  We combined in-situ scanning tunneling microscopy (STM) with the conventional
growth characterization methods of atomic force microscopy (AFM) and reflection
high energy electron diffraction (RHEED) to simultaneously assess atomic-scale
impurities and the larger-scale surface morphology of molecular beam epitaxy
(MBE) grown homoepitaxial InAs(111)A. By keeping a constant substrate
temperature and indium flux while increasing the As$_2$ flux, we find two
differing MBE growth parameter regions for optimized surface roughness on the
macro and atomic scale. In particular, we show that a pure step-flow regime
with strong suppression of hillock formation can be achieved, even on
substrates without intentional offcut. On the other hand, an indium adatom
deficient, low atomic defect surface can be observed for a high hillock
density. We identify the main remaining point defect on the latter surface by
comparison to STM simulations. Furthermore, we provide a method for extracting
root-mean-square surface roughness values and discuss their use for surface
quality optimization by comparison to scale-dependent, technologically relevant
surface metrics. Finally, mapping the separately optimized regions of the
growth parameter space should provide a guide for future device engineering
involving epitaxial InAs(111)A growth.
