Improving Gate Dielectrics for Reducing Charge Noise in Si/SiGe Quantum Dots

We report on the materials development of a novel low temperature SiO₂ gate dielectric for use in Si/SiGe quantum dot devices. X-ray Photoemission Spectroscopy (XPS) measurements show nitric acid oxidation of silicon (NAOS) or silicon-germanium alloys produces a more stoichiometric and thicker silicon oxide over other low temperature techniques [1]. Using this approach, we create a ~1.7 nm SiO₂ gate dielectric over the active region of a Si/SiGe quantum dot device coupled to a Nb microwave resonator for charge state readout. By measuring the current noise in a quantum dot we observe a 1/f power spectral density of chemical potential noise with an amplitude of 0.203 μeV²/Hz at 1 Hz which compares favorably to similar devices using ALD Al₂O₃ and native SiO₂ [2]. Further, we demonstrate low frequency Landau-Zener spectroscopy of a double dot charge qubit and discuss cavity-charge coupling experiments [3,4].

References:
[1] H. Kobayashi et al. Applied Surface Science 256 (19) 5744 (2010).
[2] E. J. Connors et al. Preprint at https://arxiv.org/abs/1907.07549
[3] S. N. Shevchenko et al. PRB 98, 195434 (2018)
[4] X. Mi et al. Phys. Rev. B 98, 161404 (2018)