  Positron annihilation spectroscopy is used to study point defects in
Zn/1-x/Mn/x/GeAs/2/ crystals with low Mn content 0 < x < 0.042 with disordered
zincblende and chalcopyrite structure. The role of negatively charged vacancies
and non-open-volume defects is discussed with respect to the high p-type
conductivity with carrier concentration 1E19 < n < 1E21 cm^-3 in our samples.
Neutral As vacancies, together with negatively charged Zn vacancies and
non-open-volume defects with concentrations around 1E16-1E18 cm^-3, increasing
with the amount of Mn in the alloy, are observed. The observed concentrations
of defects are not sufficient to be responsible for the strong p-type
conductivity of our crystals. Therefore, we suggest that other types of
defects, such as extended defects, have a strong influence on the conductivity
of Zn1-xMnxGeAs2 crystals.
