應用濕蝕刻處理於圖案化藍寶石基板之氮化鎵發光二極體特性分析

Abstract

本論文中主要研究應用濕蝕刻處理於圖案化藍寶石基板(Patterned Sapphire Substrates；PSS)進行氮化鎵發光二極體特性分析，探討濕蝕刻處理於蝕刻機制進行探討，並應用兩種不同規格的濕蝕刻處理於PSS進行氮化鎵藍光發光二極體結構的成長，分析發光二極體結構成長於兩種不同規格濕蝕刻處理於PSS對於氮化鎵發光二極體元件光電特性的影響。2.8-PSS的直徑、間距、高分別為2.8、0.2、1.8。2.9-PSS的直徑、間距、高分別為2.9、0.1、1.9。 於PSS經過濕蝕刻處理經由Scanning Electron Microscopy；SEM觀察，會在圖案化區域產生晶格面。分析圖案化區域產生的晶格面可以發現經過濕蝕刻處理後，會同時產生r-plane與n-plane。接著在濕蝕刻處理於PSS上使用氮化鎵緩衝層與濺鍍氮化鋁(PVD AlN)緩衝層成長氮化鎵薄膜，發現到使用氮化鎵緩衝層在濕蝕刻處理於PSS上成長氮化鎵薄膜，氮化鎵薄膜會同時於PSS的n-plane與c-plane成長；使用濺鍍氮化鋁緩衝層在濕蝕刻處理於PSS再成長氮化鎵薄膜，由於氮化鋁緩衝層覆蓋性佳，搭配氮化鎵薄膜成長機制可有選擇性於PSS的c-plane區域成長，進而填平圖案化之表面，由X-ray繞射儀量測氮化鎵薄膜(002)面與(102)面結果顯示，未經過濕蝕刻處理與經過濕蝕刻處理的PSS其(002)面與(102)面分別維持在500與410arcsec。 接著將濺鍍氮化鋁緩衝層可以穩定成長氮化鎵薄膜的特性，直接成長氮化鎵發光二極體在濕蝕刻處理於PSS上，再利用黃光微影製成技術製作成發光二極體元件，並量測其光電特性，其在電特性方面得到2.8規格與2.9規格的圖案化藍寶石基板發光二極體Vf都維持在3.5V，進一步驗證濺鍍氮化鋁緩衝層可以維持氮化鎵薄膜品質，在光性方面量測光輸出功率得到2.8規格的PSS經過濕蝕刻處理後提升28.2%；2.9規格的PSS經過濕蝕刻處理後提升13.5%，故使用濕蝕刻處理於PSS結合PVD AlN技術可以得到相同的氮化鎵薄膜品質且可有效地提升光輸出功率。

The main application of this paper involves the wet etching process. Patterned sapphire substrates (PSS) were fabricated and used in a GaN LED. The wet etching process was performed to explore and apply two different specifications of the wet etching process, and the GaN light-emitting diode was then characterized in terms of its optical and electrical properties. The pattern diameter, spacing, and height of the 2.8-PSS were 2.8, 0.2, and 1.8 μm. The pattern diameter, spacing, and height of the 2.9-PSS were 2.9, 0.1, and 1.9 μm. After the wet etching treatment, lattice planes were observed in the patterned region, as indicated by the SEM results. The patterned region also contained r- and n-planes. GaN buffer layers were simultaneously formed on the n- and c-planes. The sputtered AlN (PVD AlN) buffer process further enhanced the growth of the GaN on PSS .Thus, the GaN film can be selectively grown on the c-plane area of the PSS and then fill the remaining areas of the patterned surface. The (102) and (002) planes of all samples were maintained at 500 and 410 arcsec. The PVD AlN buffer layer can stabilize the growth characteristics of GaN films directly grown on GaN LEDs via the wet etching process. Photolithography technology was used to produce an LED devices, the optical and electrical properties of which were subsequently determined. The Vf of LEDs on patterned sapphire substrates with specifications of 2.8-PSS and 2.9 –PSS were maintained at 3.5 V, thereby further confirming that PVD AlN buffer layer can maintain the electrical characteristics of the GaN film. The output power increased by 28.2% in the PSS with a specification of 2.8, whereas that in the PSS with a specification of 2.9 increased by 13.5%. The wet etching process combined with PVD AlN can produce with GaN film and effectively improve the optical output power.