Interface traps of the N-type MOS structure with Ge nanocrystals characterized by G-V measurement and Si electron-luminescence

在金屬-氧化層-半導體中埋入鍺量子點作為浮動閘極，形成非揮發性奈米晶體記憶體，並藉由穿透式電子顯微鏡（Transmission electron microscopy, TEM）驗證量子點結構的形成。關於元件儲存電荷的特性，利用電容-電壓量測驗證，PMA之後，即使頻率從1000kHz降到5kHz，載子交換速度變慢，記憶窗口仍然存在，表示鍺量子點有保存載子的能力。而電導-電壓量測中比較PMA時間對電導值的影響，可以觀察到PMA 1分鐘的電導值較PMA 9分鐘的電導值小，且只有在量測頻率100kHz以上才有明顯差別，證明了PMA可以修補淺層的缺陷，並且利用電導-電壓量測的結果趨勢，模擬出缺陷的分佈模型。電導-電壓隨頻率越大峰值越大且往正偏壓位移。表示能帶邊緣的淺層缺陷密度較高，能帶中間分佈的深層缺陷密度較低。行電激發光頻譜之量測，欲了解缺陷對於發光的影響，但元件因直流觸發而導致過熱產生黑體輻射，因此改由脈衝模式觸發。找出最適合的脈衝模式為頻率1 Hz的方波脈衝， 頻率1 Hz的輸入波形較適合電洞到達矽基體的速度，若使用較快的頻率，電洞無法在一次電源開啟的時間內到達矽基體，而停留在氧化層中，需要兩到三次的電源開啟，才有辦法到達矽基體，因此發光較弱。改用脈衝觸發後，元件不會再因過熱產生黑體輻射，矽的光也增強約40倍。發光對時間的關係中也發現，PMA 13分鐘的元件發光效率最好，此結果與電導-電壓量測實驗所得結論符合，PMA可修補淺層缺陷，因此電洞更容易到達矽基體，PMA13分鐘的元件發光效率較PMA1分鐘的元件高出約兩倍。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.he 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. ample 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.口試委員審定書 i謝 ii要 iiibstract iv一章 引言 1.１ 研究動機 1.２ 論文概要 3二章 簡介 4.１ 鍺奈米粒子的形成 5.２ 非揮發性奈米晶體記憶體 8.３ 非揮發性奈米晶體記憶體之發光機制 9.３.１ 通道熱電子寫入 10.３.２ 富勒-羅得漢穿透抹除 10.４ 缺陷之特性與量測方法 11三章 元件結構之製作與量測流程 14.１ 鍺量子點金屬-氧化層-半導體結構製作流程 14.２ 量測儀器之架設 20.２.１ C-V and G-V measurement 20.２.２ E-L (Electroluminescence) spectrum 20.２.３ L-I (Luminescence intensity) 21四章 實驗結果與討論 24.１ 不同PMA時間之C-V與G-V曲線 24.２ E-L spectrum 與黑體輻射之比較 31.３ 發光機制與觸發模式 34.４ 輸入波形與不同PMA時間元件所量測之L-I 38五章 結論 4