicon, and 1.9 to 16 μm and 100–550 K for germanium. Generation of these values was based on a dispersion equation which best fits selected data sets covering wide temperature and wavelength ranges. Temperature derivative of refractive index was simply calculated from the first derivative of the equation with respect to temperature. The results are in concordance with the existing dn/dT data.

Thermal conductivity of Si–Ge superlattices

Abstract: The thermal conductivity of Si–Ge superlattices with superlattice periods 30 2 × 109 W m−2 K−1 at 200 K. Superlattices with relatively longer periods, L>130 A, have smaller thermal conductivities than the short-period samples. This unexpected result is attributed to a strong disruption of the lattice vibrations by extended defects produced during lattice-mismatched growth.

Structure and Adsorption Characteristics of Clean Surfaces of Germanium and Silicon

Abstract: Diffraction patterns obtained from atomically clean germanium surfaces contained half‐integral order beams in (110) azimuths for both (100) and (110) surfaces and in all azimuths for the (111) surface. These results are considered to be due to displacements of surface atoms from their normal bulk lattice positions in the surface plane. Adsorption of oxygen on all of these surfaces extinguished all of the diffraction beams which were not integral order.In addition to the normal surface lattice spacings of clean (111) and (100) surfaces of silicon, there were surface structures with larger spacings, most of which depended on the conditions of ion bombardment and/or subsequent heat treatment. Two such structures have been observed for the (100) surface of silicon; one is a double‐spaced lattice in the (110) azimuth, similar to that for germanium, and the other has a spacing about 8% greater than that of normal silicon and was obtained only after radiation quenching of the crystal from 1000°C. Two large‐spaced structures were observed for the (111) surface. All of these structures were extinguished by exposure to oxygen. Evidence is presented which indicates that these structures were not due to contamination but to the silicon itself.The method of determining the kinetics of gas adsorption from the low‐energy electron diffraction beams is outlined and the calculations of the fractional coverage and sticking probability are presented for oxygen. For silicon crystals, the calculations of surface coverages and sticking coefficients for oxygen were found to depend on the preceding treatments of the crystals. The rate of adsorption of oxygen was proportional to the pressure, at least for pressures below 10‐6 mm Hg, and depended on the preceding treatments of the crystals. After oxygen adsorption, the clean germanium surface could be regenerated by heating at 500°C for 30 min and for silicon it was regenerated by heating at 900°C for a few minutes. A comparison with results of other observers is given.