Enhancing the Efficiency of Nitride-Based Light-Emitting Diodes: Design of Device Structure to Reduce Droop and Polarization Effects

Nitride-based light-emitting diodes (LEDs) have tremendous potential in energy efficient solid-state lighting. However, fundamental properties of the nitride material system have made further progress towards higher efficiencies more and more difficult. Two characteristics of nitride-based devices, droop and polarization effects, are unique to this material system. The reduction of droop is approached in two ways, increasing the effective active volume to reduce Auger recombination, and increasing hole injection to improve carrier uniformity and reduce electron overflow. To implement these concepts, sophisticated structures must be designed and their physical operation must be examined. In this dissertation, these physical phenomena are studied through the design of device structures by numerical simulation (APSYS, Crosslight Inc.), and the influence of these detrimental effects is shown to be reduced considerably with these improved structures. The findings presented in this dissertation are expected to provide insight and guidance into the production of next-generation commercial LED devices.

關鍵字

light-emitting diodes ； numerical simulation ； III-nitrides ； optoelectronics

並列摘要

氮化物發光二極體（light-emitting diodes）在節能固態照明應用上有很大的潛能，但是氮化物材料系統的基本特性讓其元件效率要被繼續提升更加的困難，其中，效率衰退（efficiency droop）與極化效應（polarization effects）是此材料系統中兩個相當獨特的特性。本研究經由兩種方法降低efficiency droop：（1）藉由增加活性層的有效體積降低Auger再結合，（2）藉由增加電洞注入提升載子在活性層的均勻分布及降低電子溢流。要實現這些概念，需要先設計完整的結構並解釋元件的物理原理，本論文藉由理論模擬的方式（APSYS, Crosslight Inc.）設計元件結構並探討這些物理現象，且經由結構上的改善，上述兩項效應的影響可被有效地降低。本研究希望能提供物理分析及方向，以作為下一代商業化發光二極體元件的參考。

並列關鍵字

發光二極體；數值模擬；三五族；光電元件

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