Kazunori Moriki

Silicon-Hydrogen Bonds in Silicon Native Oxides Formed during Wet Chemical Treatments

Silicon-hydrogen bonds in silicon oxide films were detected for the first time by applying surface-sensitive X-ray photoelectron spectroscopy and were confirmed by measuring infrared absorption. The areal density of silicon-hydrogen bonds in native oxides formed in a hot solution of HNO3 is estimated to be nearly 2×1014 cm-2, and is much larger than that formed in a solution with a composition of NH4OH:H2O2:H2O=1:1.4:4.

GaInAsP/InP Surface Emitting Injection Laser with Buried Heterostructures

The first surface emitting (SE) injection laser (λ1.2 µm) with buried structure has been realized from the GaInAsP/InP system. The circular active region of 50 µm in diameter is buried by employing the LPE growth of i) maskless planar buried heterostructure (PBH) and ii) conventional masked buried heterostructure (BH). The near field was of a circular pattern of about 50 µm in diameter and it has been confirmed that the lasing occurred in the direction perpendicular to the surface by comparing output powers from the surface and the edge. The lowest threshold current of the BH SE laser was 520 mA (26 kA/cm2) at 77 K. The PBH SE laser had somewhat higher threshold than the BH SE laser at the present stage, but the PBH structure seems to be suitable for the SE laser because it has been found that it is easy to grow flatter surfaces.

Silicon-hydrogen bonds in silicon oxide near the SiO2/Si interface

The role of hydrogen peroxide in RCA standard clean was roughly clarified by angle-resolved photoelectron spectroscopy and infrared absorption spectroscopy such that the oxidation, by basic hydrogen peroxide results in a negligible amount of SiH bonds in native oxide, while the oxidation by acidic hydrogen peroxide results in a small amount of SiH bonds in native oxide. It is also found that oxidation in a boiling solution of HNO3 results in large amount of SiH bonds in native oxide as in the case of oxidation in a hot solution of HNO3.

Effect of Silicon Wafer In Situ Cleaning on the Chemical Structure of Ultrathin Silicon Oxide Film

The effect of silicon wafer in situ cleaning on the chemical structures of thermally grown silicon oxide films was studied by X-ray photoelectron spectroscopy and scanning tunneling microscopy. After the silicon wafer in situ cleaning was performed by the decomposition of native oxides in high vacuum, the nearly 1.6-nm-thick thermal oxides were formed in dry oxygen at 800°C. If the heating time for the decomposition of native oxides was too short, intermediate states transformed from native oxides were found to remain on the surface of the oxide films. On the other hand, if the heating time was too long, the amount of intermediate states at the interface was found to increase as a result of the increase in interface roughness. The optimum condition for in situ cleaning is heating at 900°C for 30 minutes in high vacuum.

Optical Beam Scanner with Phase-Variable Semiconductor Waveguides

An optical beam scanner which has the possibility of high-speed steering has been fabricated and its steering operation was confirmed. The obtained deflection angle was 0.67 degrees under 9.5 V reverse bias.

GaInAsP/InP DH Laser with a Current Blocking Layer Made by Be Implantation

A GaInAsP/InP laser (λ=1.3 µm) with a current blocking layer made by Be implantation has been fabricated. Be-ions were implanted with 70 keV into an n-InP substrate at room temperature and 2.2×1014 cm-2 of dose. Thermal annealing was applied in a furnace during the LPE (Liquid Phase Epitaxial) growth. The breaking of the forward bias associated with the blocking region was 2 V. The minimum threshold current was 160 mA for 2.5 µm width of waveguide and 250 µm cavity length.

Optical absorption in silicon oxide film near the SiO2/Si interface

The contribution of SiO2/Si interface structure to optical absorption below the optical absorption edge of fused quartz was studied by measuring the reflectance of thermally grown ultrathin silicon oxide films. From the modified Kramers-Kronig analysis of reflectance, it was found that optical absorption at the photon energy of 7.8 eV arises from Si-Si bonds in the oxide film within 6 nm of the interface and does not depend on the oxidation temperature. Approximate areal density of Si-Si bond is 7×1014 cm-2

Silicon-silicon bonds in the oxide near the SiO2/Si interface

The contribution of the SiO2/Si interface structure to optical absorption below the optical absorption edge of fused quartz was studied by measuring the reflectance of thermally grown ultrathin silicon oxide films. From the modified Kramers-Kronig analysis of reflectance, it was found that optical absorption at the photon energy of 7.8 eV arises from SiSi bonds in the oxide film within 1.4 nm of the interface. The approximate areal density of SiSi bonds is 7 × 1014 cm−2 and is approximately equal to the areal density of silicon su☐ides determined by X-ray photoelectron spectroscopy.

GaAlAs/GaAs Optical Beam Scanner Using Phased Array Waveguides

An optical beam scanner integrated with two phased array waveguides is fabricated. The optical beam scanner consists of twin GaAlAs/GaAs waveguides which are integrated with an optical branch for optical power distribution to the twin waveguides. The optical beam can be deflected about 1.0 degree by applying a reverse bias of 10 V to the pn junction in one of the waveguides.

Optical Branching Device for Arrayed Waveguides

A new optical branching device for arrayed waveguides was proposed and experimentally demonstrated. This device consists of GaAlAs/GaAs waveguides. An input optical beam can be split into eleven waveguides. Moreover, it is shown that the phase relation between the lightwaves in branch waveguides is conserved.