We report the passivation of two deep copper-related acceptor levels i
n Cu-diffused p-type GaAs by the group-I element lithium. The deep-lev
el-transient-spectroscopy (DLTS) signals of the well-known Cu-related
levels with apparent activation energies 0.15 eV and 0.40 eV disappear
in Cu-diffused samples when they are diffused with Li, but can be rea
ctivated by annealing. Photoluminescence measurements show a correspon
ding disappearance and reappearance of the copper-related luminescence
at 1.36 eV. Also we observe with DLT'S an energy level at E(V) + 0.32
eV in the Cu-Li-diff-used samples. The level is neither present in th
e Cu-diffused samples before Li diffusion nor in Cu-Li-diffused sample
s after annealing. As the level is not observed in starting materials
or solely Li-diffused samples we suggest that it is related to a Cu-Li
complex.