光致电化学法提高垂直结构发光二极管出光效率的研究?
Increase in light extraction e?ciency of vertical light emitting dio des by a photo-electro-chemical etching metho d
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摘要: 研究了在垂直结构发光二极管(VLED)器件中,光致电化学法(PEC)刻蚀N极性n-GaN的速率受不同刻蚀条件(刻蚀浓度、刻蚀时间和光照强度)的影响.并选择N极性n-GaN表面含有较理想六角金字塔结构(侧壁角为31?)的样品制成器件,研究PEC刻蚀对VLED的欧姆接触和光电性能的影响.结果表明,与未粗化样品相比, PEC刻蚀后的样品接触电阻率明显降低,形成更好的欧姆接触;其电学特性有较好的改善,光输出功率有明显提高,在20 mA电流下光输出功率增强了86.1%.对不同金字塔侧壁角度的光提取效率用时域有限差分法(FDTD)模拟,结果显示光提取效率在侧壁角度为20?—40?有显著提高,在23.6?(GaN-空气界面的全反射角)时达到最大.Abstract: The rate of photo-electro-chemical (PEC) etching on N-polar n-GaN using vertical light emitting diodes (V-LEDs) has been investigated in detail, by varying the etching parameters (etchant concentration, etching duration and light intensity). V-LED with optimal hexagonal pyramid structure (the side-wall angle is 31?) has been fabricated, and then the influence of the PEC etching on the electrical and optical properties of V-LED has been analyzed. After PEC etching, the sample has good ohmic contact with the electrode and has lower contact resistance than a reference sample. The electrical characteristics have a better improvement. And the light output power has improved obviously after PEC etching, which shows 86.1%enhancement at 20 mA. Effect of side-wall angle of the pyramids on light extraction e?ciency (LEE) in V-LEDs is theoretically calculated by finite difference time domain (FDTD) method. Simulation results show that the LEE is significantly increased for the sidewall angle between 20? and 40?, and the maximum enhancement is realized at a side-wall angle of 23.6? (the total reflection angle at the GaN/air interface).
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