Analysis of Water Vapor and Saline Environment Reliability Degradation Mechanisms in InGaN/GaN LEDs by Reverse-Bias Stress

[[abstract]]本論文提出利用逆向偏壓的方式，在短時間內快速瞭解發光二極體壽命與可靠性，並且將元件操作於乾燥、濕氣及鹽霧環境下，仔細探討元件衰退的過程。研究中使用半導體參數分析儀量測元件電流-電壓特性曲線，低溫CCD光學顯微鏡以及積分球量測元件電致發光影像以及光學特性，材料的方面我們利用掃描式電子顯微鏡(SEM)觀測元件橫截面，並從能量散佈質譜器(EDX)與二次離子質譜儀(SIMS)進行元素成分定量分析和瞭解發光層與電極周遭元素分布的變化，並搭配低頻雜訊(Low Frequency Noise)量測分析元件缺陷密度的多寡。 電性透過取對數刻度的分析，明顯觀察到元件逐漸衰退的現象，包含臨界電壓的改變、出現串聯電阻及並聯電阻等效應，說明載子藉由半導體表面態傳輸機制，或是元件在偏壓下逐步造成深層缺陷的增加最終導致失效。而從電致發光影像以及波長的變化，可以藉由逆向偏壓產生發光的現象快速辨別漏電流在元件上分布的路徑，以及電子電洞在缺陷中複合造成光譜中出現微小波包。此外由元素分布的量測，發現電極和多重量子井中的金屬元素存在電致遷移的現象，以及低頻雜訊逐漸增大進一步說明，因為較多的缺陷而產生的熱載子(Hot-Carrier Induced)，使得元件造成衰退。本實驗藉由各種分析方法觀察元件各種衰退特性，可以有效提升新產品研發效率、加速可靠性測試、製程改良與生產品管等應用。[[abstract]]In this thesis, we present a technique to quickly investigate the lifetime and reliability of light emitting diode by using the reverse-bias stress, and the devices were operated in dry air, water vapor and salty water condition. The current-voltage (I-V) curve were measured with the Agilent 4155C semiconductor parameter analyzer. The electroluminescence image and optical characterizations were measured with low temperature CCD optical microscope and integrating sphere. The material characteristics of the LEDs were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometers (EDS), secondary ion mass spectrometer (SIMS) and Low Frequency Noise (L-F Noise). The current-voltage (I-V) curve on a logarithmic scale analysis can be clearly observed the behavior of degradation, such as threshold voltage change, resistance and parallel resistance effect. The result indicates that the carrier transport mechanism by semiconductor surface states, or devices in the bias caused by the gradual increase in the deep defect eventually led to failure, and electromigration may cause LED generate damage, due to the diffusion of metal atoms. These techniques were proposed to describe an actual optical degradation and detect the device failures with the fabrication process for future industrial applications.[[note]]碩