Characterization of Fine-Pixel X-Ray Imaging Detector Array Fabricated by Using Thick Single-Crystal CdTe Layers on Si Substrates Grown by MOVPE

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

“…Epitaxially grown single crystal CdTe layers on Si substrates are promising semiconductor materials for the development of large-area x-ray imaging arrays, infrared (IR) detectors as well as high-efficiency single junction or tandem solar cells [1][2][3][4]. The strength of epitaxial growth, which allows tuning the electrical properties and the crystal thickness makes them particularly promising to develop pulse counting, energy resolving type x-ray, gamma-ray detectors as well as fast response current mode detectors that can detect radiation from rapidly changing environment [5][6][7]. However, the large differences in the lattice constants and the thermal expansion coefficients between CdTe and Si make this growth extremely challenging, that result in very defective epilayers with high dislocation densities.…”

“…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].…”

“…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]. However, the dislocation in the epilayer was the major issue that severely degraded the device's property.…”