Two In Al 1− N layers were grown simultaneously on different substrates (sapphire (0001) and Ga-polar GaN template) but under the same reactor conditions were employed to investigate the mechanism of strain-driven compositional evolution. The resulting layers on different substrates exhibit different polarities and layer grown on sapphire is N-polar. Moreover, for the two substrates, the difference in degree of relaxation of the grown layers was almost 100%, leading to a large In-molar fraction difference of 0.32. Incorporation of In in In Al 1− N layers was found to be significantly influenced by strain imposed by the under-layers. The evolutionary process of In-incorporation during subsequent layer growth along [0001], the direction of growth was investigated in detail by Auger electron spectroscopy. It is discovered that In 0.60 Al 0.40 N layer grown directly on sapphire consist of two different regions with different molar fractions: transition and uniform region. According to the detailed cross-sectional transmission electron 2 microscopy, the transition region is formed near the hetero-interface due to the partial strain release caused by the generation of misfit-dislocations. The magnitude of residual strain in uniform region decides the In-molar fraction. In Al 1− N layers were analyzed by structural and optical characterization techniques. Our present work also shows that multi-characterization approach to study In Al 1− N is prerequisite for their applications as a buffer layer.
We report on local magnetization, tunnel diode oscillators, and specific-heat measurements in a series of Ba(Ni x Fe 1−x ) 2 As 2 single crystals (0.26 x 0.74). We show that the London penetration depth λ(T ) = λ(0) + λ(T ) scales as λ (0) in both underdoped and overdoped samples. Moreover, the slope of the upper critical field [H c2 = −(dH c2 /dT ) |T →Tc ] decreases with T c in overdoped samples but increases with decreasing T c in underdoped samples. The remarkable variation of λ(0) with T c and the nonexponential temperature dependence of λ clearly indicates that pair-breaking effects are important in this system. We show that the observed scalings strongly suggest that those pair-breaking effects could be associated with quantum fluctuations near three-dimensional superconducting critical points.
Highlights•Diamond/Si bonding interface could withstand a load of high temperature as high as 800 °C.•The amorphous layer observed at the bonding interface decreased with annealing temperature.•The residual stress released in the diamond of the bonding interface decreased with annealing temperature.•The residual stress formed in the bonding interface annealed at 1000˚C is much smaller than that of diamond grown on Si.
Ga2O3, a wide-bandgap semiconductor material, offers a great potential for power and high-voltage electronic devices. We report on the growth of undoped α- and β-phase Ga2O3 using liquid-injection metal-organic chemical vapor deposition (LI-MOCVD) on sapphire substrates. Using the same precursor (gallium acetylacetonate) and deposition temperature of 700 °C, the phase selection was controlled by the sapphire substrate orientation, where the growth of α- and β-phase Ga2O3 was achieved on m- and c-plane surface, respectively. As deduced from x-ray diffraction, α-Ga2O3 films show epitaxial character, while β- Ga2O3 films exhibit highly textured structure. Oxygen flow was also found to have a strong impact on the phase purity of α-Ga2O3 for the flow rates examined. Optical and electrical properties of the layers grown at different oxygen flow rates were also studied systematically. LI-MOCVD growth of α-phase Ga2O3 layers at relatively high deposition temperature widens the high-temperature processing of the Ga2O3-based electronic and optoelectronic devices.
The oxide/semiconductor interface state density (Dit) in Al2O3/AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) structures with gate oxides grown by atomic layer deposition at low deposition temperature is analyzed in this work. MOS-HEMT structures with Al2O3 gate oxide were deposited at 100 and 300 °C using trimethylaluminum precursor and H2O and O3 oxidation agents. The structures were found to show negative net charge at oxide/barrier interface with density (Nint) of 1013 cm−2, which was attributed to the reduction of barrier surface donor density (NDS). Dit was determined using capacitance transient techniques, and the results were assessed by the simulations of the capacitance–voltage characteristics affected by interface traps. The results indicate a lower interface quality of the sample with Al2O3 grown using O3 agent compared to those with H2O, even though the former provided lowest gate leakage among the analyzed structures. Moreover, to uncover the NDS nature, Dit distributions determined here were compared to that reported previously on devices with Nint close to zero, i.e., with fully compensated surface barrier polarization charge by NDS [Ťapajna et al., J. Appl. Phys. 116, 104501 (2014)]. No clear correlation between Dit and NDS was concluded, indicating the nature of NDS to be different from that of interface states in the energy range analyzed here.
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