Development of Heterojunction Diode-Type Gamma Ray Detectors Based on Epitaxially Grown Thick CdTe on$hboxn^+$-Si Substrates

Yasuda, K.; Niraula, M.; Noda, Kei; Yokota, Masaaki; Ohashi, H.; Nakamura, Katsumi; Omura, Manaka; Shingu, I.; Minoura, Shota; Tanaka, Ryo; Agata, Y.

doi:10.1109/led.2006.884723

Cited by 18 publications

(6 citation statements)

References 10 publications

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“…Ex-situ annealing study CdTe layers with thicknesses of typically 5 μm were grown on (211) Si substrates using MOVPE. Details of the growth process are reported elsewhere [11,12]. The substrate temperature for CdTe growth in this study was kept constant at 450 °C.…”

Section: Methodsmentioning

confidence: 99%

“…To overcome these challenges, we are investigating direct growth of CdTe on Si substrates using metal organic vapor phase epitaxy (MOVPE) growth techniques without the insertion of any kinds of buffer or transition layers, for their applications in large area x-ray, gamma ray detector development. We developed a specially designed Si pretreatment process and obtained thick single crystal CdTe directly on (211) as well as (100) Si substrates [5,6,[11][12][13]. We further applied these epilayers to fabricate detectors in p-CdTe/n-CdTe/n + -Si heterojunction diode structure and demonstrated that they can detect and resolve the energy peaks from x-ray and gamma-ray sources [5,6,13].…”

Section: Introductionmentioning

confidence: 99%

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Dislocation reduction in an MOVPE-grown CdTe/Si epilayer by ex-situ annealing and its effect on the performances of gamma ray detectors fabricated

Chaudhari,

Niraula,

Okumura

et al. 2023

Phys. Scr.

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We studied ex situ thermal cycle annealing on metalorganic vapor phase epitaxy (MOVPE) grown CdTe on (211) Si substrates for dislocation density reduction and its effect on the performance of gamma-ray detector fabricated. The ex situ annealing was performed by varying temperatures from 600 °C to 1000 °C for different anneal durations and cycles varied from 1 to 7 in a hydrogen environment. Gamma-ray detector was fabricated in a p-CdTe/n-CdTe/n+-Si heterojunction diode structure. Dislocation densities were evaluated by the etch pit density (EPD) technique. Dislocation densities were decreased when the annealing temperature was increased above 800 °C. This is due to the annealing enhancing dislocations’ glide motion, which annihilate and reduce their density. The device property could be improved by subjecting the annealing during the early stage of the growth. Devices subjected to annealing showed lower dark current and improved gamma detection property when compared to the devices that were not subjected to annealing during their fabrications.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dislocation reduction in an MOVPE-grown CdTe/Si epilayer by ex-situ annealing and its effect on the performances of gamma ray detectors fabricated

Chaudhari,

Niraula,

Okumura

et al. 2023

Phys. Scr.

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“…The main interest in using CdTe/Si as substrate for the epitaxial growth of MCT is the trend toward mega-pixel focal-plane arrays and the possibility of integrating them with Si-based readout electronics . CdTe/Si heterojunctions are also a promising way to achieve large-area, thick and high-quality crystals for X-ray and gamma ray detectors for medical imaging applications working up to 140 keV energy range since bulk CdTe crystals are expensive, extremely soft, and tend to develop a high density of dislocations . Although remarkable progress has been achieved using nominal and misoriented Si(100), Si(111), and Si(211) substrates, the large difference in thermal expansion coefficients and the lattice constant mismatch of approximately 19% usually result in a high density of dislocations and other stacking defects, especially close to the interface. , …”

Section: Introductionmentioning

confidence: 99%

Nondestructive Monitoring of Defect Evolution in Epitaxial CdTe Thin Layers Grown on Si(111)

et al. 2014

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Reduction of crystalline defect density and size is a major issue in optimization of thin film for industrial scale applications. It is particularly hard to achieve defect minimization due to the lack of statistically relevant techniques where defectinduced strain information is also available. In this work, we use a combination of highresolution transmission electron microscopy and synchrotron X-ray diffraction to investigate the evolution of defects during the growth of highly mismatched cadmium telluride (CdTe) films on silicon(111) as a function of growth temperature and layer thickness. High-resolution transmission electron microscopy was employed to show that the grown layers are epitaxial, following the [111] substrate orientation, and to identify the main defect type (double twins). Detailed reciprocal space maps obtained by synchrotron X-ray diffraction were used to identify the presence of additional intensities near the ( 113) and ( 002) CdTe bulk reciprocal space positions caused by these defects. Analysis of these maps allowed to retrieve the strain of the atoms inside defects as well as to evaluate their average size and density. We show that defect density decreases as a function of temperature but increases as a function of layer thickness, while defect size and the elastic energy of the atoms inside each defect increases up to 400 °C.

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“…We have already reported that our MOVPE-grown single-crystal CdTe films on GaAs as well as on Si substrates are of detector grade and are capable of detecting gamma radiation and measuring their energy distribution. [4][5][6] The detectors were fabricated with a CdTe/n + -GaAs and CdTe/n + -Si heterojunction diode structure, where the CdTe/n + -Si detectors exhibited better performance (energy resolutions) than that of CdTe/n + -GaAs. [4][5][6] However, the detection efficiency of both types of detectors was low and mostly limited by the CdTe film thickness.…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6] The detectors were fabricated with a CdTe/n + -GaAs and CdTe/n + -Si heterojunction diode structure, where the CdTe/n + -Si detectors exhibited better performance (energy resolutions) than that of CdTe/n + -GaAs. [4][5][6] However, the detection efficiency of both types of detectors was low and mostly limited by the CdTe film thickness. For a detector working in low to medium X-ray, gamma ray energies (up to 140 keV), around a 500-lm-thick CdTe film would be required to achieve a reasonable detection efficiency.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and Characterization of MOVPE-Grown CdTe-on-Si Heterojunction Diode-Type Gamma-Ray Detectors

Yokota

Yasuda

Niraula

et al. 2008

Journal of Elec Materi

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We report on the growth of very thick (>260 lm) high-crystalline-quality single-crystal CdTe epitaxial films on (211) Si substrates in a metalorganic vapor-phase epitaxy reactor, and the development of gamma ray detectors and their radiation detection properties. Films were grown with a high growth rate varying from 40 lm/h to 70 lm/h. A heterojunction diode was fabricated by growing a 90-lm-thick CdTe layer on an n + -Si substrate, which exhibited good rectifying behavior and had a low reverse bias leakage current of 0.18 lA/cm 2 at 100 V bias. The diode clearly demonstrated its gamma radiation detection capability by resolving energy peaks from the 241 Am radioisotope during roomtemperature measurements. By cooling the diode detector to -30°C, the leakage current could be reduced by three orders of magnitude from the roomtemperature value. At this operating condition dramatic improvements in the pulse height spectrum were observed.

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Development of Heterojunction Diode-Type Gamma Ray Detectors Based on Epitaxially Grown Thick CdTe on$hboxn^+$-Si Substrates

Cited by 18 publications

References 10 publications

Dislocation reduction in an MOVPE-grown CdTe/Si epilayer by ex-situ annealing and its effect on the performances of gamma ray detectors fabricated

Dislocation reduction in an MOVPE-grown CdTe/Si epilayer by ex-situ annealing and its effect on the performances of gamma ray detectors fabricated

Nondestructive Monitoring of Defect Evolution in Epitaxial CdTe Thin Layers Grown on Si(111)

Fabrication and Characterization of MOVPE-Grown CdTe-on-Si Heterojunction Diode-Type Gamma-Ray Detectors

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