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a b s t r a c tBridgman-grown cadmium zinc telluride (CdZnTe or CZT) and cadmium manganese telluride (CdMnTe or CMT) crystals often have Te inclusions that limit their performances as X-ray-and gamma-raydetectors. We present here the results of post-growth thermal annealing aimed at reducing and eliminating Te inclusions in them. In a 2D analysis, we observed that the sizes of the Te inclusions declined to 92% during a 60-h annealing of CZT at 510 1C under Cd vapor. Further, tellurium inclusions were eliminated completely in CMT samples annealed at 570 1C in Cd vapor for 26 h, whilst their electrical resistivity fell by an order of 10 2 . During the temperature-gradient annealing of CMT at 730 1C and an 18 1C/cm temperature gradient for 18 h in a vacuum of 10 À 5 mbar, we observed the diffusion of Te from the sample, so causing a reduction in size of the Te inclusions. For CZT samples annealed at 700 1C in a 10 1C/cm temperature gradient, we observed the migration of Te inclusions from a lowtemperature region to a high one at 0.022 μm/s. During the temperature-gradient annealing of CZT in a vacuum of 10 À 5 mbar at 570 1C and 30 1C/cm for 18 h, some Te inclusions moved toward the hightemperature side of the wafer, while other inclusions of the same size, i.e., 10 mm in diameter, remained in the same position. These results show that the migration, diffusion, and reaction of Te with Cd in the matrix of CZT-and CMT-wafers are complex phenomena that depend on the conditions in local regions, such as composition and structure, as well as on the annealing conditions.

Surface damages occur in Cadmium zinc telluride (CdZnTe) wafers for radiation detection devices during dicing and polishing. This often results in increased leakage current that limits the performance of the detector. An effective method of removing the surface damage and thus reducing the leakage current is through the use of chemical treatments. The effects discussed in this study include: chemical polishing with a mixture of hydrogen bromide solution followed by passivation with ammonium fluoride in a hydrogen peroxide solution. The effects on the current-voltage measurements and the spectral response were monitored over a 2-week period. X-ray photoelectron spectroscopy (XPS) was also obtained to observe the formation of chemical species on treated surfaces. The resistivity of the treated CdZnTe samples is on the order of 10 10 ohm-cm. The current in the I-V measurements increased rapidly immediately following the chemical polishing and surface passivation, and decreased steadily afterwards. The spectral response showed that the 59.5-keV peak of Am-241 was stable in the same position over the test period.

Room temperature semiconductor detectors such as cadmium zinc telluride (CdZnTe) are often subject to surface damage during fabrication processes, thus affecting detector performance. The surface defects are usually removed through mechanical and chemical polishing, and passivation processes. This paper compares the effects of two surface passivation chemical solutions on CdZnTe detectors. The two chemicals studied are ammonium fluoride in hydrogen peroxide (NH 4 F + H 2 O 2 + H 2 O) and potassium hydroxide in hydrogen peroxide (0.1 g of KOH + 10 ml of 30% H 2 O 2 ) solutions. X-ray photoelectron spectroscopy analysis showed that the NH 4 F-based solution is more effective at converting Te species on the CZT wafer surfaces into a more stable TeO 2 layer, with values of 4.90 and 5.34 for the Te3d 3/2 O 2 /Te3d 3/2 and Te3d 5/2 O 2 /Te3d 5/2 peakheight ratios respectively, compared to the KOH-based solution which has 1.25 and 1.19 respectively. Analysis of the 59.5-keV peak of Am-241 showed that the sample passivated with the NH 4 F-based solution has a better energy resolution (FWHM = 9.83%) compared to the one passivated with the KOH-based solution (FWHM = 14.60%).

Cadmium manganese telluride (CdMnTe) is one of the semiconductor materials with potential applications at room-temperature for nuclear and radiological detection. CdMnTe crystals grown by Bridgman technique are prone to tellurium inclusions and related defects that limit their performance as X-rays and gamma-rays detectors. The major reason for this is that they are grown in a tellurium-rich environment. These defects could trap charges that are generated by X-rays and gamma rays thereby degrading the charge transport properties of the detectors and reducing their carrier lifetime. This in turn leads to poor performance by the detector. One of the solutions to this problem is post-growth thermal annealing. In this paper we present experimental results of annealing a CdMnTe wafer at 720 o C and in cadmium vapor. The CdMnTe wafer and cadmium were sealed in a quartz ampoule at a vacuum of 10-5 mbar. We used a three-zone furnace that enabled us to adjust the three heating elements to get a flat region of 720 o C in the temperature profile where the wafer was annealed. Infrared transmission microscopy showed changes to the sizes and positions of the tellurium inclusions. There are reductions in the dimensions of the medium-size Te inclusions. Some Te inclusions were completely eliminated while others broke up to form much smaller inclusions. Current-voltage measurements showed that the resistivity of the CdMnTe wafer was reduced by 71 %, from 2.44 x 10 5 -cm to 7.17 x 10 4 -cm after annealing in Cd vapor.