Electron Capture Probability of the Upper Copper Acceptor Level in Germanium

The doping of a germanium sample is arranged so that the minority carrier lifetime is inversely proportional to the electron capture probability of the upper acceptor level introduced by copper atoms. It is found that the lifetime decreases exponentially with increasing temperature. A suggested interpretation is that only electrons of energy greater than 0.22 ev above the bottom of the conduction band can enter the second copper acceptor level.