研究目的
Investigating the charge noise mechanism and developing a technique for reducing the noise in the quantum point contacts (QPCs) that form the tunnel junctions of quantum dots (QDs), and which are also used as charge sensors.
研究成果
A MOS dual-gate QPC device was fabricated and the charge noise was characterized. The frequency and the fluctuation amplitude of RTN were successfully suppressed by application of an appropriate global gate bias determined by considering the charge noise from both the local gates and the global gate.
研究不足
The study identifies that both the global gate and the local gates cause charge noise to trap sites, indicating that the fundamental solution to achieve even lower charge noise is considered to be optimization of the device fabrication process or improved cleaning processes to prevent the generation of defects that can trap electrons.
1：Experimental Design and Method Selection:
The study employs a metal oxide semiconductor (MOS) device to reduce electron tunneling from the local gate to trap sites and demonstrates a reduction of the charge noise using the global gate.
2：Sample Selection and Data Sources:
A Si/SiGe wafer grown by ultra-high vacuum chemical vapor deposition was used. The device structure includes a thick graded buffer layer, a Si
3：7Ge3 buffer layer, strained Si quantum well, Si7Ge3 spacer, phosphorous doped Si7Ge3 spacer, and a Si cap layer. List of Experimental Equipment and Materials:
Ohmic contact to the 2DEG is formed on the wafer by annealing Au/Sb/Au at 500°C. The local gates to form QPCs and the global gate of Ti/Au are deposited and are isolated by a HfO2 insulator layer.
4：Experimental Procedures and Operational Workflow:
The QPC current (IQPC) as a function of the local gate voltage (VQPC) for various global gate voltages (Vtop) was measured. Real-time fluctuations of the current were also measured to characterize the noise.
5：Data Analysis Methods:
The noise spectrum was calculated by applying a fast Fourier transform (FFT) to the real time QPC current trace.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容
