It was found that Cu-related shallow acceptor complexes existed in monocrystals that had been grown in vacuum, and were doped with As and Cu. Photo-thermal ionization spectroscopy of samples that had been quenched from 673K revealed 2 sets of hydrogenic lines with ground-state binding energies of 0.00915 and 0.01005eV. The line intensity ratios of corresponding transitions (1s-np) of the 2 hydrogenic series exhibited a Boltzmann dependence. This showed that the 2 series belonged to the same impurity complex with a split ground state. By taking account of the crystal growth conditions, together with the changes in donor concentration that were deduced from variable temperature Hall effect measurements, it was concluded that As and substitutional Cu formed the new acceptor complex, A(Cus,As) since Cu was the only rapidly diffusing species at this low annealing temperature. This complex was expected to have C3v symmetry, in agreement with preliminary piezo-spectroscopic measurements.

G.Sirmain, O.D.Dubon, W.L.Hansen, C.S.Olsen, E.E.Haller: Journal of Applied Physics, 1996, 79[1], 209-13