Investigation of single pixel DePMOSFETs under cryogenic conditions

Abstract

The observation of astrophysical objects in the mid-infrared requires Blocked Impurity Band (BIB) detectors based on n-doped Silicon. Because of the low binding energy of the shallow impurities (42 meV to 54 meV), infrared radiation in the electromagnetic spectrum of 10 to 40 microns can excite electrons from the shallow impurities into the conduction band. To ensure the occupation of these impurities and to prevent high leackage current the BIB detector has to be cooled down to 5 K to 10 K. It is desirable to observe faint astronomical objects with such a detector, which can be achieved with a high Signal to Noise ratio. One possibility is an implemented DePMOSFET [1] on the BIB detector in order to be free of interconnection stray capacitance. We investigate the DePMOSFET at a temperature scale from 300 K down to 5 K. We show first results of characteristic and dynamic measurements of the single pixel DePMOSFET at low temperature. We irradiate the single pixel with a 55Fe source and take a spectrum of the K α - and K β - line. The clear mechanism is investigated at temperatures lower than 50 K. The aim is a BIB detector based on an integrated amplifier with the DePMOSFET as a promising candidate.