  The electronic, magnetic, thermoelectric, and topological properties of
Heusler compounds (composition $XYZ$ or $X_2 YZ$) are highly sensitive to
stoichiometry and defects. Here we establish the existence and experimentally
map the bounds of a \textit{semi} adsorption-controlled growth window for
semiconducting half Heusler FeVSb films, grown by molecular beam epitaxy (MBE).
We show that due to the high volatility of Sb, the Sb stoichiometry is
self-limiting for a finite range of growth temperatures and Sb fluxes, similar
to the growth of III-V semiconductors such as GaSb and GaAs. Films grown within
this window are nearly structurally indistinguishable by X-ray diffraction
(XRD) and reflection high energy electron diffraction (RHEED). The highest
electron mobility and lowest background carrier density are obtained towards
the Sb-rich bound of the window, suggesting that Sb-vacancies may be a common
defect. Similar \textit{semi} adsorption-controlled bounds are expected for
other ternary intermetallics that contain a volatile species $Z=$\{Sb, As,
Bi\}, e.g., CoTiSb, LuPtSb, GdPtBi, and NiMnSb. However, outstanding challenges
remain in controlling the remaining Fe/V ($X/Y$) transition metal
stoichiometry.
