Characterisation and quantification of the ‘Excess-Leakage-Current’ effect in Redlen HF-CdZnTe at > 106 ph s-1 mm-2

DOI: 10.1088/1748-0221/20/10/P10021

Authors: B. Cline (UKRI STFC Rutherford Appleton Laboratory) , D. Banks (UKRI STFC Rutherford Appleton Laboratory) , M. Bishop (UKRI STFC Rutherford Appleton Laboratory) , A. Davis (UKRI STFC Rutherford Appleton Laboratory) , J. Harris (UKRI STFC Rutherford Appleton Laboratory) , M. Hart (UKRI STFC Rutherford Appleton Laboratory) , S. Knowles (UKRI STFC Rutherford Appleton Laboratory) , T. Nicholls (UKRI STFC Rutherford Appleton Laboratory) , J. Nobes (UKRI STFC Rutherford Appleton Laboratory) , S. Pradeep (UKRI STFC Rutherford Appleton Laboratory) , M. Roberts (UKRI STFC Rutherford Appleton Laboratory) , M. C. Veale (UKRI STFC Rutherford Appleton Laboratory) , M. D. Wilson (UKRI STFC Rutherford Appleton Laboratory) , V. P. Dhamgaye (Diamond Light Source) , O. J. L. Fox (Diamond Light Source) , K. J. S. Sawhney (Diamond Light Source) , S. Scully (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Instrumentation , VOL 20

State: Published (Approved)
Published: October 2025
Diamond Proposal Number(s): 36472

Abstract: In this paper, results are presented from the characterisation of a 2 mm thick Redlen Technologies high-flux-capable Cadmium Zinc Telluride (HF-CZT) sensor hybridised to the small-pixel, spectroscopic-imaging HEXITEC_MHz ASIC. Dynamic datasets were taken on the B16 Test Beamline at the Diamond Light Source to study a previously-identified 'excess-leakage-current' phenomenon in HF-CZT, where additional leakage current was temporarily generated upon the application of an X-ray flux. A study of the response of the detector as a function of X-ray intensity demonstrated a measurable excess leakage current signal above 105 ph s-1 mm-2. At a 20 keV flux of 7.81 × 106 ph s-1 mm-2, this effect contributed a signal equivalent to 3.79 ± 1.59 nA mm-2in addition to the expected photocurrent. On removal of X-rays at this flux, this excess leakage current took ∼ 10 s to decay below the noise floor of the detector. This long lifetime has implications for detectors required to operate at high frame rates and fluxes. The use of a small-pixel detector also allowed the spatial variation of this effect to be studied. A per-pixel comparison between the magnitude of the excess leakage current and the spectroscopic performance of the pixel showed no correlation. This suggests that the phenomenon is less likely to be a bulk-crystal effect and more likely the result of the properties of the CZT surface or metal/semiconductor interface. An Arrhenius analysis of the temperature-dependence of the dark and excess leakage currents in the detector yielded values of 0.69 ± 0.04 eV and 0.13 ± 0.01 eV respectively. The change in dark current with temperature is consistent with deep levels pinning the Fermi level close to the mid band gap, whilst the activation energy of the excess leakage current suggests shallower defects at the metal-semiconductor interface are responsible.

Subject Areas: Physics, Engineering


Instruments: B16-Test Beamline

Added On: 14/10/2025 14:42

Discipline Tags:

Detectors Physics Engineering & Technology

Technical Tags:

Imaging