Electron Wave Interfernce in Nano-Scale Open Dots on InAs Surface Inversion Layer and InAs/AlGaSb Quantum Well Fabricated Using AFM Oxidation
Atsushi NAKASHIMA, Takahiro FUJITA, Youji NAKAJIMA, Masato NAKAI, Toshihiko MAEMOTO, Shigehiko SASA and Masataka INOUE
Abstract:Electron interference effects at 4.2 K were studied in nano-scale open dots fabricated in InAs surface inversion layers and in an InAs/AlGaSb quantum well. These structures were fabricated using AFM oxidation. We have observed periodic oscillations and aperiodic fluctuations on both systems. We investigated oscillation period using Fast Fourier Transform analysis. We found that for the InAs surface inversion layers the oscillation periods correspond to that of Aharonov-Bohm effect iAB effectj in agreement with the dot size. In contrast, for the InAs/AlGaSb quantum well, the deduced oscillation period did not correspond to the dot size. These results suggest that the observed AB oscillations are caused by the channel formed along the dot periphery due to the electron transfer from the InAs oxide to the InAs. Aperiodic fluctuations were characterized using correlation field analysis. For InAs/AlGaSb quantum well, correlation field was increased due to smaller skipping radius, as magnetic field increased. For InAs inversion layers, the correlation fields were not changed because the dot size is smaller than the cyclotron radius. The estimated electron phase breaking times tf were 1 psec and 10 psec for the InAs surface inversion layers and quantum well, respectively. The longer tf in InAs than that of GaAs systems at 4.2 K indicates the importance of electron interference in InAs even at higher temperatures. Key Words:Nano-scale open dot, InAs, AFM oxidation, Aharonov-Bohm effect, Ballistic