Microstructures on Ge detectors with amorphous Ge contacts

A new method for structuring germanium detectors with amorphous Ge contacts (a-Ge contacts) is presented. The method is based on the established technique for performing position sensitive structures by, means of photolithography and subsequent plasma etching of grooves through implanted contacts. First prototype was manufactured from n-type germanium. The p/sup +/-contact was performed by boron implantation and the amorphous Ge contact by, evaporation of germanium. The 0.30 /spl mu/m thick germanium layer was then covered with 0.27 /spl mu/m thick layer of evaporated aluminium. A simple 50 strip structure with a pitch of 615 /spl mu/m was produced on the a-Ge contact. The grooves between the strips were 13 /spl mu/m deep and 56 /spl mu/m wide. The coincidental spectra of adjacent strips indicate that practically no charge losses were caused by the existence of the groove between these strips. Further investigations are going on like test of structured a-Ge contacts on p-type germanium and improving the energy resolution of the strips on the a-Ge contacts using the cooled first stage of a preamplifier. But already the first results prove, that good functioning structures on the a-Ge contacts can be created by means of plasma etched grooves. Narrow grooves, even below 10 /spl mu/m, can be easily fabricated. Energy measurements with practically no energy losses influenced by the grooves can be performed.