GaN layers grown by metal organic vapour phase epitaxy on sapphire were imaged by synchrotron radiation X-ray topography. The threading dislocations could not be resolved in the topographs due to their high density, but a smaller density of about 105 cm-2 misfit dislocations were seen in the interface between GaN and sapphire by using large-area backreflection topography. The misfit dislocation...

The birefringence of a low-loss, high-reflectance coating applied to an 8-cm-diameter sapphire crystal grown in the m-axis direction has been mapped. By monitoring the transmission of a high-finesse Fabry-Perot cavity as a function of the polarization of the input light, we find an upper limit for the magnitude of the birefringence of 2.5 x 10(-4) rad and an upper limit in the variation in dire...

Due to its excellent thermal, mechanical, and optical properties, sapphire is one of the most suitable material for integrated optical devices. Although this hard crystalline material is particularly difficult to process, fabrication of Ti-doped sapphire surface channel waveguides by surface structuring [1,2] of planar waveguides or ion in-diffusion [3] has been demonstrated. Generally, device ...

We report the development of 520–540 nm green light emitting diodes LEDs grown along the nonpolar a axis of GaN. GaInN /GaN-based quantum well structures were grown in homoepitaxy on both, a-plane bulk GaN and a-plane GaN on r-plane sapphire. LEDs on GaN show higher, virtually dislocation-free crystalline quality and three times higher light output power when compared to those on r-plane sapphi...

The cryo scanning electron microscopy (cryo-SEM) as well as high-pressure-freezing (HPF) belongs to cutting edge techniques in electron microscopy of hydrated samples [1]. However, their combination is not always easily applicable. Here, we present a way of combining high-pressure-freezing using EM PACT2 (Leica Microsystems) that fixes hydrated samples on a 1.4 mm sapphire discs and high resolu...

We demonstrate a thin-film flip-chip (TFFC) process for LEDs grown on freestanding c-plane GaN substrates. LEDs are transferred from a bulk GaN substrate to a sapphire submount via a photoelectrochemical (PEC) undercut etch. This PEC liftoff method allows for substrate reuse and exposes the N-face of the LEDs for additional roughening. The LEDs emitted at a wavelength of 432 nm with a turn on v...

Radiation from magnetized plasmas is in general elliptically polarized. In order to convert the elliptical polarization to linear polarization, mirrors with grooved surfaces are currently employed in our collective Thomson scattering diagnostic at ASDEX Upgrade. If these mirrors can be substituted by birefringent windows, the microwave receivers can be designed to be more compact at lower cost....

High-crystalline aluminum nitride (AlN) thin films are essential for device applications, and epitaxial growth is a promising approach to improve their crystalline quality. However, high substrate temperature usually required the growth, which not compatible with complementary metal-oxide-semiconductor (CMOS) process. Furthermore, it very difficult obtain AlN on deposited metal layers that some...

GaN growth on nitridated sapphire (0001) by rf plasma-assisted metal-organic molecular-beam epitaxy is shown to exhibit a highly superlinear growth rate and a transition from strained, smooth growth to relaxed cluster growth during the first layer. A coupled rate-equation model suggests that the growth rate arises from both the site-dependent reactivity of precursor molecules and a layer-depend...

We have studied the molecular structure of liquid alkanes confined between a flexible elastomeric poly(dimethyl siloxane) lens and a rigid sapphire substrate using surface-sensitive infrared-visible sum frequency generation spectroscopy. The reduction in the gauche defects suggests ordering of liquid alkanes under confinement. The cooling of confined liquid below the freezing temperature leads ...