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

TL;DR

This study uses dual-wavelength Photo-Hall effect spectroscopy to investigate deep levels in high-resistive CdZnTe, revealing how specific illumination conditions influence mobility and photoconductivity, and identifying deep level properties affecting device performance.

Contribution

It introduces a combined monochromator and laser diode approach to analyze deep levels and their effects on mobility and photoconductivity in CdZnTe, with a detailed model fitting.

Findings

Negative differential photoconductivity observed and explained.

Deep level at Ev+1.0 eV causes mobility decrease.

Five deep levels characterized and modeled.

Abstract

Photo-Hall effect spectroscopy was used in the study of deep levels in high resistive CdZnTe. The monochromator excitation in the photon energy range 0.65-1.77 eV was complemented by a laser diode high-intensity excitation at selected photon energies. A single sample characterized by multiple unusual features like negative differential photoconductivity and anomalous depression of electron mobility was chosen for the detailed study involving measurements at both the steady and dynamic regimes. We revealed that the Hall mobility and photoconductivity can be both enhanced and suppressed by an additional illumination at certain photon energies. The anomalous mobility decrease was explained by an excitation of the inhomogeneously distributed deep level at the energy Ev+1.0 eV enhancing thus potential non-uniformities. The appearance of negative differential photoconductivity was interpreted by an intensified electron occupancy of that level by a direct valence band-to-level excitation. Modified Shockley-Read-Hall theory was used for fitting experimental results by a model comprising five deep levels. Properties of the deep levels and their impact on the device performance were deduced.