Effect of La doping on interface barrier between Si-passivated Ge and insulating HfO₂

By analyzing internal photoemission of electrons from Si/SiO_x-passivated Ge into insulating HfO₂ we found that insertion of additional La interlayer between SiO_x and HfO₂ leads to dramatic increase (more than by factor of 20) of the barrier transparency. However, no measurable variation of the interface barrier height is observed suggesting that La induces intermixing of near-interface oxide stack resulting in development of additional density of states corresponding to conduction band of LaO_x and HfO_x sub-networks. At the same time, photoemission results indicate the presence of discrete positive charges in the near-interface oxide layer which may explain the observed ∝1 V shift of capacitance-voltage curves. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)