To enhance light extraction effciency, high-quality InGaN-based light emitting diodes (LED) was grown on cone-shaped patterned sapphire (CPSS) by using metal organic chemical vapor deposition (MOCVD). From the transmission electron microscopy (TEM) observation, the CPSS was confirmed to be an efficient way to reduce the threading dislocation density in the GaN epilayer. A sharp and high intensi...

We study electroabsorption (EA) behavior of InGaN/GaN quantum structures grown using epitaxial lateral overgrowth (ELOG) in correlation with their dislocation density levels and in comparison to steady state and time-resolved photoluminescence measurements. The results reveal that ELOG structures with decreasing mask stripe widths exhibit stronger EA performance, with a maximum EA enhancement f...

High-quality strain-relaxed SiGe templates with a low threading dislocation density and smooth surface are critical for device performance. In this work, SiGe films on low temperature Si buffer layers were grown by solid-source molecular beam epitaxy and characterized by atomic force microscope, double-axis x-ray diffraction, photoluminescence spectroscopy, and Raman spectroscopy. Effects of th...

We investigated the migration of a symmetric tilt, low-angle grain boundary (LAGB) under applied shear stress in the presence of extrinsic dislocations. The results demonstrate that there is a threshold stress for the LAGB to depin from extrinsic dislocations. Below the threshold stress, the LAGB remains immobile at zero dislocation climb mobility, while for finite climb mobilities, it migrates...

Very high strain hardening coefficients (=G/23) are observed for aluminum-alloyed face-centered cubic Hadfield steel single crystals under tensile loading. Alloying with aluminum suppressed deformation twinning in two of the three crystallographic orientations studied, and transmission electron microscopy results revealed the existence of dense dislocation walls (sheets) along crystallographic ...

Hydride vapour phase epitaxy grown allepitaxial p-i-n structures were studied by synchrotron X-ray topography. Three types of process induced dislocations were found: short threading dislocations, long straight interfacial dislocations and circular arc dislocations. The majority of the dislocations observed are short straight threading dislocations, the density of which is typically about 5000 ...

This article presents an experimental investigation on ductile-mode micro-milling of monocrystalline silicon using polycrystalline diamond (PCD) end mills. Experimental results indicate that the irregular fluctuation of cutting force always induces machined surface failure, even in ductile mode. The internal mechanism has not been investigated so far. The multiscale discrete dislocation plastic...

We have employed the semidiscrete variational generalized Peierls-Nabarro model to study the dislocation properties of aluminum. The generalized-stacking-fault ~GSF! energy surface entering the model is calculated by using first-principles density functional theory ~DFT! and the embedded-atom method ~EAM!. Various core properties, including the core width, dissociation behavior, energetics, and...

We use time-dependent HRTEM to reveal that stable dislocation pairs in graphene are formed from an initial complex multi-vacancy cluster that undergoes multiple bond rotations and adatom incorporation. In the process, it is found that the transformation from the formed complex multi-vacancy cluster can proceed without the increase of vacancy because many atoms and dimers are not only evaporated...

Relaxed SiGe attracted much interest due to the applications for strained Si/SiGe high electron mobility transistor, metal-oxide-semiconductor field-effect transistor, heterojunction bipolar transistor, and other devices. High-quality relaxed SiGe templates, especially those with a low threading dislocation density and smooth surface, are critical for device performance. In this work, SiGe film...