Preparation, Characteristics, and Applications of High-Voltage Silicon Surface-Barrier Detectors

Surface-barrier detectors have been fabricated from high-resistivity (up to 20,000 ohm cm.) n-type silicon by means of a technique which allows them to be operated at large reverse-bias voltages without guard rings. Reaction protons of 17 Mev energy obtained from (d, p) reactions at the Argonne National Laboratory Tandem Van de Graaff accelerator have been stopped with a reverse bias of 700 volts on a detector made of 20,000 ohm cm. material. The detector area is 28 sq. mm., and it was cooled by means of a thermoelectric device described below. Under these conditions the measured energy resolution is 29 Kev for the protons, and the leakage current is 0.1 microampere. This detector operates satisfactorily at reverse biases up to 1800 volts. At this voltage its measured energy resolution for 1 Mev electrons is 35 Kev at room temperature, and its leakage current is 1.12 microamperes. Special precautions required when the detectors are used at accelerators are discussed. The methods used to form the inversion layers of these detectors and to protect their edges are discussed in some detail since it is necessary that the reverse bias be withstood with both low noise and low leakage current to obtain good energy resolution. The characteristics of some of these detectors have been observed for a period of two years, and conditions necessary for their stability with time are given. The detectors have also been tested in a vacuum of 2 x 10-6 mm.