High-resolution CdTe nuclear radiation detectors in a new M–π–n design

High-energy resolution and good charge collection properties have been achieved with CdTe detectors in a new M–π–n design, where a thin iodine-doped n-CdTe epilayer is grown on the high resistivity p-type (π-type) CdTe crystal wafer at a low substrate temperature of 150°C to form the n-layer of the device. The improved spectroscopic performance is obtained due to the use of high-quality crystal wafer and the effective junction fabrication technique that resulted very low leakage currents. The low leakage current enabled us to apply high electric field on the detector, which results in complete charge collection, and the measured spectra show symmetric full-energy peaks with no peak tailing. Energy resolutions of 1.4, 1.7, and 4.2 keV FWHM were obtained at room temperature with a 2 mm×2 mm×0.5 mm detector at the 59.5, 122, and 662 keV gamma-peaks, respectively, without the use of any kinds of pulse correction electronics. Their room-temperature stability was also improved considerably by applying high bias voltages, while they were fully stable on a slight cooling. Performance of detectors at and below room temperatures and their stability issues will be presented.