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Optical properties of MBE-grown GaAs/AlAs quantum wells (QW's) on GaAs(100) channeled substrates with submicron slope facets are reported for the first time. Quantum wells were prepared on GaAs(100) substrates with 2.2 μm wide (311)A slope facets under the MBE condition of an almost normal incident angle of the Ga beam to the slope facet, which results in 18% larger Ga flux intensity in the slope region than in the (100) flat region. During MBE growth, the (311)A facet disappeared and 0. μm wide (211)A and 1.6 μm wide (411)A facets emerged. The thickness of the GaAs layer on (211)A is 20% larger, while the thickness of the GaAs layer on (411) is almost the same as that on (100) flat region. The cathodoluminescence spectra from the QW's in the slope region shows the red shift from that of the QW's in the (100) flat region (787 nm → 797 nm), indicating the possible lateral confinement of carriers in the submicron wide (211)A slope region on the GaAs channeled substrates.

Photoluminescence measurements (4.2 K) were carried out for pseudomorphic InxGa1−xAs/AlAs quantum wells (x = 0.155, well width Lw = 56, 84, 169 A) grown by MBE on GaAs(100) channeled substrates which have the (100) flat region and the (111)A slope region on their surface. Effective band-gap energies(Eg) of the InGaAs/AlAs QW's on the (111)A slope region was investigated for the first time. When Lw is small (56 and 84 A in the (100) region), Eg values of the (111) region are large than those of the (100) region, but when Lw is large (Lw = 169 A in the (100) region), Eg of the (111) region becomes smaller than that of the (100) region because of the effect of piezoelectric field induced by the strain in the (111)A region, indicating the possibility of the lateral confinement of carriers not only in the (100) flat region but also in the (111)A slope region for pseudomorphic InGaAs/AlAs QW's grown on (100) GaAs channeled substrates.

Molecular beam epitaxy of GaAs doped with Si on a vicinal surface of (111)A, (211)A and (311)A have been examined. The variations of the impurity concentrations are dependent on the growth conditions and are affected by the angle of the substrates. The impurity concentrations are compared with a model calculation which is based on microscopic surface structures and kinematical surface reactions. Growth modes are monitored by reflection high-energy electron diffraction intensity oscillations. A doping mechanism of Si atoms into GaAs films is proposed.

Overgrowth of GaAs and GaAs/AlAs heterostructures on GaAs channeled substrates by MBE was studied. Grooves along [01 1 ] were made on a (100) GaAs substrate by selective etching. There are two kinds of crystal planes on the substrate: a (100) plane (flat region) and a (111)A plane (slope region). We first demonstrated the resonant tunneling of electrons preferentially through a small (111)A slope region (12 μm wide) of GaAs/AlAs double-barrier structures grown on the channeled substrates.

A new upper bound ofmv < 13 eV at 95% CL has been obtained on the electron anti-neutrino mass. Thus results is based on a more than tenfold improvement in data relative to our previous measurements of the β-spectrum in 3H decay, and its in conflict with the finite mass of 17

We report the successful formation of lateral p-n junctions by molecular beam epitaxy (MBE) of Si-doped GaAs on (111)A substrates patterned with equilateral triangles. The idea of lateral p-n junctions with a triangular p-type region encircled with three crystallographically equivalent n-type slopes is based on the three-fold symmetry of the (111)A surface and the acceptor nature of the dopant Si on the (111)A surface in contrast to the donor nature on surfaces with the other orientations. Bad surface morphologies of layers grown on the (111)A surface have been a barrier against practical applications of this surface. We have successfully improved the (111)A surface morphology by pre-growth thermal cleaning, at both higher temperatures and higher As pressures. The formation of lateral p-n junctions is confirmed by spatially resolved cathodoluminescence measurements. This lateral p-n junction can be applied to structures that demand lateral carrier confinement, such as surface emitting laser diodes.

Background and Purpose: Despite clear trends toward minimally invasive surgery, information about laparoscopic partial nephrectomy (LPN) in Japan is sparse. We conducted a retrospective survey to clarify time trends for LPN and analyze surgical and oncologic outcomes. Patients and Methods: A nationwide survey was performed. Between 1998 and 2008, 1375 patients underwent LPN at 54 institutions. Complications, patterns of tumor recurrence, and recurrence-free survival were analyzed. Results: Renal pedicle clamping was used in 1031 (75%) cases, and renal cooling was performed in 64%. Median warm/cold ischemic time was 37/53 minutes. Median tumor size was 2.26 cm (interquartile range 1.6 to 2.7). Multivariate analysis identified total operative time, operative blood loss, and surgical margin status as independently associated with high grade (grade 3–5) urologic and nonurologic complications. Despite increases in central tumor, a trend was seen toward shorter warm/cold ischemic time in recent cases, ...