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 an initial prototype CdTe pixel detector based on the CdTe diode. The detector has 400 pixels with a pixel size of 625 × 625 μm2. 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.
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