Effects of thermal annealing and long-term ageing on electronic defects in CdSe thin films

Defect distributions in CdSe thin films, 'as deposited', following thermal annealing, and after 10 years' storage under room conditions are investigated. Steady-state photoconductivity measurements at low temperatures suggest a decrease in the density of 'slow' recombination centres following annealing or storage. Transient photocurrent and thermally stimulated current spectroscopics reveal a peak in the density of states at 0.65 eV below the conduction band edge in the as-deposited film. This broadens and shifts towards the conduction band edge on annealing. Stored films exhibit an almost flat defect distribution, which may result from a combination of both types of defect. Raman scattering measurements suggest that both storage and annealing result in increased structural order