![]() However, due to high sheet resistance and the large work function difference between graphene and p-GaN, the use of graphene as a TCL adversely increases the operating voltage of LEDs 7, 11, 12, 13, 14. It has been demonstrated that the transparent 3D graphene foam was very effective in current spreading to enhance the performance of blue LEDs 11. One the other hand, graphene has been considered a promising material to replace ITO in GaN-based LEDs as a transparent conductive electrode 11, 12, 13, 14, 15, 16, 17, because of its high transmittance in the UV region, carrier mobility, and conductivity. Although device performance can be improved by using Indium Tin Oxide (ITO) used as a transparent conducting layer (TCL), the exclusive use of these oxides becomes problems such as cost, rarity supply of indium, and low optical transmittance in the ultraviolet wavelength regions 7, 8, 9, 10. Low resistance and transparent Ohmic contact to p-type GaN are crucial to improve current injection and light extraction efficiency of GaN-based LEDs 7, 8, 9, 10. III-nitrides have become the key material for light emitting diodes (LEDs), laser diodes, and solar cells 1, 2, 3, 4, 5, 6. These research results provide important information for the carrier transport, carrier capture, and recombination processes in InGaN/GaN MQW LEDs with graphene transparent conductive electrodes. In short, the LED samples, with the help of graphene electrodes, are shown to have a better carrier transport efficiency, better carrier capture efficiency, and more electron-hole recombination. Furthermore, as more carrier injected into the active regions of LEDs, thanks to graphene transparent conductive electrodes, excessive carriers need more time to proceed carrier recombination processes in QWs and result in a longer carrier recombination time. In addition, a shorter hole transport time will also expedite hole capture processes and result in a shorter capture time and better light emitting efficiency. The combined experimental and theoretical results clearly indicate that those LEDs with graphene transparent conductive electrodes at p-junctions will have a shorter hole transport time along the lateral direction and thus a more efficient current spreading and a larger luminescence area. In addition, the TREL data will be further analyzed by employing a 2- N theoretical model of carrier transport, capture, and escape processes. The results demonstrate that the applications of graphene electrodes on LED devices will spread injection carriers more uniformly into the active region and therefore result in a larger current density, broader luminescence area, and stronger EL intensity. In this work, InGaN/GaN multiple-quantum-wells light-emitting diodes with and without graphene transparent conductive electrodes are studied with current-voltage, electroluminescence, and time-resolved electroluminescence (TREL) measurements.
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