**2. Elemental semiconductor material**

Nowadays, almost 95% of all the semiconductors are fabricated on Si material. Si semiconductors began to be used in the mid-1960s. The silicon devices demonstrate better and stable properties at room temperature. Furthermore, generating high-purity silicon wafer can be relatively easily achieved by the so-called Czochralski process. This is a method of crystal growth used to obtain single crystals of semiconductors, where high-quality silicon dioxide can be grown at room temperature [3–8]. From the economic perspective, high-purity Si for

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

device applications is much cheaper due to the fact that Si consists of 25% of the Earth's crust in the form of silica and silicates, which makes Si the second-abundant material after oxygen. As of now, Si technology is the leading technology surpassing all other material applications combined. However, a preferred choice of material for advanced ICs during the beginning of the semiconductor era in 1960 was interestingly Ge over Si after the invention of the first transistor with Ge in 1947. In the twenty-first century, the return of advanced Ge devices preparing post-Si device era invites us to look into advantages of Ge advanced devices, which makes it only possible with current state-of-art advanced technologies for at least next 50 years.

silicon and tin; therefore, it was called eka-silicon (Es), with estimated atomic weight of 72.0, which is not far off from 72.630, the standard atomic weight in modern chemistry [2, 9]. Although Ge is 50th in the relative abundance of elements in the Earth's crust, Ge came to be known relatively late in the history of chemistry due to the fact that it is rarely discovered in high concentration [2]. In 1886, a German chemist, Clemens Winkler was able to isolate it, and

Introductory Chapter: Advanced Material and Device Applications with Germanium

http://dx.doi.org/10.5772/intechopen.80872

3

Until the late 1930s, Ge was considered to be a poorly conducting metal [10], rather than a semiconductor, which made Ge economically insignificant. However, this had changed after World War II when Ge's semiconducting properties of diodes were found. In other words, the switching property of Ge diodes initiated the initial development of Ge devices [11, 12]. The first application was for the use in radar units as a frequency mixer element in microwave radar receivers by producing pure Ge crystal mixer diodes with the point-contact Schottky diode structure during the war period. During the post-war period, the development and manufacturing of solid-state Ge devices became a major stream in the semiconductor industry. From 1950 to the early 1970s, the Ge-related market increased for applications in transistors, diodes, and rectifiers [13]. For example, in the US, a few hundred pounds of production in 1946 greatly grew to more than 45 metric tons until 1960 in order to meet the market demand. However, soon after, high-purity silicon began replacing germanium in transistors, diodes, and rectifiers [13]. For example, the company that became Fairchild Semiconductor was founded in 1957 with the express purpose of producing silicon transistors. Silicon has superior electrical properties, but it requires much greater purity and that could not be commercially achieved in the early years of semiconductor electronics. Meanwhile, demand for germanium in fiber optics communication networks, infrared night vision systems, and polymerization catalysts increased dramatically. These end users represented 85% of worldwide germanium consumption in 2000 [12, 13].

Under the standard temperature (273.15 K) and pressure (105 Pa), Ge is a brittle, silverywhite, semi-metallic element [12]. As pure Ge is not mined as a primary material, Ge can be produced as a by-product of base metal refining [14]. Ge can be mostly found in the form of sphalerite zinc ores where it is concentrated in amounts as great as 0.3%, argyrodite (a sulfide of germanium and silver), and germanite (containing 8% of the element) [14, 15]. With sphalerite zinc ores, Ge concentrates are first purified using a chlorination and distillation process

Ge metal powder. Ge powder is cast into bars at high temperatures over 1720.85 F, which are treated by the zone-refining process to isolate and remove impurities. After this process, highpurity Ge metal bars are finally produced. Commercial Ge metal is often more than 99.999% pure. Zone-refined Ge can further be grown into crystals, which are sliced into thin pieces for

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**).

) [15]. Germanium tetrachloride is hydrolyzed

), which is reduced with hydrogen to form

found it similar to antimony, named in honor of his home country.

that produces germanium tetrachloride (GeCl4

use in semiconductors and optical lenses [15].

**3. Applications and opportunities of germanium**

and dried, producing germanium dioxide (GeO2

In 1947, two scientists at the Bell Telephone Laboratories, John Bardeen and Walter Brattain, made a triangular insulating wedge where two thin gold contacts with approximately 50-umwide gap were glued on. They pressed this wedge into a slab of Ge and made a third contact on the bottom of the slab. They applied forward bias between one gold contact and the bottom of the Ge slab while applying reverse bias between the other gold contact and the bottom. This turned a small signal into a larger signal with the flow of current through this configuration, which had changed forever the history of semiconductors by inventing the first transistor—the amplifier and switch, arguably the most important invention of the twentieth century (see **Figure 1**).

At the critical juncture of the post-Si era, serious efforts searching for a new semiconductor material to replace long-standing Si devices began. In the past 10 years, most of leading semiconductor companies have begun to consider a certain change in components of their IC design such as the current-carrying channel, which is the very heart of a transistor. The idea is to replace the Si with a material that can move current at significantly greater rates. Compared to Si channels, alternative transistors with such channels could allow design engineers to design faster, denser, and low-power circuits, meaning better and cheaper smartphones, computers, and numerous IoT gadgets and applications in the market.

