III-질화물, III-인화물계, III-비소화물 기반 발광 다이오드에서 내부 양자 효율, 광 추출 효율, 방사형 효율, 주입 효율에 대한 비교 분석

Comparative Analysis on Internal Quantum, Light-Extraction, Radiative, and Injection Efficiencies in III-Nitride-, III-Phosphide-, and III-Arsenide-based Light-Emitting Devices

This study attempts to understand and elucidate the factors limiting/determining the External quantum efficiency (EQE) of Light-emitting devices (LEDs) depending on material systems, i.e., III-arsenide (GaAs), III-phosphide (AlGaInP), and III-nitride (GaInN), via the temperature measurements (30-500 K). The behaviors of EQEs are investigated carefully in terms of the thermal droop and efficiency droop, revealing that the thermal droop in the AlGaInP and GaAs LEDs, while the efficiency droop in the GaInN LEDs are critical factors limiting the EQE. Since the EQE is determined by combining the Light-extraction efficiency (LEE) and the Internal quantum efficiency (IQE), it significantly depends on temperature and current injection levels. This study examines the causes of thermal and efficiency droop for different material system-based LEDs. To deepen the insight, the EQE is separated into the IQE and the LEE. Further, the IQE is separated into the radiative efficiency (RE) and the injection efficiency (IE). The analysis shows that the LEE plays a significant role in the thermal droop for the AlGaInP and GaAs LEDs. Meanwhile, the IE and RE play a significant role in the EQE reduction of the blue and red LEDs at high temperatures and high current injection. Through the experiment, it was found that EQE in IR and red LEDs were significantly affected by thermal efficiency reduction caused by temperature, while efficiency droop due to increased driving current had a greater impact on blue LED.