Placement of Ge quantum dots in silicon nitride substrate and realization of Ge quantum dots visible-light photo-diodes

• Main Authors: Yu-Jui Chang, 張宇瑞
• Other Authors: Pei-Wen Li
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/53720075419728919435

碩士 === 國立中央大學 === 電機工程研究所 === 99 === In this thesis, we demonstrated the precise placement of Ge quantum dots (QDs) in Si3N4 and SiO2 matrices by selectively oxidizing poly-SiGe-on-SiO2 or -Si3N4. Thereby, we are able to modulate electronic structure of Ge QDs by means of altering their size and the host materials based on the quantum confinement effects. The QD size and crystallinity appear to be strongly influenced by the host materials. Using the catalytically-enhanced local oxidation of Si3N4 by Ge QDs, we have successfully placed the Ge QDs into Si3N4 layer. We investigate the unique migration behavior of Ge QDs burrowing into the underneath Si3N4 by transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis, so that we can precisely control the position, size and the crystal morphology of Ge QDs embedded in Si3N4. The power dependent and temperature dependent photoluminescence (PL) spectra show that the peak centered at 3.3 eV is dominated by free exciton transition in the Ge QDs. The PL spectra reveal a blueshift in peak energy as the dot size decreases. We have fabricated both uniform-sized or grading-sized Ge QDs array for high performance visible-light photo-diodes by repeating the stack deposition and oxidation of Si3N4/poly-SiGe/SiO2 in layer-cake technique. The significant photocurrent enhancement in Ge QD photodiodes is inferred from the photoexcited exciton tunneling or photoinduced conduction currents.