CATHODOLUMINESCENCE AND ELECTRON BEAM INDUCED CURRENT STUDY OF HYDROGEN TREATMENT OF p-n GaAs JUNCTION

The effects of hydrogen diffusion on p-n GaAs junctions have been studied by electron beam induced current (EBIC) and cathodoluminescence (CL) at room temperature. Hydrogen passivates both the acceptors in the p-side of the junction and the donors in the n-side of the junction. As a consequence the diffusion lengths increase, the surface recombination velocities decrease, and, finally, the CL intensity increases after the hydrogen treatment. The observation of hydrogen effects on both sides of the junction indicates that hydrogen diffuses at least in the neutral charge state. We also observe an electron-beam induced reactivation of the passivated centers after exposition of the sample for some minutes to the electron-beam

A simple high-temperature superconducting thin-film optical bolometer

The authors have demonstrated the operation of a simple optical bolometer by irradiating a constriction in a Y1Ba2Cu3O7-δ thin film with chopped laser light at λ=633 nm. The change in film resistivity was measured by lock-in detection of the AC component in the current-biased mode. Operating optimally near 77 K, the bolometer shows detectivity of 5 mV W-1 and NEP of 10-6 W Hz-1/2. The authors discuss the possibility of methods to improve these figures by at least three orders of magnitud

Superconducting YBa2Cu3O7-δ thin films on GaAs with conducting indium-tin-oxide buffer layers

Superconducting YBa2Cu3O7-δ (YBCO) thin films have been grown in situ on GaAs with conducting indium-tin-oxide (ITO) buffer layers. Superconducting onset is about 92 K with zero resistance at 60 K. ITO buffer layers usually form Schottky-like barriers on GaAs. The YBCO film and ITO buffer layer, grown by ion beam sputter codeposition, are textured and polycrystalline with a combined room-temperatures resistivity of about 1 mΩ c

In situ growth of superconducting YBa2Cu3O7-δ thin films on Si with conducting indium-tin-oxide buffer layers

Superconducting YBa2Cu3O7-δ (YBCO) thin films have been grown in situ on Si with conducting indium-tin-oxide (ITO) buffer layers. ITO allows YBCO to be electrically connected to the underlying Si substrate. Both the YBCO film and ITO buffer layer, grown by ion beam sputtering, are textured and polycrystalline with a combined room-temperature resistivity of about 2 mΩ cm. Superconducting onsets are 92 K with zero resistance at 68

Compositional dependence of the elastic constants and the lattice parameter of Al(x)Ga(1-x)As

Near infrared Brillouin scattering and high resolution x-ray diffraction is used for a precise determination of the elastic constants and the relaxed lattice parameters of Al(x)Ga(1-x)As epitaxial layers (0.1 <= x <= 1.0). The composition of the layers is specified by inductively coupled plasma atomic emission spectroscopy, photoluminescence, and Raman spectroscopy. For the elastic constants we get a composition independent value of 118.9 ¤ 0.7 GPa for C11, a nonlinear increase in C12and a linear decrease in C44 with increasing AI composition. The Poisson ratio shows a linear increase for x < 0.8 and a downward bowing for higher Al concentrations to the AlAs value of v=0.325¤0.004. The effect of lattice mismatch induced strain on the elastic properties is investigated on free standing epitaxial layers. The trend in ionicity from the GaAs to the AlAs bonds are deduced from phenomenological expressions for the bond-bending and bond-stretching forces which are calculated from the elastic constants. The lattice parameters of the unstrained crystals are obtained from the measured full metric of the tetragonally strained layers and the Poisson ratios. The combined results of Brillouin scattering, x-ray diffraction, and compositional analysis confirm the deviation of the Al(x)Ga(1-x)As lattice parameter from Vegard's law, and provides the first direct and accurate determination of the quadratic bowing parameter