Characterization of growth defects in thin GaN layers with X‐ray microbeam

Abstract

The spatially resolved distribution of strain, misfit and threading dislocations, and crystallographic orientation in uncoalesced GaN layers grown on Si(111) by maskless cantilever epitaxy or by pendeo epitaxy on SiC was studied by white beam Laue X-ray microdiffraction, scanning electron and orientation imaging microscopy. Tilt boundaries formed at the column/wing interface depending on the growth conditions. A depth dependent deviatoric strain gradient is found in the GaN. The density of misfit dislocations as well as their arrangement within different dislocation arrays was quantified. Two different kinds of tilt (parallel and perpendicular to the stripe direction) manifested themselves by mutually orthogonal displacements of the (0006) GaN Laue spot relative to the Si(444) Laue spot. The origin of the tilts is discussed with respect to the miscut of the Si(111) surface and misfit dislocations formed at the interface. Regular oscillations of the conventional wing tilt were observed. Irregular crystallographic tilts fluctuations were found in the direction parallel to stripes. The amplitude of fluctuations is an order of magnitude smaller for layers with a lower defects density.

Gallium nitride heterostructures on 3D structured silicon

“…GaN growth suffers from the lack of native substrates. Usually, sapphire, SiC or silicon serves as the substrate, but all of these induce large strain as well as high dislocation densities in the epilayers [1][2][3]. In the case of silicon, complicated strain engineering has to be employed especially due to the strong thermal mismatch in addition to a large lattice mismatch [4].…”

GaN and LED structures grown on pre‐patterned silicon pillar arrays

“…sapphire, SiC, Si, induce high densities of dislocations and cracks in the GaN epilayer which deteriorate the device performance [1][2][3]. Recently, GaN nanorods attracted great interest due to their superior properties.…”

White X‐ray microdiffraction analysis of defects, strain and tilts in a free standing GaN film

“…However both methods are based on the growth of the wings of GaN overhanging over trenches in the substrate or GaN. The latter typically result in the formation of a wing tilt angle (WT) decreasing life expectancy of the optoelectronic devices [4][5][6][7][8]. Recently defect reduction in planar nonpolar (1 100) m-plane GaN films was achieved via lateral epitaxial overgrowth by hydride vapor phase epitaxy [9][10][11][12].…”