Other characterization techniques have been used, though. Among them, electron microscopies are valuable tools for acquiring defect densities and the structure of the involved interfaces down to the atomic level. For instance, they reveal the interfaces between GaP and Si as well as the interfaces between the bulk GaP and the numerous antiphase domains. The GaAs|GaInP interface has also been studied extensively by scanning tunneling microscopy and spectroscopy, scanning transmission electron microscopy, as well as photoluminescence and Hall measurements. All these studies concluded with the formation of extra multinary interlayers (GaInAs, GaAsP, or even GaInAsP). However, these techniques provide either electronic or chemical information while PES in principle may provide both at the same time.