Pure germanium bonds to aluminum in such a way that atomically distinct interfaces are created. This leads to the formation of a monolithic metal-semiconductor-metal heterostructure. This was reported on the website of the Vienna Technical University.

The particular advantage of this approach is that completely new technologies do not need to be developed. Mature and well-established semiconductor technologies can be used to create germanium-based quantum electronics.

“Germanium is a material that plays an important role in semiconductor technology to develop faster and more energy-efficient components. However, it is extremely difficult to manufacture high quality electrical contacts because even small impurities at the contact points can have a large impact on electrical properties. Therefore, we decided to develop a new manufacturing method that provides reliable contact properties, ”explained Dr. Masiar Sistani from the Institute of Solid State Electronics at TU Wien.

Temperature is the key. When germanium and nanoscale aluminum come into contact and heat up, the atoms of both materials begin to mix. At the same time, their speed is different. Germanium atoms move rapidly into aluminum, while aluminum atoms hardly penetrate germanium.

“If you connect two aluminum contacts to a thin germanium wire and raise the temperature to 350 ° C, germanium atoms diffuse beyond the edge of the nanowire. This creates voids into which aluminum can easily penetrate. As a result, only a few nanometers in the middle of the nanowire is made of germanium, the rest is filled with aluminum, ”explained Sistani.

This new method forms a perfect single crystal in which aluminum atoms are arranged in a single pattern. A perfectly clean transition is formed between germanium and aluminum.

The new heterostructure possesses excellent physical properties required for quantum technologies: high carrier mobility, excellent controllability of electric fields, and is well combined with already established microelectronic technologies.