An intentionally grown GaN film with laterally patterned Ga-and N-face polarities is studied using in situ UV-photoelectron emission microscopy PEEM. Before chemical vapor cleaning of the surface, the emission contrast between the Ga-and N-face polarities regions was not significant. However, after cleaning the emission contrast between the different polarity regions was enhanced such that the N-face regions exhibited increased emission over the Ga-face regions. The results indicate that the emission threshold of the N-face region is lower than that of the Ga face. Moreover, bright emission was detected from regions around the inversion domain boundaries of the lateral polarity heterostructure. The PEEM polarity contrast and intense emission from the inversion domain boundary regions are discussed in terms of the built-in lateral field and the surface band bending induced by the polarization bound surface charges. © 2003 American Institute of Physics.