Luminescence behavior and compensation effect on the hole concentration in the sol-gel Zn_1-xCu_xS_y films with different compositions

This study determines the effect of Cu and S content on the structural, luminescence and electrical properties of sol-gel Zn_1-xCu_xS_y films. The dependence of acceptors [interstitial sulfur (S_i)] and donors [sulfur vacancy (V_S)] on the film composition allows the hole concentration of Zn_1-xCu_xS_y samples to be tuned. It is found that an increased Cu/Zn molar ratio leads to a reduced probability of the formation of V_S, which increases the hole concentration. An increase in Cu/Zn and S/Zn molar ratios leads to a significantly increased probability of the formation of S_i and a reduced probability of the formation of V_S, which significantly increases the hole concentration. Clearly, compensation effects limit the hole concentration of Zn_1-xCu_xS_y samples. The results show that S_i is the origin of the p-type conductivity. It is also shown that a suitable choice of composition increases acceptor-like defect formation in Zn_1-xCu_xS_y.