Relation between sputtering parameters and optical and electrical properties of Ga doped ITO transparent conductive oxide

Abstract

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 degrees 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 cm(2)/Vs) at relatively low resistivity (0.90 m Omega cm) although the free electron concentration is kept low (1.4x10(20) cm(-3)) to prevent excessive free-carrier absorption. Thus, high transmission of the layer (similar to 80% at 400 - 1500 nm) is obtained.