A copper-related acceptor complex in vacuum grown germanium crystals

A copper-related shallow acceptor complex has been discovered in germanium single crystals grown in vacuum and doped with arsenic and copper. Photothermal ionization spectroscopy of samples quenched from 673 K reveals two sets of hydrogenic lines with ground state binding energies of 9.15 and 10.05 meV. The line intensity ratios between corresponding transitions (1s-np) of the two hydrogenic series follow a Boltzmann dependence. This shows that the two series belong to the same impurity complex with a split ground state. Taking into account the crystal growth conditions together with the changes in the donor concentration deduced from variable temperature Hall effect measurements, we conclude that arsenic and substitutional copper form the new acceptor complex A(Cu-s,As) since copper is the only fast-diffusing species at this low annealing temperature. This complex is expected to have C-3 upsilon symmetry in agreement with preliminary piezospectroscopy measurements. (C) 1996 American Institute of Physics.