User:Pearsallt/sandbox

In his retirement, Smil has developed a public presence as a regular contributor to the IEEE Spectrum, a widely-read technology digest published by the IEEE the world’s foremost international body representing electrical engineers. His articles promote the continued use of fossil fuels :dismissing, for example, electrical vehicles as a wasteful technology distraction and renewable energies such as windpower as being fundamentally inadequate for public power grids.

Recently Smil has waded into epidemiology and public health fields in order to comment on the COVID-19 epidemic. His 2021 commentary in the IEEE Spectrum stated a cause and effect relationship in Sweden between excess deaths from COVID and the presence of foreigners in the population

“There is no doubt that Sweden’s numbers were inflated, in part, by the relatively high share in its population of the foreign born (who are more vulnerable to infection)—a quarter of the people are immigrants, and nearly a third have at least one parent born abroad.”

Smil has evolved from an iconoclast regarding environmental issues to a commentator typical of those from the far-right who like Smil also promote the continued extraction and use of coal and oil, who claim that the media have created a COVID pandemic crisis out of an unimportant disease, and that foreigners are responsible for elevated disease rates.

Indium Gallium Arsenide

Nomenclature
Indium Gallium Arsenide is a popular designation for Gallium Indium Arsenide (GaInAs). GaInAs is a pseudo-binary alloy composed of two III-V semiconducting materials: (GaAs)X and (InAs)1-X. The alloy is miscible over the entire compositional range from GaAs (bandgap = 1.42 eV at 300K) to InAs (bandgap = 0.34 eV at 300K). GaXIn1-XAs is a technologically important semiconductor widely exploited in optical communications, photovoltaics, sensor and laser applications.

According to standards of the IUPAC The preferred nomenclature for the alloy is GaXIn1-XAs where the group-III elements appear in order of increasing atomic number, as in the related alloy system AlXGa1-XAs.

Electronic and Optical Properties: Measurements on polycrystalline samples
Gallium Indium Arsenide has a lattice parameter that increases linearly with the concentration of InAs in the alloy. The liquid-solid phase diagram shows that during solidification from a solution containing GaAs and InAs, GaAs is taken up at a much higher rate than InAs, depleting the solution of GaAs. During growth from solution, the composition of first material to solidify is rich in GaAs while the last material to solidify is more rich in InAs. This feature has been exploited to produce ingots of GaInAs with graded composition along the length of the ingot. However, the strain introduced by the changing lattice constant causes the ingot to be polycrystalline, and limiting the characterization to a few parameters, with uncertainty due to the continuous compositional grading in the materials.

$$ Gain = \frac{\mu_{\rm e}}{\mu_{\rm h}} + \frac{\mu_{\rm e}V}{\pi L^2}$$

Properties of single-crystal GaInAs
Single crystal epitaxial films of GaInAs can be deposited on a single crystal substrate of III-V semiconductor having a lattice parameter close to that of the specific Gallium Indium Arsenide alloy to be synthesized. There are three substrates that can be used: GaAs, InAs and InP. A good match between the lattice constants of the film and substrate is required to maintain single crystal properties and this limitation permits small variation in composition on the order of a few per cent. Therefore the properties of epitaxial films of GaInAs grown on GaAs are very similar to GaAs and those grown on InAs are very similar InAs.

T.P. Pearsall was the first to show that epitaxial films of GaInAs could be grown on InP substrates. Ga0.47In0.53As is the alloy whose lattice parameter matches InP at 300K.

GaInAs lattice-matched to InP is a semiconductor with properties quite different from GaAs, InAs or InP. It has an energy band gap of 0.75 eV, an electron effective mass of 0.041 and an electron mobility close to 10,000 cm2V-1sec-1 at room temperature, all of which are more favorable for many electronic and photonic device applications when compared to GaAs, InP or even Si.

The bandgap energy of GaInAs can be determined from the peak in the photoluminescence spectrum, provided that the total impurity and defect concentration is less than 5 x 1016cm-3. The bandgap energy depends on temperature and increases as the temperature decreases, as can be seen in Fig. 3 for both n-type and p-type samples. The bandgap energy at room temperature is 0.75 eV, and lies between that of Ge and Si. By coincidence the bandgap of GaInAs is perfectly placed for photodetector and laser applications for the long-wavelength transmission window, the C-band) for optical fiber telecommunications.

