氮化鎵發光二極體晶片之接面溫度研究與數值模擬

Abstract

本論文中，我們利用離子佈植技術製作了具自我散熱機能之發光二極體，並且使用順向偏壓法和紅外線熱像儀來量測發光二極體的接面溫度。實驗結果顯示，利用離子佈植技術製作之發光二極體的接面溫度皆遠低於缺乏此結構之發光二極體的接面溫度，藉由精準的紅外線熱像儀來量測，在100毫安培的電流之下可以測量到高達15℃的溫差，同時適宜的設計離子佈植區域更可以在100毫安培的電留下達到30.6%的發光強度增強。最重要的，利用高解析度的熱像儀影像，局部低溫區域的存在可直接被證實。 同時，藉由考慮發光二極體之帶電載子的分佈情形和發光強度的衰減以及其接面溫度，我們建立了一個完整的數值模擬模型。同時我們改變高電阻區域的深度、寬度以及間隔，模擬出帶電載子以及接面溫度在平面上的分佈情形。帶電載子因為高電阻區域的存在強迫轉向，形成一低功率損耗的區域，進而建立局部的低溫區域。並且藉由接面溫度的分佈圖，我們可以明顯觀察到此低溫區域的存在。此外我們考慮不同電流之下所伴隨不同程度的發光強度衰減，引入一項衰減參數進而發展出了一套模擬發光二極體發光強度衰減的模型。因此藉由此數值模擬，我們可以設計出具備自我散熱機能之發光二極體。 藉由數值模擬以及實驗的結果，利用高電阻區域來降低發光二極體接面溫度的效果是十分明顯且確定的。

In this thesis, we design and fabricate the on chip heat-dissipating LEDs by using ion implantation technology. With such structure, the local cold zones are built up to help heat dissipation due to current diverting mechanism. Two methods are used to measure the junction temperature of GaN based LEDs in this thesis. One is diode forward voltage method and the other is IR thermometer. From the experimental results, junction temperature of ion-implanted LEDs is about 15℃ lower than that of conventional one by IR thermometer at 100mA injection current. Optical power of a LED with appropriate design of ion-implantation regions can achieves 30.6% enhancement at 100mA. And the existence of local cold zones is directly proved with thermometer images. Furthermore, we build a complete simulation model of GaN based LEDs by considering the electrical carrier distribution, junction temperature and optical power behaviors at high injection. We plot the carrier distributions and junction temperature profiles with various depths, widths and intervals of high-resistivity stripes, and we can apparently observe the relative-low temperature regions are established. The current diverting effect and the heat accumulation can be optimized from analyses in the thesis. Moreover, we develop our own model to imitate the power saturation by introducing the saturation factor, which is evaluate by considering different driving current accompanying different saturation effect. This simulation provides a numerical method to design a low junction temperature LED with high-resistivity regions. The LEDs with low junction temperature can be achieved by creating local high-resistivity regions through both numerical and experimental evidences.