Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/10747
標題: 利用雷射掃描及化學蝕刻技術製作具倒立六角錐結構之氮化銦鎵發光元件
InGaN-based Light-Emitting Diodes with Hexagonal Inverted Pyramid Structures Through Laser Scribing and Chemical Etching Processes
作者: 黃琬淳
Huang, Wan-Chun
關鍵字: Laser scribing
雷射掃瞄
chemical etching
InGaN-based LED
hexagonal inverted pyramid structures
化學蝕刻
氮化銦鎵發光元件
倒立六角錐結構
出版社: 材料科學與工程學系所
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摘要: 在本論文中,利用雷射掃描及化學側向蝕刻技術,在N-face 氮化鎵底部製作具倒立六角錐的晶格蝕刻面之發光二極體,對此發光元件的光, 電特性加以探討。將氮化銦鎵發光二極體磊晶片經由雷射做背面掃描熔融氮化鎵/藍寶石基板界面之低溫緩衝層,再藉由加熱氫氧化鉀溶液進行側向蝕刻,形成氮化鎵{10Π}穩定蝕刻晶格面,此元件稱Roughened Patterned Backside Light-Emitting Diode (RPB-LED)。氮化鎵緩衝層所扮演的角色為犧牲層,用於雷射的熔融及側向蝕刻,蝕刻速率約為26μm/min。具倒立六角錐N-face 氮化鎵表面結構之發光二極體,於接近氮化鎵/藍寶石基板界面相較於一般傳統發光二極體擁有較大之光散射效應,且在發光強度量測上有47%提升。 接著,我們將其技術應用於具圖案化藍寶石基板之發光二極體(pattern sapphire substrate-LED, PS-LED),來探討其倒立六角錐結構在此種基板上之影響效應。PS-LED強度本身較傳統LED要來的強,是由於圖案化的藍寶石基板,此種基板可增加光散射強度,實驗結論為BRPS-LED其光取出強度較PS-LED高21.4%,所以BRPS-LED整體強度提升效應是存在的。在發散角部份,BRPS-LED具有較大的發散角,是由於倒立六角錐結構造成光散射影響。且在背面取光部分,其PS-LED因圖案化之關係將光反射到正面取光,所以背面取光較弱,而做過處理之BRPS-LED其正面取光不但可提升,亦可提升背面光取出效率。 最後,將此技術改變雷射掃描線間距條件分別應用在平的藍寶石基板之發光二極體與圖案化藍寶石基板之發光二極體,並比較兩者之差異。透過電性分析,兩者的光強度在20mA下,隨雷射掃描線間距越小其光強度越強,是由於雷射掃描線越多所形成的背面角錐越多,所以光散射越強,可提升整體的光強度。在平的藍寶石基板之發光二極體中,其發散角會隨雷射掃描線間距越小而角度變小,是因為在氮化鎵與基板界面所形成的錐會使光趨於軸向發光,錐越多光會越集中於正上方發光。相反地,在圖案化藍寶石基板之發光二極體中,圖案化藍寶石基板本身就會使光趨於軸向發光,其發散角會隨雷射掃描線間距越小而角度變大,而角錐的光集中效應在此比圖案化基板要小,所以角錐在此扮演光散射的角色。
The InGaN-based light-emitting diodes (LEDs) with a roughened patterned backside on the N-ace GaN surface were fabricated through a crystallographic etching process to increase light extraction efficiency. After laser decomposition, laser scribing, and a lateral crystallographic wet etching process at the GaN/Al2O3 interface, stable crystallographic etching planes were formed as the GaN {10Π} planes that included an angle with the top GaN (0001) plane measured at 58o. The GaN buffer layer acted as the sacrificial layer for the laser decomposition process and the lateral wet etching process with a 26μm/min etching rate. The LED with the inverted pyramidal N-face GaN surface close to the GaN/Al2O3 interface has a larger light scattering process than the conventional LED. The light output power of the LED with the backside roughened surface had a 47% enhancement when measured in LED chip form. Then, this technique was used on the InGaN-based LED structure grown on a patterned-sapphire substrate (PS-LED) to form the hexagonal inverted pyramid structures. The light output power of the BRPS-LED with the backside roughened surface had a 21.4% enhancement compared to a conventional PS-LED in chip form. The larger divergent angle of BRPS-LED could be caused by light-scattering process from the inverted pyramidal-shaped structures on the roughened patterned backside surface at the GaN/Al2O3 interface. The high light intensity at the normal direction of the PS-LED caused by the higher light scattering process on the triangle-shaped patterned sapphire structure. In the BRPS-LED structure, the high light intensity was observed at the normal direction and the backside direction that was caused by the higher light scattering process on the inversed cone-shaped structure and the patterned sapphire substrate. We use the method on flat-sapphire LED and pattern-sapphire LED with different laser scribing line spacing and both LEDs were be compared. At 20mA operating current, the LED structures with the laser scribing multi-lines had the higher light emission intensity on the both LED structures that was caused by the forming the backside pyramidal-shaped structures. On the flat-sapphire LED, the smaller laser scribing line spacing results in the smaller divergent angle due to “the light-gathering at the axial from the pyramidal-shaped structures on the roughened the patterned backside surface at the GaN/Al2O3 interface. On the contrary, it occurs on pattern-sapphire LED that the higher divergent angle is owing to the smaller laser scribing line spacing because the pattern sapphire has more gathering light emission than the pyramidal-shaped structures effect that induces the light-scattering.
URI: http://hdl.handle.net/11455/10747
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