ELECTRON SCATTERING IN BURIED InGaAs/HIGH-K MOS CHANNELS

Hall electron mobility in buried QW InGaAs channels, grown on InP substrates with HfO₂ gate oxide, is analyzed experimentally and theoretically as a function of top barrier thickness and composition, carrier density, and temperature. Temperature slope α in μ ~ T^α dependence is changing from α=-1.1 to +1 with the reduction of the top barrier thickness indicating the dominant role of remote Coulomb scattering (RCS) in interface-related contribution to mobility degradation. Insertion of low-k SiO_x interface layer formed by oxidation of thin in-situ MBE grown amorphous Si passivation layer has been found to improve the channel mobility, but at the expense of increased EOT. This mobility improvement is also consistent with dominant role of RCS. We were able to a obtain a reasonable match between experiment and simple theory of the RCS assuming the density of charges at the high-k/barrier interface to be in the range of (2-4)×10¹³ cm⁻².