Atsuya Yamamoto

Analysis of solid phase crystallization in amorphized polycrystalline Si films on quartz substrates

The solid phase crystallization of amorphized Si films on quartz substances is studied by means of the transmission electron microscope observation of grain growth. The amorphous Si films are prepared by Si ion implantation into polycrystalline Si films deposited by low‐pressure chemical vapor deposition. It has been found that the twin formation in grains at the early stage of the crystallization accelerates the growth rate preferentially in a 〈112〉 direction. During the twin growth about a given 〈112〉 direction, other twins also grow from the twin boundary dendritically in some other 〈112〉 directions, leading to the formation of a large grain of dendritic structure.

Recrystallization Mechanism for Solid Phase Growth of Poly-Si Films on Quartz Substrates

The recrystallization mechanism for solid-phase growth of poly-Si films amorphized by ion implantation on quartz substrates is clarified on the basis of an experimental finding obtained through the TEM observation. It is found that the {110} textured nucleation occurs. The preferential growth in the directions along twin boundaries then leads to the formation of the dendritic structure.

A self-aligned ridge substrate laser fabricated by single-step MOVPE

Abstract A novel self-aligned structure semiconductor laser, called a self-aligned ridge substrate (SAR) laser has been successfully fabricated by a single-step MOVPE process. The single-step process is attained by the epitaxial growth on a ridge formed along the 〈011〉 direction on a (100) substrate, taking advantage of the anisotropic and isolated growth on the ridged substrate. As a result the current-injection region and the active region are formed in a self-aligned manner. A CW operation under a threshold current of 46 mA typically has been obtained at room temperature in the SAR laser.

Picosecond Dynamics of Electron-Hole Plasma in GaAs/AlAs Multiple Quantum Well Structure

Picosecond temporal character of high-density electron-hole plasma (EHP) in GaAs/AlAs multiple quantum well structure has been studied by means of time-resolved luminescence spectroscopy. The EHP with carrier density NQW of 3–4×1017 cm-3 is formed, where carrier induced band-gap shrinkage of 10–20 meV takes place. Temporal character of luminescence due to the EHP is well explained by time variation of NQW. Increase of NQW results from carrier trapping with trapping time of ~60 ps, and subsequent decrease of NQW results from radiative recombination with bimolecular recombination coefficient of 4.5×10-8 cm3s-1.

Picosecond luminescence spectroscopy of electron-hole plasma in GaAs/AlAs quantum well structure

Abstract Picosecond dynamics of high-density electron-hole plasma (EHP) in GaAs/AlAs multiple quantum well structure is studied by means of time-resolved luminescence spectroscopy. The picosecond temporal character of the EHP is well explained by carrier trapping process with trapping time of ☆60 ps, and radiative recombination process with bimolecular recombination coefficient of 9.0x10-8 cm3s-1.