本論文主要研究成長不同濃度之n型GaN薄膜於奈米柱GaN/藍寶石基板來改善Planar GaN發光二極體之電流擁擠現象，期望應用在大電流密度下提升整個GaN發光二極體電流擴散之均勻性。文中首先分別成長不同濃度之n型GaN薄膜於傳統GaN基板及奈米柱GaN/藍寶石基板，接著量測分析其n型GaN薄膜在兩者基板之間的材料特性差異，接著成長不同濃度之n型GaN薄膜的GaN發光二極體結構應用在此兩者基板上，並探討不同濃度之n型GaN薄膜對於GaN發光二極體之光電特性表現的差異性。 由GaN發光二極體電流擴散原理得知，使n型GaN薄膜電阻值與表面氧化銦錫( ITO )薄膜電阻值越匹配，其電流分佈越均勻，因此本研究是藉由成長高濃度的n型GaN薄膜來降低n型GaN薄膜之電阻值，而成長較高濃度的n型GaN薄膜會因為過多的Si摻雜而使得薄膜品質較差，為了不讓增加Si摻雜而影響GaN薄膜品質，我們使用奈米柱GaN/藍寶石基板成長GaN薄膜，可抑制薄膜缺陷密度不因摻雜高濃度Si而增加。 我們再利用奈米柱GaN/藍寶石基板成長GaN發光二極體結構，並比較結構中有不同濃度之n型GaN薄膜對於影響電流在GaN發光二極體分佈的均勻性。由量測結果得知，使用奈米柱GaN/藍寶石基板比傳統GaN基板成長之GaN發光二極體，其光輸出功率在20 mA下，由5.8 mW上升至6.5 mW，提高約12％，而在相同使用奈米柱GaN/藍寶石基板，我們調整n型GaN薄膜電阻值使其和氧化銦錫( ITO )薄膜電阻值匹配，其光輸出功率在20 mA下由6.5 mW上升至7.5 mW，順向電壓皆為3.4 V。 經本研究結果得知，使用奈米柱GaN/藍寶石基板所成長的GaN發光二極體與傳統GaN發光二極體有較佳的光電特性表現，且在此奈米柱GaN/藍寶石基板所成長的GaN發光二極體結構下，最佳的 n型GaN薄膜之濃度為1.6╳1019/cm3，並量測大電流密度注入條件下，能改善其電流擁擠現象，使電流分佈更為均勻，增加光輸出功率。 This thesis investigation, we studied the growth of different concentrations of n-type GaN film on the nanorods GaN / sapphire substrate to improve the p-side-up mesa-structure GaN LED of the current crowding, expectations used in high current density to enhance the current spreading uniformity of GaN LED. First, Growth of different concentrations of n-type GaN film on the nanorods GaN / sapphire substrate, the surface morphology and structural characteristics were analyzed. Next, we make use of theory to calculate the current distribution of different concentrations of n-type GaN film grown on the nanorods GaN / sapphire substrate.When the resistance of n-type GaN film and the transparent current layer were match so that the current is distributed will be even. Therefore, we grow high concentrations of n-type GaN film to reduce the resistance of n-type GaN film, but heavily Si-doped of n-type GaN film could made film quality has poor. So, we using nanorods GaN / sapphire substrate could effectively suppress the threading dislocation density by increasing Si-doped of n-type GaN film. The measurement results revealed that GaN LED grown on nanorods GaN / sapphire substrate GaN substrate, at 20mA injection current, the optical output power was enhanced by 12%, respectively, compared to those of a conventional LED.We adjusted the different reisistance of n-type GaN film grown on nanorods GaN / sapphire substrate, the light output power was enhanced by 15%, because of changing n-type GaN film resistance could let the current distributed evenly.
