This review provides numerical and graphical information about many (but by no means all) of the physical and electronic properties of GaAs that are useful to those engaged in experimental research and development on this material. The emphasis is on properties of GaAs itself, and the host of effects associated with the presence of specific impurities and defects is excluded from coverage. The geometry of the sphalerite lattice and of the first Brillouin zone of reciprocal space are used to pave the way for material concerning elastic moduli, speeds of sound, and phonon dispersion curves. A section on thermal properties includes material on the phase diagram and liquidus curve, thermal expansion coefficient as a function of temperature, specific heat and equivalent Debye temperature behavior, and thermal conduction. The discussion of optical properties focusses on dispersion of the dielectric constant from low frequencies [κ0(300)=12.85] through the reststrahlen range to the intrinsic edge, and on the ass...

Semiconducting and other major properties of gallium arsenide

The effects of microcrystal size and shape on the one phonon Raman spectra of crystalline semiconductors

Local mechanical stress is currently an important topic of concern in microelectronics processing. A technique that has become increasingly popular for local mechanical stress measurements is micro-Raman spectroscopy. In this paper, the theoretical background of Raman spectroscopy, with special attention to its sensitivity for mechanical stress, is discussed, and practical information is given for the application of this technique to stress measurements in silicon integrated circuits. An overview is given of some important applications of the technique, illustrated with examples from the literature: the first studies of the influence of external stress on the Si Raman modes are reviewed; the application of this technique to measure stress in silicon-on-insulator films is discussed; results of measurements of local stress in isolation structures and trenches are reviewed; and the use of micro-Raman spectroscopy to obtain more information on stress in metals, by measuring the stress in the surrounding Si substrate is explained.

https://iopscience.iop.org/article/10.1088/0268-1242/11/2/001/pdf

Micro-Raman spectroscopy to study local mechanical stress in silicon integrated circuits

This paper gives a brief review of the effect of temperature and pressure on Raman spectra. Anharmonicity, defined by the cubic, quartic and higher terms in the potential expansion, is shown to be responsible for various properties such as dilatation or for variations of wavenumber and half-width of Raman bands with temperature and pressure, or may be strongly involved in phase transitions. This contribution does not pretend to be an exhaustive review on the subject but aims to introduce some basic concepts in a tutorial way before showing how intricated are these manifestations of anharmonicity. Copyright © 2003 John Wiley & Sons, Ltd.

Effect of pressure and temperature on Raman spectra of solids: anharmonicity

Silicon, germanium, and related alloys, which provide the leading materials platform of electronics, are extremely inefficient light emitters because of the indirect nature of their fundamental energy bandgap. This basic materials property has so far hindered the development of group-IV photonic active devices, including diode lasers, thereby significantly limiting our ability to integrate electronic and photonic functionalities at the chip level. Here we show that Ge nanomembranes (i.e., single-crystal sheets no more than a few tens of nanometers thick) can be used to overcome this materials limitation. Theoretical studies have predicted that tensile strain in Ge lowers the direct energy bandgap relative to the indirect one. We demonstrate that mechanically stressed nanomembranes allow for the introduction of sufficient biaxial tensile strain to transform Ge into a direct-bandgap material with strongly enhanced light-emission efficiency, capable of supporting population inversion as required for providing optical gain.

https://www.pnas.org/content/pnas/108/47/18893.full.pdf

Direct-bandgap light-emitting germanium in tensilely strained nanomembranes

In this paper we report measurements of the effects of large static uniaxial stress along [001], [111], and [110] on the frequency of the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ensuremath{\approx}0$ optical phonons in Ge, GaAs, GaSb, InAs, and ZnSe using first-order Raman scattering. In the absence of stress, the first-order Stokes-Raman spectrum of diamond-type materials exhibits a single peak which corresponds to the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ensuremath{\approx}0$ triply degenerate optical phonons (${F}_{2g}$ or ${\ensuremath{\Gamma}}_{{25}^{\ensuremath{'}}}$) while the zinc-blende materials exhibit two peaks, corresponding to the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ensuremath{\approx}0$ LO and TO phonons. The application of the uniaxial stress causes polarization-dependent splittings and/or shifts which are linear in the stress. From these observed splittings and shifts we have obtained experimental values for the phenomenological coefficients ($p, q, \mathcal{r}$) which describe the changes in the "spring constant" of these optical phonons with strain. Comparison of the experimental values is made with several theoretical considerations based on bond-stretching and bond-bending interactions between atoms. The shift due to the hydrostatic component of the strain yields a value for the mode-Gr\"uneisen parameter, which is compared with the results of hydrostatic-pressure measurements. For the zinc-blende-type materials, the doubly degenerate TO-phonon line exhibits both a splitting and shift with stress, while only a shift is observed for the singlet LO-phonon line. In the case of the III-V compounds, one of the split TO lines has a stress dependence equal to that of the LO-phonon line, while this is not the case for the group II-VI material (ZnSe) we have investigated. This latter result is interpreted in terms of the stress dependence of the effective charge.

Stress-Induced Shifts of First-Order Raman Frequencies of Diamond- and Zinc-Blende-Type Semiconductors

Photoreflectance and electroreflectance in silicon

The seasonal performance of a heat pump indicates its average performance during the heating and/or cooling season, taking into account the different energy demands and their variability over time. Several European and international regulations and policies related with energy efficiency and the reduction of the carbon footprint of energy related products are affecting the heat pump industry. Among them, the ecodesign regulations impose minimum energy efficiency values for heat pumps, efficiencies that are based on the seasonal coefficient of performance. This work is focused on a domestic brine-to-water heat pump for low-temperature applications. The methodology to determine its seasonal coefficient of performance (SCOP) according to the European standard EN 14825 is explained and evaluated based on experimental results. The impact on the SCOP of using some technology options such as fixed or variable speed compressors, and fixed or variable outlet temperature operation is evaluated. Results show that between the lowest and highest efficient option, the SCOP can be improved by 26%.

/pdf/seasonal-efficiency-of-a-brine-to-water-heat-pump-with-269pjdp6.pdf

F. Cerdeira

Papers

Stress-Induced Shifts of First-Order Raman Frequencies of Diamond- and Zinc-Blende-Type Semiconductors

Photoreflectance and electroreflectance in silicon

Seasonal Efficiency of a Brine-to-Water Heat Pump with Different Control Options according to Ecodesign Standards