High resolution CdTe x- and gamma-ray detectors with a laser-formed p-n junction

Abstract

Room temperature In/CdTe/Au diode detectors have been developed with record energy resolution (0.7% FWHM at the 662 keV peak of ¹³⁷Cs) and electrical and detection properties of the detectors have been investigated. The detectors were fabricated using laser-induced doping of a thin surface layer of semi-insulating CdTe crystals with In. High resistivity p-like CdTe(111) crystals pre-coated with an In dopant film were irradiated with nanosecond laser pulses in a water environment that made it possible to introduce and activate In dopant atoms with high concentration and form a steep p-n junction in the surface region of the crystals. Multiple laser irradiation of the samples from the In-coated side increased forward current of the diodes and decreased reverse one. The special surface processing was used, including chemical and thermal procedures, to modify the surface state of the CdTe crystals before deposition of an In dopant film and electrodes. Finally, the room temperature CdTe-based X- and γ-ray radiation detectors with a p-n junction have been obtained with extremely high energy resolution.