氮化銦鎵發光二極體成長於圖案化矽基板之結構與光電特性研究

Abstract

在本論文中，我們探討氮化銦鎵發光二極體成長在微米與奈米尺度圖案化矽(111)基板上之結構、光學與電學特性。X光繞射實驗結果顯示氮化鎵薄膜成長於奈米尺度的圖案化矽基板上具有較佳的晶體結構，顯示此樣品受到矽基板牽制而造成的應力較低。除此之外，由Williamson-Hall分析得知，在奈米尺度圖案化矽基板上成長的氮化鎵薄膜內含較低的線差排密度，此結果與穿透式電子顯微鏡影像分析結果吻合，從電子顯微鏡影像圖中可以清楚看到奈米尺度的磊晶側向成長技術可減少氮化鎵薄膜內的線差排形成。 在光學特性部分，變功率光激螢光實驗結果顯示，成長於奈米尺度圖案化矽基板上的發光二極體隨著雷射激發功率增強，量子井的發光波段產生較小的藍位移現象，表示量子史塔克侷限效應被有效地抑制，這可歸因於奈米尺度圖案化基板減緩了量子井結構所受的張應力所致。此外，由變溫光激螢光實驗結果得知，成長於奈米尺度圖案化矽基板上的發光二極體相對於成長於微米尺度圖案化矽基板的發光二極體有較好的載子侷限能力。在電學特性部分，成長於奈米尺度圖案化矽基板上的發光二極體相對於成長在微米尺度圖案化矽基板上者之電激螢光光譜有較小的藍位移現象、較小逆向偏壓漏電流以及減緩發光效率下降。以上這些結果可證實使用奈米尺度圖案化矽基板可降低量子井結構的應力及結構缺陷密度，進而提高發光二極體的品質及效能。

In this study, we investigated the structural, optical and electrical characteristics of InGaN-based light emitting diodes (LED) grown on micro- and nano-patterned Si (111) substrates (MPLED and NPLED). The result of X-ray diffraction revealed that the GaN layer grown on the nano-patterned Si (NPSi) substrate had higher degree of mosaicity, indicating less strain in this sample. Moreover, the density of threading dislocation densities in the GaN film grown on NPSi was reduced as indicated by Williamson-Hall analysis results, that is also consistent with the transmission electron microscopy (TEM) results. The results elucidate that nanoscale epitaxial lateral overgrowth (NELOG) effectively reduces the density of threading dislocations in GaN film grown on NPSi. Power dependent photoluminescence (PL) measurements show that NPLED has a smaller peak blue shift with increasing pumping power as compared with that of the MPLED, revealing a reduced quantum confined Stark effect (QCSE). This phenomenon is attributed to the reduced strain in NPLED. Furthermore, NPLED shows better carrier confinement than MPLED as revealed by temperature dependent PL measurements. In terms of device performance, NPLED exhibits smaller electroluminescence (EL) peak wavelength blue shift, lower reverse leakage current and lower efficiency droop, compared with the MPLED. These results suggest that using NPSi as the substrate for InGaN based LED growth can effectively reduce the tensile strain and density of threading dislocations of the GaN layer and improve the optical and electrical performance of the LED.