Diffusion and Defects in Elementary and Compound Semiconductors
Electrical characterisation of impurities and defects in semiconductors
We investigated by deep level transient spectroscopy (DLTS) a series of epitaxially grown n-type
Si1-xGex layers for X between 0 and 0.50 after in-diffusion of Ir. The measurements
reveal two deep electron traps, which are attributed to the Ir0/+- donor state and Ir-/0
acceptor state of isolated Ir atoms on substitutional sites. The corresponding DLTS peaks are broadened for
X>0 in comparison to those in pure silicon (X=0) due to statistical fluctuations of the SiGe alloy
composition in the local environment of the Ir atoms. In addition, the position of the corresponding energy
levels in the SiGe bandgap varies with composition. In silicon wafers (X=0) additional energy levels were
found after rapid quenching from the Ir diffusion temperature (1100 - 1200oC). These
levels are attributed to complexes of Ir with (fast diffusing) unwanted impurities. They can be removed by
annealing at 600oC.
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