Design and fabrication of enhanced lateral growth for dislocation reduction in GaN using nanodashes

The semiconductor gallium nitride is the material at the centre of energy-efficient solid-state lighting and is becoming increasingly important in high-power and high-frequency electronics. Reducing the dislocation density of gallium nitride planar layers is important for improving the performance and reliability of devices, such as light-emitting diodes and high-electron-mobility transistors. The patterning of selective growth masks is one technique for forcing a three-dimensional growth mode in order to control the propagation of threading defects to the active device layers. The morphology of the three-dimensional growth front is determined by the relative growth rates of the different facets that are formed, and for GaN is typically limited by the slow-growing {1 −1 0 1} facets. We demonstrate how the introduction of nanodash growth windows can be oriented in an array to preserve fast-growing {1 1 −2 2} facets at the early stage of growth to accelerate coalescence of three-dimensional structures into a continuous GaN layer. Cathodoluminescence and Electron Channelling Contrast Imaging methods, both used to measure the threading dislocation density, reveal that the dislocations are organised and form a distinctive pattern according to the underlying mask. By optimising the arrangement of nanodashes and the nanodash density, the threading dislocation density of GaN on sapphire epilayers can be reduced significantly from 109 cm−2 to 3.0 × 107 cm−2. Raman spectroscopy, used to monitor the strain in the overgrown GaN epilayers, shows that the position of the GaN E2H phonon mode peak was reduced as the dash density increases for a sample grown via pendeo-epitaxy whilst no obvious change was recorded for a sample grown via more conventional epitaxial lateral overgrowth. These results show how growth mask design can be used to circumvent limitations imposed by the growth dynamics. Moreover, they have revealed a greater understanding of the influence of the growth process on the dislocation density which will lead to higher performing electronic and optoelectronic devices as a result of the lower dislocation densities achieved

ZnO nanostructures prepared by RF sputtering

ZnO is shortly reviewed as significant material for nanotechnology. Sputtered ZnO thin films showed colummar polycrystalline structure with preffered orientation in direction, resistivity ~ 1 Wcm and optical bandgap Eg = 3,33 eV. Nanoclusters of Au and ZnO were formed by use of RF sputtering

Ordered thin films of magnetic nanoparticles

The investigation of physical properties of bulk materials is a traditional approach in materials science. During last decades the interest has been focused on two-dimensional ordered systems of nanometer-size particles with unusual mechanical, electrical, magnetic, optical, chemical properties, which are perspective for applications in electronics, optics, computer science and medicine. In this paper we report on the preparation of well ordered Langmuir-Blodgett films of g- Fe2O3 nanoparticles with an average size of 10nm. Arrangement and homogeneity were confirmed by scanning electron microscopy as well as atomic force microscopy. Magnetic properties were measured by the magneto-optical Kerr effect

Raman spectroscopy used to assess the temperature and mechanical stress in thin films of microelectronic structures

We are grateful to the scientific grant agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic for financial support of project VEGA No. 1/0947/16.In this experimental work we examined the temperature and mechanical stress in the thin films of microelectronic structures based on GaN and AlN by Raman spectroscopy. The rise in temperature in the Raman spectrum is shown by shifting the Raman bands toward lower wavenumbers. Similarly like with changes of temperature, the changes of the positions of Raman bands may indicate the changes of mechanical stress in the structure. It was confirmed experimentally that in the case of tensile stress the Raman bands are shifted towards lower wavenumbers, and under compressive stress to higher wavenumbers

Design and fabrication of enhanced lateral growth for dislocation reduction in GaN using nanodashes

The semiconductor gallium nitride is the material at the centre of energy-efficient solid-state lighting and is becoming increasingly important in high-power and high-frequency electronics. Reducing the dislocation density of gallium nitride planar layers is important for improving the performance and reliability of devices, such as light-emitting diodes and high-electron-mobility transistors. The patterning of selective growth masks is one technique for forcing a three-dimensional growth mode in order to control the propagation of threading defects to the active device layers. The morphology of the three-dimensional growth front is determined by the relative growth rates of the different facets that are formed, and for GaN is typically limited by the slow-growing {1 −1 0 1} facets. We demonstrate how the introduction of nanodash growth windows can be oriented in an array to preserve fast-growing {1 1 −2 2} facets at the early stage of growth to accelerate coalescence of three-dimensional structures into a continuous GaN layer. Cathodoluminescence and Electron Channelling Contrast Imaging methods, both used to measure the threading dislocation density, reveal that the dislocations are organised and form a distinctive pattern according to the underlying mask. By optimising the arrangement of nanodashes and the nanodash density, the threading dislocation density of GaN on sapphire epilayers can be reduced significantly from 109 cm−2 to 3.0 × 107 cm−2. Raman spectroscopy, used to monitor the strain in the overgrown GaN epilayers, shows that the position of the GaN E2H phonon mode peak was reduced as the dash density increases for a sample grown via pendeo-epitaxy whilst no obvious change was recorded for a sample grown via more conventional epitaxial lateral overgrowth. These results show how growth mask design can be used to circumvent limitations imposed by the growth dynamics. Moreover, they have revealed a greater understanding of the influence of the growth process on the dislocation density which will lead to higher performing electronic and optoelectronic devices as a result of the lower dislocation densities achieved

Dataset for 'Design and fabrication of enhanced lateral growth for dislocation reduction and strain management in GaN using nanodashes'

This dataset contains the results of scanning electron microscopy (SEM) secondary electron (SE) images, panchromatic cathodoluminescence (CL) imaging and Electron Channelling Contrast Imaging (ECCI) and Raman spectroscopy on GaN epitaxial layers. These techniques were used to assess the morphology of the GaN crystal growth, and the dislocation density and strain in planar layers

Dataset for 'Design and fabrication of enhanced lateral growth for dislocation reduction and strain management in GaN using nanodashes'

This dataset contains the results of scanning electron microscopy (SEM) secondary electron (SE) images, panchromatic cathodoluminescence (CL) imaging and Electron Channelling Contrast Imaging (ECCI) and Raman spectroscopy on GaN epitaxial layers. These techniques were used to assess the morphology of the GaN crystal growth, and the dislocation density and strain in planar layers