Characterization of inversion domains in GaN by electric force microscopy in conjunction with transmission electron microscopy and wet chemical etching

Inversion domains (IDs) in III-nitride semiconductors degrade the performance of such devices, and so their identification and elimination is critical.An inversion domain on a Ga-polarity samples appears as an N-polarity domain, which has a polarization reversed with respect to the rest of the surface and therefore has a different surface potential. Surface-contact- potential electric force microscopy (SCP-EFM) is an extension of atomic force microscopy (AFM) that allows imaging of the surface electrostatic potential. Previously, we established the particular mode of operation necessary to identify inversion domains on III-nitrides using a control sample. We have now studied inversion domains in GaN films grown by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). The existence of inversion domains was also verified by transmission electron microscopy (TEM) using multiple dark field imaging. In MOCVD grown GaN, we found predominant Ga-polarity with very low density of IDs, while in the MBE GaN, a mix polarity feature was identified