Relation Between Sputtering Parameters and Optical and Electrical Properties of Ga Doped ITO Transparent Conductive Oxide

A ceramic target with Ga:In:Sn=4:64:32 metal ratio has been sintered and used for RF sputtering process to develop high quality Ga doped ITO (GITO) transparent conductive oxide layers, particularly for photovoltaic applications. The sputtering parameters (sputtering power, oxygen flow, and substrate temperature) have been varied first and optimized with respect to the resistivity measurements. The layers deposited under optimized conditions were then post-annealed at different temperatures (200 – 500 °C) either in the air or in nitrogen atmosphere in order to further improve the conductivity. The deposited 200 nm thick GITO layer has high electron mobility (50 cm2/Vs) at relatively low resistivity (0.90 mΩcm) although the free electron concentration is kept low (1.4×1020 cm-3) to prevent excessive free-carrier absorption. Thus, high transmission of the layer (∼80% at 400 – 1500 nm) is obtained.