Scanning Microscopy


Panchromatic (integral) and spectrally resolved cathodoluminescence characterization was used to investigate the near surface gettering properties of Cu in liquid-encapsulated, Czochralski-grown, undoped semi-insulating (SI) GaAs. Samples from two sources were investigated to determine if gettering treatments applied to GaAs result in improvements in uniformity similar to those observed in gettered Si. Before Cu contamination, typical cellular structure is observed for all samples. Experimentally, it is found that the panchromatic CL images change significantly after Cu doping and subsequent gettering processing for all samples. A contrast reversal is generally observed after Cu contamination. After gettering, the image of the samples from one source remained reversed whereas the image of samples from the other source showed a second contrast reversal. Typically, both samples exhibit bright regions after gettering which closely correspond to the dislocation structure. More detailed spectrally resolved CL indicates that Cu luminescence correlates well in most cases with the band edge emission. In only a few cases were discernible differences noted. It is concluded that Cu is observed in locations from which nonradiative recombination centers have been effectively removed.

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