Compensation and Photosensitivity in CdTe Doped With Indium

To better our knowledge of the characteristics of semi-insulated cadmium telluride (CdTe) doped with indium (In), we explored the role of deep levels in compensation and trapping. We assessed the defects and their distribution across a wafer in several ways; by measuring dark resistivity and photose...

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Bibliographic Details
Published in:IEEE transactions on nuclear science 2009-08, Vol.56 (4), p.1724-1730
Main Authors: Babentsov, V., Franc, J., James, R.B.
Format: Article
Language:English
Subjects:
Cadmium compounds
Cadmium telluride
Cadmium tellurides
CdTe
Charge measurement
Compensation
compensation mechanism
Conductivity
Current measurement
deep donor
Defects
Electron traps
Emission
Energy measurement
Indium
Photoluminescence
Photosensitivity
radiation detectors
Spectroscopy
Spectrum analysis
Thermoelectricity
Trapping
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Summary:To better our knowledge of the characteristics of semi-insulated cadmium telluride (CdTe) doped with indium (In), we explored the role of deep levels in compensation and trapping. We assessed the defects and their distribution across a wafer in several ways; by measuring dark resistivity and photosensitivity maps, photoluminescence, Photo-Induced Current Transient Spectroscopy (PICTS), and Thermoelectric Effect Spectroscopy (TEES). We determined that electron trapping to a near midgap level in CdTe:In begins when the Fermi-level lies above this level. We demonstrated first that a small movement (ap 1divide2 kT) of the Fermi-level downward significantly increases electron trapping. PICTS and TEES measurements confirmed the presence of a positively charge electron trap at E C -0.65 eV (plusmn 0.05 eV) with a high capture cross-section. This level transforms into a neutral one when the Fermi-level moves above it. Photoluminescence measurements detected this energy level that, when positively charged, was responsible for a 0.68-eV emission, while in a neutral state, it was accountable for an emission peak located at 0.87 eV. We discuss the nature of the deep donors, considering the latest ldquoab initiordquo calculations: also, the Te anti-site is compared to complex defects, such as H-O Cd .
ISSN:0018-9499
1558-1578
DOI:10.1109/TNS.2009.2015316