Optical and Material Characteristics of InAs/GaAs Quantum Dots and Ga2O3/GaAs Thin Film

• Main Authors: Pin-Fang Huang, 黃品方
• Other Authors: Hao-Hsiung Lin
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/52536408399133308806

碩士 === 臺灣大學 === 電子工程學研究所 === 95 === This thesis concerns with the studies on the optical properties and material characteristics of thermal annealing InAs/GaAs quantum dots and Ga2O3/GaAs. Many optical measurements are carried out to study the physical properties according to the conditions of thermal annealing. Many peculiar phenomena have been observed, which are very useful for understanding as well as application of these materials. (1) Characterization of the InAs/GaAs quantum dots with spacer annealed under AS4： InAs quantum dots were deposited onto GaAs layer with different growth temperature spacer layer by molecular beam epitaxy and compared using temperature dependence photoluminescence measurements, power dependence photoluminescence measurements and atomic force microscope (AFM).From the AFM measurement, we can know the sample annealed at lower temperature has lager size quantum dots and smaller density of quantum dots. And the size of quantum dots is getting smaller and the density of quantum dots is getting larger as the annealing temperature increase. The photoluminescence energy was considerably increased for samples grown in lower temperature. So the energy of quantum dots related with the size of quantum dots. We also analyzed samples by the peak positions, FWHMs, and PL integrated intensity as a function of temperature. The sample annealed at 500 has better optical properties and less activation energy and the density of quantum dots is most uniform. Power-dependent photoluminescence measurements also confirm the contention. (2) Characterization of the InAs/GaAs quantum dots with spacer annealed under P2： The samples had the same growth conditions just annealed under P2. From the AFM charts, the amount of quantum dots is destroyed and decreased. It rely on the bonding of phosphorus atoms and arsenic atoms. When the annealing temperature is getting higher, the chemical reaction is getting violent, so the alloy of InPxAs1-x was grown instead of InAs. The photoluminescence energy was decreased for samples grown in higher temperature. And we find an interesting phenomenon in the temperature-dependent photoluminescence measurement of the sample annealed at 500 . The two broad peaks are attributed to the combined size distribution of the bimodal quantum dots. The change of peak intensity between them can be explained the movement of the carriers in the quantum dots as the temperature increased. (3) Characterization of thermal annealing Ga2O3 thin films： Ga2O3 thin films were deposited onto GaAs substrate with different annealing temperature. We can know the change in binding energy as the different annealing temperature and suppose the composition of samples is changed by X-ray Photoelectron Spectroscopy (XPS) measurement. Subsequently, we confirmed the increase of ratio of oxygen to gallium assuredly as the annealing temperature increased by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) measurement. Finally, from the X-ray diffraction (XRD) measurement analysis, we can identify the relations between the quality of the interface and annealing temperature by the increased peak positions and decreased FWHMs in the spectra.