High-Resolution CdTe Detectors and Their Application to Gamma-Ray Imaging

CdTe X/γ-ray Detectors with Different Contact Materials

“…The partial pressures of both argon and oxygen in the vacuum chamber during the deposition process were 400 mPa. The magnetron power was~150 W. The deposition process lasted for 10 min at the CdTe substrate temperature of~100 • C. In terms of the practical application of the developed CdTe-based structures for detection of X/γ-ray radiation, it is important to analyze the reverse branches of the I-V characteristics when the Schottky contact is biased positively with respect to the MoO x -Mo ohmic contact because of diode-type detectors operate under reverse bias [4][5][6][7][8]. It should be noted that the reverse currents in the heterostructures under investigation are equal to several nanoamperes at bias voltages of~50-100 V at room temperature (Figure 3).…”

“…The I-V characteristics of the In/CdTe/Au diodes, measured in dark conditions at room temperature, showed excellent rectifying properties, especially taking into account the fact that CdTe crystals used for detector fabrication were semi-insulating (Figure 8). In the case of unirradiated In/CdTe/Au samples with just deposited In and Au electrodes (Figure 8a), the rectification was due to a high Schottky barrier at the In/CdTe interface that was typical for an In electrical contact and semi-insulating p-like CdTe and this was widely used for fabrication of Schottky diode detectors [5][6][7][8][9][10]14]. Moreover, the rectification significantly increased after laser irradiation of the In/CdTe structure (Figure 8b,c).…”

“…Among many suitable semiconductors, used for X/γ-ray (in other words, high-energy, nuclear, or ionizing radiation) detectors, cadmium telluride (CdTe) is the most studied, employed, and attractive compound because of its favorable physical properties [ 2 , 3 , 4 , 5 , 6 ]. Indeed, an optimal set of electrical and electronic characteristics of high-resistivity CdTe makes this material basic and still promising for compact uncooled X/γ-ray detectors covering a wide energy range from a few keV to tens MeV, which are widely used in science, industry, security, ecology, medicine, space astronomy and many other application fields [ 3 , 4 , 5 , 6 , 7 , 8 ]. Among the excellent features of this semiconductor, there are key advantages that should be highlighted: large atomic numbers of the compound components ( Z Cd = 48 and Z Te = 52) provide high absorption efficiency for X/γ-photons, stopping power and, therefore, high radiation attenuation coefficient; wide bandgap energy ( E g ~ 1.5 eV) and therefore, fairly high electrical resistivity (ρ > 10 9 Ω·cm) along with suitable charge transport properties allow CdTe-based detectors to operate without liquid nitrogen or Peltier cooling [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ].…”

“…Indeed, an optimal set of electrical and electronic characteristics of high-resistivity CdTe makes this material basic and still promising for compact uncooled X/γ-ray detectors covering a wide energy range from a few keV to tens MeV, which are widely used in science, industry, security, ecology, medicine, space astronomy and many other application fields [ 3 , 4 , 5 , 6 , 7 , 8 ]. Among the excellent features of this semiconductor, there are key advantages that should be highlighted: large atomic numbers of the compound components ( Z Cd = 48 and Z Te = 52) provide high absorption efficiency for X/γ-photons, stopping power and, therefore, high radiation attenuation coefficient; wide bandgap energy ( E g ~ 1.5 eV) and therefore, fairly high electrical resistivity (ρ > 10 9 Ω·cm) along with suitable charge transport properties allow CdTe-based detectors to operate without liquid nitrogen or Peltier cooling [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. As a result, uncooled CdTe-based detectors make it possible to achieve high radiation detection efficiency, energy resolution, and fast timing response to be efficiently employed in portable detecting devices [ 5 , 6 , 7 , 8 , 9 , 10 ].…”

“…High-resistivity CdTe single crystals have been successfully used in the fabrication of room temperature X/γ-ray detectors in two principally different ways (basic technologies): (i) creation of two ohmic electrical contacts; (ii) formation of diode structures either with a Schottky contact or p-n junction [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. CdTe detectors with two ohmic contacts operate at low bias voltage and have good time stability of functional parameters (detection efficiency and energy resolution).…”