The influence of a thermal treatment on hole trap generation in nitrogen doped ZnSe on GaAs was investigated by means of deep level transient spectroscopy. The samples were grown by molecular beam epitaxy (MBE) on highly zinc doped p-type GaAs(001) substrates. p-type doping of the ZnSe epilayer was performed by applying a rf nitrogen plasma during MBE growth. In order to carry out electrical measurements Schottky contacts were prepared by evaporating gold (Au) on top of the ZnSe. A dominant hole trap with a thermal activation energy of about 0.65 eV, showing a strong temperature dependence of the hole capture cross section, was determined. It was found that the concentration of this trap increases by more than one order of magnitude after an annealing of the Au/ZnSe/GaAs samples at 550 K and that it is responsible for hole compensation effects. © 1997 American Institute of Physics.