Characterization of bulk and surface transport mechanisms by means of the photocurrent technique

Crucial points for the ternary materials, as CdZnTe, for X and Gamma detectors are the transport properties related with bulk defect density and nature, and, on the other hand, the quality of contacts, surfaces with high defect density, hence strong recombination rate. The photocurrent technique allows both to study bulk material properties and to obtain contact quality information. From steady-state photocurrent spectra information were obtained about the bulk trap levels, about the kinds of contact layer defects, and on the distributions of electric field in the sample volume. By varying the bias, with constant wavelength, instead, we can obtain the value of transport parameters like the product mobility-lifetime μt and the ratio S/μ, this last one related to the contact surface properties of the sample. The authors exploit the peculiarity of this technique by studying planar samples, comparing the achieved results with the results from X and Gamma ray spectroscopy.