非等温模型下LED芯片性能与衬底的关系

发光二极管(LED)中载流子的输运及复合决定了其非均匀的内热源强度及分布,而芯片温度又影响载流子的输运及复合,两者具有强烈的耦合关系。本文利用非等温多物理场耦合模型对以蓝宝石、Si及SiC为衬底的 LED芯片的内量子效率、光谱特性及光电转换效率进行了系统研究。结果表明:以SiC为衬底的LED芯片具有最小的效率下垂效应(Efficiency droop)及最高的光谱强度和光电转换效率。这是因为与其他两种衬底的LED芯片相比,以SiC为衬底的LED芯片具有最好的散热性能,因此非均匀温度场对其载流子输运及复合的影响最小,使得活性区中的载流子浓度显著增强,漏电流明显下降。

Relationship Between Light-emitting Diode Performance and Different Substrates Working Under Non-isothermal Model

The carrier transport and recombination in light-emitting diodes(LEDs) determine the non-uniform intensity and distribution of the internal heat source.The non-uniform temperature field also influences the carrier transport and recombination in LEDs.Thus the carrier transport and recombination are strongly coupled with temperatures.In this paper,the internal quantum efficiency,spectrum characteristic and photoelectric conversion efficiency of LEDs with substrates of sapphire,Si and SiC are systematically studied by a non-isothermal multi-physics-field coupling model.It is shown that the LED with SiC substrate has the smallest efficiency droop effect and exhibits the highest spectrum intensity and photoelectric conversion efficiency,among the LEDs with substrates of sapphire,Si and SiC.This is because the LED with the substrate of SiC has the best thermal dissipation capability,thus the non-uniform temperature field has the smallest effect on the carrier transport and recombination,leading to the significantly enhanced carrier concentration in the active region and decreased current leakage.