Experimental characterization of Silicon Drift Detector for X-ray spectrometry: Comparison with theoretical estimation

• SDD based X-ray spectrometer is developed and characterized.
• A novel technique adapted for measuring the SDD reverse saturation current.
• Temperature dependence of the SDD reverse saturation current is measured.
• Ideality constant of the SDD is estimated and compared with theoretical values.
• Investigated the noise performance of the SDD and the spectrometer system.

Reverse saturation current and the ideality factor (η) are the main parameters that affect the performance of a radiation semiconductor detector in different space environmental conditions. We have measured both of these parameters for the Silicon Drift Detector (SDD) used as a radiation detector in the X-ray spectrometry for space borne applications having the active area of 40 mm2 and 109 mm2 with 450 μm thick silicon. The measured reverse saturation current is compared with the theoretically estimated values using diode equation for various detector operating temperatures and shown that there is a strong dependence of reverse saturation current with ideality factor. Subsequently, using the reverse saturation current ratio method, the slope ratio for small area to the large area SDD is derived and compared with the theoretical slope ratio obtained using the measured ideality factor. It is shown that the slope ratios closely match with the diode equation of the form which has the ideality factor in both the product and exponential terms for these SDDs. The measured spectral energy resolution is ∼150 eV at 5.9 keV for both small and large area SDDs when operated at −40 °C and −65 °C respectively. The noise performance of the spectrometer is also measured in terms of Equivalent Noise Charge (ENC) for various detector operating temperatures and shown that the value of ENC in rms noise electrons is minimal for the pulse shaping time of 3.3 μs.