氮化銦鎵三元混晶與同電子性摻雜砷之氮化鎵薄膜之光性研究

Abstract

在本論文中，我們利用拉慢光譜（Raman）、冷激光光譜（Photoluminescence，PL）、冷激光激發光譜（Photoluminescence excitation，PLE）、霍爾量測（Hall measurement）、原子力顯微鏡（Atom force microscopic， AFM）等方法研究成長再氧化鋁（Al2O3 ，Sapphire）基板上之氮化銦鎵三元混晶與同電子性摻雜砷之氮化鎵薄膜之光學性質及晶格結構。關於氮化銦鎵三元混晶的樣品，我們可以觀察到表面的波動情形隨銦的組成增加而更趨嚴重，由PLE我們可以清楚的觀察到來自於不同銦組成的氮化銦鎵能帶的能量吸收且隨銦組成增加而越加嚴重。另外，在砷摻雜之氮化鎵薄膜的量測結果發現，在低於氮化鎵一般正常長晶溫度（1050℃）時，砷摻雜的情形有助於降低氮化鎵薄膜載子濃度且維持相當的電子遷移率直到溫度低至 950℃及同時在光譜上亦維持較窄的半高寬。而且，在相同長晶溫度下，砷的融入有助於改善晶格的排列使得在拉慢工普勝降低TO模的出現，同時也會舒張部分的應力以致聲子的頻率隨砷的流率增加而降低。因此，在氮化鎵薄膜的低溫成長時，有砷的摻雜下似乎有助於改善部分的品質且有效的延伸長晶溫度至較低的溫度。

Abstract The InxGa1-xN:Si / GaN heterostructure grown on the (0001) sapphire substrates by metalorganic chemical vapor phase epitaxy (MOVPE) has been investigated by AFM, PL, and PLE. We have observed clearly the spatial fluctuation of In at high In concentration and the transitions from the InxGa1-xN band-edge. The yellow emission as resulted from the photoexcited carriers above the GaN A exciton a has also been proved. We also studied the isoelectronic As-doping effects in GaN films grown by MOVPE. Two series of As-doped GaN, one grown at various temperatures (from 1050 to 800℃) and the other under different tertiary butylarsine (TBA) flow rates (from 0 to 100 sccm) were investigated by PL, PLE, Raman and Hall measurements. High mobility can be obtained even at a temperature of 950℃ and the low background concentration of approximately 5×1017 cm-3 at 900℃. The narrow linewidths of PL and Raman signals are observed by increasing the As-incorporation The As-doped induced strain along the c-axis (the large A1(LO) frequency shifts) easily. Our results suggest that the use of As-doping is helpful to the growth of GaN at low temperature and expanded the growth temperature window.