The existence and properties of such a material were first predicted by Dmitri Mendeleev in 1869, by filling a gap in the carbon family, in his periodic table of elements, located between

**Figure 1.** A stylized replica of the first transistor [2].

silicon and tin; therefore, it was called eka-silicon (Es), with estimated atomic weight of 72.0, which is not far off from 72.630, the standard atomic weight in modern chemistry [2, 9]. Although Ge is 50th in the relative abundance of elements in the Earth's crust, Ge came to be known relatively late in the history of chemistry due to the fact that it is rarely discovered in high concentration [2]. In 1886, a German chemist, Clemens Winkler was able to isolate it, and found it similar to antimony, named in honor of his home country.

device applications is much cheaper due to the fact that Si consists of 25% of the Earth's crust in the form of silica and silicates, which makes Si the second-abundant material after oxygen. As of now, Si technology is the leading technology surpassing all other material applications combined. However, a preferred choice of material for advanced ICs during the beginning of the semiconductor era in 1960 was interestingly Ge over Si after the invention of the first transistor with Ge in 1947. In the twenty-first century, the return of advanced Ge devices preparing post-Si device era invites us to look into advantages of Ge advanced devices, which makes it only possible with current state-of-art advanced technologies for at least next 50 years.

2 Advanced Material and Device Applications with Germanium

In 1947, two scientists at the Bell Telephone Laboratories, John Bardeen and Walter Brattain, made a triangular insulating wedge where two thin gold contacts with approximately 50-umwide gap were glued on. They pressed this wedge into a slab of Ge and made a third contact on the bottom of the slab. They applied forward bias between one gold contact and the bottom of the Ge slab while applying reverse bias between the other gold contact and the bottom. This turned a small signal into a larger signal with the flow of current through this configuration, which had changed forever the history of semiconductors by inventing the first transistor—the amplifier and switch, arguably the most important invention of the twentieth century (see **Figure 1**).

At the critical juncture of the post-Si era, serious efforts searching for a new semiconductor material to replace long-standing Si devices began. In the past 10 years, most of leading semiconductor companies have begun to consider a certain change in components of their IC design such as the current-carrying channel, which is the very heart of a transistor. The idea is to replace the Si with a material that can move current at significantly greater rates. Compared to Si channels, alternative transistors with such channels could allow design engineers to design faster, denser, and low-power circuits, meaning better and cheaper smartphones, com-

The existence and properties of such a material were first predicted by Dmitri Mendeleev in 1869, by filling a gap in the carbon family, in his periodic table of elements, located between

puters, and numerous IoT gadgets and applications in the market.

**Figure 1.** A stylized replica of the first transistor [2].

Until the late 1930s, Ge was considered to be a poorly conducting metal [10], rather than a semiconductor, which made Ge economically insignificant. However, this had changed after World War II when Ge's semiconducting properties of diodes were found. In other words, the switching property of Ge diodes initiated the initial development of Ge devices [11, 12]. The first application was for the use in radar units as a frequency mixer element in microwave radar receivers by producing pure Ge crystal mixer diodes with the point-contact Schottky diode structure during the war period. During the post-war period, the development and manufacturing of solid-state Ge devices became a major stream in the semiconductor industry. From 1950 to the early 1970s, the Ge-related market increased for applications in transistors, diodes, and rectifiers [13]. For example, in the US, a few hundred pounds of production in 1946 greatly grew to more than 45 metric tons until 1960 in order to meet the market demand. However, soon after, high-purity silicon began replacing germanium in transistors, diodes, and rectifiers [13]. For example, the company that became Fairchild Semiconductor was founded in 1957 with the express purpose of producing silicon transistors. Silicon has superior electrical properties, but it requires much greater purity and that could not be commercially achieved in the early years of semiconductor electronics. Meanwhile, demand for germanium in fiber optics communication networks, infrared night vision systems, and polymerization catalysts increased dramatically. These end users represented 85% of worldwide germanium consumption in 2000 [12, 13].

Under the standard temperature (273.15 K) and pressure (105 Pa), Ge is a brittle, silverywhite, semi-metallic element [12]. As pure Ge is not mined as a primary material, Ge can be produced as a by-product of base metal refining [14]. Ge can be mostly found in the form of sphalerite zinc ores where it is concentrated in amounts as great as 0.3%, argyrodite (a sulfide of germanium and silver), and germanite (containing 8% of the element) [14, 15]. With sphalerite zinc ores, Ge concentrates are first purified using a chlorination and distillation process that produces germanium tetrachloride (GeCl4 ) [15]. Germanium tetrachloride is hydrolyzed and dried, producing germanium dioxide (GeO2 ), which is reduced with hydrogen to form Ge metal powder. Ge powder is cast into bars at high temperatures over 1720.85 F, which are treated by the zone-refining process to isolate and remove impurities. After this process, highpurity Ge metal bars are finally produced. Commercial Ge metal is often more than 99.999% pure. Zone-refined Ge can further be grown into crystals, which are sliced into thin pieces for use in semiconductors and optical lenses [15].
