Setsu Suzuki

Effect of Si‐Ge buffer layer for low‐temperature Si epitaxial growth on Si substrate by rf plasma chemical vapor deposition

Silicon epitaxial growth on the Si‐Ge buffer layer at a low substrate temperature by the rf plasma chemical vapor deposition using SiH4 and GeH4 has been investigated. The electron Hall mobility of the homoepitaxial layer grown at 750 °C with a growth rate of 14 A/sec coincides with that of bulk Si, but for a high growth rate of 33 A/sec, the mobility was limited to within half the value of bulk Si. However, a small amount of Ge introduced in an initial stage of growth to form the Si‐Ge buffer layer improved the crystalline quality of the ensuing Si epitaxial layer with a high growth rate. The electron Hall mobility of the Si layer grown on the Si‐Ge buffer layer was a similar value of bulk Si in a low carrier concentration of 6×1015 cm−3. The crystalline quality of the grown Si layers was examined by the combination of Rutherford backscattering spectrometry and transmission electron microscopy.

Epitaxial growth of Si–Ge layers on Si substrates by plasma dissociation of SiH4 and GeH4 mixture

Silicon–germanium epitaxial layers were formed on (111) oriented Si substrates by the plasma dissociation of a mixture of SiH4 and GeH4. A growth rate of 33 A/sec was obtained at a substrate temperature of 750 °C for Si–Ge epitaxial growth using 1×10−2 Torr of SiH4 and 1×10−4 Torr of GeH4 mixture as source materials. The introduction of GeH4 to SiH4 provided a good nucleation for epitaxy. Less than 1% of GeH4 is sufficient to reduce the concentration of the crystalline defects such as voids which form in the epitaxial layers at low substrate temperature with a high growth rate. The electron Hall mobility of layers coincided with that of bulk Si in the temperature range between 77 °K and room temperature.

Si film as an annealing cap for Si‐implanted GaAs

A Si film formed by vacuum deposition as an annealing cap for a Si‐implanted GaAs substrate has been studied. GaAs substrates implanted with 3×1013 Si ions/cm2 at 100 keV were furnace annealed with Si caps at temperatures between 750 and 900 °C for 15 min. The existence of Ga and/or As atoms in the Si cap film was not detected in the Rutherford backscattering spectra of the Si films after annealing. The differential Hall measurement showed that the carrier concentration profile distributed within the ion implanted region. The Si cap film has feasible characteristics for annealing of Si‐implanted GaAs.

Formation of MoSi2 by pulsed electron beam irradiation onto a vapor deposited molybdenum/silicon structure

A molybdenum disilicide layer was formed by pulsed electron beam irradiation onto a vapor deposited Mo film on a Si substrate. The electron beam with a duration of almost 1 μs was generated by glow discharge of He at a pressure of 1×10−5 Torr in a vacuum chamber equipped with a capacitor of 1 μF that was charged at 7 kV. The total energy stored in the capacitor was 25 J and the irradiated area was almost 1 in. in diameter. The qualitative and structural characterizations were performed by Auger electron spectroscopy (AES), transmission electron diffraction (TED), and transmission electron microscopy (TEM). A depth profile by AES showed that a uniform MoSi2 layer was formed toward the Mo surface from the Mo/Si interface and that C and O contaminants were swept away from the silicide. The hexagonal MoSi2 phase was uniquely identified in the irradiated layer and the TEM micrographs showed uniform polycrystalline grains of a size of 800 A.

Silicon Epitaxy by Plasma Dissociation of Silane

A plasma epitaxy system has been designed to realize low temperature epitaxial growth of silicon. In this system control on the silane dissociation rate and the silicon deposition rate is done separately with the aid of RF glow discharge. Investigations by RBS, TED and TEM techniques proved that layers grown by this method at as low as 700°C kept good crystalline quality. Electrical measurements have been also carried out and revealed that the electrical properties of the layers grown at 750°C were equivalent to those of bulk silicon.

BaTiO3 based relaxor ferroelectric epitaxial thin-films for high-temperature operational capacitors

The epitaxial growth of 0.6[BaTiO3]–0.4[Bi(Mg2/3Nb1/3)O3] (BT–BMN) relaxor ferroelectric thin-films on (100) Nb doped SrTiO3 substrates has been achieved and the structure is investigated for high-temperature capacitor applications. The post growth annealing decreases the oxygen vacancy and other defects in BT–BMN films, resulting in the enhancement of dielectric constant. An insertion of intermediate SrRuO3 layers as an electrode instead of Pt, sandwiching the film, is found to be more effective in enhancing the dielectric constant. A very high dielectric constant exceeding 400 was achieved from high-temperature annealed film and the film showed an excellent dielectric constant stability of below 11% in the temperature range of 80–400 °C. This will enable smaller, high-temperature tolerant, monolithically integrated thin-film capacitors on power semiconductor devices.

The Apparatus with a Microprocessor for the Photoluminescence Spectra Correction and Processing

An apparatus using a microprocessor is fabricated in order to correct and process the measured photoluminescence data. This is more advantageous for the data correction and processing than those mentioned before; moreover, it can be applied to other spectrophotometries. An application of the apparatus to the photoluminescence spectra measurements of heavily doped n-type GaAs with heat-treatment or ion implantation, is described. It is found that the emission peak at 1.255±0.003 eV (half width: 0.11 eV) is attributed to an excess of arsenic atoms, excess As–Si complex or Ga vacancy-Si complex.

Low resistance ohmic contacts containing Sb to GaP

Abstract A comparison has been made of the contact resistances of AuZn and AuZnSb alloyed contacts to p-type GaP and of AuGeNi and AuGeNiSb alloyed contacts to n-type GaP. The addition of antimony contact materials reduces the contact resistance and this reduction is greatest when the process of contacting is carried out at temperatures below 500°C.

Combinatorial Nanoscience and Technology for Solid-State Materials

In this era of global competition in advanced science, technology, and industry, high-throughput materials exploration is the key to taking an initiative in research and dominating high-tech markets in the world. While material scientists and engineers have for a long time relied on a slow pinpoint trial-and-error process of materials development, an emerging notion is to bring informatics to the design of libraries of materials in combination with smart synthesis and characterization to screen the properties of new materials at a rate that is orders of magnitude higher than is possible in the conventional one-by-one process.

Heteroepitaxial growth of nonpolar Cu-doped ZnO thin film on MnS-buffered (100) Si substrate

The preparation of nonpolar ZnO and Cu-doped ZnO thin films on Si substrates was studied for the application to the fabrication of green-light-emitting diodes. The use of rocksalt MnS and wurtzite AlN as buffer layers is a key technology for achieving the heteroepitaxial growth of nonpolar ZnO thin film on a (100) Si substrate. X-ray diffraction and photoluminescence measurements revealed that deposition under a high oxygen partial pressure (~1 Torr) can enhance the nonpolar crystallization of undoped ZnO, and can simultaneously suppress the formation of defects such as oxygen vacancies. These techniques can be also applied to the growth of Cu-doped ZnO. A room-temperature photoluminescence study revealed that nonpolar -oriented Cu-doped ZnO film exhibits enhanced green emission owing to the doped Cu ions.