Microbeam high-resolution x-ray diffraction in strained InGaAlAs-based multiple quantum well laser structures grown selectively on masked InP substrates

Structural and optical properties of the InGaAlAs-based multiple quantum well (MQW) 1.3 μm laser structures produced on InP (001) substrates by metal organic vapor phase epitaxy (MOVPE) technique in the regime of selective area growth (SAG) have been studied. An x-ray beam of 10 μm diameter generated by a microbeam high-resolution x-ray diffraction (μ -HRXRD) setup based on an imaging one-bounce capillary optic and a three-bounce channel cut Si(004) analyzer crystal has been utilized to measure the diffraction curves from MQW structures grown between oxide mask stripes. The high angular resolution achieved in our experiments allowed accurate measurements of θ-2θ scans over a broad range of angles that was necessary for utilization of fitting algorithms for quantitative analysis of the strain and thickness of individual layers in the MQW structures. The thickness and strain variations in the quantum well and the barrier layers of the MQW SAG structure have been analyzed as a function of the oxide mask width in the range of 15-140 μm with the gap between the oxide masks in the range of 15-80 μm. Dramatic structural changes from the perfect quality MQW's in the SAG structures with the narrow oxide masks (less than 45 μm) to the strain relaxed MQW's in the SAG regime with the wide oxide masks (more than 50 μm) have been experimentally detected. The spontaneous photoluminescence emission between 1.3 and 1.51 μm from the simultaneously grown InGaAlAs-based MQW SAG laser structures have been measured. Using a combination of μ -HRXRD results with the microphotoluminescence data, the optimal SAG mask parameters for the growth of integrated InGaAlAs-based optoelectronic light-emitting components and devices have been determined.