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.