An x-ray diffraction technique is presented for the determination of the strain tensor in an epitaxial layer grown on a crystallographically distinct substrate. The technique utilizes different diffracting planes in the layer and in a reference crystal fixed to the layer, and is illustrated by application to an -4000 A (001) silicon layer grown on a (01 l2) sapphire wafer. The principal strains...

High threading dislocation (TD) density in GaN-based devices is a long unresolved problem because of the large lattice mismatch between GaN and the substrate, which causes a major obstacle for the further improvement of next-generation high-efficiency solid-state lighting and high-power electronics. Here, we report InGaN/GaN LEDs with ultralow TD density and improved efficiency on a sapphire su...

In this article, the growth and coalescence of semipolar (112̄2) oriented GaN layers, deposited on pre-structured r-plane sapphire substrates, is studied with the help of Si-doped marker layers. It has been found to be very important to adjust the shape of the initial GaN stripes by varying the growth temperature to obtain not only a smooth surface, but also a low density of basal plane stacking...

In order to reduce the effort needed to create self-separated, freestanding gallium nitride (GaN) layers by thick growth in hydride vapor phase epitaxy (HVPE), we established a two-step facet-controlled lateral overgrowth (FACELO) process in HVPE. Just as for the metalorganic vapor phase epitaxy (MOVPE) FACELO process, the template is produced by MOVPE growth directly on sapphire. This initial ...

We applied a new Migration Enhanced Metalorganic Chemical Vapor Deposition (MEMOCVD) epitaxial technique for growing AlN/GaN/InN epitaxial films and heterostructure layers on 2”, 3” and 4” substrates. The growth of the AlN/GaN/InN layers was carried out using controlled precursor pulsed flows to achieve accurate thickness control over large area substrates. This technique bridges the gap betwee...

The development of high emission power green light emitting diodes chips using GaInN/GaN multi quantum well heterostructures on sapphire substrate in our group is being reviewed. We analyze the electronic bandstructure in highly polarized GaInN/GaN quantum wells to identify the appropriate device structures. We describe the optimization of the epitaxial growth for highest device performance. Ap...

We present a method of epitaxially growing thermodynamically stable gallium nitride (GaN) nanorods via metal-organic chemical vapor deposition (MOCVD) by invoking a two-step self-limited growth (TSSLG) mechanism. This allows for growth of nanorods with excellent geometrical uniformity with no visible extended defects over a 100 mm sapphire (Al2O3) wafer. An ex-situ study of the growth morpholog...

We demonstrate the fabrication of vertical InGaN light-emitting diodes (LEDs) on large-area free-standing membranes, using a mechanical lift-off technique enabled by 2D h-BN. 30 μm-thick electroplated copper deposited epilayer (i) gives rigidity to structure, preventing crack generation, (ii) functions as back mirror and heat sink, (iii) enables one-step self-lift-off transfer LED structures fr...

Ultrasonic-assisted grinding processing can effectively reduce the surface roughness and enhance efficiency in of hard brittle materials. However, most common ultrasonic assisted is a type contact where tool directly contacts workpiece, which means that it necessary to accurately control pre-pressure on workpiece. The will inevitably increase complexity device, easy wear workpiece because impro...