InGaN-based Light-Emitting Diodes with Hexagonal Inverted Pyramid Structures Through Laser Scribing and Chemical Etching Processes

• Main Authors: Wan-Chun Huang, 黃琬淳
• Other Authors: 林佳鋒
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/55523082852487246105

碩士 === 國立中興大學 === 材料科學與工程學系所 === 98 === 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.