Abstract: A method for the examination of electrically active impurities of semiconductor materials or semiconductor structures is disclosed. The method comprises the steps of providing a junction in a sample taken from the semiconductor to be tested, inserting the sample in a microwave field, providing a space charge layer in the junction by applying a reverse bias thereto, filling the electrically active defects of the space charge layer, and examining the thermal emission process proceeding to reach a thermal equilibrium state that occurs following the filling step by measuring the change of the microwave field that takes place due to changes in microwave absorption in the sample during the thermal emission process. The microwave field should be present at least during the examination of the transient microwave absorption.