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Due to the functional limitations of SiO2 for SOI applications, alternative dielectric materials have been investigated. Alternative SOI materials in this work include, AlN and AlGaN. The dielectrics were deposited using MOCVD, and with the aid of PECVD deposited SiO2, and the SiO2 was directly bonded to a handle Si wafer. Tensile tests were performed on the samples to examine the fracture behavior and maximum tensile stresses, with results being comparable to a traditional SOI. Characterization was undertaken using TEM to understand the microstructural and interfacial properties of alternative SOI. High crystal quality Al(Ga)N was achieved on a Si(111) substrate that generally contained well defined chemical interfaces. Finally, synchrotron X-ray diffraction topography was used to understand the topographical strain profile of the device and handle wafers. Topography results showed different strain network properties between the device and handle wafer. This work has demonstrated preliminary feasibility of using alternative dielectrics for SOI applications.

Large-area back-reflection and transmission X-ray diffraction topographs of bonded silicon-on-insulator (SOI) wafers made with synchrotron radiation allowed direct and simultaneous imaging of bonding-induced strain patterns of both the 7 μm thick (011) top layers and the (001) Si substrates of the SOI structures. The bonding-induced strain pattern consists of cells having a diameter of about 40 μm. Section topographs show a lattice misorientation of the adjacent cells of about 0.001° and the maximum observed strain-induced lattice plane rotation ten times larger, i.e. about 0.01°. Topographs made after etching away the insulator layer show no indication of residual strain or defects either in the silicon-on-insulator layer or in the substrate. This is in agreement with the experimentally determined maximum bonding stress of 30 MPa, which is much smaller than the estimated stress needed to nucleate dislocations.

Ammonothermally grown GaN is a promising substrate for high-power optoelectronics and electronics thanks to its scalability and high structural perfection. Despite extensive research, ammonothermal GaN still suffers from significant concentrations of impurities. This article discusses the evolution of impurity incorporation during growth of basic ammonothermal GaN, in specific whether the impurity concentration changes temporally along the growth direction and how the autoclave influences the impurity concentration. The effect of the impurities on the structural, electrical and optical properties of the grown crystal is also discussed. The chemical analysis is carried out by time of flight secondary ion mass spectroscopy (ToF-SIMS) and laser-ablation inductively-coupled plasma mass spectroscopy (LA-ICP-MS). Strain and dislocation generation caused by impurity concentration gradients and steps are studied by synchrotron radiation x-ray topography (SR-XRT). Fourier transform infrared (FTIR) reflectivity is used to determine the effect of the impurities on the free carrier concentration, and the luminescent properties are studied by low temperature photoluminescence (PL). The influence of the autoclave is studied by growing a single boule in multiple steps in several autoclaves. LA-ICP-MS and ToF-SIMS ion intensities indicate that the impurity concentrations of several species vary between different autoclaves by over an order of magnitude. SR-XRT measurements reveal strain at the growth interfaces due to impurity concentration gradients and steps. Oxygen is determined to be the most abundant impurity species, resulting in a high free carrier concentration, as determined by FTIR. The large variation in Mn concentration dramatically affects PL intensity.

White beam synchrotron radiation X-ray topography (SR-XRT) and X-ray diffraction (XRD) measurements were used to non-destructively study the defect structure of a bulk GaN wafer, grown by the ammonothermal method. SR-XRT topographs revealed high crystal quality with threading dislocation density 8.8×10 4 cm −2 and granular structure consisting of large, slightly misaligned grains. The threading dislocations within grains were identified as mixed and screw type, while no pure threading edge dislocations were observed.

GaP0.98N0.02 layers having a thickness from 75 nm to 600 nm are grown on GaP substrates by metalorganic vapor phase epitaxy. Back-reflection X-ray topographs made with a synchrotron radiation of the thick GaP0.98N0.02 layers reveal images of misfit dislocations. The critical thickness of the grown GaP0.98N0.02 layer on GaP substrate is evaluated from the topographs to be about 200 nm. The strain relaxation is also observed from high resolution X-ray diffraction curves. X-ray diffraction curves and atomic force microscopy studies indicate that the GaP0.98N0.02 layers with thickness smaller than 200 nm possess a very good crystal quality, an atomically smooth surface with a roughness less than 0.3 nm and a well-defined interface without misfit dislocations between the layer and the substrate.

Owing to its great potential in optoelectronic devices, a lot of effort has recently been put into improving the crystal quality of heteroepitaxial GaN. In this study, GaN layers grown on patterned GaN/sapphire substrates are non-destructively investigated by X-ray diffraction techniques. The effect of the patterning is characterized by determining the strain and lattice tilt and twist in the overgrown GaN layers. High resolution X-ray diffraction (HRXRD) scans and reciprocal space maps (RSMs) were utilized for this purpose. Synchrotron radiation X-ray topography (SR-XRT) was used to examine the microstructure of the samples. The patterning was found to significantly improve the crystal quality of the GaN layers, especially by reducing the amount of edge dislocations. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this study, homoepitaxial GaN grown on ammonothermal GaN substrates is non-destructively investigated by synchrotron radiation X-ray topography (SR-XRT) and X-ray diffraction (XRD). The homoepitaxial GaN layer was found to be of excellent crystal quality with individual dislocations clearly visible in the SR-XRT images. SR-XRT images and XRD rocking curves suggest the dislocations are mainly of mixed type. To the best of our knowledge the measured dislocation density is the lowest reported in a homoepitaxial GaN film (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Near-surface InGaAs/GaAs quantum well and strain-induced InGaAs/GaAs quantum dot structures are coated with AlN by plasma-enhanced atomic layer deposition. Due to its relatively low fabrication temperature (

We demonstrate that higher crystalline quality, lower strain and improved electrical characteristics can be achieved in gallium nitride (GaN) epitaxy by using a silicon on insulator (SOI) substrate compared to a bulk Si substrate. GaN layers were grown by metal-organic vapor phase epitaxy on 6-inch silicon (Si) and SOI wafers using the standard step graded AlGaN and AlN approach. The GaN layers grown on SOI exhibited lower strain according to X-ray diffraction analysis. Defect selective etching measurements suggested that using a SOI substrate reduces the dislocation density approximately by a factor of two. Furthermore, growth on SOI substrate allows to use a significantly thinner AlGaN buffer compared to bulk Si. Synchrotron radiation X-ray topography analysis confirmed that the stress relief mechanism in GaN on SOI epitaxy is the formation of dislocation network to SOI device Si layer. In addition, the buried oxide layer significantly improves the vertical leakage characteristics as the onset of the breakdown is delayed by approximately 400 V. These results show that the GaN on SOI platform is promising for power electronics applications.

The large-area defect structure of high-quality ammonothermal GaN was studied by synchrotron radiation X-ray topography (SR-XRT) and high-resolution X-ray diffraction (XRD). The threading dislocation densities of mixed and screw dislocations were determined separately by SR-XRT and were 3.2 × 104 and 3.1 × 103 cm−2, respectively. Threading edge dislocations were not observed. SR-XRT images show that TMDs are clustered on a large scale and form short dislocation arrays with an average spacing between dislocations of 12 µm. XRD rocking curves were used to measure an average lattice tilt of 10 arcsec caused by the dislocation arrays.

Nitrogen substitution and formation of point defects in GaP(1−x)Nx layers (x ranging from 0.01 to 0.04) grown on GaP substrates are characterized by channelling Rutherford backscattering, nuclear reaction analysis and positron annihilation spectroscopy measurements. It is observed that the substitutionality of nitrogen into GaP decreases from a value of 0.91 to that of