Germanium (Ge): Semiconductor Material and Germanium Oxide Synthesis for Optical Applications

Germanium (Ge) is a chemical element with atomic number 32 and atomic weight 72.64, located in Period 4, Group IVA of the periodic table. It is a lustrous, hard, gray-white metalloid with properties similar to silicon and tin. Germanium is insoluble in water, dilute HCl, and weak alkalis but dissolves in aqua regia, concentrated HNO₃, or H₂SO₄. It exhibits amphoteric behavior, dissolving in molten alkalis, peroxides, or alkali metal nitrates/carbonates. Germanium remains stable in air under normal conditions.

Applications

1. Semiconductor manufacturing (transistors, diodes, IR optics).
2. Germanium oxide (GeO₂) production (fiber optics, phosphors).

Product Series

Health and Safety Information

Packaging Specifications

• Standard packaging: 50 kg/drum, 500 kg/pallet, ton bags
• Sample packaging: 500 g/bag, 1 kg/bottle

Chemical Properties of Germanium

Germanium is chemically stable and does not react with air or water vapor at room temperature, but quickly forms germanium dioxide (GeO₂) at 600–700°C. It does not react with hydrochloric acid or dilute sulfuric acid. In hot concentrated sulfuric acid, germanium dissolves slowly. It dissolves readily in nitric acid and aqua regia. The reaction between alkaline solutions and germanium is weak, but molten alkali in air can rapidly dissolve germanium. Germanium does not react with carbon, so it can be melted in graphite crucibles without carbon contamination.

Oxidation Behavior

Germanium oxidizes at relatively high temperatures, accompanied by weight loss due to the formation of GeO, which is highly volatile. Researchers have studied the oxidation process of germanium surfaces: first, germanium is reduced with CO at 600°C to remove surface-bound or adsorbed oxygen. Then, germanium is oxidized under 10 kPa oxygen pressure at 25–400°C, forming the first oxide layer within just 1 minute. When the temperature exceeds 250°C, the second oxide layer forms quickly. As the temperature increases further, the oxidation rate slows significantly. After oxidizing at 400°C for 3 hours, a GeO₂ film with a thickness of 1.75 nm is formed.

Dissolution Behavior in Different Solvents

Germanium exhibits different corrosion and dissolution behaviors in various solvents. N-type germanium has a slightly more positive dissolution potential than p-type, so it dissolves faster in the same solution. Germanium is easily soluble in hot acids, hot alkalis, and H₂O₂ with oxidizers. It is poorly soluble in dilute sulfuric acid, hydrochloric acid, and cold alkaline solutions. Germanium is insoluble in water at 100°C, but in oxygen-saturated water at room temperature, its dissolution rate approaches 1 μg/(cm·h).

Extraction Method of Germanium

The extraction method of germanium involves first chlorinating germanium concentrate with concentrated hydrochloric acid to produce germanium tetrachloride (GeCl₄). The main impurity, arsenic, is then removed by hydrochloric acid solvent extraction. Next, the product undergoes two rounds of distillation in a quartz column and is washed with high-purity hydrochloric acid to obtain high-purity GeCl₄. High-purity water is used to hydrolyze GeCl₄, yielding high-purity germanium dioxide (GeO₂). Some impurities remain in the hydrolysis mother liquor, so the hydrolysis process also serves as a purification step. The pure GeO₂ is dried and calcined, then reduced with hydrogen at 650–680°C in a quartz tube within a reduction furnace to obtain metallic germanium. Ultra-high-purity germanium for the semiconductor industry (with impurities below 1/10¹⁰) can be obtained using zone refining technology.

Key Reactions

$$4\text{HCl}+{\text{GeO}}^2\to {\text{GeCl}}^4+2{\text{H}}^2\text{O}$$$${\text{GeCl}}^4+(n+2){\text{H}}^2\text{O}\to {\text{GeO}}^2\cdot n{\text{H}}^2\text{O}+4\text{HCl}$$$${\text{GeO}}^2+2{\text{H}}^2\to \text{Ge}+2{\text{H}}^2\text{O}$$