Germanium-related deep electron traps in ALD-grown HfO2 insulators studied through Exhaustive PhotoDepopulation Spectroscopy

Abstract

Energy distribution of deep gap states related to incorporation of Ge impurity into insulating HfO2 is characterized using Exhaustive Photo-Depopulation Spectroscopy technique. While the undoped (Ge-free) HfO2 layers exhibit a 1-eV broad distribution of acceptor states (electron traps) centered at 2eV below the oxide conduction band, incorporation of Ge gives rise to additional acceptor levels with the energy depth of about 3eV. At the same time, a measurable density of donor states (hole traps) is found neither in the Ge-free nor in the Ge-doped HfO2 layers.