Investigation of InP single crystal by LST and photoluminescence-Influence of dopants, dislocations and size of crystals

Laser scanning tomography (LST) has been used to characterize a large number of InP crystals to get an overview of the microprecipitates existing in the crystals. The crystals were doped with usual dopants such as S, Sn, Fe, ND, etc. In the case of sulphur doped crystals, dislocation free as well as dislocated crystals were analyzed. Photoluminescence mapping and dislocation etching were carried out to correlate the different patterns obtained. The density, yield of scattering and distribution of defects depends on the dopant element. In sulphur doped ingots, LST reveals an uniform distribution of numerous and small precipitates. This is true for dislocated as well as for dislocation-free material. Besides these small precipitates, bigger ones are observed only in the dislocated InP samples. In tin doped samples, which are not dislocation free, the distribution looks like S doped samples with dislocations. In iron doped samples, there is a very faint background. Lines and points are revealed. From this first page of the study, it appears that the large precipitates are located on the dislocation, as is the case in GaAs crystals. The density and configuration of defects observed by chemical etching and photoluminescence compared to the configuration of large precipitates obtained by LST enhance the assumption that the large precipitates are lying on the dislocations.<
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