Copper impurity behaviour in CdTe films

Recrystallized CdTe-films with Cu-impurities exhibit time dependences of physical parameters, the character of which is given by the previous temperature processes. It follows from the analysis of the Hall effect measurements, which are obtained under equilibrium, quasi-equilibrium, and non-equilibrium conditions that the time variations of the parameters are connected with the precipitation of the supersaturated Cu-impurities solution and with the dissolution of these impurities. It is shown that the measured 1/T dependences of the hole density and the hole mobility cannot be explained only by the process of the precipitation and the dissolution of the precipitated Cuimpurities but also by the attending precipitation and dissolution of the Cd vacancies within the temperature cycle. Moreover the conclusion is done that the Cu-impurities have amphoteric properties and form neutral complexes (CuCd−Cu)* that means that a selfpurification of the semiconductors can be observed. These processes are used for the interpretation of the found small electrical activity of Cu atoms.