Gamma Ray Detectors Made from High Purity Germanium

A solution regrowth technique for growing P+ and N+ contacts on high purity germanium is described. Copper contamination of the high purity germanium is minimized by using KCN to remove copper from the surface of the germanium and by the gettering ability of molten indium in contact with the germanium. Diodes with leakage currents as low as 3 × 10-11 amp for 2000 volts applied to a fully depleted 4 mm thick detector have been fabricated. Preliminary measurements show that the resolution obtained with these diodes is comparable to the best Li drifted germanium detectors at 60 keV and 122 keV. Diodes have been warmed to room temperature as many as five times with no degradation in resolution.