**3. Applications and opportunities of germanium**

In general, the United States Geological Survey (USGS) classified Ge applications into five groups such as IR optics (30%); fiber optics (20%); polyethylene terephthalate—PET (20%); electronic and solar (15%); and phosphors, metallurgy, and organic applications (5%) (see **Figure 2**).

**Figure 2.** US Ge applications [12].

As mentioned earlier, zone-refined Ge crystals are grown and sliced to form lenses and window for IR and/or thermal imaging optical systems [15]. A major developer and customer is the military, for the application of advanced weapon systems such as small hand-held and weapon-mounted devices.

As for spintronics, Ge is an emerging material for spin-based quantum computing applications. After finding the Ge property of spin transport at room temperature in 2010 [17], scientists recently showed very long coherence times of donor electron spins in Ge [16–18].

**Figure 3.** A typical single optical fiber, demonstrating core silica (1) with germanium oxide dopants, (2) cladding, (3)

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Soon after the birth of Ge transistors, Si transistors' replacement of Ge transistor happened in the early 1970s due to the reasons mentioned earlier. Today, however, scientists' efforts to achieve lower-power and higher-speed transistors have brought Ge back to the main interest of the semiconductor industry. By implementing Ge as current-carrying channel (channel) of the transistor, transistors are improved based on a fundamental property, which is the mobility of electrons and holes. Electrons move nearly three times as readily in Ge as they do in Si near room temperature. Furthermore, holes move about four times as readily in Ge. This is ultimately related to the difference in band structure between Ge and Si. Consequently, the faster these electrons and holes can move, the faster the resulting circuits can be. Since less voltage can be applied to draw

Since Ge band gap is small, 0.67 eV, Ge is transparent in the infrared wavelengths, which makes it possible to employ them in infrared spectroscopes and other extremely sensitive optical equipment such as infrared detectors. There are a number of infrared optical applications for Ge which can be readily cut and polished into windows and lenses [16, 20–22]. In particular, military applications rely on Ge optical properties. For instance, Ge is used in the front optic of thermal imaging cameras working in the 8–14-μm range for passive thermal imaging and for hot-spot detection in the military, mobile night vision, and firefighting appli-

those charge carriers along, circuits can also consume considerably less energy [19].

cations (see **Figure 4**) [16, 20, 23, 24].

buffer, and (4) jacket [16].

In fiber optics, telecommunication is possible by confining the light signal to their core, with Ge fibers acting as a waveguide for the electromagnetic light wave. Hence, the higher refractive index of the center of the fibers can improve the confinement of the light signal. Doping fused silica with Ge dopants can improve the refractive index in the silica glass of fiber optic lines by reducing signal loss (see **Figure 3**).

Regarding the production of PET plastics, roughly 17 metric tons of germanium dioxide is consumed each year as a polymerization catalyst. PET plastic is primarily used in beverage, liquid containers, and food.

In recent years, Ge has seen increasing use in precious metal alloys [12, 16]. In sterling silver alloys, for instance, it reduces firescale, increases tarnish resistance, and improves precipitation hardening. A tarnish-proof silver alloy trademarked Argentium contains 1.2% germanium [12, 16].

Introductory Chapter: Advanced Material and Device Applications with Germanium http://dx.doi.org/10.5772/intechopen.80872 5

**Figure 3.** A typical single optical fiber, demonstrating core silica (1) with germanium oxide dopants, (2) cladding, (3) buffer, and (4) jacket [16].

As for spintronics, Ge is an emerging material for spin-based quantum computing applications. After finding the Ge property of spin transport at room temperature in 2010 [17], scientists recently showed very long coherence times of donor electron spins in Ge [16–18].

Soon after the birth of Ge transistors, Si transistors' replacement of Ge transistor happened in the early 1970s due to the reasons mentioned earlier. Today, however, scientists' efforts to achieve lower-power and higher-speed transistors have brought Ge back to the main interest of the semiconductor industry. By implementing Ge as current-carrying channel (channel) of the transistor, transistors are improved based on a fundamental property, which is the mobility of electrons and holes. Electrons move nearly three times as readily in Ge as they do in Si near room temperature. Furthermore, holes move about four times as readily in Ge. This is ultimately related to the difference in band structure between Ge and Si. Consequently, the faster these electrons and holes can move, the faster the resulting circuits can be. Since less voltage can be applied to draw those charge carriers along, circuits can also consume considerably less energy [19].

