Abstract
The reliability of the determination of the density of local states in inhomogeneous samples from space-charge-limited current-voltage characteristics is examined. It is shown that the densities of states may be determined with an error as large as several orders of magnitude, depending on spatial distributions of the states. The energies of the local states may be determined to within a few kT. The equations derived in the paper are applied to experimental results on a-Si:H reported in the literature allowing for a reconstruction of the spatial distribution of local states.