Matter is what matters

In order to go beyond the state of the art, we develop novel materials and nanostructures with enhanced properties. For example, novel piezoelectric materials are needed for more efficient and compact acoustic devices operating well into GHz frequency range. Investigation of coupling between phonons and quantum systems motivates us to research growth of high-quality semiconductor quantum wells and quantum dots, as well as deterministically fabricated color centers. We also push the limits of the micro- and nanostructure fabrication by using advanced patterning and growth methods. These advances are a backbone of our research.

Current focus points

  • Novel piezoelectrics: We study high-quality piezoelectric materials (e.g., GaAs, ZnO, AlN) as well as emerging ones (e.g., AlScN) for the generation of acoustic waves with record-high frequencies above 20 GHz.
  • Quantum systems: Semiconductor quantum wells and LDE-grown quantum dots as well as color centers in 2D materials (e.g., SiC) are the focus here.
  • Photonic platforms: Combining MBE growth with photo- and electron beam lithography and FIB, we grow patterned microcavities, which allow us to engineer photonic and phononic density of states.
  • Understanding nano-sound: Using numerical simulations, we aim to unveil the mechanisms responsible for acoustic losses and factors limiting the coupling strength of GHz strain in nanostructures.

Selected Publications

Author: P. L. J. Helgers, J. A. H. Stotz, H. Sanada, Y. Kunihashi, K. Biermann & P. V. Santos
Title: Flying electron spin control gates
Source: Nat. Commun. 13, 5384 (2022)

Author: M. Yuan, K. Biermann, S. Takada, C. Bäuerle, & P. V. Santos, 
Title: Remotely pumped GHz antibunched emission from single exciton centers in GaAs
Source: ACS Photonics 8, 3, 758–764 (2021)

Author: K. Biermann, P. L. J. Helgers, A. Crespo-Poveda, A. S. Kuznetsov, A. Tahraoui, B. Röben, X. Lü, L. Schrottke, P. V. Santos & H. T. Grahn
Title: In-situ control of molecular beam epitaxial growth by spectral reflectivity analysis
Source: J. Cryst. Growth 557, 125993 (2021)