Recently, GaN has attracted much attention for short wavelength LEDs, LDs and future opto-electronic integrated devices. In our study, Boronmonophosphide(BP) grown on Si(100) by MOCVD is used for growing cubic-GaN (c-GaN). The epitaxial growth of GaN/BP/Si has been carried out. We observed the crystal defects by scanning electron microscope(SEM), transmission electron microscopy(TEM), and surface X-ray diffraction(XRD). The dislocation density in the BP layer markedly decreased with increasing the thickness. However the difference of the lattice constant between BP and Si leads to high dislocation densities in GaN layer. Therefore, the epitaxial growth of Si doped BP on Si has been carried out, in order to observe the effect of Si doping on BP crystalline quality. We observed the crystal defects by XRD and cross-sectional TEM. The dislocation of interfaces will be discussed.

It has been found that the blue light emission of LED is remarkably enhanced by using optical window of CaF2 disk doped with Eu2O3. The CaF2 crystals doped with Eu2O3 strongly absorb UV light with 330~420nm optical wavelength as a cutting filter. Instead, CaF2 crystals emit 420~425nm wavelength visible light. As a result, the UV light shifts to a light of around 420nm wavelength, and the LED light emission intensity markedly increases. In our experiments, the UV components were absorbed, while, around 420nm emitting light has been strengthened by more than 30%. The FWHM value is improved by around 30%.

We have focused to grow cubic GaN (c-GaN) on Si(100) substrates using boronmonophosphide (BP) buffer crystals. The growth of GaN was carried out by MOVPE on BP/Si(100) substrate of 2 inches in diameter. By the several evaluations, it was recognized that when the growth temperature is around 750˚C, c-GaN was dominant. The typical growth rate was about 0.5μm/h. We obtained c-GaN layer over 2.5μm thick without cracking.

This paper describes the growth mechanism of silicon whisker on a silicon substrate using hot filament CVD reactor. Only hydrogen is used as source gas. The particle layer could be obtained at high filament current condition under hydrogen ambient. XPS analysis result suggests that the particle is composed of tungsten silicide. The deposition condition of the particle layer is much depended on the substrate size, surface condition and the distance between the substrate and the filament. The experimental results suggest that the silicon hydride, which generated at the silicon surface by hydrogen radical etching, react with the tungsten filament material around the filament, depositing on the silicon substrate. The silicon surface is etched by hydrogen radical and its resultant surface morphology is much depended on the particle deposition pattern. Many silicon whiskers, which diameter is varied from 10 to 50 nm, are observed on the textured silicon surface when the residence time of the source gas in the reactor is long. Each whisker has a silicon particle on their tip. The silicon hydride generated by the hydrogen radical etching is much absorbed to the silicide particle when the source gas residence time is long, enabling the silicon whisker growth from the particle. The results suggest that nm size whisker structure is much stable compare to the bulk silicon against etching reaction.

We have focused to grow cubic GaN (c-GaN) on Si(100) substrates using boronmonophosphide(BP) buffer crystals. We have successfully grown BP crystals by MOVPE technique with electrically n-type and thickness deviation is within several % along 2inch wafer under undoped conditions. The electrical conductivity is less than 0.5mohm∙cm. We have preliminary grown GaN by RF-MBE technique, before we carry out mass-producing MOVPE on larger diameter Si substrates. It has been found the cubic type GaN has been successfully grown on the substrates by measuring X-ray diffraction. The crystal quality and defect generation were observed by TEM. It has been found that there are much more dislocations than 109cm-2 generated at GaN/BP interface.

The hydrogen microwave remote plasma CVD was introduced to fabricate carbon nanotubes(CNTs). C2H2 or CH4, used as source gas react with hydrogen radicals introduced from the cavity. In this experiment, hydrogen radical etching effect on the substrate surface could be controlled independently. We confirmed CNTs growth at 400°C under adequate hydrogen radical etching effect on the substrate surface. The result directly suggests that the etching effect of hydrogen radicals on the reaction surface contribute to the low temperature growth of CNTs. The CNT thickness did not depend on the hydrogen radical etching effect but the catalyst layer thickness.

Boronmonophosphide(BP) is one of the suitable materials for a buffer layer between the c-GaN(100) and Si(100) substrates. The growth of BP layer was carried out by MOCVD on Si(100) substrate of 2 inch in diameter. The growth rate was over 2 μm/h without any troubles such as the bowing or cracking. In addition, the thickness of BP epitaxial layer was uniform over a wide area. A careful analysis of x-ray diffraction suggested that the growth of BP epitaxial layer inherited the crystal orientation from Si(100) substrate. Cross-sectional TEM images showed some defects like dislocations near the interface between BP layer and Si substrate. The Hall effect measurements indicated that the conduction type of BP films grown on the both n-Si and p-Si substrates was n-type without impurity doping, and that the mobility and carrier concentrations were typically 357cm2/Vs and 1.5×1020cm−3(on n-Si) and 63cm2/Vs and 1.9×1019cm−3(on p-Si), respectively. In addition, c-GaN was grown on the substrate of BP/Si(100) by RF-MBE.

This paper describes the surface texturing mechanism on crystalline Si using hydrogen radicals generated by a tungsten hot filament. Inverted pyramid or labyrinthV groove structure could be obtained by particle deposition before etching. Mesh like tungsten particle layer, works as an etching mask against hydrogen radical, was obtained when silicon substrate was used. On the other hand, tungstem particles were not deposited as mesh like pattern when SiO2/Si substrate was used. The results suggest that evaporation of silicon hydrides from the silicon surface by hydrogen radical etching causes the mesh like pattern deposition of tungsten particles. Increase of filament current enables short time texturing process of less than 1 minute.

In Czochralski-grown (CZ) silicon single crystals, antimony (Sb) doping decreases the oxygen concentration by enhancing oxygen evaporation from the melt surface. In this study, Ar ambient pressures of around 100 Torr over the silicon melt were found to suppress evaporation of oxide species. To clarify the effect of the growth chamber ambient pressure on oxygen concentration, heavily Sb-doped CZ silicon crystals were grown under Ar pressures of 30, 60, and 100 Torr. Increasing Ar pressure increases the oxygen and Sb concentrations at the melt surface. The oxygen concentration under an Ar pressure of 100 Torr was 1.2 times higher that under 30 Torr when the solidified fractions are 0.5 or larger. The oxygen evaporation rate is controllable by gas phase transport of Sb2O at high Ar pressures.

We report drain-current (Id) deep level transient spectroscopy (DLTS) spectra and liquid-encapsulated-Czochralski-technique (LEC) GaAs crystal effect on low-frequency-oscillation (LFO) of wide gate (400-μm) Si-implanted GaAs metal- semiconductor field- effect- transistors (MESFETs). In the range of this experiment we could not find distinguishing DLTS peaks surely to be linked with Id-LFO of the MESFETs. Stoichiometric-melt growth LEC-boules showed relatively large Id-LFO phenomena. As-rich-melt growth LEC-boules showed tolerance to Id-LFO. We conclude that Id-LFO is not directly linked to deep centers themselves but interaction between deep centers and potential profiles and electrons. Stability of potential profile or band profile depends on “pinning’ center, which affects Fermi-level or quasi-Fermi-level stability. ‘Pinning’ center such as EL2s of ‘LEC GaAs crystals” is essential.