Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/10317
標題: 雷射分解氮化鎵/藍寶石基板界面層之技術開發
Development of the laser decomposition process on GaN/sapphire interface layers
作者: 陳思涵
Chen, Sih-Han
關鍵字: GaN
氮化鎵
sapphire
laser decomposition
藍寶石基板
雷射分解
出版社: 材料科學與工程學系所
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摘要: 本論文利用雷射於元件平台區處理在不損傷電極之前提下,於元件n和p電極間之平台區域進行雷射掃描處理再搭配光輔助電化學濕式蝕刻法和化學濕式蝕刻法進行蝕刻,於藍寶石基板和GaN材料界面間產生空氣空孔和倒立的錐狀結構,成功的製備出空氣空孔和倒立的錐狀結構於圖案化GaN發光二極體元件中。本論文將探討放射狀的太陽結構下方具有空氣空孔之倒立的錐狀結構之圖案化GaN發光二極體元件(PLH-LED)和元件側壁條狀的翅膀結構下方具有空氣空孔和倒立的錐狀結構之圖案化GaN發光二極體元件(FF-LED)相較於個別傳統發光二極體(ST-LED)之光性和電性特性差異。 實驗一:PLH-LED,使用ST-LED進行試片正面雷射鑽孔處理並搭配上光輔助電化學濕式蝕刻製作出PLH-LED。而於電激發螢光(EL)量測中,PLH-LED相較於ST-LED之發光強度提升約有19 %之提升效果,是因為放射狀的太陽結構下方具有空氣空孔之倒立錐狀結構能增加光取出之區域。而於325 nm光激發螢光(PL)量測中,可明顯的觀察出在側蝕區域MQW之訊號從ST-LED之458.4 nm飄移至PLH-LED之449.9 nm,此波長之飄移方向為藍移,其是因為PLH-LED有應力釋放之效應產生,可有效降低壓電場效應,使能帶變得較為平緩。 實驗二:FF-LED,使用ST-LED進行試片正面雷射切割處理,切出切割道,接著進行試片背面雷射掃描裂解處理並搭配上化學濕式蝕刻製作出FF-LED。而於EL量測中,5 μm、10 μm、15 μm和20 μm雷射線間距之FF-LED相較於ST-LED之提升比例分別為49.42 %、62.57 %、19.58 %和11.90 %,10 μm雷射線間距之FF-LED呈現較高之發光強度提升比例,其是因為5 μm雷射線間距之FF-LED蝕刻通道較10 μm雷射線間距之FF-LED大,蝕刻後產生之倒立的錐狀結構可能已有過蝕現象,使倒立的錐狀結構產生崩塌。而於EL和PL量測中,對波長部分而言,FF-LED相較於ST-LED均有波長藍移之現象產生,其是因為製程產生之空氣空孔,造成藍寶石基板和GaN部分分離所致。於Raman光譜量測中,本實驗只挑選倒立的錐狀結構密度最高之5 μm雷射線間距之FF-LED進行量測,可明顯得知5 μm雷射線間距之FF-LED之應力值(0.29 GPa)小於ST-LED之應力值(0.99 GPa),由此可證明FF-LED之空氣空孔和倒立的錐狀結構有助於應力之釋放。 本論文之實驗均證明了波長藍移現象是因為空氣空孔結構可使藍寶石基板和GaN部分分離,使降低GaN和基板晶格不匹配所產生之應力,可有效降低壓電場,進而使能帶變得較為平緩,所以導致波長藍移;而發光效率之提升是因為倒立的錐狀結構其傾斜角度,導致光之全反射機率增加,進而提升光取出效率,成功的探討空氣空孔和倒立的錐狀結構於圖案化發光二極體元件之貢獻和影響。利用雷射處理和光輔助電化學濕式蝕刻技術,於GaN和藍寶石基板界面間產生空氣空孔和倒立的錐狀結構,利用兩種不同製程,製作高取光效率發光二極體,應用於高效率之發光元件當中。
GaN-based light-emitting diode (LED) structures had an air-void structure and a tapered GaN structure at the GaN/sapphire interface through a laser decomposition process and a wet etching process to increase light extraction efficiency. In this study, we analyzed optical and electrical of these two kinds of LEDs, a LED with a Photoelectrochemical (PEC) treated laser-drilled hole structure (PLH-LED) and a LED with a finger fork structure (FF-LED), compared to the standard LED (ST-LED). In the PLH-LED, the inverted cone-shaped GaN structure was formed around the laser-drilled hole as a light scattering structure to enhance the light extraction efficiency at central mesa region. The light output power of the PLH-LED had an approximate 19% enhancement when compared to the ST-LED at 20 mA. The photoluminescence peak wavelength of the InGaN active layer was slightly blueshifted from 458.4 nm for the ST-LED to 449.9 nm for the PLH-LED that could be caused by partially reducing the compressive strain induced piezoelectric filed by forming the radiated-cone-shaped structure at GaN/sapphire interface. High light emission intensity for the PLH-LED structure was observed around the laser-drilled hole pattern as a result of a higher light-scattering process occurring at the radiated-cone-shaped structure for the InGaN-based LED applications. In the FF-LED, the structure was fabricated through a laser scribing, laser decompose process with different line spaces and a chemical wet etching process that the InGaN active layer was not damaged in the process. The light output power of the FF-LEDs had about 49% (with 5 μm spacing), 63% (10 μm), 20% (15 μm), and 12% (20 μm) enhancement when compared to the ST-LED at 20 mA, respectively, that was caused by a partial compressed strain release at the GaN/sapphire interface by forming the tapered GaN structure. The compressed strain of the 5μm-spacing FF-LED was measued at a 0.29 GPa compared with the ST-LED (0.99 GPa) through the Raman spectra measurement that caused by forming the air void and inverted pyramid shaped structures on the roughened patterned backside at the GaN/Al2O3 interface. In the FF-LED structure, the piezoelectric field in the InGaN active layer was reduced by forming the air void structure and inverted pyramid shaped structure. The air void and inverted pyramid shaped structures at the GaN/Al2O3 interface were fabricated through these two kinds of fabrication processes on the GaN LED structures to enhance light extraction efficiency and reduce the compressive strain induced piezoelectric filed for the high efficiency GaN-based LED applications.
URI: http://hdl.handle.net/11455/10317
其他識別: U0005-2606201210131200
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