TA Success Stories: High-resolution bandgap mapping of GaAsBi, from the National Center for Physical Sciences and Technology in Lithuania to LPS Orsay

06/04/2022 | Success Stories

TA Success Stories: High-resolution bandgap mapping of GaAsBi, from the National Center for Physical Sciences and Technology in Lithuania to LPS Orsay

NCPST and LPS Orsay logos
NCPST and LPS Orsay logos

Many successful projects stem from transnational access provided by ESTEEM3. This week, we focus on the “High-resolution bandgap mapping of GaAsBi” project from the National Center for Physical Sciences and Technology (Lithuania) which was granted access to the International Laboratoire de Physique des Solides (LPS) at the CNRS in Paris (France) one of the ESTEEM3 TA providers.

The “High-resolution bandgap mapping of GaAsBi” project, carried by Dr. Tadas Paulauskas from the National Center for Physical Sciences and Technology (Lithuania), focuses on combined high-spatial and spectral resolution mapping of electronic structure variations in semiconducting GaAsBi alloys using STEM-EELS.

The project was granted access to facilities and expertise of the InternationalLaboratoire de Physique des Solides (LPS) at the CNRS in Paris (France) in Autumn 2019, as part of the transnational access campaign of ESTEEM3.

The main results of the project

The GaAsBi alloy represents the emerging class of bismuth-containing group III–V semiconductors. The incorporation of dilute amounts of large Bi atoms into GaAs lattice causes significant bandgap reduction and large spin-orbit band splitting. This offers advantageous properties for infrared optoelectronic devices, including lasers, photodetectors, and multi-junction solar cells.

In this project combined atomic-resolution STEM-HAADF imaging and monochromated EELS were employed to examine the structure-property relationships in GaAsBi. The HAADF images were analyzed by numerical atom-counting techniques to reveal the distribution of Bi atoms. The observed CuPtB-type ordering of Bi atoms was for the first time related to the pronounced optical anisotropy of these alloys. In addition, bulk plasmon peak shifts were mapped in GaAsBi using EELS. This allowed to quantify the local lattice strain and identify phase-separated domains, providing highly complementary information to X-ray diffraction-based techniques.

Successful outcomes

Dr. Tadas Paulauskas published two scientific publications in renowned journals:

Interested in Transnational Access to the leading European state-of-the-art Transmission Electron Microscopy (TEM)? Find out more about the procedure here!