电极耦合层对GaN基蓝光LED出光特性的影响

Effect of coupling layer of p-contact on light-extraction efficiency of nitride-based light-emitted diodes

光提取效率的提高对GaN基蓝光LED的广泛应用有重要的影响.计算了以Ni/Au基金属化方法形成的p型GaN电极的折射率,通过分析电极层中的能流传输情况在电极上设计高折射率的耦合层来减少电极层对光的吸收以及提高光的透射,耦合层通过采用圆台结构来减少光在空气/耦合层界面上的全反射以提高GaN基蓝光LED的光提取效率。应用传输矩阵法计算的结果表明,光学厚度为π/2,折射率为2.02的ITO耦合层能使450 nm的蓝光在膜系上的透射率提高到75%。

Extensive application of GaN-based blue LED is greatly affected by increase in light-extraction efficiency. Refraction index of Ohmic contact to p-type GaN developed by oxidizing Ni/Au thin films is calculated. Power flow propagation within the p-contact is analyzed and coupling layer with proper refraction index over the p-contact is design to reduce light-absorption and reflection by p-contact. Frustum of cone structure scheme of ITO layer is applied to attenuating total reflectance （ATR） of the interface between air and ITO so that light-extraction efficiency of GaN-based LED can be increased. Result calculated by transfer matrix method shows that transmissivity of coupling layer/p-contact films at 450 nm wavelength increases to 75% for the ITO coupling layer with optical thickness of π/2 and refraction index of 2.02.