X-ray microbeam techniques and applications

We describe x-ray microprobes capable of producing beams down to 0.5 μm for an x-ray wavelength of 1 A. Taking advantage of x-ray sensitivity to strain and their ability to penetrate deep into a sample, we apply the microprobe to measure strain distributions and multi-quantum well thickness in a lithographically patterned semiconductor laser for optical communications. By measuring the positions and widths of the superlattice Bragg peaks we determine the superlattice thickness at which the large crystallographic strain of 1.3 % introduces misfit dislocations, which seriously degrade device performance.