Quantum confinement of charge carriers in semiconductor nanostructures have garnered considerable attention in the past few decades. With new materials being discovered and advanced growth techniques allowing them to be engineered into nanoscale devices with atomic precision, the localization of charge carriers is becoming easier to control. The focus of this dissertation is to highlight the employed growth techniques and the characterization of the device structures studied in our lab.
In the first project of the dissertation we examined the temporal dynamics of the Optically Generated Electric Field (OGEF) within a CQD device. We demonstrated the potential of using the interdot transition as a sensitive probe to measure electric fields by using photovoltaic band flattening in a Schottky diode structure. A modulated high energy laser was used to create the OGEF leading to photovoltaic band flattening. A CW laser with energy required to create the interdot transition was used to monitor the electric field in the device and characterize the temporal behavior of the field to determine rise time and decay time as well as to show how they depend on different variables.
In the Second project we report on monolayer TMD metal semiconductor metal photodetectors produced using a CVD process. The photodetectors showed maximum responsivity of up to 15 A/W. The response time of the devices is found to be on the order of 1 µs, an order of magnitude faster than previous reports. The main project in this dissertation involved using the CVD growth technique employed in developing TMD devices to create deterministic single photon emitters (SPEs) by carrying out the growth on etched substrates. While we have seen successful growth with TMDs growing over perturbations, SPEs are yet to be found. However, in the process of developing these devices we were able to address several challenges in our technique.
As highlighted in previous work in the group while the growth technique employed does yield interesting results, achieving growth 100% of the time is a challenging problem. However as showcased in the third project this issue was resolved by careful selection of parameters and has led to the development of precursor-free growth of metal/metal oxide device structures. It was also found that post growth devices had current leakage through the anode and cathode. The cause of this issue has been found to be the metal deposited on the substrate prior to growth and a solution has been provided, in the form of thicker oxides. Finally, analyzing the top of our metal electrodes post growth we have found them to contain a layer of TMD over them making the analysis of the electrical characterization of the TMD device convoluted. Here we have an initial solution in the form of Pt.