Very high mobilities for holes in strained germanium quantum wells

After being supplanted by silicon 50 years ago, germanium is currently making a comeback. Strained germanium quantum wells have superior properties, including very high mobilities for holes and strong spin-orbit coupling, making it a promising candidate material for spin quantum computation. Furthermore, germanium is compatible with industrial silicon technology, such that many concepts can be borrowed to realize advanced devices.

We are able to grow strained germanium quantum well structures and have developed a fabrication scheme for these structures. We observe Schubnikov-de Haas oscillations, the quantum Hall effect, signs of the fractional quantum hall effect and find state-of-the-art mobilities for a 2D hole gas in germanium.

Currently we are working on the fabrication of more advanced structures, such as quantum point contacts and quantum dots in this system. Furthermore, we are studying the novel effects that arise when contacting the germanium quantum well with superconductors. This gives rise to intriguing questions such as what happens when superconductivity is introduced in low-dimensional hole systems.