氫氧化四甲基銨側壁處理之微米級氮化銦鎵/氮化鋁鎵紫外光發光二極體研究

Abstract

使用在光鋐科技股份有限公司購買之紫外光波長的InGaN/AlGaN磊晶片製造方形發光區域的微米等級發光二極體，本實驗製程的元件有多個尺寸，發光區域的邊長有3µm、5µm、10µm、15µm、20µm、25µm、50µm、75µm以及100µm。整套實驗包含了元件及光罩設計、製程，還有最後的電性和光學量測。 在p型電極及p型半導體之間加入一層氧化銦錫透明導電層來增加電流流經元件的均勻性，同時可以縮小p型電極在發光區域上覆蓋的面積，以減少被電極遮住的光子。在乾蝕刻元件以後，我們將晶片泡入氫氧化四甲基銨(TMAH)中濕蝕刻，可以消除感應耦合式電漿蝕刻(ICP-RIE)對元件造成的側壁缺陷，將側壁平坦化，如此一來便能減少側壁的表面非輻射複合，達到外部量子效率的提升，另外，消除缺陷的同時也可以一併使得元件的漏電流縮小。

In this experiment, micro-scale light-emitting diodes (LEDs) with square light-emitting areas were manufactured using InGaN/AlGaN epitaxial wafers, with ultraviolet wavelengths. The devices in this experimental process come in various sizes, with the side lengths of the light-emitting areas being 3µm, 5µm, 10µm, 15µm, 20µm, 25µm, 50µm, 75µm, and 100µm. The entire experiment includes device and mask design, processing, and final electrical and optical measurements. To increase the uniformity of current flowing through the device, indium tin oxide (ITO) transparent conductive layer was added between the p-type electrode and the p-type semiconductor. This also allows for a reduction in the area covered by the p-type electrode over the light-emitting region, minimizing the blockage of photons. After dry etching the device, the wafer was immersed in tetramethylammonium hydroxide (TMAH) for wet etching, which eliminates sidewall defects caused by inductively coupled plasma etching (ICP-RIE) and flattens the sidewalls. This reduces surface non-radiative recombination on the sidewalls, leading to an improvement in external quantum efficiency. Additionally, while eliminating defects, it also helps to reduce the leakage current of the device.