- 學位論文
利用MBE 成長硒化銅鋅磊晶層及特性研究
Growth and Characterization of CuxZn1-xSe epilayers by MBE
摘要
本篇論文是利用分子束磊晶法成長一二六族的硒化銅鋅磊晶 層，並且利用反射光譜、光激螢光譜、拉曼散射、X 光繞射量測、原 子力顯微鏡、X 光光電子能譜儀以及霍爾量測等，來研究探討磊晶層 的光學特性及結構性質。研究發現磊晶層成長速率會隨著銅的溫度上 升而加快；當光激螢光譜在低溫20K 且銅溫度小於900℃，我們可以 在近能隙的地方發現銅‐束縛激子訊號，我們把銅低於900℃的樣品列 為摻雜狀態，而銅‐束縛激子訊號會隨著銅溫度上升而逐漸減弱甚至 消失；比較摻雜的硒化鋅磊晶層與輕摻雜的硒化銅鋅磊晶層，從低溫 光激螢光譜我們發現少量摻雜的銅做為表面活性劑進入硒化鋅磊晶 層，造成束縛激子有些許的紅移現象。我們利用X 光光電子能譜儀 得知在銅摻雜溫度為1000℃時摻雜濃度達到35.08 %，此時固態熔解 率達到飽和狀態；銅摻雜溫度在高溫時，高能量的銅原子轟擊表面， 結果發現磊晶層表面的平坦度會隨著銅的摻雜溫度提升變得越來越 崎嶇。最後我們成功做出高載子濃度的P 型硒化銅鋅，載子濃度達到 7.94×1019cm-3，比目前文獻上P 型硒化鋅的載子濃度都還要高。
並列摘要
CuxZn1-xSe epilayers were grown on GaAs substrates by molecular beam epitaxy (MBE). The optical properties, structural property and doping concentration are studied by using reflectance, photoluminescence (PL), Raman scattering, X-ray diffraction, atomic fource microscopy, Hall measurement, and X-ray Photoelectron Spectrometer (XPS) etc. The growth rate of epilayers increases with the raising of Cu flux. From PL spectra at 20 K, Cu-(acceptor) bound excitons can be observed in near-band-edge when Cu cell temperature less 900 ℃, which is assigned as the doping region. As Cu cell temperature increased, the acceptor bound excitons emission became gradually weaker and even disappeaed. Compare the un-doped and lightly Cu doped ZnSe PL spectra, the bound exciton peak reveals a small energy red shift, that may be caused by the Cu acting as surfactant. The dissolvable rate of solid state is saturation, when copper doping into ZnSe at 1000 ℃, by XPS. Besides, the doping concentration is as high as 35.08%. The average roughness is getting rugged when Cu cell temperature is getting higher. The possible reason is that the high energy of Cu atom bombards the surface. Finally, high III carrier concentration of P-type ZnSe was observed as the Cu cell temperature raised to 1000 ℃. The hole concentration is reached to 7.94×1019 cm-3. It is higher than reporter by the published P-ZnSe epilayer.