GaAs X-ray coordinate detectors

GaAs coordinate detectors for X-ray systems of scanning type have been developed. Two modifications of the detectors have been constructed for ionizing radiation detection in parallel and perpendicular to the electric field direction in the detector bulk. The detectors have 64 active regions with 100 μm pitch. In order to reach the minimum value of coupling capacitance and resistance coupling between active regions, the latter is separated by narrow gaps on unit cells. The gaps are made by means of reactive ion etching. The detectors are fabricated on the base of vapor-phase epitaxial material 40–45 μm in thickness with free carriers concentration of p0=1012 cm−3. Input capacitance of a detector cell is 0.25 pF, dark current is 30–50 pA per cell. The detectors have almost 100% charge collection efficiency for all types of ionizing radiation. High resolution of the detector allows to detect structures of a spectrum from the 241Am source in the energy range of 14–17 keV.