Study Of P-type Transparent Conductive Oxides Films

Transparent conductive oxide (TCO) thin films have been widely researched in recent years. The limited conductivity of p-type TCO films has been the main difficulty for its application in electronic devices. Being an important or potential transparent conductive material, the theoretical and experimental study for p-type SnO₂ or p-type Sb₂O₅ films will be important for the manufacture of transparent electronic devices.The first principle calculation had been performed for SnO₂ and Sb₂O₅ supercells. The results showed that O vacancy in SnO₂ is the main reason for leading to n-type conductive SnO₂. Among the Al, Ga and In impurities, In can introduce shallowest acceptor level in SnO₂ and thus produce most holes, but the substitutional indium (In_sn) with high concentration will induce large lattice distortion in SnO₂ and lead to low hole mobility. In-Ga co-doped SnO₂ will reduce the lattice distortion effect induced by In impurity, and increase the hole mobility of p-type SnO₂. Based on the above theoretical results, both p-type In-doped SnO₂ and In-Ga co-doped SnO₂ films had been successfully prepared with spray pyrolysis. The holes concentration of In-doped SnO₂ films can be up to 4×10¹⁸cm^-3, but its hole mobility is very low, which lead to the maximum conductivity of 2.368×10^-3Ω ^-1cm^-1. Although hole concentration of the In-Ga co-doped SnO₂ films was a little lower than that of the In-doped SnO₂ films, its electrical conductivity of 5.952 Ω ^-1cm^-1 was higher because of its higher hole mobility. In additional, the first principle calculation for Sb₂O₅ supercells showed that Sb interstitial defects in Sb₂O₅ is the main reason for leading to n-type conductive Sb₂O₅. Among the Si, Ge and Sn impurities, both Ge and Sn can introduce shallow acceptor level in SnO₂ and thus produce high holes concentration. P-type Sn-doped Sb₂O₅ films with the conductivity of 5.392Ω^-1cm^-1 had also been successfully prepared with magnetron sputtering.