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Single-crystalline CdTe films were grown in both (133) and (211) surface orientations on (211) Si substrates by vapor-phase epitaxy using metallic Cd source as a group-II precursor. The orientation of epitaxial films depended on the ratio of group-II and -VI precursors, i.e., II/VI. The orientation of epitaxial films was changed from (133) to (211) by increasing the II/VI under the CdTe growth condition. The surface morphology for (133) CdTe was smooth, whereas the surface for (211) CdTe was composed of hillocks with (111), (110), (101), and (100) facets. The full width at half maximum (FWHM) of the epitaxial films with the same thickness showed that the crystalline quality of (133) CdTe was better than that of (211) CdTe. The dependence of the orientation between (133) and (211) CdTe films on (211) Si substrates on the II/VI was explained by the difference between the step-flow growth on the step and the spontaneous nucleation on the terrace.

We successfully performed epitaxial CdTe growth on a Si (211) substrate with vapor-phase epitaxy using a cost-effective metallic cadmium source as a group-II precursor. The thermodynamic data demonstrate that the combination of metallic Cd and diisopropyl-telluride (DiPTe) with a H2 carrier gas enables the growth of CdTe crystals. A CdTe single crystal with a (422) surface orientation was obtained when a growth temperature between 600°C and 650°C was employed. The surface morphology and crystalline quality were improved with increasing film thickness. The full-width at half-maximum of the x-ray rocking curves with a film thickness of 15.7 μm for the skew-symmetrical (422) and asymmetrical (111) reflection were 528 arcsec and 615 arcsec, respectively.

Deep-level luminescence at 3.3 eV related to the presence of Al vacancies (V Al ) was observed in room temperature photoluminescence (RT-PL) spectra of homoepitaxial AlN layers grown at 1450 °C by hydride vapor-phase epitaxy (HVPE) and cooled to RT in a mixture of H 2 and N 2 with added NH 3 . However, this luminescence disappeared after removing the near surface layer of AlN by polishing. In addition, the deep-level luminescence was not observed when the post-growth cooling of AlN was conducted without NH 3 . Secondary ion mass spectrometry (SIMS) studies revealed that although the point defect density of the interior of the AlN layers remained low, the near surface layer cooled in the presence of NH 3 was contaminated by Si impurities due to both suppression of the surface decomposition by the added NH 3 and volatilization of Si by decomposition of the quartz reactor walls at high temperatures. The deep-level luminescence reappeared after the polished AlN wafers were heated in presence of NH 3 at temperatures above 1400 °C. The surface contamination by Si is thought to generate V Al near the surface by lowering their formation energy due to the Fermi level effect, resulting in deep-level luminescence at 3.3 eV caused by the shallow donor (Si) to V Al transition.

GaN with a film thickness of 200–600 μm was grown on the as-grown three-dimensional supercritical acidic ammonia technology (SCAATTM) bulk seed that comprised only semipolar { 10 1 ¯ 1 ¯ } planes at a temperature as high as 1390 °C by tri-halide vapor phase epitaxy; further, the GaN film was also characterized. The FWHM value of the X-ray rocking curves was ∼40″, which was almost similar to the value of the used seed. The curvature radii were as large as 40–64 m. Further, the carrier concentrations were observed to be as small as 5.1 × 1017–9.1 × 1017 cm−3. However, the basal plane stacking fault densities were observed to be 3.4 × 101–5.4 × 101 cm−1 and were observed to increase during the growth process because of the as-grown SCAATTM seed surface condition.

