2016-08-012024-05-15https://scholars.lib.ntu.edu.tw/handle/123456789/663445摘要：在本研究主題當中，利用頗面穿隧掃描顯微鏡(XSTM)及掃描穿隧能譜術(XSTS)結合可調控的雷射光源激發電子電洞對在樣品上，利用此一技術可探討在矽基板及氮化鎵薄膜的異質介面上的電子特性變化，進一步探討在薄膜上的穿隧電流變化源自於在結晶缺陷所激發的額外光生載子，利用雷射光源結合穿隧能譜可提供更多資訊關於表面的結晶品質。<br> Abstract: The potential of sub-bandgap laser-excited cross-sectional scanning tunneling microscopy and spectroscopy is demonstrated to probe the defect states in semiconductor. The characterization method is achieved by growing GaN layers on Si(111) without intentional buffer layers. According to high-resolution transmission electron microscopy (HRTEM) and Cathodoluminescence(CL) spectroscopy, the GaN layers consist of crystallites with varying crystal orientations and hence contain high defect states densities. In order to clarify discrepancy between band-to-band excitation and defect state excitations, we use sub band-gap laser excitation. An obvious increase in the tunneling current at positive sample voltages is observed during the GaN layers with high defect density illuminates by sub-bandgap laser. Nevertheless, no effect is found in high quality GaN epitaxial layers. This observations result from the excitation of free charge carriers at defect states. Thus, sub-bandgap laser-excited scanning tunneling spectroscopy is a powerful tool to characterize defect states.氮化鎵電子結構異質介面載子傳輸掃描穿隧式顯微GaNelectronic structureheterojunctionscarrier transportscanning tunneling microscopy (STM)