Impact of fixed charge on metal-insulator-semiconductor barrier height reduction

Abstract

Recently, the insertion of ultrathin insulators to form metal-insulator-semiconductor (MIS) contacts has been used extensively to reduce the Schottky barrier height and to shift the Fermi level pinning. In this paper, we investigate the physical non-idealities of the ultrathin insulator in Al/Al2O3/n-GaAs MIS through stoichiometry, density, and bandgap measurements. These structural non-idealities electrically manifest as bulk and interface fixed charges that are found to contribute to the observed barrier height reduction. The effect of fixed charge has not been considered before, and when combined with the previously reported interface dipoles, it provides a more thorough understanding of the MIS contacts.