DLTS of silver in germanium: evidence for an amphoteric impurity

The defect parameters of substitutional silver in germanium have been investigated with DLTS. Silver, when diffused into germanium introduces four occupancy levels in the band gap. Three of them are already known from Hall experiments: the acceptor levels with ionisation enthalpies E v +0.116 eV, E c -0.261 eV and E c -0.113 eV. The fourth level, a very deep donor situated at E v +0.035 eV, has never been reported before. This new level implies that silver is the third known amphoteric impurity in germanium, besides gold and cobalt.