Electron paramagnetic resonance was used to study the donor that is responsible for the n-type conductivity in unintentionally doped (UID) beta-Ga2O3 substrates. We show that in as-grown materials, the donor requires high tempeature annealing to be activated. In partly activated materials with the donor concentration in the 10(16) cm(-3) range or lower, the donor is found to behave as a negative-U center (often called a DX center) with the negative charge state DX- lying similar to 16-20 meV below the neutral charge state d(0) (or E-d), which is estimated to be similar to 28-29 meV below the conduction band minimum. This corresponds to a donor activation energy of E-a similar to 44-49 meV. In fully activated materials with the donor spin density close to similar to 1 x 10(18) cm(-3), donor electrons become delocalized, leading to the formation of impurity bands, which reduces the donor activation energy to E-a similar to 15-17 meV. The results clarify the electronic structure of the dominant donor in UID beta-Ga2O3 and explain the large variation in the previously reported donor activation energy. Published by AIP Publishing. Funding Agencies|Linkoping Linnaeus Initiative for Novel Functional Materials (LiLi-NFM); Council for Science, Technology and Innovation (CSTI); Cross-ministerial Strategic Innovation Promotion Program (SIP); NEDO, Japan

Magnetic nanostructures embedded in silicon wafers were successfully fabricated by the damascene technique using electron beam lithography. The magnetic properties of embedded square dots (1μm in width and 100nm in height), rectangular dots (300nm×100nm in area and 100nm in height), and circular dots (100nm in diameter and 100nm in height) were investigated. Magnetic force microscopy (MFM) and vibrating sample magnetometer (VSM) measurements showed that the perpendicular anisotropy increased with the aspect ratio, due to a decrease in the areal size. Fine magnetic structures of the 300nm×100nm pattern were clearly resolved by using a special MFM with a low-moment tip.

An ab initio-based approach was made to understand the influences of temperature and beam equivalent pressure (BEP) on the structural stability of GaAs surfaces. The theoretical approach incorporates free energy of vapor phase; therefore we can calculate how structural stability of GaAs surfaces depends on the temperature and beam equivalent pressure. By the theoretical investigations, temperature and BEP dependences of the stability of GaAs(001)-(4×2) β 2 were predicted. The results agree with experimental results, and feasibility of the theoretical approach was confirmed. Furthermore, the relative stability of Ga adatom among the case of that on GaAs(001)-(2&times4) β 2 and (11n)A (n = 2, 3 and 4) surfaces were studied. The results imply that Ga on (113)A is the most stable amongst (001) and all (11n)A surfaces. This is because the strain around the Ga adatom on (113)A is the smallest in the systems.

High temperature growth of thick GaN layers on GaAs (111)A substrates was performed using a two-step growth process by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE). Temperature ramping rate of the low-temperature (LT)-grown GaN buffer layer was found to be a key factor controlling the crystalline quality of subsequently grown GaN layer at high temperature. When a 50 nm thick LT-GaN buffer layer grown at 550 °C is heated to 1000 °C, it is essential to apply a temperature ramping rate of 15 °C/min or more in order to grow a high-quality GaN layer with a specular surface on a GaAs (111)A substrate.

The influence of the source gas supply sequence prior to growth and the NH3 input partial pressure (P o NH3) on the nucleation of InN islands during the initial stages of hydride vapor phase epitaxy on a nitrided (0001) sapphire substrate was investigated. The crystalline quality of the InN layer after subsequent lateral growth was also examined. When NH3 was flowed prior to growth, single-crystal hexagonal InN islands formed. When InN was grown with a higher P o NH3, the number of InN islands decreased remarkably while their diameter increased. The crystalline quality of InN grown on the hexagonal islands with a high P o NH3 significantly improved with increasing growth time. A strong PL spectrum was observed only from InN layers grown with a high P o NH3. It was thus revealed that an NH3 preflow and a high P o NH3 are effective for producing InN with high crystalline quality and good optical and electrical properties.

In order to study the potential sputtering processes in collisions between highly charged ions and surfaces, we conducted secondary-ion mass spectroscopy, measured simultaneously with the scattered atoms at grazing incidence angles. Efficient proton emission was observed in both metal (A1) and wide-gap semiconductor (GaN) surfaces. We conclude that the electron capture by highly charged ions above the surface caused the efficient proton emission. The three-dimensional momentum of protons emitted from the surface was successfully visualized, and the anisotropic angular distribution of the momentum was observed. Contrary to the adsorbed atoms or molecules, no efficient emission of the substrate atoms was observed in the metal (A1) surface.