Dual-wavelength Photo-Hall effect spectroscopy of deep levels in high resistive CdZnTe with negative differential photoconductivity

摘要

Photo-Hall effect spectroscopy was used in the study of deep levels in highresistive CdZnTe. The monochromator excitation in the photon energy range0.65-1.77 eV was complemented by a laser diode high-intensity excitation atselected photon energies. A single sample characterized by multiple unusualfeatures like negative differential photoconductivity and anomalous depressionof electron mobility was chosen for the detailed study involving measurementsat both the steady and dynamic regimes. We revealed that the Hall mobility andphotoconductivity can be both enhanced and suppressed by an additionalillumination at certain photon energies. The anomalous mobility decrease wasexplained by an excitation of the inhomogeneously distributed deep level at theenergy Ev+1.0 eV enhancing thus potential non-uniformities. The appearance ofnegative differential photoconductivity was interpreted by an intensifiedelectron occupancy of that level by a direct valence band-to-level excitation.Modified Shockley-Read-Hall theory was used for fitting experimental results bya model comprising five deep levels. Properties of the deep levels and theirimpact on the device performance were deduced.