We study the solid-source MBE growth of InAs films embedded in Al0.48I
n0.52As lattice matched to InP. Under As-stable conditions, the high s
train of the InAs film induces a morphological phase transition from l
ayer-by-layer to island nucleation. In contrast, during MBE growth wit
hout direct AS4 flux, islanding is inhibited. The In-stabilized surfac
e imposes kinetic limitations to the migration of adatoms and forces l
ayer-by-layer nucleation, thus acting as a virtual surfactant. This te
chnique produces samples of superior structural and optical quality ex
hibiting high luminescence efficiency up to room temperature.