Fabrication of Novel GeOx-cladded Ge Quantum Dots and Quantum Dot Gate Nonvolatile Memory using GeOx-Ge Qd\u27s

In this dissertation, the floating gate type quantum dot gate nonvolatile memory device has been investigated. The electrical characterization and simulation of the fabricated quantum dot nonvolatile memory (QD-NVM) devices is presented. The electrical characterization includes program, erase, and read operations and the memory retention and endurance measurements. In addition, QD synthesis and their incorporation as the floating gate (along with material characterization) is presented in fabricated QD-NVM devices. ^ The synthesis of the germanium oxide cladding on the germanium quantum dots is one of the key interests in this research. Owing to the electrical and physical isolation of the quantum dots due to germanium oxide cladding, it provides a larger threshold voltage shift due to tight packing and higher density of quantum dots. GeOx cladding on the QDs enhances the data retention by avoiding the lateral dot-to-dot conduction, thereby reducing charge leakage. A threshold voltage of 1.5 V was observed in the first GeOx-Ge QD-NVM device when pulsed with a 20 µs stress pulse. The experimental data indicates that there is about a 0.1 V shift in the threshold voltage of that device over a period of one year. Similarly, 1.6 V of threshold voltage shift was observed in the second device and the retention data indicates negligible shift in the threshold voltage over a period of one year. Similar results were observed in the II-VI based QD-NVM devices.