.inas / Gaas Self-organized Quantum Dot Memory,

Self-assembled semiconductor quantum dots (SA-QDs), created by Stranski-Krastanov growth mode, have been intensively studied in recent years because of their importance in device applications and fundamental physics. However, in a practical situation of devices, a precise knowledge of the electronic level structure in QDs and thorough understanding of the charge carrier exchange between the QDs and their host materials are an no end job, and there is a continually great incentive to explore the electronic characteristics of QD structures.We have reported the fabrication and the electrical characterization of novel memory devices, based on pHEMT structure self-assembled quantum dots. So far these are the first devices working at room temperature, and they are fully electrical controlled. We have carried out the hysteresis, real-time and bias-cooling C-V measurements.The thesis begins with a chapter summarizing the necessary background materials on the fabrication technology of quantum dots and the working principle of the quantum dot based memory device. Devices based on four different structure samples have been fabricated and measured. A retention time of several seconds was achieved. We have also provided a physical explanation of the memory operation, as being electron trapping in deep levels induced by the QD layer. The memory effect is due to the deep levels induced by the QD layer, and rather than the charging and discharging of intrinsic energy levels in QDs, which is demonstrated by the hysteresis, real-time and bias-cooling C-V measurements.Further investigation of the deep levels is also required to control accurately the energy level position and to improve the structure design. Particularly should be verified if the deep energy levels change by changing the SA-QDs growth condition. Hope this dissertation may give some advices on the research of the SA-QDs based memory devices.