| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 96 === In this work, Metal-Oxide-Semiconductor structure with germanium nanocrystals formed by E-gun evaporator for charge storage and luminescence is fabricated. Fabricated devices are characterized by Transmission Electron Microscope. In the characterization of memory performance of devices with different PMA time, high frequency capacitance-voltage (C-V) measurement is used to measure the memory window for comparing the charge storage capacity. Frequency varied from 1000kHz to 5kHz which means exchanging speeds are slower, but the memory windows still exist. The carriers charged in Ge dots are independent of frequency. On the other hand, in conductance-voltage (G-V) measurement, the conductance of sample with PMA 1 minute is larger than sample with PMA 9 minutes, when frequency is more than 100 kHz. The result helps us to establish the model of the trap distribution, and characterize that PMA can neutralize the shallow trap. The peak values are larger with higher frequency and shift to positive bias, which means that the slow trap density is larger near band edge and smaller in mid band.
The luminescence mechanism is figured out by electron -luminescence (E-L) measurement. Holes are hopping though the traps in SiO2, and into Si substrate to recombination with the majority carriers-electrons. Triggered by DC mode, blackbody radiation caused by heat would effect Si E-L measurement. For improving luminescence efficiency, device must be triggered by the optimum frequency-1Hz matched the velocity of hole tunneling though oxide. Holes will be trapped in oxide instead of passing through in higher frequency, hence the recombination electron-hole pairs decreased. Luminescence of Si increased about 40 times, because of triggered by pulse mode.
Sample with PMA 13 minutes has better luminescence efficiency than sample with PMA 1 minute more than twice in time-domain luminescence measurement. This result agree with G-V measurement, which is PMA can neutralize the fast traps and make holes pass through oxide easier.
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