Hiroyoshi Komiya

Melt compositions of II–VI compounds during crystal growth in a high-pressure furnace

Abstract The melt compositions of ZnS, CdS, ZnSe, ZnTe, CdSe, and CdTe during crystal growth in a high-pressure Bridgman furnace have been investigated by the chemical analysis of quenched melts. The following results are obtained: (1) the melt compositions are essentially stoichiometric for ZnS, Cd-rich for CdS, and chalcogen-rich for the selenides and tellurides, and (2) the melt compositions are very close to stoichiometric for the sulfides and selenides, but for the tellurides they deviate considerably from the stoichiometric composition. These results have been analyzed on the basis of a simple model which assumes that the component gases of the compound diffuse out of the crucible containing the melt slowly enough for three-phase equilibrium to be maintained inside the crucible. According to this model the observed melt composition depends on the relative diffusion rates of the metal and chalcogen gases and on the relationship between the partial pressures of these gases and the melt composition.

Electro-reflectance near the fundamental edge of GaSe

Abstract Electro-reflectance of GaSe single crystal has been investigated in the spectral region from 1·97 to 2·13 eV. By analyzing the electro-reflectance signals with Kramers-Kronig relation, the energies of the exciton levels and the fundamental edge are assigned both at 300 and 90°K. An additional new structure is observed below the ground state exciton. Electric field and temperature dependences of the structure have been explored and a possibility of the existence of some local states (defect or impurity state) is postulated and discussed.

Investigation of rare earth ions in ZnSe

Abstract The electrical properties of rare earth ions (Er+3, Tm+3 and Eu2+) doped into ZnSe crystals have been investigated by observing their optical absorptions, luminescent spectra, their Zeeman effects and ESR. The rare earth ions in the crystal from some kinds of centers close coupled with codopants or lattice defects, and they have emitted strong luminescence of the rare earth ions in the set group of (Er3+, Cu), (Tm3+, Cu) and (Tm3+, Li). The electronic structures of the latter two sets are the same, and Tm3+ exists in a crystal field of cubic symmetry. Parameters of the crystal field have been determined to suit best to the spectra obtained. Magnetic field induced absorption was observed in the absorption lines of ZnSe: Er, P by the pulse magnetic field Zeeman effect. From the ESR results of Eu2+ ions in ZnSe, it has been made clear that Eu2+ ions also exist in the crystal field of cubic symmetry.

Optical Spectra of Tm3+ Ions in ZnSe:Tm, Li and ZnSe:Tm, Cu Crystals

The absorption and luminescence spectra were observed below 77°K by using a high resolution spectrograph. The crystal field spectra show that the structures of some Tm 3+ centers are common to both of ZnSe:Tm, Cu and ZnSe:Tm, Li crystals. One of the common centers has a cubic symmetry and the crystal field parameters A 4 0 =15.1 cm -1 and A 6 0 =-2.5 cm -1 . The Tm 3+ ion in this center shows strong emission. Discussions on the model of this center and on the excitation mechanism are given.

Infrared absorption and Raman scattering due to localized vibrational mode of Be in zinc-chalcogenides

Abstract The localized vibrational modes of Be in ZnS and ZnSe are observed by using the infrared absorption and Raman scattering. The concentration dependent shift of local mode line is found in ZnS: Be. For these systems, anharmonic potential constants are calculated up to the 4th order. Fundamental local mode of ZnTe: Be is also measured.

Anomalous electro-reflectance signals near the fundamental edge of zinc selenide

Abstract A new structure has been found in the low temperature (90°K) electroreflectance spectra of ZnSe. The energies of the L0 phonon assisted exciton creation process and of the fundamental edge including excitons are assigned.

Application of Diffusion from Implanted Polycrystalline Silicon to Bipolar Transistors

A new impurity doping method utilizing diffusion from implanted polycrystalline silicon has been developed. The method was applied to base diffusion in the fabrication of low noise npn transistors, and the characteristics have been significantly improved. Pulsive noise was eliminated and noise figure at 10 Hz was 3.5~4.0 dB. Excellent flat dependence of hFE on collector current was obtained.

Infrared absorption due to localized vibrational mode of beryllium in cadmium sulfide and selenide

Abstract The polarized infrared absorption due to the fundamental and 2nd-harmonic excitation of the localized vibration of Be in CdS and CdSe is observed. The splitting and the polarization property are in accord with C 3 ν point symmetry of Be impurity. The anharmonic potential coefficients are obtained up to the 3rd order. The Raman scattering from Be localized mode is also measured in the case of CdS: Be.

The application of gas plasma to the fabrication of MOS-LSI

The gas plasma technique was applied to the etching of Si 3 N 4 , poly-Si, SiO 2 and the multi-layer films in fabrication of MOS-LSI. For Si 3 N 4 film in the selective oxidation process, the so-called side-etching can be controlled from negative, zero to positive, by varying the plasma conditions. The Al-gate MOS-LSIs fabricated by this process work well and havegood reliability, and their wafer yield was better than that of devices fabricated by the process using the wet-chemical etching. The gas plasma technique could give the tapered etching of poly-Si film in the Si-gate process and also smooth edges without under-cutting in the multi-layer structures including the MNOS and SNOS. SiO 2 films could be etched successfully by the gas plasma technique, but the processing time may be too long depending on processes.

An Injection Type Electro-Luminescence in ZnSe-Sno2 Hetero-Junction

Injection type electro-luminescence has been observed in the forward biased ZnSe-SnO2 heterostructure junction. The junction shows good rectification characteristics. Clearly separated four main emission bands are found at energies of 2.00, 2.35, 2.70 and 2.80 eV at 90 K. Emission light intensity has almost no frequency dependence from DC up to 10 KHz. Injection current and temperature dependence of the emission spectra are demonstrated. The C-V characteristic and the spectral response of photovoltaic effects are also measured to determine the potential profile of the junction.