Effect of dislocations on electrical and electron transport properties of InN thin films. I. Strain relief and formation of a dislocation network

The strain-relaxation phenomena and the formation of a dislocation network in 2H-InN epilayers during molecular beam epitaxy are reported. Plastic and elastic strain relaxations were studied by reflection high-energy electron diffraction, transmission electron microscopy, and high resolution x-ray diffraction. Characterization of the surface properties has been performed using atomic force microscopy and photoelectron spectroscopy. In the framework of the growth model the following stages of the strain relief have been proposed: plastic relaxation of strain by the introduction of geometric misfit dislocations, elastic strain relief during island growth, formation of threading dislocations induced by the coalescence of the islands, and relaxation of elastic strain by the introduction of secondary misfit dislocations. The model emphasizes the determining role of the coalescence process in the formation of a dislocation network in heteroepitaxially grown 2H-InN. Edge-type threading dislocations and dislocations of mixed character have been found to be dominating defects in the wurtzite InN layers. It has been shown that the threading dislocation density decreases exponentially during the film growth due to recombination and, hence, annihilation of dislocations, reaching 109 cm−2 for 2200 nm thick InN films.Unión Europea NMP4-CT2003-505614Unión Europea NMP4-CT-2004-500101Comisión Interministerial de Ciencia y Tecnología MAT2004-01234 Españ

Raman studies of Ge-promoted stress modulation in 3C-SiC grown on Si(111)

We present a study of the stress state in cubic silicon carbide (3C-SiC) thin films (120 and 300 nm) grown by solid-source molecular-beam epitaxy (SSMBE) on Si(111) substrates modified by the deposition of germanium prior to the carbonization of Si. μ -Raman measurements were used to determine the residual stress existing in the 3C-SiC layers. The stress is found to decrease linearly with increasing Ge quantity but with different strength depending on the 3C-SiC thickness deposited after the introduction of Ge. Based on secondary ions mass spectroscopy (SIMS) and transmission electron microscopy (TEM) analyses it is suggested that the Ge introduced prior to the carbonization step remains in the near-interface region and reduces the Si outdiffusion, which further reduces the stress state of the 3C-SiC layers

Ge-modified Si(100) substrates for the growth of 3C-SiC (100)

An alternative route to improve the epitaxial growth of 3C-SiC (100) on Si(100) was developed. It consists in covering the silicon wafers with germanium prior to the carbonization step of the silicon substrate. Transmission electron microscopy and μ -Raman investigations revealed an improvement in the residual strain and crystalline quality of the grown 3C-SiC layers comparable to or better than in the case of 3C-SiC grown on silicon on insulator substrates. These beneficial effects were reached by using a Ge coverage in the range of 0.5-1 monolayer

Engineering of III-Nitride Semiconductors on Low Temperature Co-fired Ceramics

This work presents results in the feld of advanced substrate solutions in order to achieve high crystalline quality group-III nitrides based heterostructures for high frequency and power devices or for sensor applications. With that objective, Low Temperature Co-fred Ceramics has been used, as a noncrystalline substrate. Structures like these have never been developed before, and for economic reasons will represent a groundbreaking material in these felds of Electronic. In this sense, the report presents the characterization through various techniques of three series of specimens where GaN was deposited on this ceramic composite, using diferent bufer layers, and a singular metal-organic chemical vapor deposition related technique for low temperature deposition. Other single crystalline ceramic-based templates were also utilized as substrate materials, for comparison purposes

Engineering of III-nitride semiconductors on low temperature Co-fired ceramics

This work presents results in the field of advanced substrate solutions in order to achieve high crystalline quality group-III nitrides based heterostructures for high frequency and power devices or for sensor applications. With that objective, Low Temperature Co-fired Ceramics has been used, as a non-crystalline substrate. Structures like these have never been developed before, and for economic reasons will represent a groundbreaking material in these fields of Electronic. In this sense, the report presents the characterization through various techniques of three series of specimens where GaN was deposited on this ceramic composite, using different buffer layers, and a singular metal-organic chemical vapor deposition related technique for low temperature deposition. Other single crystalline ceramic-based templates were also utilized as substrate materials, for comparison purposes

Characterization of Buffer Layers for SiC CVD

Silicon Carbide has been grown by rapid thermal carbonization of (100) and (111) Si surfaces at atmospheric pressure using 1 lpm hydrogen (H2) as a carrier gas and propane (C3H8) with concentrations ranging from 0.025-1 5%. RHEED investigations have shown single crystalline SiC as well as additional phases depending on the propane concentration. A set of kinetic phase diagrams were determined. The chemical nature was examined by AES. At concentrations below 0,1% additional silicon and an increasing number of defects were found. The growth on (100) substrates has shown a change in orientation toward (111). Above 0.6% a carbon rich polycrystalline layer covering completely the surface was formed. The carbon has both graphitic and carbidic nature. The graphitic content could be decreased by post deposition H2 annealing without changing the polycrystalline nature of this top layer. Best crystallinity were found at 1250°C, 0.15% propane and 30-90 S