Electrical and optical characterization of extended defects in SIMOX structures

A novel electron beam induced current (EBIC) technique, which utilizes two adjacent front contacts (one Schottky and one Ohmic), has been developed to characterize electrically active extended defects in the silicon overlayer of SIMOX structures. The results have been compared with photoluminescence measurements on the same samples. EBIC measurements on n-type SIMOX layers show that dislocations and precipitates present in the overlayer act as recombination centres. PL spectra exhibit dislocation-related emission, the intensity of which correlates with the change in density of extended defects measured by EBIC as the experiments are scanned across the wafer. P-type SIMOX material is found to contain stacking fault tetrahedra and pyramidals at the upper silicon - oxide interface and threading dislocations extending across the Si overlayer, but the PL emission of these defects is negligible. Thinning the overlayer by a sacrificial oxidation process creates oxidation-induced stacking faults in the overlayer, which give rise to strong dislocation-related PL emission. It is demonstrated that electrically active extended defects in the silicon overlayers of SIMOX structures are also optically active, and that PL measurements can provide a valuable insight into the electrical activity of the thin overlayers in these structures.