MBE低溫成長砷化鎵之電流傳輸機制研究與陽極氧化成長氧化膜之方法

Abstract

由於MBE成長之LT GaAs其具有高阻值特性,且品質也比一般SI.GaAs substrate 與傳統氧化膜為好,因此近幾年來引起廣泛注意與研究.但到目 前為止,對於其絕緣性電流傳輸的機制研究很少談及,而本論文就是針對這 個部分為主體,做詳盡的探討與研究.在整個電流傳輸過程之中,在小偏壓 處一般是考慮由熱平衡載子濃度造成,一旦溫度降低,此效應便不明顯,而 在此同時又有電流存在,因此我們引入了 hopping效應的觀念去嘗試解釋 此種現像,並由理論來fit實驗結果.而在大偏壓處,由於熱平衡載子效應已 經不明顯,而此時電流傳輸的主載是由兩端所注入載子所支配,於是我們使 用SCL來分析此種結果.經由上述模型我們可合理解釋整個結構之電流傳輸 糢型,並與DLTS之量測深態能階得到合理的結果.隨後我們也使用C-V量測 其電容值,發現其值幾乎不隨電壓而變,此可以平行電容板之概念來解釋, 而LT GaAs確實為一高阻值材料.在論文第二部分,我們使用陽極氧化法形 成氧化膜,此法對於低熔點與高揮發性的半導體材料,提供了一個有效形成 氧化膜的方法,因為其具有可在室溫成長與時間短之特性,有效地解決 III-V族材料不可在高溫處理的難題,這對於III-V 族材料MOS元件之製作 助益很大. According to the characteristics of high restivity of the MBE grown low temperature GaAs and the better quality than the common used SI.GaAs substrate,the low temperature growth of GaAs has caused worldwide interesting and research in recently years.But lots of reports on the characteristics of low temperature GaAs have no definite conclusions.In addition,there is few reports on the semiconductor-insulator -semiconductor( SIS)structure about the electronic transport mechanism. Therefore,we present the detailed analysis of the current transport mechanism in the form of SIS structure.In the current transport,it is dominated by thermal equilibriumarrier concentration at small bias.When measured temperatureowering,it is less aparent.therefore,hopping effect is intro-uced to explain the experimental data.In the region of largeias,current transport is dominated by injecction carriers fromwo high doping layers,so space charge limited theorem is usedo analize the phenomena.An active energy (Et=0.72eV)was obtainy fittting the temperature dependent resistivity which compareith DLTS data.From a simple parallel capacitancce model,thehickness of the structure can be estimated and consistentith the realistic thicness of the low temperature grown GaAsWe prove that the LT GaAs is high restivity materials.