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III-V semiconductor field effect transistors require an insulator/channel interface with a low density of electrically active defects and a minimal interface dipole to avoid Fermi level pinning. We demonstrate that an atomically abrupt and unpinned interface can be formed between an In0.53Ga0.47As (100) channel and an Al2O3 dielectric layer grown by atomic layer deposition (ALD) when oxidation of the substrate surface is prevented before and during oxide deposition. X-ray photoelectron spectra and electron microscopy indicate that in situ desorption of a protective As2 layer on the In0.53Ga0.47As (100)−4×2 surface followed by ALD of Al2O3 produced an atomically abrupt interface without Fermi level pinning. Temperature-dependent and frequency-dependent capacitance-voltage and conductance-voltage analysis of the resulting Pt/Al2O3/InGaAs capacitors are consistent with movement of the Fermi level through the InGaAs band gap. Moreover, the nearly ideal flat band voltages observed for gate metals of widely varying work function indicate a small oxide/semiconductor interface dipole. Density functional theory calculations of the electronic structure of an ideal amorphous Al2O3/InGaAs (100) interface predict a weak perturbation of the InGaAs electronic structure if its oxidation is avoided, consistent with experiment.

To increase complementary metal oxide semiconductor ͑CMOS͒ device performance, new materials are introduced in the gate stack ͑high-k dielectrics and metal gates͒ and the transistor channel ͑Ge, III-V materials͒. In this work we study the atomic layer deposition ͑ALD͒ of hafnium oxide on Ge and GaAs substrates. Passivation layers are required to achieve a sufficiently low interface state density, but these might also influence the growth behavior and dielectric quality. Therefore, we investigate the effect of surface preparation, for example, native oxide, wet clean, thermal oxidation, and S-passivation, for the HfCl 4 /H 2 O and tetrakis diethylamino hafnium = ͑͑C 2 H 5 ͒ 2 N͒ 4 Hf ͑TDEAH͒/H 2 O processes. The growth of HfO 2 from initial submonolayer coverage to continuous HfO 2 film is studied by means of Rutherford backscattering, static time-of-flight secondary ion mass spectroscopy, and X-ray photoelectron spectroscopy. HfCl 4 /H 2 O ALD depends on the surface preparation. The growth is enhanced on oxide surfaces ͑thermally grown GeO 2 , HF-cleaned Ge, and GaO x -AsO y ͒ and inhibited on oxide-free substrates ͑HBr-cleaned Ge͒. The initial island growth regime is least pronounced on germanium oxide. In contrast, TDEAH/H 2 O ALD is independent of the surface preparation. The growth is inhibited in the first ϳ20 cycles on native oxide and S-passivated GaAs ͓͑NH 4 ͒ 2 S treatment͔, but the initial island growth regime is quickly followed by the two-dimensional growth regime.Over the past decades, silicon has dominated the semiconductor industry thanks to the unique material properties of Si and SiO 2 . To increase device performance and reduce production costs, the dimensions of complementary metal oxide semiconductor ͑CMOS͒ devices have been continuously scaled down. However, as the gate dielectric thickness has reached a few monolayers, further thinning no longer improves the performance due to the unacceptably high gate leakage current density. To allow continuation of Moore's law, new materials such as high-k dielectric layers and metal gates are being introduced. The semiconductor industry has recently implemented hafnium-based gate dielectric layers in its 45 nm technology node. 1 For future technology nodes, Ge and III-V materials are potential new channel materials for p-and n-channel metal oxide semiconductor devices, respectively, due to their higher intrinsic carrier mobilities as compared to Si.One of the key issues for integrating Ge and III-V materials in CMOS devices is achieving a good electrical passivation of the interface. 2 Passivating interfacial layers between the Ge channel and the high-k dielectric have been developed, for example a thin ͑ϳ0.6 nm͒ epitaxial Si passivation layer, 3,4 germanium oxynitride, 5 S-passivation, 6,7 and thermally grown GeO 2 . 8-10 Atomic layer deposition ͑ALD͒ is often used to deposit the high-k dielectrics, as the low deposition temperature may preserve the electrical quality of the passivation layer. 11 However, as ALD depends on surface reactions, the chemic...

This work focuses on the separation and quantification of fixed bulk oxide charge, fixed charge at the dielectric-semiconductor interface and interface state charge components in the Pt=Al 2 O 3 =In 0.53 Ga 0.47 As metal-oxide-semiconductor (MOS) system. The availability of atomic layer deposited Al 2 O 3 dielectrics over n-and p-type In 0.53 Ga 0.47 As with a range of well-controlled thickness values opens up an experimental route for the determination of the interface state density (D it ) independently of the total fixed oxide charge using capacitance-voltage measurements taken at 1 MHz and À50 C. Low temperature forming gas annealing (350 C) significantly reduces the amount of fixed charge. The interface fixed charge is reduced from $ À8.5 Â 10 12 cm À2 preanneal to $ À7.4 Â 10 11 cm À2 postanneal and the bulk oxide charge is reduced from $1.4 Â 10 19 cm À3 preanneal to $5 Â 10 18 cm À3 postanneal. The forming gas anneal also has a significant effect on the interface state charge, reducing its density from 1.3 Â 10 13 cm À2 preanneal to 4 Â 10 12 cm À2 postanneal.

An elastic protein with a secondary structure distinct from all well-known load-bearing proteins is found in the byssus of the giant clam, Tridacna maxima . The byssus consists of a bundle of hundreds of individual threads, each measuring about about 100 μm in diameter, which exhibit a tendon-like mechanical response. The amino acid composition of Tridacna byssus, however, is unlike tendon collagen, lacking high glycine, proline, and hydroxyproline. Wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) measurements suggest that the constituent nanofibrils of the byssal threads are distinct from known secondary structure motifs previously reported for elastic proteins including the collagen triple-helix, the β-sheet nanocrystalline domains of silks, or the double-stranded coiled-coil regions of intermediate filaments. Instead, X-ray diffraction data indicate a structural organization in which four coiled-coil α-helices form a stable rope-like structure, which then further pack in a pseudohexagonal lattice to form nanofibrils. Amino acid composition analysis shows unusually high concentrations of acidic as well as basic residues, suggesting that the four-helix structure is stabilized by strong ionic interactions between oppositely charged residues in neighboring strands. The composition also suggests additional stabilization by disulfide cross-linking. On a larger scale, scanning and conventional transmission electron microscope (STEM and TEM) observations indicate that the nanofibrils exhibit an alternating periodicity of about 500 nm along the axial direction. A molecular model that combines the mechanical properties with the structural characteristics of the Tridacna byssal threads is proposed.