Investigation of striations in doped InP wafers by scanned photoluminescence and spatially resolved SIMS
Scanned photoluminescence (SPL) is used in the laboratories for the assessment of the homogeneity of InP wafers grown as substrate material for monolithic optoelectronic integrated circuits. A typical feature in SPL images of doped InP wafers are growth striations occurring as circular patterns. To clarify the origin of these striation patterns the authors have compared PL intensity line profiles extracted from SPL images with line profiles of dopant concentrations measured with secondary ion mass spectroscopy (SIMS). Their measurements on two n-type InP wafers, one doped with Fe and the other doped with Fe, Ga and Sb revealed that the spatial modulation of the PL intensity visible as a striation pattern coincides with the striation-related fluctuations of the dopant concentrations. In both samples the modulation of the PL intensity is anti-correlated with the Fe striations. They conclude that the recombination behaviour is mainly influenced by fluctuations of the deep acceptor Fe.