We report the effect of codoping of Mn–Be and the modified doping on an increment of the total hole concentration. Both the Mn-doped and Be-doped samples exhibit hole concentrations higher than 1×1019 cm−3 at room temperature. In contrast, the Mn–Be codoped sample shows a remarkable decrease in its hole concentration and mobility. Therefore, the resistivity is increased by more than 102 times of the Be-doped sample. This dramatic deterioration is probably caused by the complex defects due to the codoping. We performed the spatially separated doping of Mn and Be in GaAs and found that the hole concentration increases and the mobility shows no decrease for this sample. It is expected that the complex defect concentration is decreased considerably.

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