Control of faceting during epitaxy is critical for nanoscale devices. This work identifies the origins of gaps and different facets during regrowth of InGaAs and InAs adjacent to patterned features. Molecular beam epitaxy near SiO2 or SiNx led to gaps, roughness, or polycrystalline growth, but low-arsenic metal modulated epitaxy produced smooth and gap-free (001) planar growth up to the gate. The resulting self-aligned field effect transistors (FETs) were dominated by FET channel resistance rather than source–drain access resistance. Higher As2 fluxes led first to conformal growth, then pronounced {111} facets sloping up away from the mask.