Development of p-Channel Charge-Coupled Device for NeXT, the Next Japanese X-ray Astronomical Satellite Mission

Abstract

We are developing an X-ray charge-coupled device (CCD) for the next Japanese X-ray astronomical satellite mission, NeXT (New X-ray Telescope/Nonthermal energy eXploration Telescope). We developed a trial product of the p-channel CCD fabricated on an n-type silicon wafer. It is possible to have a thick depletion layer of ∼300 µm with a p-channel CCD because it is easy to obtain high resistivity using an n-type silicon wafer compared with a p-type silicon wafer. We evaluated the performance of the p-channel CCD. The imaging area of the CCD consists of 512×512 pixels with a pixel size of 24×24 µm 2 . The horizontal charge transfer inefficiency (CTI) of the CCD can be improved by reducing the operating temperature and increasing the readout frequency. We obtained the best horizontal CTI of (0.98±0.09)×10 -5 with an energy resolution of (202±6) eV full width at half maximum (FWHM) for 5.9 keV X-rays and a readout noise of 18 e - (rms) when the CCD was operated at a temperature of -110 °C and a readout frequency of 67 kHz. We measured the thickness of the depletion layer to be (290±33) µm from the detection efficiency of the 22.4 and 24.9 keV emission lines from 109 Cd.