3-D GaAs radiation detectors

A novel type of GaAs radiation detector featuring a 3-D array of electrodes that penetrate through the detector bulk is described, The development of the technology to fabricate such a detector is presented along with electrical and radiation source tests. Simulations of the electrical characteristics are given for detectors of various dimensions. Laser drilling. wet chemical etching and metal evaporation were used to create a cell array of nine electrodes. each with a diameter of 60 mum and a pitch of 210 mum. Electrical measurements showed I-V characteristics with low leakage currents and high breakdown voltages. The forward and reverse I-V measurements showed asymmetrical characteristics. which are not seen in planar diodes. Spectra were obtained using alpha particle illumination. A charge collection efficiency of 50% and a S/N ratio of 3: 1 were obtained. Simulations using the MEDICI software package were performed on cells with various dimensions and were comparable with experimental results. Simulations of a nine-electrode cell with 10 mum electrodes with a 25 mum pitch were also performed. The I-V characteristics again showed a high breakdown voltage with a low leakage current but also showed a full depletion voltage of just 8 V