Kazuo Kuramoto

Focused Si Ion Implantation in GaAs

A 160-keV, submicron-focused Si ion implantation in MBE-GaAs was made using a 100 kV maskless implanter with a Au–Si–Be alloy ion source. Obtained Raman spectra indicated that compared with the implantation current densities of an unfocused ion beam, the higher current density (about 104 times greater) of the focused beam resulted in less implantation-induced and residual (after annealing up to 500°C) damage. Moreover, 850°C annealing led to a higher electrical activity of focused implanted Si-ions but almost the same optical quality of conventional implantation.

Sn Ion Doping during GaAs MBE with Field Ion Gun

Low energy Sn ion doping of growing MBE-GaAs at 550°C was made using a liquid metal field ion gun. From Raman measurements, no disordered structures were detected in the grown films. However, the films showed high resistivity and the activation of Sn differed from that of Zn for p-type ion doping previously reported. A broad and weak emission at around 1.28 eV was observed in a photoluminescence spectrum taken at 4.2 K. These suggest that radiation damage caused by Sn ion irradiation remains in the films.

First Observations of 0.1 μm Size Particles on Si Wafers Using Atomic Force Microscopy and Optical Scattering

We have developed a new technique on the basis of an optical scattering phenomenon to link the coordinates of a commercially available wafer inspection system (WIS) to an analyzer with a high precision of ±0.1 μm. This new technique has been installed in a large sample atomic force microscope (AFM) capable of observing wafers of 8 in. size. One of the most remarkable features of this newly developed AFM is the ability to observe the same position on a wafer before and after certain processes. In this paper, we report on the results of the first observations of 0.10 μm size particles such as crystal-originated particles (COPs) and dusts on a polished (100) CZ-type Si wafer before and after SC1 cleaning by using the newly developed AFM. It was first found that the 0.10 μm size COPs are inherently juts before SC1 cleaning. After SC1 cleaning, these COPs turned into a deep crystalline pit. These pits run parallel to the axis of the wafer and have four facets with an angle of 54° with respect to the surface of the wafer. Second, the actual size of the dust particles were found to be much bigger than expected by using the WIS. The difference is considered to be attributed to the correction method used in the WIS by comparing with 0.10 μm in size polystyrene latex standard particles. These results show that the AFM combined with an optical scattering system is useful in the evaluation of 0.1 μm sized particles as well as in the wafer cleaning process.

Characteristics of carbon incorporation in GaAs grown by gas source molecular beam epitaxy

Abstract Nominally undoped p-type GaAs has been grown by gas source molecular beam epitaxy (GSMBE) using triethygallium and arsine. The temperature dependence of carbon incorporation has been investigated. It has been found that there exists an optimum growth temperature (Tg) of about 550 ° C, at which the lowest carbon incorporation and the highest Hall mobility are attained. At Tg higher than 550 ° C with a V/III ratio of 5, the carrier concentration exhibits an Arrhenius type dependence on Tg with an activation energy of 2.2 eV. In contrast, when Tg is lower than 550 ° C, the carrier concentration increases with decreasing Tg. Defect induced bound exciton peaks have been observed in the photoluminescence spectra except for the sample grown at the optimum growth temperature. A qualitative model to explain the characteristics of carbon incorporation will be discussed.

Electrical and optical properties of InP grown by MBE using P+ ion beam

Abstract InP layers have been grown on Fe-doped semi-insulating InP substrates by molecular beam epitaxy using a low energy P + ion beam under various conditions: V/III flux ratios were from 1.2 to 2.2, and growth temperatures were from 400 to 490°C. The electrical and optical properties of the epilayers are described. The unintentionally doped epilayers were n-type, and there existed two shallow donor levels with activation energies of 4 and 7 meV and two deep donor levels with activation energies of 125 and 175 meV. The carrier concentration and mobility increased with decreasing V/III flux ratio and/or increasing growth temperature. The carrier concentration and mobility measured at 80 K were 1.2x10 16 cm -3 and 21200 cm 2 /V°s for the sample grown at 490°C and with a V/III flux ratio of 1.9. Photoluminescence spectra and SIMS profiles showed that Fe atoms diffuse into epilayers from substrates and pile up near the surface.

Polar-Polar Interaction and Boundary Phase Structure Between Reinforcement and Matrix in a Polymer Composite

Abstract This paper describes an attempt to correlate the nature of polar-polar interaction between the reinforcement and matrix in a polymer composite with the boundary phase structure formed in contact with the reinforcement. It is shown by analyzing the mechanical dispersion data that the reinforcement-matrix interaction of Kevlar fiber reinforced poly(hydroxypropyl ether of bisphenol A) (P) is increased by blending poly(ethylene oxide) (E) or poly(ethylene adipate) (A) as a part of matrix, and that E is more efficient than A for the increase of the interaction. These results can be supported at the molecular level from the inspection of the Fourier transform infrared spectra on the Kevlar fiber coated with matrix polymers and the mixture of matrix polymers with benzanilide, which is used as a model compound of Kevlar fiber. It can be shown from the electron spectroscopy for chemical analysis on the films of PIE and P/A blend polymers formed on nylon 6 substrate (N), which is also used as a model mater...

GaAs P-Layer Formation by Be Ion Implantation

A novel, nearly hazardless Be ion implantation technique has been realized by adopting BeO ceramic material as an ion source. This method made possible a continuous Be ion current of several tens of µA without noticeable contamination. High dose Be ion implantation experiments were carried out using this technique and it has been found that Be atom activation can be improved by hot implantation and subsequent lower temperature annealing.

Thermal Decomposition Analysis of Spin-Coated Films of Partly Protected Polyvinylphenol with the t -Butoxycarbonyl Group Using Time-Resolved IR

Thermal decomposition of spin-coated films of partly protected polyvinylphenol with the t-butoxycalbonyl (tBOC-PVP) group has been investigated by monitoring the intensity of the carbonyl stretching peak of the tBOC group by using temperature-variable time-resolved infrared spectroscopy (TR/IR). The temperature programming method has been used for determining the activation energy (Ea) of the thermal decomposition. We compared the thermal decomposition behavior of tBOC-PVP films with that of the powders and the behavior of a 22% protected tBOC-PVP film with that of a 66% protected tBOC-PVP film. It was found that the Ea of the 22% protected tBOC-PVP film is distinctively higher than the others including the result given from thermogravimetric analysis (TG). In addition, the Ea of the 22% protected tBOC-PVP film increased up to 50 kcal/mol with the decrease of the remaining tBOC group, while the others were constant at 30 kcal/mol. Diglyme, which was used as the solvent in the 22% protected tBOC-PVP film, was residual after the temperature increased above 80 °C, and the reaction velocity of the tBOC group increased in accordance with the generation of the OH group. These results suggest that the OH group, which accelerates the thermal decomposition of tBOC-PVP, is hindered by the residual solvent in the case of the 22% protected tBOC-PVP films.

Fe and Al Concentrations in High Resistivity InP Layer Grown by Low-Temperature Liquid Phase Epitaxy

High-resistivity InP layers grown by low-temperature liquid phase epitaxy from In-P-Fe-Al solutions were characterized by secondary ion mass spectrometry. Fe and Al concentrations in InP were found to be over 1016 cm-3. In the growth from In-P-Fe-Al solutions on S-doped InP substrates, the concentration of Fe and Al increased at the interface where electrical characteristics of the crystal drastically change.