The effects of plasma enhanced atomic layer deposition (PEALD)-AlN interfacial passivation layer (IPL) on the Al2O3/In0.53Ga0.47As interfaces qualities are studied with different plasma powers. The improvement in electrical properties, including capacitance-voltage (C–V) hysteresis, frequency dispersion, and interface state densities \((D_{\mathrm {\mathbf {it}}})\) are demonstrated on the Al2O3/n, p-In0.53Ga0.47As MOS capacitors. The excellent \(C-V\) behaviors are observed on both type of In0.53Ga0.47As-based MOS devices by performing a thin AlN-IPL at the plasma power of 150 W. To explore the interaction between PEALD-AlN layer and In0.53Ga0.47As surface, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analyses have also been characterized.