利用二維光子晶體探討空氣佔有率與氮化銦鎵發光二極體光萃取率之關係

Abstract

本篇論文使用電子束微影系統以及電感耦合式電漿乾蝕刻於氮化銦鎵/氮化鎵發光二極體之P型氮化鎵上以製作光子晶體結構，探討光子晶體之空氣佔有率與發光二極體光萃取率之關係。以聚焦離子束顯微鏡確定光子晶體線寬及深度，且利用微觀光致激發螢光頻譜系統及倒立式螢光顯微鏡量測發光二極體出光強度。 本論文實驗主題可分為五大部分，第一部分為調整電感耦合式電漿乾蝕刻氣體比例調整，預設蝕刻氮化鎵參數會使得蝕刻表面崎嶇不平，藉由調降氬氣流量而得到平坦蝕刻表面。第二部分為二維凸柱結構轉變至一維光柵結構，固定週期於400nm下改變空氣佔有率，且製作兩組深度150nm及180nm，兩組數據皆於空氣佔有率55%可得到最佳光萃取率。 第三部分為氮化鎵發光二極體成長於雙面拋光藍寶石基板，固定週期於400nm下製作二維凸柱結構且改變空氣佔有率，使用微觀光致激發螢光顯微鏡量測是將雷射光從樣品正面打入且正面收光，其結果在空氣佔有率55%可得到最佳光萃取率，而使用倒立式螢光顯微鏡量測是將雷射光從樣品背面打入且正面收光，其結果在空氣佔有率60%可得到最佳光萃取率，其差距本論文認為是收光系統之差異所造成，故認為仍是空氣佔有率55%可得到最佳光萃取率。 第四部份為二維凸柱結構之深度變化，固定週期於450nm下製作二維凸柱結構且改變空氣佔有率，製作深度範圍從150nm至780nm，共9組深度，其結果皆於空氣佔有率55%可得到最佳光萃取率，將空氣佔有率55%之各組深度之相對PL強度對深度作圖，可得到週期性變化，其週期峰值所在深度可以公式預測，其預測結果與實驗結果相近。 第五部分為二維孔洞結構，固定週期於400nm及450nm下製作二維凸柱結構且改變空氣佔有率，各製作兩組深度150nm及200nm，其四組結果皆於空氣佔有率45%可得到最佳光萃取率，再將週期400nm及450nm於深度150nm之二維凸柱結構與二維孔洞結構做比較，二維凸柱結構光萃取率皆高於二微孔洞結構，最後將實驗結果以實驗室模擬成果及文獻資料來解釋其物理意義。

The dissertation is focus on the fabrication of the photonic crystals on the P-type GaN of the InGaN-based light-emitting diode by electron-beam lithography and inductively coupled plasma reactive-ion etching. We study the relation between the air duty cycle and the light extraction efficiency of InGaN-based light-emitting diode. After the fabrication process of photonic crystal, we use the Focus-ion Beam to measure the line-width and the depth of the photonic cyrstals and detect the output light intensity of light emitting diode by the Micro-PL spectrum system and the inverted microscope. The main focus of the dissertation is divided into five parts. First, we adjust the recipe of the default GaN etching recipe of the inductively coupled plasma reactive-ion etching. Second, we change the two-dimensional post photonic crystals into one-dimensional photonic crystals with period at 400nm and depth at 150nm and 180nm. The two series of experiment data revel that we can get the optimized light extraction efficiency with air duty cycle at 55%. The third part is that we change the air duty cycle by altering the line-width of the two-dimensional post photonic crystals with period at 400nm and depth at 150nm on the P-type GaN of the light-emitting diode grown on the double-polished sapphire substrate. We get the optimized light extraction efficiency with air duty cycle at 55% according to the data measured by Micro-PL system, and get the optimized light extraction efficiency with air duty cycle at 60% according to the data measured by inverted microscope. The disparity of these results is due to the difference of the measurement system. The fourth part is that we change the air duty cycle by altering the line-width of the two-dimensional post photonic crystals with period at 450nm and nine different depth which is from 150nm to 780nm on the P-type GaN of the light-emitting diode. We get the optimized light extraction efficiency with air duty cycle at 55% at all the different depths. If we plot the relation between relative PL peak intensity with air duty cycle at 55% and depth, we get the periodic graph. The periodic peak of the depth could be work out by the formula, and the results of the formula are close to the results of the experiment data. The last part is that we change the air duty cycle by altering the line-width of the two-dimensional hole photonic crystals with period at 400nm and 450nm and depth at 150nm and 200nm on the P-type GaN of the light-emitting diode. These four series of data revel that we get the optimized light extraction efficiency with air duty cycle at 45%. If we compare the relative PL peak intensity between two-dimensional post photonic crystals and two-dimensional hole photonic crystals with period at 400nm and 450nm and depth at 150nm, we find that two-dimensional post photonic crystals could get the better light extraction efficiency. Finally, we describe the physical meaning of the experiment data results by the simulation results of our laboratory and some literatures.