Optoelectronic properties of chlorine- and oxygen-doped CdTe thin films

The influence of oxygen codopant upon the optoelectronic properties of chlorine-doped CdTe films is being investigated. It is shown that a small quantity of oxygen decreases the resistivity of films, whereas at higher concentrations oxygen codopant increases the resistivity of films up to 6 orders of magnitude. A subsequent annealing in tellurium vapor pressure decreases the resistivity of films. It is supposed that an anomalous resistivity drop around 0.22 kPa is caused by shallow acceptor complexes that oxygen forms with group I impurities like copper and silver. At higher concentrations oxygen forms isoelectronic complexes with cadmium vacancies, which cause a high resistivity of films. Te annealing extracts oxygen from the films as Te forms with dissolved oxygen tellurium oxide TeO2 which easily sublimates. Photoconductivity of the oxygen and chlorine-doped CdTe films is poor, or is not detected.