Electrical properties of the HfO2–Al2O3 nanolaminates with homogeneous and graded compositions on InP

•Vertical composition of the HfO2–Al2O3 nanolaminates was engineered on InP by ALD.•Dielectric properties were compared with similar physical thickness and CET.•The graded film has better interfacial characteristics than the homogeneous film.•The homogeneous film exhibited better leakage reliability than the graded film.

For possible application to a gate dielectric in high-performance III-V transistors, nanolaminated HfO2–Al2O3 films with artificial compositional profiles were deposited on n-type InP substrates using atomic layer deposition. The films were vertically graded (HfO2 and Al2O3 at the surface and interface regions, respectively) and had a homogeneous composition. To compare their electrical properties, a similar physical thickness and capacitance-equivalent thickness (CET) were maintained, and the graded structure showed an increase in the Al2O3 content near the high-k and InP interface region without an increase in CET, which suppresses the In incorporation at the near-interface region and reduces the density of the interface trap. However, doing so results in a degradation of the leakage current characteristics under voltage stressing when compared to homogeneously-nanolaminated films.