Development of nuclear radiation detectors with energy discrimination capabilities based on thick CdTe Layers grown by metalorganic vapor phase epitaxy

We report on the development of nuclear radiation detectors based on epitaxially grown thick single crystalline CdTe layers. The optimization of the CdTe growth on the GaAs substrates in a metalorganic vapor phase epitaxy resulted high-structural quality and thick CdTe layers of thickness up to 200 μm. Radiation detectors were fabricated in p-CdTe/n-CdTe/n⁺-GaAs structure, where a 2-5 μm thick iodine-doped n-CdTe buffer layer was first grown on the n⁺-GaAs substrate, followed by about 100-μm-thick undoped p-like CdTe layer. The detectors exhibited good rectification property and good charge transport property. They showed reverse bias leakage currents typically from 1 to 5 μA/cm² at 40-V bias, and clearly demonstrated energy discrimination capability by resolving the 59.5-keV gamma peak from the ²⁴¹Am radioisotope during the radiation detection test. Some results on direct growth of CdTe epilayers on Si substrates are also presented.