Characterisation of defects in InP substrates

Abstract

Unusual inclusion-like defects (grappes) which occur in many LEC InP ingots have been studied in an {001} Ge-doped wafer by optical microscopy of the etched wafer surface, reflection and transmission X-ray topography, and transmission polarised infra-red microscopy. The defects produced a variety of different contrast features on reflection X-ray topographs. By using all the techniques in combination to examine individual defects it was deduced that the observed contrast effects were consistent with previous postulates regarding the structures of these defects. Essentially, all the defects are similar in structure but vary in diameter from 5–200 μm, and consist of central core regions surrounded by prismatic dislocation loop arrays. It was also established that the majority of defects are situated on line dislocations, and they possess effective Burgers vectors which differ from those of the dislocations on which they are located.