Here, we report on significant material information provided by semi-contact phase-images in a wide range of hard III-nitride surfaces. We show that the phase contrast, which is fundamentally related to the energy dissipation during tip-surface interaction, is sensitive to the crystalline nature of the material and thus could potentially be used to determine the crystalline quality of thin nitride layers. Besides, we found that the structural defects, especially threading dislocations and cracks, act as selective sites where energy mainly dissipates. Consequently, in nitrides defects with very low dimensions can actually be imaged with phase-contrast imaging.