Evolutionary inverse design numerical approaches for improved III-Sb devices
III-Sb semiconductor materials cover a huge range of possible nanostructures, starting from compressively strained type-II GaSb/GaAs quantum dots (QDs) or, if the roles are interchanged, tensile strained GaAs/GaSb QDs, to Sb-containing QDs on other substrates such as GaP, just to mention a few examples. Owing to the large space of possible III-Sb heterostructures, applications include memory cells, lasers, LIDAR, detectors in the infra-red range, or quantum light sources. However, large parts of the opportunities linked to the III-Sb are either unexplored or even unknown, which led us look for a systematic approach to find optimal solutions for given target properties, namely the inverse design method.
Our approach is to employ evolutionary strategies to systematically scan the configuration space for optimal design candidates. The configuration space is spanned by the morphological parameters describing the nanostructure in question. In our case the parameters are comprised of size, shape, chemical composition, and growth axis of quantum dots. The associated target properties could be a given wavelength and maximal oscillator strength or wave function overlap, respectively, at this wavelength, or – if memory cells are looked for – hole localization energies respective retention times. The prospective software module will be equipped with an open, generic interface to nextnano++ (provided by NEXTNANO) and tiberCAD (provided by TiberLab).
The evolutionary strategy is not only applicable to inverse design but also to the inverse bandstructure problem. Here, the target properties are replaced by measured spectroscopic signatures of existing samples and the task is to narrow down possible nanostructures that could yield such spectra. Thus, expensive high-resolution TEM/STM characterization could be avoided.