Luminescence microscopy for quality control of material and processing

A photoluminescence topography system is devised on the basis of an optical IR microscope. The system offers full versatility and simple operation of the microscope combined with the high sensitivity characteristic for luminescence, whose emission intensity varies strongly with crystal quality. Results obtained on InGaAsP/InP demonstrate the system's capabilities: in substrate characterization, luminescence microscopy turns out to be a nondestructive alternative to dislocation etching, but, in addition, it makes defects visible which are not revealed by etching. On epitaxial layers, with the technique, the correlations between various defects in the substrate and resulting layer quality are analyzed. As an application to process control, defect generation is investigated during thermal degradation. Two yet unknown degradation effects are discovered which develop even if protection by an Sn-P-melt is used.