1. State Key Laboratory of Mechanical Transmission, College of Physics, Chongqing University, Chongqing 400044, China; 2. College of Software, Chongqing College of Electronic Engineering, Chongqing 401331, China; 3. College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400047, China; 4. Chongqing Engineering Research Center of Graphene Film Manufacturing, Chongqing 401331, China; 5. College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 401331, China
Abstract 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.
Fund: Project supported by the National High-Technology Research and Development Program of China (Grant No. 2015AA034801), the Foundation of the State Key Laboratory of Mechanical Transmission of Chongqing University (Grant Nos. SKLMT-ZZKT-2017M15, SKLM-ZZKT-2015Z16, and SKLMT-KFKT-201419), the National Natural Science Foundation of China (Grant Nos. 11374359, 11304405, and 11544010), the Natural Science Foundation of Chongqing (Grant Nos. cstc2015jcyjA50035 and cstc2015jcyjA1660), the Fundamental Research Funds for the Central Universities, China (Grant Nos. 106112017CDJQJ328839, 106112014CDJZR14300050, 106112016CDJZR288805, and 106112015CDJXY300002), and the Sharing Fund of Large-scale Equipment of Chongqing University (Grant Nos. 201606150016, 201606150017, and 201606150056).
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