Keeping Capacitance Small: The Quest to Integrate Electronics on High-Resistivity, Fully Depleted Detectors

It was 1983 when the first experimental result proved that it was possible to produce a semiconductor detector of virtually any area (even as big as a wafer) and sensitive throughout the whole volume but with a tiny, low-capacitance collecting electrode. The device was fully depleted of carriers, as in a reverse junction single diode but through the full wafer thickness, and the generated carriers are drifted in a controlled way toward the collecting electrode. At that time, the device was called a silicon drift chamber (SDC), and it was the realization of a long-pursued dream of the scientists working in the detector field: to create a large detector, simple in operation, but still able to take advantage of the highest possible energy resolution obtainable through such a low-capacitance contact. This class of detectors, allowing position reconstruction of the interaction event with micrometer position resolution and precise charge reconstruction of the released energy within a few electrons, is indeed one of the greatest achievements of the career of Emilio Gatti and the best product of his deep and fruitful scientific and personal collaboration with Pavel Rehak of Brookhaven National Laboratory in Upton, New York.