As mentioned earlier, zone-refined Ge crystals are grown and sliced to form lenses and window for IR and/or thermal imaging optical systems [15]. A major developer and customer is the military, for the application of advanced weapon systems such as small hand-held and

In fiber optics, telecommunication is possible by confining the light signal to their core, with Ge fibers acting as a waveguide for the electromagnetic light wave. Hence, the higher refractive index of the center of the fibers can improve the confinement of the light signal. Doping fused silica with Ge dopants can improve the refractive index in the silica glass of fiber optic

Regarding the production of PET plastics, roughly 17 metric tons of germanium dioxide is consumed each year as a polymerization catalyst. PET plastic is primarily used in beverage,

In recent years, Ge has seen increasing use in precious metal alloys [12, 16]. In sterling silver alloys, for instance, it reduces firescale, increases tarnish resistance, and improves precipitation hardening. A tarnish-proof silver alloy trademarked Argentium contains 1.2% germanium [12, 16].

weapon-mounted devices.

**Figure 2.** US Ge applications [12].

liquid containers, and food.

lines by reducing signal loss (see **Figure 3**).

4 Advanced Material and Device Applications with Germanium

Since Ge band gap is small, 0.67 eV, Ge is transparent in the infrared wavelengths, which makes it possible to employ them in infrared spectroscopes and other extremely sensitive optical equipment such as infrared detectors. There are a number of infrared optical applications for Ge which can be readily cut and polished into windows and lenses [16, 20–22]. In particular, military applications rely on Ge optical properties. For instance, Ge is used in the front optic of thermal imaging cameras working in the 8–14-μm range for passive thermal imaging and for hot-spot detection in the military, mobile night vision, and firefighting applications (see **Figure 4**) [16, 20, 23, 24].

impacted by the process. The contributing authors are experts in their field with great in-depth knowledge, which is contained in this book. The authors strongly feel that this contribution

Introductory Chapter: Advanced Material and Device Applications with Germanium

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Department of Electronics and Computer Engineering Technology, Indiana State University,

[1] Smith RA. Semiconductors. 2nd ed. London: Cambridge University Press; 1979

[2] Wikipedia. History of the transistor [Internet]. Available from: https://en.wikipedia.org/

[3] Haller E. Ge-based devices from materials to devices. Materials Science in Semiconductor

[4] Teal GK, Sparks M, Buehler E. Single crystal germanium. Proceedings of the IRE.

[5] Prabhakaran K, Ogino T. Oxidation of Ge(100) and Ge(111) surfaces: An UPS and XPS

[6] Electronics History 4-Transistors [Internet]. [Updated: 2008]. National Academy of Engi-

[7] Greenwood NN, Earnshaw A. Chemistry of the Elements. 2nd ed. Oxford: Butterworth-

[8] Holleman AF, Wiberg E, Wiberg N. Lehrbuch der Anorganischen Chemie. 102nd ed.

[9] Masanori Kaji DI. Mendeleev's concept of chemical elements and the principles of chem-

[10] Germanium for Electronic Devices [Internet]. W.K./The New York Times. May 10, 1953. Available from: https://www.nytimes.com/1953/05/10/archives/germanium-for-

[11] Computer History Museum. Semiconductor diode rectifiers serve in WW II [Internet].

neering. Available from: http://www.greatachievements.org/?id=3967

istry. Bulletin for the History of Chemistry. 2002;**27**(1):4-16

might be of interest to readers and help to expand the scope of their knowledge.

Address all correspondence to: sanghyun.lee@indstate.edu

wiki/History\_of\_the\_transistor

study. Surface Science. 1995;**325**:263-271

Berlin/New York: de Gruyter; 2007

Processing. 2006;**9**:408

1952;**40**:906-909

Heinemann; 1997

electronic-devices.html

[Accessed: Aug 22, 2008]

**Author details**

Terre Haute, USA

**References**

Sanghyun Lee

**Figure 4.** Germanium photodetector comprised of various layers of germanium [21].
