High k/III-V structures: Interfaces, oxides quality and down scaling
In this paper, we present our studies on high k/InGaAs and high k/InSb structures, focusing on the interfaces, oxides qualities as well as down scaling the gate oxide. We indicate the free movement of Fermi level in both kinds of n- and p-InGaAs MOSCAPs. The effect of gases plasma treatments in the improvement of gate oxides as well as high k/InGaAs interface quality is also discussed. For high k/InSb structure, the effect of post deposition annealing temperatures on electrical properties of this structure is presented. Finally, we present our efforts on down scaling the equivalent oxide thickness of these structures into sub-nm size.
Interface study of high-k/InAs/n-GaSb MOSCAP structures
Interface properties of Al 2 O 3 , HfO 2 and TiO 2 of 5 nm on GaSb substrate passivated with 2nm InAs were studied and compared. The interface properties of Al 2 O 3 /InAs/n-GaSb and HfO 2 /InAs/n-GaSb structures are reported, but no interface characterization of TiO 2 /InAs/n-GaSb has been done till today. In this paper, the capacitance voltage (C-V) characteristic of Al 2 O 3 /InAs/n-GaSb, HfO 2 /InAs/n-GaSb and TiO 2 /InAs/n-GaSb MOSCAP structures were simulated using TCAD tool at 300K. Thereafter, interface trap density (D it ), threshold voltage (V th ), flatband voltage (V fb ) and surface potential (Φ s ) were obtained by C-V and compared. The D it values for Al 2 O 3 /InAs/n-GaSb, HfO 2 /InAs/n-GaSb and TiO 2 /InAs/n-GaSb MOSCAP structures were determined by Termann method and found to be 3.38×1012 cm−2eV−1, 1.15×1012 cm−2eV−1 and 9.11×1011 cm−2eV−1 respectively. It is interesting to note that the D it value reduces by 65% in case of HfO 2 /InAs/n-GaSb, whereas by 75% in case of TiO 2 /InAs/n-GaSb structure compared to Al 2 O 3 /InAs/n-GaSb structure. Furthermore, the TiO 2 /InAs/n-GaSb structure has insignificant threshold voltage variation and much less flatband voltage variation for different oxide thicknesses ranging from 5nm to 10nm.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME