Compensation and Photosensitivity in CdTe Doped With Indium

• 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
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2009.2015316

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 .