Detection of ionizing radiation by charge storage in shallow levels in semiconductors at cryogenic temperatures

At cryogenic temperatures, ionized impurities act as traps with large capture cross sections. Phosphorus ions in the i-region of a p-i-n diode at 4.2K have been used to trap carriers produced by the passage of Compton electrons and 40 GeV pions. The p-i-n diode acts as a detector and a memory element which can be read out by applying a fast reverse bias pulse of 2-3 volts per micron to quantum mechanically field ionize the shallow impurity traps. The released charge is detected by a charge sensitive amplifier. VLSI arrays of p-i-n detectors utilizing in situ charge storage have significant implications for high resolution particle detection of high multiplicity events encountered in high energy physics experiments.