High resolution CdTe detector and applications to imaging devices

Using a high quality Cadmium Telluride (CdTe) wafer, we formed a Schottky junction and operated the detector as a diode (CdTe diode). The low leakage current of the CdTe diode allows us to apply a much higher bias voltage than was possible with the previous CdTe detectors. For a relatively thin detector of ≈ 0.5 mm thick, the high bias voltage results in a high electric field in the device. Both the improved charge collection efficiency and the low-leakage current lead to an energy resolution of 1.1 keV FWHM at 60 keV for a 2×2 mm² device and 2 keV for a 10×10 mm² device at 5°C without any charge-loss correction electronics. For astrophysical applications, we have developed a an initial prototype CdTe pixel detector based on the CdTe diode. The detector has 400 pixels with a pixel size of 625 × 625 μ². Each pixel is gold-stud bonded to a fanout board and routed to a front end ASIC to measure pulse height information for each γ-ray photon.