研究目的
Investigating the dependence of low-frequency charge noise spectra on temperature and aluminum-oxide gate dielectric thickness in Si/SiGe quantum dots with overlapping gates.
研究成果
The charge noise in Si/SiGe quantum dots increases with aluminum-oxide gate dielectric thickness and shows strong dot-to-dot variations in temperature dependence. The noise is attributed to a nonuniform distribution of two-level systems near the semiconductor surface. Reducing the aluminum oxide thickness is suggested as a means to mitigate charge noise.
研究不足
The study is limited to low-frequency charge noise and does not address high-frequency noise components. The exact nature of the two-level systems causing the noise is not fully understood.
1：Experimental Design and Method Selection:
The study involves measuring the low-frequency charge noise spectra in Si/SiGe quantum dots with varying aluminum-oxide gate dielectric thicknesses and at different temperatures. The Dutta-Horn model is employed to analyze the noise spectra.
2：Sample Selection and Data Sources:
Quantum dots are fabricated on an undoped Si/SiGe heterostructure with a Si quantum well. Devices with different gate-oxide thicknesses are used.
3：List of Experimental Equipment and Materials:
Devices are cooled in a dilution refrigerator. Current noise spectra are acquired using an SR570 low-noise current preamplifier and an SR760 spectrum analyzer.
4：Experimental Procedures and Operational Workflow:
Current noise spectra are measured with the plunger gate voltage set on different positions of a transport peak and in the Coulomb blockade regime. The temperature is varied from 50 mK to 1 K.
5：Data Analysis Methods:
The charge noise spectrum is extracted from the current noise spectrum using the lever arm and the derivative of the current with respect to the plunger gate voltage. The Dutta-Horn model is used to analyze the temperature and frequency dependence of the noise.
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