Persistent photoconductivity effects have been characterized inn-typeAl0.15Ga0.85N/GaNheterostructures using both monochromatic light and room light illumination. Time constants of∼1×104 shave been observed, and measurements of photocurrent specta performed using various illumination geometries and techniques have shown that defect levels exist in both theAl0.15Ga0.85Nand GaN layers. Broad distributions of defect levels with excitation energies lower than the bandgap energies are found in bothAl0.15Ga0.85Nand GaN, and evidence is observed that these levels contribute significantly to the aforementioned persistent photoconductivity effects. The photocurrent spectra also reveal the presence of a level with an excitation energy of 3.36 eV that contributes to the persistent photoconductivity in the heterostructure. ©1998 American Institute of Physics.