Reflection Anistropy Spectroscopy Study of the Near Surface Electric Field in Low-Temperature Grown GaAs (001)

We have evaluated an ‘‘effective depletion width’’ of =\u3c 45 Å and the sign (n-type/upward band bending) of the near surface electric field in low-temperature grown GaAs ~001! using the optical method of reflection anisotropy spectroscopy in the vicinity of the spin-orbit split E1 , E1 + Delta1 optical features. Our results provide evidence that surface Fermi level pinning occurs for air exposed (001) surfaces of undoped low temperature grown GaAs

Measurement of the band offsets between amorphous LaAlO3 and silicon

The conduction and valence band offsets between amorphous LaAlO3 and silicon have been determined from x-ray photoelectron spectroscopy measurements. These films, which are free of interfacial SiO2, were made by molecular-beam deposition. The band line-up is type I with measured band offsets of 1.8+/-0.2 eV for electrons and 3.2+/-0.1 eV for holes. The band offsets are independent of the doping concentration in the silicon substrate as well as the amorphous LaAlO3 film thickness. These amorphous LaAlO3 films have a bandgap of 6.2+/-0.1 eV. (C) 2004 American Institute of Physics

Growth and properties of epitaxial rare-earth scandate thin films

Epitaxial rare-earth scandate thin films of 100-1500 nm in thickness have been prepared by pulsed laser deposition on SrTiO3(100) and MgO(100) substrates. Stoichiometry and crystallinity were investigated by Rutherford backscattering spectrometry/channelling (RBS/C), transmission electron microscopy, and X-ray diffraction. Electrical measurements on microstructured capacitors with a SrRuO3 bottom electrode and Au top contacts reveal dielectric constants of 20 to 27, leakage currents of 0.85 to 6 mu A/cm(2) at 250 kV/cm, and breakdown fields of 0.6 to 1.2 MV/cm. The optical bandgaps of the films range from 5.5 to 6 eV. The results substantiate the high potential of rare-earth scandates as alternative gate oxides

Rare-earth scandate single- and multi-layer thin films as alternative gate oxides for microelectronic applications

Thin films of rare-earth scandates (REScO3) as well as multi-layers of scandates and titanates have been prepared using pulsed laser deposition. Epitaxial films were grown on SrRuO3/SrTiO3(100) as well as amorphous films on silicon substrates. The epitaxial films are investigated to measure the physical properties of the crystalline material. Electrical measurements (CV, leakage current) show for example high epsilon(r) > 20 for the scandates and epsilon(r) > 35 for the epitaxial and amorphous multi-layer films. A diffusion of the new materials into silicon is not observed

Optical constants of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} lattice-matched to GaSb(001): Experiment and modeling

The optical constants {epsilon}(E)[={epsilon}{sub 1}(E)+i{epsilon}{sub 2}(E)] of two epitaxial layers of GaInAsSb/GaSb have been measured at 300 K using spectral ellipsometry in the range of 0.35--5.3 eV. The {epsilon}(E) spectra displayed distinct structures associated with critical points (CPs) at E{sub 0} (direct gap), spin-orbit split E{sub 0}+{Delta}{sub 0} component, spin-orbit split (E{sub 1}, E{sub 1}+{Delta}{sub 1}) and (E{sub 0}{prime}, E{sub 0}{prime}+{Delta}{sub 0}{prime}) doublets, as well as E{sub 2}. The experimental data over the entire measured spectral range (after oxide removal) has been fit using the Holder model dielectric function [Phys.Rev.B 56, 4037 (1997)] based on the electronic energy-band structure near these CPs plus excitonic and band-to-band Coulomb enhancement effects at E{sub 0.}, E{sub 0}+{Delta}{sub 0} and the E{sub 1}, E{sub 1}+{Delta}{sub 1} doublet. In addition to evaluating the energies of these various band-to-band CPs, information about the binding energy (R{sub 1}) of the two-dimensional exciton related to the E{sub 1}, E{sub 1}+{Delta}{sub 1} CPs was obtained. The value of R{sub 1} was in good agreement with effective mass/k{sup {rightharpoonup}}{center_dot}p{sup {rightharpoonup}} theory. The ability to evaluate R{sub 1} has important ramifications for recent first-principles band structure calculations which include exciton effects at E{sub 0}, E{sub 1}, and E{sub 2} [M.Rohlfing and S.G.Louie, Phys.Rev.Lett. 81, 2312 (1998) and S. Albrecht et al., Phys.Rev.Lett. 80, 4510 (1998)]. The experimental absorption coefficients in the region of E{sub 0} were in good agreement with values obtained from a linear interpolation of the end point materials. The experimental results were compared to a recent evaluation and fitting (Holden model) of the optical constants of GaSb