Depth-resolving structural analysis of GaN layers by skew angle x-ray diffraction

The method of skew angle x-ray diffraction is presented as the example of GaN-based light emitting diodes (LED) grown by metalorganic vapor phase epitaxy on silicon substrates. This technique in conjunction with a newly developed calculation algorithm allows the depth-resolving structural analysis of multilayer structures. The analysis algorithm, basing on a triangular matrix approximation for the intensity decrease in dependence on the layer depth, the absorption coefficient, and the incident angle, provides information on the real full width at half maximum (FWHM) values of the GaN (101_3) reflection in distinct depths of the device. The sensitivity of this technique was found to be smaller than 50 nm. We show the different characteristics of the measured and calculated FWHMs for two GaN-based LEDs containing a fivefold InGaN/GaN-multi-quantum well.