A high mobility of 2250 cm2/V·s of a two-dimensional electron gas (2DEG) in a metalorganic chemical vapor deposition-grown AlGaN/GaN heterostructure was demonstrated. The mobility enhancement was a result of better electron confinement due to a sharp AlGaN/GaN interface, as confirmed by scanning transmission electron microscopy analysis, not owing to the formation of a traditional thin AlN exclusion layer. Moreover, we found that the electron mobility in the sharp-interface heterostructures can sustain above 2000 cm2/V·s for a wide range of 2DEG densities. Finally, it is promising that the sharp-interface AlGaN/GaN heterostructure would enable low contact resistance fabrication, less impurity-related scattering, and trapping than the AlGaN/AlN/GaN heterostructure, as the high-impurity-contained AlN is removed.