CV Characterization of Si/SiGe Heterostructures at Cryo Temperatures

The usage of semiconductor devices as quantum dots is a promising way to achieve a large number of qubits located on a small area. To further improve the quality of such devices, it is crucial to get a firm understanding of the defect location and energies in the device. Recent studies show that a large number of defects are located at the Si/SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> interface and get filled by tunneling processes, resulting in non-equilibrium conditions and anomalous behaviors in various electrical measurements, such as unexpected shifts in capacitance and transfer characteristics. In this study, we perform CV measurements at cryogenic temperatures (T = 4 K) to analyze the distinct operating stages during which different device layers become populated by carriers. These measurements are used to analyze the behaviour of the occurring shift of Vth in the buried silicon quantum well (SiQW). Furthermore, the recovery of these Vth shifts has been investigated by using different light sources to illuminate the devices.