LED用石墨烯复合透明电极厚度组合的仿真与优化

为降低石墨烯(Gr)透明电极与p-GaN之间的肖特基势垒与接触电阻,进行了将银、金、镍和铂四种金属或氧化镍作为中间层引入它们两者之间的尝试。使用有限元方法模拟研究了Gr与金属或氧化镍的不同厚度组合对LED的光、热和电特性的影响。发现:透明导电层的透光率和LED芯片的表面温度均随石墨烯和金属或氧化镍厚度的增加而降低;1.5nm的Ag、Ni、Pt,1nm Au或1nm的NiO_x分别与3层(3L)Gr复合时为优化厚度组合,其中,1.5nm Ni/3L Gr为最佳Gr/金属复合透明电极。     

Design of transparent broadband double-sided absorbing metamaterial

By designing the ordered structure on the key physical dimensions, metamaterial can obtain extraordinary physical properties. The method gives transparent conductive absorbing metamaterial with broadband and high absorptivity. In this paper, a kind of absorbing metamaterial with indium tin oxide (ITO) glass substrate is designed. The design method of double-sided etched an open loop and linear metamaterial periodic structures is adopted. The thickness of the absorbing metamaterial is 2.5 mm. The research shows that the working bandwidth is between 8.9 GHz and 17.4 GHz, the absorption rate is 90%, and the transmittance of visible light is 85% on average. The absorbing metamaterial has wide application value to solve the problem of visualization and absorption characteristics.     

Simulation on effect of metal/graphene hybrid transparent electrode on characteristics of GaN light emitting diodes

In order to decrease the Schottky barrier height and sheet resistance between graphene(Gr) and the p-GaN layers in GaN-based light-emitting diodes(LEDs), some transparent thin films with good conductivity and large work function are essential to insert into Gr and p-GaN layers. In this work, the ultra-thin films of four metals(silver(Ag), golden(Au), nickel(Ni), platinum(Pt)) are explored to introduce as a bridge layer into Gr and p-GaN, respectively. The effect of a different combination of Gr/metal transparent conductive layers(TCLs) on the electrical, optical, and thermal characteristics of LED was investigated by the finite element methods. It is found that both the TCLs transmittance and the surface temperature of the LED chip reduces with the increase of the metal thickness, and the transmittance decreases to about 80% with the metal thickness increasing to 2 nm. The surface temperature distribution, operation voltage, and optical output power of the LED chips with different metal/Gr combination were calculated and analyzed. Based on the electrical, optical, and thermal performance of LEDs, it is found that 1.5-nm Ag or Ni or Pt, but 1-nm Au combined with 3 layered(L) Gr is the optimal Gr/metal hybrid transparent and current spreading electrode for ultra-violet(UV) or near-UV LEDs.