Method for modulating the wafer bow of free-standing GaN substrates via inductively coupled plasma etching

Studies about wafer bow of freestanding GaN substrates grown by hydride vapor phase epitaxy

“…4). Similarly, Chen et al [11] found a linear decrease of the curvature after inductively plasma etching of freestanding GaN samples from initially 670 km À 1 to 0 and eventually to convex bowing. We currently can only speculate why their results are quite different to ours taking into consideration the differences in the details of the epitaxial processes and/or the influence of the dry-etch procedure on the wafer bow.…”

Alternately double‐sided growth of low‐curvature GaN templates on sapphire substrates using hydride vapor phase epitaxy

“…In contrast, the XRC‐FWHM decreases significantly with decreasing slit width for the SSG GaN template of 25‐μm thickness. The radius of curvature is calculated using the following equation : where is the broadening owing to the curvature of the crystal sample, R is the bowing radius of the GaN template, and w is the area irradiated by the X‐ray. Considering the slit width, d , and incident angle, θ , of the X‐rays used in the XRD measurements, w is expressed as .…”

“…The main mechanisms of the wafer bowing and lattice tilt are thought to arise from a difference in thermal expansion coefficients between GaN and the foreign substrate . In addition, one cause of convex bowing is considered to be the built‐in strain caused by dislocation gradients between the top and bottom surfaces and inhomogeneous point defects . In particular, the curvature of a HVPE‐grown sample is inferior to that obtained using certain other growth methods, such as the Na‐flux and ammonothermal methods .…”

“…In particular, the curvature of a HVPE‐grown sample is inferior to that obtained using certain other growth methods, such as the Na‐flux and ammonothermal methods . In order to overcome this disadvantage, many approaches have been proposed, such as post‐growth treatment, three‐dimensional growth, buffer layer technique, and optimization of growth conditions . Leach et al in Kyma Technologies reported a novel technology, flat layers at all temperatures (FLAAT), using a polycrystalline GaN film on a back side of a substrate.…”

InGaN-Based Light-Emitting Diodes Fabricated on Nano Patterned Sapphire Substrates with Pillar Height of More than 600 nm by Nanoimprint Lithography

“…However, owing to a large sapphire substrate, wafer bowing becomes a critical issue because of the difficulty in processing it for LED chips. [1][2][3][4][5] In terms of growth time, a GaN layer on a nano patterned sapphire substrate (nano-PSS) can be embedded more rapidly than that on a conventional PSS owing to the smaller pillar height of the nano-PSS. In addition, the conventional PSS is fabricated using a stepper, which contributes to the long process.…”