Interface of GaP/Si(001) and antiphase boundary facet-type determination

GaP/Si(001) virtual substrates are highly interesting for solar cells and optoelectronic device applications. While antiphase disorder at the resulting surface of the virtual substrate—after a few tens of nm GaP—can be suppressed, the structural and electronic properties of the actual GaP-to-Si interface and of the antiphase domains within the GaP are still of high importance. Here, we compare scanning tunneling microscopy data of the prepared Si(001) 2$°$ off-oriented substrate with cross-sectional scanning tunneling microscopy data (XSTM) taken after GaP$0.98$N$0.02$/GaP growth. Besides regions where an intermixing of Si with GaP cannot be excluded, we also observe sections with a quite abrupt appearance. In addition, basic knowledge for use of contrast mechanisms occurring in XSTM experiments at antiphase boundaries will be established in order to understand their atomic structure. Thereby, we present a structural model for an entire antiphase domain cross section, including antiphase boundary facet-type determination. Furthermore, we find indications that the majority of the antiphase boundaries within this sample exhibit an equal number of so-called wrong bonds and that XSTM will allow to directly determine the electronic impact of the antiphase boundaries on its surroundings in the future.