| Atomic-layer deposition is used to grow HfO2 and Al2 O3 thin films on InAs substrates to form high-k-InAs metal-oxide-semiconductor capacitors. Devices are formed using various substrate pretreatments, film growth temperatures and thicknesses, contact metals, and post-metallization anneals. X-ray photoelectron spectroscopy, transmission electron microscopy, and ellipsometry are used to physically characterize the films, while current-voltage and impedance measurements are used for electrical characterization. Hafnium dioxide films with equivalent silicon dioxide thicknesses as low as 0.76 nm are reported with leakage current densities as low as 9.2 x 10-2 A/cm2 at +1 V gate bias. Interface trap densities are measured by the Terman method to be in the 1013 cm-2 eV-1 range at midgap. TEM and XPS data suggest the high trap densities in the HfO2-InAs capacitors are associated with an interfacial layer likely composed of native indium oxides. XPS measurements indicate that these oxides are not present after the Al2O3 ALD process, eliminating a source of Fermi-level pinning and reducing the number of interface traps. The devices fabricated in this work are compared to other III-V MOS work and International Technology Roadmap for Semiconductors performance targets to assess the viability of metal-high-k-InAs MOS gate stacks. |
