Quantitative atomic resolution at interfaces: Subtraction of the background in STEM images with the example of (Ga,In)P/GaAs structures

The III/V semiconductor heterostructures are part of many devices. Often, interfaces play a crucial role as they influence charge carrier transport and recombination. The knowledge of the interface structure at an atomic level is vital for a controlled performance in the devices. In the present paper, to quantitatively evaluate the interface, high angle annular dark field (HAADF) imaging in scanning transmission electron microscopy (STEM) is utilized. (Ga,In)P/GaAs has been chosen as an example material system, as this interface can be grown under many highly different conditions and as it is a lattice-matched interface. Moreover, as atoms with highly different atomic number form this interface, they can be used to study the influence of diffuse scattering in STEM HAADF on composition evaluation with atomic resolution. It is shown that the STEM HAADF image background intensity can significantly influence the characterization; therefore, a background intensity map subtraction method is also shown with the focus of applicability to the mixed III/V alloys and keeping atomic resolution. In this paper, we investigate four technologically relevant (Ga,In)P/GaAs interfaces grown at highly different conditions and correlate the revealed interfacial features as well as the chemical compositions with the growth conditions to optimize the growth processes. It is found that growth at 525 °C leads to sharper interfaces. A binary GaP interlayer between GaAs and (Ga,In)P can lead to more abrupt transitions at each sublattice, group III as well as group V; however, the interface becomes wider overall.