In this work we investigate the effect of different III–V surface passivation strategies during atomic layer deposition of Al2O3. X-ray photoelectron spectroscopy indicates that bare As-decapped and sulfur passivated In0. 53Ga0. 47As present residual oxides on the surface just before the beginning of the Al2O3 deposition while the insertion of a Ge interface passivation layer results in an almost oxide free Ge–III–V interface. The study of the initial growth regimes, by means of in situ spectroscopic ellipsometry, shows that the growth of Al2O3 on Ge leads to an enhanced initial growth accompanied by the formation of Ge–O–Al species thus affecting the final electrical properties of the stack. Alternatively, deposition on decapped and S-passivated In0. 53Ga0. 47As results in a more controlled growth process. The sulfur passivation leads to a better electrical response of the capacitor that can be …