Y. Horino

Metastable GaAsBi Alloy Grown by Molecular Beam Epitaxy

GaAs1-xBix has been grown at a substrate temperature (Tsub) between 350 and 410°C by molecular beam epitaxy. The relationship between GaBi molar fraction (x) evaluated by Rutherford backscattering spectroscopy and the lattice constant showed good linearity. To achieve Bi incorporation into the epilayer, As flux was adjusted in a limited range on the brink of As shortage on the growing surface. The Bi incorporation was saturated at a large Bi flux, probably due to a low miscibility of Bi with GaAs. The value of x increased up to 4.5% with decreasing Tsub to 350°C.

Widening of optical bandgap of polycrystalline InN with a few percent incorporation of oxygen

The absolute concentration of oxygen in polycrystalline InN was measured using a combination of Rutherford backscattering and x-ray photoemission spectroscopy. Polycrystalline InN was grown on quartz and glassy carbon at 500 °C by molecular-beam epitaxy using In metal and activated nitrogen species generated in rf plasma. The optical bandgap of polycrystalline InN increased from 1.55 to 2.27 eV with increasing oxygen concentration from 1% to 6%. Polycrystalline InN with an optical bandgap of 1.9 eV, which has often been reported, contains oxygen of a molar fraction of 3%.

Direct measurement and improvement of local soft error susceptibility in dynamic random access memories

Abstract Soft errors induced in a dynamic random access memory (DRAM) have been measured using a nuclear microprobe. Soft error susceptibility of the local position and structure to the soft error has been clarified. Collection efficiency of charge carriers, induced by incident ions on reverse biased p-n junctions with barrier well structures, has been verified for various implantation doses for well formation.

Nano-indentation testing for plasma-based ion-implanted surface of plastics

We have developed a technique to modify the surface of plastics to improve the hardness. Carbon ions were implanted with 20 and 10 keV energy into the plastic surface using the conventional ion-implantation and the plasma-based ion-implantation methods. The modified surface was loaded to 1 mN and unloaded using the diamond tip of the nano-indentation equipment. We found that the deformation of the modified surface was elastic deformation. According to the surface Youngs modulus FEM simulation of plastics, surface Youngs modulus was improved from 1.8 to 25 GPa using the plasma-based ion-implantation process.

Well Structure by High-Energy Boron Implantation for Soft-Error Reduction in Dynamic Randam Access Memories (DRAMs)

The susceptibility against soft-errors in dynamic random access memories (DRAMs) has been evaluated using nuclear microprobes by monitoring various addresses of a memory cell array to determine the influence of upper wiring layers such as word lines, bit lines and other patterns. The correlations between irradiated positions of microprobes and monitored cell positions were discussed. The effect of buried implanted layers against carrier collection has also been investigated using ion-beam-induced-current (IBIC) measurement. IBIC measurement revealed that the retrograde well structure was more effective in suppressing soft errors than conventional well structures in bulk or epitaxial substrates.

New III-V semiconductor InGaAsBi alloy grown by molecular beam epitaxy

A new Bi-containing III–V semiconductor InGaAsBi alloy was firstly grown by molecular beam epitaxy (MBE). The high crystalline quality of the InGaAsBi epilayer with smooth interfaces was confirmed by X-ray diffraction measurements. Up to 2.5% Bi was incorporated in the film based on Rutherford back scattering (RBS) results. The RBS channeling spectra give clear evidence that the Bi atoms were substitutionally located in the InGaAs zinc-blende lattice sites.

Estimation of the Charge Collection for the Soft-Error Immunity by the 3D-Device Simulation and the Quantitative Investigation

The charge collection induced by incident particles was estimated by the 3-dimensional device simulation and the quantitative evaluation method using the nuclear microprobe. The role of the buried p +layer was well analyzed in terms of the soft-error immunity of DRAMs. The methods developed here are applicable to optimize the well structure for the soft-error immunity of advanced DRAMs.

Lattice Distortion of GaAsBi Alloy Grown on GaAs by Molecular Beam Epitaxy

GaAs1-xBix alloys were grown on GaAs by molecular beam epitaxy (MBE). The lattice constants perpendicular and parallel to the surface of epilayers were estimated by high-resolution X-ray diffraction (XRD) analysis. The GaBi molar fraction was estimated by the Rutherford backscattering spectroscopy (RBS). GaAs1-xBix epilayers with GaBi molar fractions less than 5% were almost coherently grown on GaAs substrate with compressive strain. The lattice mismatch between GaAs1-xBix (x=5%) and GaAs was estimated to be approximately 0.5%.

Simultaneous mass-analyzed positive and negative low-energy ion beam deposition apparatus

Abstract We have developed a new concept low-energy ion beam deposition apparatus. This machine can generate mass-analyzed very low energy ion beams with positive and negative charges at the same time. It is possible to deposit these ions not only simultaneously but also alternatively. The name is Taotron and the nickname is PANDA (Positive And Negative-ions Deposition Apparatus). The aiming specifications of this apparatus are: (1) available positive ions are H, B, C, N, O, Si, Fe, etc. and negative ions are H, B, C, O, Si etc., (2) ion energy range covers 10 eV to 20 keV, (3) typical ion beam current is ≥ 10 μA (for 10 eV oxygen ions with both charges) and the beam size is ≥ 10 mm ⊘, (4) the base pressure of the deposition chamber is in the order of 10 −8 Pa and the pressure during deposition is in the order of 10 −6 Pa.

New Semiconductor GaNAsBi Alloy Grown by Molecular Beam Epitaxy

GaNyAs1-x-yBix epilayers were grown on GaAs by molecular beam epitaxy for the first time. Multilayered samples consisting of GaAs1-xBix, GaNyAs1-y and GaNyAs1-x-yBix showed distinct X-ray diffraction (XRD) peaks ascribed to each layer. The GaBi molar fraction, x, estimated by the combination of Rutherford backscattering spectroscopy and XRD was controlled in a range up to 4.0%. The GaN molar fraction estimated from the angular spacing of the XRD peak between GaAs1-xBix and GaNyAs1-x-yBix increased up to 8.0% with increasing supply of activated nitrogen generated in rf plasma.