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Cadmium telluride (CdTe) detectors are usually subjected to elevated temperatures during postprocessing and bonding them to readout electronics while fabricating imaging arrays. We studied the effects of low-temperature and short duration rapid thermal annealing of CdTe bulk as well as CdTe epitaxial-layer-based detectors with evaporated gold contacts. The detectors were annealed in the temperature range of 100 °C–300 °C, and its effect on the detector dark current, gamma detection property, and response stability was studied. For the bulk-detectors, the detector dark current decreased and gamma detection properties as well as the performance stability improved after annealing. However, such improvements were moderate for epitaxial-layer-based detectors. The study of the metal–semiconductor interface of annealed detectors revealed that diffused gold, elemental oxygen, and tellurium oxide existed and extended deep inside the bulk portion in epitaxial detectors; however, they were confined in the surface regions only in bulk-detectors, which likely be the causes of observed results in these two types of detectors. [ABSTRACT FROM AUTHOR]

Effects of cyclic rapid thermal annealing of metalorganic vapor-phase epitaxy grown single-crystal CdTe layers on (211) Si substrates are investigated. Typically, 5- $\mu \text{m}$ -thick CdTe layers were grown directly on the Si substrates after some substrate pretreatments but without growing other intermediate layers, and annealed ex-situ in a flowing hydrogen atmosphere. We varied the annealing temperature from 500 °C to 1000 °C, annealing times from 30 to 90 s, and the number of annealing cycles from 1 to 9. Improvement in the crystal quality was confirmed by the full-width at half-maximum values of double-crystal rocking curves for the annealing temperatures between 800 °C and 900 °C. Furthermore, the 4.2-K photoluminescence measurement and the current–voltage measurements revealed that the conductivity type and the resistivity of the crystals do not change after annealing. [ABSTRACT FROM AUTHOR]

Growth of large area single crystal CdTe layers was studied on $25 \times 25$ mm2 (211) Si substrates using metalorganic vapor phase epitaxy. High crystalline quality thick crystals with very good material uniformity were obtained. A 2-D monolithic detector array comprising ( 20 \times 20$ ) pixels was developed and evaluated. Each pixel is 1.12 \times 1.12$ mm2 size in a 1.17-mm pitch and consists of a p-CdTe/n-CdTe/n+-Si heterojunction diode structure, which is isolated from the surrounding pixels by making deep vertical cuts. The detector array exhibited highly uniform and low dark current, typically less than 0.5- /cm2 per pixel at an applied reverse bias of 50 V. The spectroscopic performance was separately confirmed by dicing out a small portion from the array which clearly resolved energy peaks from 241Am gamma isotopes at room temperature. On the other hand, a significant improvement in the detection property was observed by cooling it to −30 °C. [ABSTRACT FROM AUTHOR]

H2/Ar electron cyclotron resonance plasma processing of the high-resistivity (111) CdTe crystals was studied to find its effect on the leakage current and the gamma ray detection properties of the detectors. All the crystals were chemically etched in a bromine–methanol (BM) solution prior to the plasma processing to obtain a smooth surface. A remarkable reduction in both the surface and the bulk leakage current was observed in the plasma processed detectors when compared with the unprocessed one. The gamma detection property of the detectors, both the spectral resolution and the peak shape, was also significantly improved. X-ray photoelectron spectroscopy confirmed that an excess Te-rich surface layer was present on the BM etched crystal, however, such layer was removed, and the surface atomic ratio was modified after the plasma processing. The improvement in the detector performance could be related to the change in the surface chemical states of the crystals. Hence, this could be a promising process for improving the detectors performance and their stabilities. [ABSTRACT FROM PUBLISHER]

Optimization of CdTe crystal growth by adjusting effective Te/Cd ratio at the growth surface, as well as growth-interrupted annealing together with detector array fabrication techniques were studied to achieve large-area, uniform x-ray spectroscopic imaging arrays. The p\-CdTe/n\-CdTe/n^ +\-Si heterojunction diode-type detector arrays were fabricated by using epitaxially grown thick single crystal CdTe layers on n^ +\-Si substrates, where pixels were patterned by making deep vertical cuts on p-CdTe side using a dicing saw. The study was first focused on development of 2D (8 \times 8) array using 12.6~\mm \times 11.4~\mm size wafers, which confirmed uniform dark current distribution among the pixels. We further demonstrated possibility of making larger arrays by fabricating (18 \times 18) array using a 25~\mm \times 25~\mm size uniform single crystal CdTe epilayer grown on Si substrate. [ABSTRACT FROM PUBLISHER]