Detection characteristics of Ge detectors with microstructured amorphous Ge contacts

The established technique for performing position sensitive structures by means of photolithography and subsequent plasma etching of grooves through detector contacts was applied for amorphous germanium contacts (a-Ge contacts). A simple 50 strip structure with a pitch of 615 /spl mu/m was produced. Charge sharing between two adjacent strips (33 mm long) was investigated with the help of 60 keV photons and 5.8 MeV /spl alpha/-particles. No charge losses could he detected irradiating the front (structured) contact of the 16 mm thick detector by 60 keV photons. The same was concluded for /spl alpha/-particles hitting the rear, not structured p/sup +/-contact made by boron implantation. Moreover, excellent position information for a-particles, with an accuracy of about 30 /spl mu/m, could be extracted in this case. Surprising results were obtained for /spl alpha/-particles impinging on the front contact. No coincidental signals from the two adjacent strips caused by a-particles could be observed. But a normally positive signal from one of the strips coincided occasionally with a negative signal from the other strip and vice versa. Using a cooled FET assembly mounted near a strip an energy resolution of 0.78 keV [FWHM] for 60 keV photons was achieved and slightly better for lower energies. Even better energy resolutions will be probably possible, because the measuring set up was far from being optimized.