Interface charge densities and conduction-band offset energies for liquid-phase epitaxially grown n-N isotype In0.53Ga0.47As/InP heterojunctions have been measured using capacitance-voltage methods. Extremely low interface charge densities have been obtained in some samples, and they are found to be independent of both the measurement temperature and the magnitude of lattice mismatch. Our samples show a clear peak and notch in the apparent free-carrier concentration profile at temperatures as low as 83 K. This is in contrast to results reported previously where the notch, due to the carrier depletion at the heterojunction, was observed to vanish at low temperature. An electron trap has been identified in one of the samples. The trap is uniformly distributed within the bulk of the In0.53Ga0.47As layer at a density of 5×1014 cm−3. In spite of the presence of this relatively low density defect, the heterojunctions grown for this study apparently have considerably lower interface defect densities than observed by others.