ALBERT

Notes: A Weissenberg camera for macromolecules with imaging plate data collection system at BL6A and BL18B stations in the Photon Factory is introduced and evaluated. The special feature of these systems is considered matching for both SR-x rays and protein crystallography. This system is user-friendly and can collect a large amount of data to higher resolution from the crystal with large unit cell dimensions. A newly developed camera can be used as a time-resolved Laue camera and a Weissenberg camera. A large image reader (IPR4080) that can scan 400×400 mm2 and 400×800 mm2 sizes of imaging plates has been developed and evaluated. The new data collection system combined with the new camera and IPR4080 will be installed at the BL18B station in October 1994. © 1995 American Institute of Physics.

Notes: Magnetic bar codes can be used in unclean environments, where widely used optical bar code systems cannot be applied. Readout system for magnetic bar codes can also be made much simpler than optical ones. A new magnetic bar code system is proposed, in which binary information is coded in the sign of tilted angles of magnetic strips from a given standard direction. This scheme is unique compared to the conventional optical bar code, where width or space of the parallel pattern carries information, or an already reported magnetic bar code, where cross sectional shapes of pattern engraved in a ferromagnetic body carries information. Each of the magnetic strips brings about magnetic anisotropy due to its shape effect, hence angular dependent permeability in the proximity of the strip. The sign of the tilted angle of each magnetic strip is detected inductively through the angular dependent permeability by using a magnetic pickup head with a pair of cross-coupled figure-eight coils, where the sign of mutual inductance between the primary and the secondary figure-eight coil has one to one relationship to the sign of the tilted angle.Because the detection of the tilted angle is independent of scanning speed, variation in the scanning speed of the readout head does not affect the performance. In our preliminary study, the proposed magnetic bar code system was examined using pickup head consisting of a pair of cross-coupled 10-turn figure-eight coils which was embedded in a rectangular ferrite rod with cross-shape groove on the top surface of 6.5×3 mm dimension. The head was made thinner in the scanning direction to allow dense alignment of the pattern. Two kinds of pattern were made: the one was by aligning short amorphous wires (5 mm in length and 120 μm in diameter) on the plastic film and the other by using a thin (10 μm in thickness) copper film with tilted slits backed by an amorphous ribbon. These samples of magnetic bar code patterns were scanned with lift-off of 1 mm under the operating condition of 120 kHz and 200 mA. Amplitudes of the positive and the negative peak of the output voltage well exceeded 10 mV. Density of the pattern in the preliminary study was 7 bits for the bar code length of 2.6 cm. We will discuss several factors to make density of the pattern higher. Because the pickup coils can be assembled with planar coils and because the magnetic bar code itself is thin, the total system of this bar code scheme can be realized in thin form. © 1996 American Institute of Physics.

Notes: The lateral variation of the emission energy of GaAs masklessly grown on V-grooved Si is imaged with cathodoluminescence wavelength imaging. This newly developed unique experimental approach allows, for the first time, to directly visualize and quantify the extreme homogeneity of this novel growth mode and the lateral variation of Si impurity incorporation in such semiconductor microstructures. It represents an essential characterization tool for micropatterned optoelectronic monolithic integrated circuits.

Notes: The diffusion coefficient of ion-implanted Zn and the Al-Ga interdiffusion coefficient in an Al0.5Ga0.5As/GaAs superlattice (SL) are extracted from secondary-ion mass spectroscopy profiles for four diffusion times at 750 °C. The zinc diffusion coefficient goes as the square of the zinc concentration, implying local thermal equilibrium, and is over 200 times smaller than reported values for gaseous-source Zn diffusions at 650 °C in GaAs. The SL disordering rate increases with increasing zinc concentration and is attributed to the diffusion of positively charged column III interstitials (Ga+mI or Al+mI) with m between 2 and 3.

Notes: A phase-locked laser array with refractive-index waveguides and emitting a low phase-aberration beam is described. A fundamental supermode operation of an evanescent-coupled three-element laser array which emits up to 200 mW in a single diffraction-limited beam is achieved. The full beam angle at the half-power point is 3.2° in the direction of parallel to the p-n junction. This phase aberration is less than λ/14 from 50 to 150 mW. The extremely low phase aberration (0.022λ) is measured at 50 mW.

Notes: GaAs growth properties and first successful maskless selective growth on the etched groove Si substrates are reported. No crystal growth occurs on the {111} Si sidewalls of the V grooves, and the GaAs layers grow only on the {100} planes. The cross-sectional shapes of the selective grown layer depend on the direction of the V grooves. The selectivity also remains even in Al0.3Ga0.7As-grown layers. The selective growth mechanisms are discussed.

Notes: InAs/GaAs single quantum well structures have been grown by metalorganic chemical vapor deposition. The grown wells are 1.03, 1.3, and 1.7 InAs monolayers thick. The 4 K photoluminescence spectra exhibit strong and narrow peaks, their energy decreasing smoothly with increasing well thickness. The noninteger value is interpreted on the model that the interface is macroscopically flat but has valleys and hills with their lateral extent smaller than excitons. The effective interface position is determined by their relative lateral extent.

Notes: We have developed a high-power, semicylindrical-shaped waveguide inner stripe laser diode (SCILD) using a current confinement structure. The structure is optimized for high-power operation without catastrophic optical damage (COD) which limits the maximum available optical power. We confirm that the optical electric field shape in the LD waveguide layer obtained from our analysis coincides with the micrograph of the COD on the device facet. The SCILD is emitted in the fundamental transverse mode up to 190 mW. The full beam angles between the half-power points were 10° and 30° in the directions parallel and perpendicular to the junction plane, respectively. The characteristic temperature of the threshold current was 152 K.

Notes: Electron transfer into the L and X bands of GaAs is observed in the dependence of transfer ratio α (collector current Ic/emitter current Ie) of an AlGaAs/GaAs hot-electron transistor upon emitter-base voltage Veb. The α-Veb curve and its variation with temperature change confirms the idea that electron transfer to the higher bands randomizes the electron motion and is effective in reducing α. The differential transfer ratio Δα (dIc/dIe) shows double peaks and a clear shoulder. The lower-energy peak may indicate the onset of elastic intervalley scattering.