利用脈衝雷射濺鍍光電半導體硒化鎵於不同基板之研究

Abstract

我們已經成功的濺鍍硒化鎵薄膜於不同基板上面。從(004)x-ray繞射的位置以及半高寬我們發現由於晶格不匹配較小，成長在矽基板Si(111)上面的品質比成長在氮化鎵(GaN)跟氧化鋁(Sapphire)基板上來的好。我們也發現在成長初期薄膜的c軸長度會被拉長，增加量由大到小依序是硒化鎵濺鍍在Sapphire，GaN跟Si(111)基板上。我們也可以由拉曼光譜平行c軸震動的A1’mode以及垂直c軸震動的E’(LO)mode來鑑別硒化鎵薄膜品質。從A1’mode的分析我們發現趨勢跟x-ray繞射是一致的。另外，我們也發現因為c軸被拉長而造成A1’mode往低頻位移的現象，類似的現象也被觀察到[23]。從原子力顯微鏡(AFM)的分析得知薄膜的成長模式為島狀加層狀成長。這個結果跟用屬於凡得瓦長晶的分子束磊晶(MBE)的層狀成長模式不一樣。經由x-ray繞射，拉曼光譜以及原子力顯微鏡的分析，我們發現成長的行為不是凡得瓦長晶或是準凡得瓦長晶。因此在利用脈衝雷射來成長硒化鎵薄膜時，晶格不匹配也是我們所要考慮的一個重要參數。

We have successfully fabricated GaSe thin films on different substrates. From (004) peak position and FWHM of XRD, we observe that quality of GaSe/Si(111) series is the best compared to GaSe/GaN and GaSe/Sapphire at the same thickness due to small lattice mismatch. We also find that c-axis length of GaSe thin films were stretched larger at initial stage of deposition and the increasing amount (□c) are GaSe/Sapphire, GaSe/GaN and GaSe/Si(111) in order. The crystalline of GaSe thin films can also be evaluated by Raman Al’ mode which vibrates along c-axis and E’(LO) mode which vibrates perpendicular to the c-axis of GaSe. From the analysis of FWHM of A1’mode, the tendency is identical compared with XRD result. In addition, we also find that the A1’mode shift to lower frequency due to the c-axis length stretched larger which were presumed in accordance with ref[23]. From AFM analysis, the growth mode might be SK mode. The result is different from GaSe deposited by MBE system (layer by layer mode) which belong to VdWE. After the analysis of XRD, Raman spectra and AFM, we find that the behavior is unlike VdWE or quai-VdWE. Hence the lattice mismatch is an important parameter we must consider when we deposit GaSe thin films by pulsed laser deposition.