From Surface Data To Bulk Properties: A Case Study For Antiphase Boundaries In Gap On Si(001)

The orientation, atomic structure, and charge state of defects in crystals have a large influence on the functionality of resultant semiconductor devices. Two-dimensional defects are especially challenging to analyze, as they are embedded within the bulk. We developed a data analysis procedure using information from atomically resolved cross-sectional surface data from two non-parallel surfaces, enabling us to draw conclusions about two-dimensional defects within the bulk. Using antiphase boundaries (APBs) in GaP on Si(001) as a model system, we show that this approach can be applied to any material and microscopy method. For the GaP/Si (001) system and for two-side cross-sectional scanning tunneling microscopy as the experimental tool, the procedure shows that the commonly discussed {111} and {112} APBs do not arise in the investigated sample, whereas the data strongly indicates that previously not recognized {123} APBs are present. Furthermore, a statistical analysis allows a calculation of the net excess charge carrier density introduced into the crystal by the APBs. Its value is negligible compared to the density of wrong bonds that characterize the APBs, since negative and positive excess charges compensate each other almost completely. Moreover, we suggest that controlled enhancement of the formation of APBs may also lead to applications in thermoelectric devices.