The technical deliverables were all about determining dopant densities with 50 nm resolution in III-V samples geared towards solar cell applications. Here, multi-junction solar cells and quantum dot based solar cells were in the focus.
In order to reach these objectives:
- METAS developed design specifications for various test samples fabricated by collaborators within the project.
- The SMM’s spatial resolution was demonstrated to be ~50 nm by scanning a tunnel junction.
- A wide range of different samples has been measured (multilayer/-junctions samples, quantum dots, etc.).
- In collaboration with METAS’ AFM group, the topography of a quantum dot sample has been determined. Demonstrating its degradation and the need for new, clean samples.
The major outcome of the project is a versatile calibration routine to determine carrier densities being functional even on GaAs. The results obtained compare well with reference method SIMS (Secondary Ion Mass Spectrometry) and the algorithm is also universally applicable to different SMM setups within a wide frequency range.
In the course of the project, general SMM improvements to meet technical challenges regarding spatial resolution and sensitivity had to be achieved:
- Microscope head, electric circuits for impedance matching and the sample holder were completely redesigned.
- The SMM’s self-written control software was revised and extended.
- A new sample preparation routine, which is generally applicable also for future pro-jects, was introduced.
