Invention of the quantum dot structures opened the new era of sub-micron devices. The experiments focus mainly on the electrical properties and the optical properties. Quantum dot memory was fabricated with the conventional heterojunction structure in first time. Quantum dot field effect transistor was proposed to show the memory operation of InAs QD. In C-V measurement, the hysteresis of first sweep and second sweep was observed. The hysteresis was shown in the range of 200 kHz and this result indicated the memory operation of InAs QD. This result was supported by Pulsed I-V measurement. Input pulse duration should be at least 4 μs to fully charging the QD layers. This is coinciding with the hysteresis characteristic in C-V measurement. The sample of heterostructure FET that is not containing the QD was investigated. From the C-V measurement, the hysteresis of this sample did not show the existence of QD. Optical properties were investigated and measured the absorption transitions. In appendix chapters, the QW and the QD modulated barrier diode were proposed. The modulated barrier structure was used to reduce the dark current and the p-n-p structure was applied to use the hole transition in valence band. InGaAs/GaAs QW was grown on the S. I. GaAs wafer and showed ~ 3 μm the mid-infrared absorption in valence band. InAs/GaAs QD structure adopted the QW structure and showed the valence band absorption at ~ 2.8 μm wavelength, at first.