Effective Mass The electron effective mass of GaInAs M*/m° = 0.041 is the smallest for any semiconductor material that functions at room temperature, that is, with an energy bandgap greater than 0.5 eV. The effective mass is determined from the curvature of the energy-momentum relationship: stronger curvature translates into lower effective mass and a larger radius of delocalization. In practical terms, a low effective mass leads directly to high carrier mobility, favoring higher speed of transport, and greater current carrying capacity. A lower carrier effective mass favors increased tunneling current, a direct result of delocalization.

There are two types of charge carriers in the valence band: light holes: m*/m° = 0.051 and heavy holes: m*/m° = 0.2 S.Y. Lin, C.T. Liu D.C. Tsui, E.D. Jones and L.R. Dawson, Appl.Pys. Lett. 55, Pp.666-8 (1989). The electrical and optical properties of the valence band are dominated by the heavy holes, because the density of these states is much greater than for light holes. This is reflected in the mobility of holes at 295K, which is a factor of 40 less than that for electrons. Cyclotron resonance of two‐dimensional holes in strained‐layer quantum well structure of (100)In0.20Ga0.80As/GaAs S. Y. Lin, C. T. Liu, D. C. Tsui, E. D. Jones, and L. R. Dawson Appl. Phys. Lett. 55, 666 (1989) | Cited 14 times

Applications
The principal application of GaInAs is infrared photodetection. The spectral response of a GaInAs photodiode is shown in Fig 5. Avalanche photodiodes offer the advantage of additional gain at the expense of response time. These devices are especially useful for detection of single photons in applications such as quantum key distribution where response time is not critical. Avalanche photodetectors require a special structure to reduce reverse leakage current due to tunnelling. The first practical avalanche photodiodes were designed and demonstrated by Nishida in 1979. In 1980, Pearsall developed a photodiode design that exploits the uniquely short diffusion time of high mobility of electrons in GaInAs, leading to an ultrafast response time. Fifteen years later, this structure was further developed in the 1990’s and named the UTC, or uni-travelling carrier photodiode. Other important innovations include the integrated photodiode – FET receiver and the engineering of GaInAs focal-plane arrays.

References T.P. Pearsall and M.A. Pollack, Semiconductors and Semimetals, vol 22D, Ed; W.T. Tsang, (New York, Academic Press, 1985)

T.P. Pearsall and R.W. Hopson, Jr, Electronic Materials Conference, Cornell University, 1977, published in J. Electron. Mat. 7, pp.133-146, (1978).

K. Nishida, K. Taguchi, and Y. Matsumoto, Appl. Phys. Lett. 35, pp.251-3, 1979

T.P. Pearsall and M. Piskorski A. Brochet, and J; Chevrier, IEEE J. Quant Electron QE-17, pp255-9, 1981

T.P. Pearsall, R.A. Logan C.G. Bethea, Electron Lett, 19, pp 611-612 1983.

N. Shimizu, N. Watanabe, T. Furuta, a,d T; Ishibashi, IEEE Photoni Tech. Letters, 10, 412-4, 1998

R.F. Leheny, R.E. Nahory, M.A. Pollack, A.A. Ballman, E.D. Beebe, J.C. DeWinter, and R.J. Martin, Electron./ Lett 16, pp353-5 1980.

Environmental safety Registration,_Evaluation,_Authorisation_and_Restriction_of_Chemicals

The synthesis of GaInAs, like that of GaAs most often involves the use of arsine(AsH3), an extremely toxic gas. Synthesis of InP likewise most often involves phosphine (PH3). Inhalation of these gases neutralizes oxygen absorption by the blood stream, and can be fatal within a few minutes if the toxic dose levels are exceeded


 * $$\frac{1}{\mu} = \frac{1}{\mu_{\rm impurities}} + \frac{1}{\mu_{\rm lattice}}$$