Investigation on the passivation, band alignment, gate charge, and mobility degradation of the Ge MOSFET with a GeO x /Al2O3 gate stack by ozone oxidation

Abstract Ge has been an alternative channel material for the performance enhancement of complementary metal–oxide–semiconductor (CMOS) technology applications because of its high carrier mobility and superior compatibility with Si CMOS technology. The gate structure plays a key role on the electrical property. In this paper, the property of Ge MOSFET with Al 2 O 3 /GeO x /Ge stack by ozone oxidation is reviewed. The GeO x passivation mechanism by ozone oxidation and band alignment of Al 2 O 3 /GeO x /Ge stack is described. In addition, the charge distribution in the gate stack and remote Coulomb scattering on carrier mobility is also presented. The surface passivation is mainly attributed to the high oxidation state of Ge. The energy band alignment is well explained by the gap state theory. The charge distribution is quantitatively characterized and it is found that the gate charges make a great degradation on carrier mobility. These investigations help to provide an impressive understanding and a possible instructive method to improve the performance of Ge devices.