The electronic band structures of wurtzite GaN and InN are calculated by the empirical pseudopotential method (EPM) with the form factors adjusted to reproduce band features which agree with recent experimental data and accurate first-principles calculations. The electron and hole effective masses at the Γ point are obtained using a parabolic line fit. Further, using the effective-mass Hamiltonian and the cubic approximation for wurtzite semiconductors, band edge dispersion at the Γ point obtained using the k.p method is fitted to that calculated using the EPM by adjusting the effective-mass parameters. Thus, we derived important band structure parameters such as the Luttinger-like parameters for GaN and InN which will be useful for material design in wide-gap nitride-based semiconductor lasers employing InGaN. The results also showed that the cubic approximation is fairly successful in the analysis of valence band structures for wurtzite nitrides.

An alternative surface passivation process for high-k Ge metal-oxide-semiconductor (MOS) device has been studied. The surface SiH4 annealing was implemented prior to HfO2 deposition. X-ray photoelectron spectroscopy analysis results show that the SiH4 surface passivation can greatly prevent the formation of unstable germanium oxide at the surface and suppress the Ge out-diffusion after the HfO2 deposition. The electrical measurement shows that an equivalent oxide thickness of 13.5Å and a leakage current of 1.16×10−5A∕cm2 at 1V gate bias was achieved for TaN∕HfO2∕Ge MOS capacitors with the SiH4 surface treatment.

The kinetics of the interfacial layer (IL) growth between Hf aluminates and the Si substrate during high-temperature rapid thermal annealing (RTA) in either N2 (∼10 Torr) or high vacuum (∼2×10−5 Torr) is studied by high-resolution x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy. The significant difference of the IL growth observed between high vacuum and relatively oxygen-rich N2 annealing (both at 1000 °C) is shown to be caused by the oxygen species from the annealing ambient. Our results also show that Hf aluminates exhibit much stronger resistance to oxygen diffusion than pure HfO2 during RTA in N2 ambient, and the resistance becomes stronger with more Al incorporated into HfO2. This observation is explained by the combined effects of (i) smaller oxygen diffusion coefficient of Al2O3 than HfO2, and (ii) higher crystallization temperature of the Hf aluminates.

Articles you may be interested inWhispering gallery modes in zinc-blende AlN microdisks containing non-polar GaN quantum dots Appl. Phys. Lett. 102, 081105 (2013); 10.1063/1.4793653 Erratum: "Ab initio study of lattice vibration and polaron properties in zinc-blende AlxGa1−xN alloys" [J. Appl. Electronic and positron properties of zinc-blende structure of GaN, AlN, and their alloy Ga 1−x Al x N J. Appl. Phys. 93, 9730 (2003); 10.1063/1.1573739 Deposition factors and band gap of zinc-blende AlNThe electronic properties of wide-energy gap zinc-blende structure GaN, AlN, and their alloys Ga 1Ϫx Al x N are investigated using the empirical pseudopotential method. Electron and hole effective mass parameters, hydrostatic and shear deformation potential constants of the valence band at ⌫ and those of the conduction band at ⌫ and X are obtained for GaN and AlN, respectively. The energies of ⌫, X, L conduction valleys of Ga 1Ϫx Al x N alloy versus Al fraction x are also calculated. The information will be useful for the design of lattice mismatched heterostructure optoelectronic devices based on these materials in the blue light range application.

The thermal stability and electrical characteristics of HfTaO gate dielectric with polycrystalline-silicon gate have been investigated. The incorporation of Ta into HfO2 enhances the crystallization temperature of film dramatically. Transmission electron microscopy micrographs confirm that HfTaO with 43% Ta film remains amorphous even after activation annealing at 950°C for 30s, and the formation of low-κ interfacial layer is observably reduced. The capacitance–voltage curve of metal–oxide–semiconductor capacitor using HfTaO gate dielectric fits well with simulated curve, indicating good interface property between HfTaO and substrate. In addition, the boron penetration behaviors of HfTaO films are sufficiently suppressed as manifested by the narrow flat-band voltage shift. The negligible flat-band voltage shift in HfTaO with 43% Ta film is observed and attributed to its amorphous structure after device fabrication.

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High temperature oxidation and annealing are found to be desirable to achieve a uniform germanium (Ge) profile in silicon germanium on insulator (SGOI) layers formed using germanium condensation technique. This work investigates the amorphization mechanism, which was considered as an undesirable consequence of lowering the temperature during Ge condensation when oxidations are conducted at 900 or 950°C. A dual layer SGOI stack, composed of an amorphous layer above a crystalline layer, was obtained at low temperature condensation as characterized using transmission electron microscope and Auger analysis. A possible mechanism is presented. Si0.4Ge0.6OI and Si0.25Ge0.75OI layers can be achieved without amorphization through oxidation/annealing at 1050°C and two oxidations at 1050 and 1000°C, respectively.

Electron mobility in strained silicon and various surface oriented germanium ultrathin-body (UTB) metal-oxide semiconductor field-effect transistors (MOSFETs) with sub-10-nm-body thickness are systematically studied. For biaxial tensile strained-Si UTB MOSFETs, strain effects offer mobility enhancement down to a body thickness of 3 nm, below which strong quantum confinement effect renders further valley splitting via application of strain redundant. For Ge channel UTB MOSFETs, electron mobility is found to be highly dependent on surface orientation. Ge͗100͘ and Ge͗110͘ surfaces have low quantization mass that leads to a lower mobility than that of Si in aggressively scaled UTB MOSFETs.