Charge detection in silicon double quantum dot nanodevices

This dissertation focuses on the characterisation of double quantum dots in silicon nano-transistors fabricated with complementary metal-oxide-semiconductor (CMOS) compliant technology. The progressive reduction of the dimension of electronic components searched by microelectronics industry and the research on quantum dots for quantum information processing (QIP) have been regarded as independent fields. In the last years an approach combining this two aspects has gained interest: the fabrication of semiconductor nano-devices in CMOS compliant and preindustrial technology for the study of quantum mechanic effects. The core material used in this approach is silicon: it is a standard material in classical electronics and is characterized by long coherence times. In particular double quantum dot system are appealing for QIP because of their possible implementation in different quantum bit architectures. This thesis reports on the work done at Laboratorio MDM-IMM-CNR (Agrate Brianza) and for three months at Hitachi Cambridge Laboratory during the three years Nanostructures and Nanotechnology PhD course of Università di Milano-Bicocca. I first describe the formation of a double quantum dot in a single gate nano-transistor. The quantum dots are located at the corners of the channel but the presence of a single gate doesn't allow for controlling the system. Nevertheless, one of them is hybridized with a single donor in strong coupling with the leads. The conservation of valley parity index during tunneling influences transport processes both at first and second order. The Kondo-perturbed regime manifests in the first spin-valley shell. Subsequently, I report the electrical characterization of multigate T-shaped devices. Here a single electron transistor is used to charge sense nearby quantum dots. Such architecture allows for tuning the number of the quantum dots, which at low filling are disorder-assisted, and a double quantum dot can be studied both from charge sensing and single charge dynamics measurements. I then investigate an alternative readout technique. The rf-reflectometry, by connecting a resonator to one of the gates, enables to study double quantum dots in split-gate nano-transistors, exploiting more compact and simple device architectures. In addition, the increased sensitivity with respect to standard DC-measurements can be exploited to investigate the few-electron regime. Finally, I report on the design and characterisation of a cryogenic printed circuit boards (PCBs) set for the broadband characterisation of multigate devices. One PCB hosts a custom CMOS transimpedance amplifier with selectable gain, maximum bandwidth of 250 kHz, minimum equivalent input noise of 4 pA rms. The high frequency lines are designed to ensure the transmission of ns pulses with low crosstalk up to few GHz in order to perform single charge manipulation.