X‐Ray Diffraction Microstrain Analysis for Extraction of Threading Dislocation Density of GaN Films Grown on Silicon, Sapphire, and SiC Substrates

Abstract

X‐Ray diffraction microstrain characterization is a technique which enables the quantification of threading dislocations by measuring the radial microstrain field surrounding these defects. This work demonstrates how to accurately perform these measurements on a broad range of GaN samples. In particular, for GaN grown on Si substrates with large stress gradient through the layer, the measurements need to be performed on the (20–25) reflection to avoid being affected by a macrostrain influence. A comparison of this characterization with cathodoluminescence and X‐ray diffraction lattice misorientations measurements shows differences in the measurement depth, so the results are affected by the various evolutions of dislocations densities through the layers of the different samples. Independently of the measurement depth, the analysis also highlights a dependence of the X‐ray measurements results on the type of sample, in particular the starting substrate. Microstrain measurements appear therefore as being well suited for the comparison of threading dislocations densities between similar GaN layers. It can be used to replace lattice misorientations measurements, or be associated with them to obtain an edge versus screw dislocations ratio.

H3PO4-based wet chemical etching for recovery of dry-etched GaN surfaces

“…Larger holes might be the emergence points of dislocations with a screw component, while smaller ones are pure edge type. The total density of threading dislocations is therefore 1.9x10 9 cm -2 , in line with observations by Yon et al [41] on similar samples. However, it is important to note that after 60 minutes, some of the large holes have hexagonal structures of different sizes, which is likely due to their overlapping making an accurate counting of dislocations difficult (Fig.…”

ZnSe Nanoparticles for Thermoelectrics: Impact of Cu-Doping

“…The grain size was estimated using the Scherrer relation [36,37], D = 0.9λ/β where D is the crystallite size, β is full width at half maximum of the highest int (111) peak, λ is the wavelength of X-ray radiation (1.542 Å of Cu Kα) and θ is the B angle. The dislocation density (δ), that is the number of defect present in the sampl calculated using the Williamson and Smallmman's relation [38], δ = 1/D 2 , and the microstrain was calculated according to the formula ε = (βcot(θ))/4 [39]. The grain size was estimated using the Scherrer relation [36,37], D = 0.9λ/β cos θ, where D is the crystallite size, β is full width at half maximum of the highest intensity (111) peak, λ is the wavelength of X-ray radiation (1.542 Å of Cu Kα) and θ is the Bragg's angle.…”

“…The grain size was estimated using the Scherrer relation [36,37], D = 0.9λ/β cos θ, where D is the crystallite size, β is full width at half maximum of the highest intensity (111) peak, λ is the wavelength of X-ray radiation (1.542 Å of Cu Kα) and θ is the Bragg's angle. The dislocation density (δ), that is the number of defect present in the sample, was calculated using the Williamson and Smallmman's relation [38], δ = 1/D 2 , and the lattice microstrain was calculated according to the formula ε = (βcot(θ))/4 [39].…”