Abstract
The two-dimensional (2D) triangle lattice air hole photonic crystal (PC) GaN-based light-emitting diodes (LED) with double-layer graphene transparent electrodes (DGTE) have been produced. The current spreading effect of the double-layer graphene (GR) on the surface of the PC structure of the LED has been researched. Specially, we found that the part of the graphene suspending over the air hole of the PC structure was of much higher conductivity, which reduced the average sheet resistance of the graphene transparent conducting electrode and improved the current spreading of the PC LED. Therefore, the work voltage of the DGTE-PC LED was obviously decreased, and the output power was greatly enhanced. The COMSOL software was used to simulate the current density distribution of the samples. The results show that the etching of PC structure results in the degradation of the current spreading and that the graphene transparent conducting electrode can offer an uniform current spreading in the DGTE-PC LED.PACS: 85.60.Jb; 68.65.Pq; 42.70.Qs
Highlights
The GaN-based light-emitting diodes (LED) have recently attracted considerable interest because of advantages in low energy consumption, high brightness, and long lifetime
The B2# sample shows uniform light emitting over the entire LED surface, indicating that the double-layer graphene film offers a sufficient current spreading
The work voltage of the A2# is 1 V lower than that of A0#, while the work voltage of the B2# sample is 1.5 V lower than that of B0#. This indicates that the double-layer graphene can greatly reduce the series resistance of LED, especially for photonic crystal (PC) LED due to improving the current spreading
Summary
The GaN-based light-emitting diodes (LED) have recently attracted considerable interest because of advantages in low energy consumption, high brightness, and long lifetime. They have been widely used in various applications, such as full-color displays, general lighting, etc. The low light extraction efficiency (ηextr) is a primary obstacle to the realization of higher brightness GaN LED [4,5,6]. With spatially periodic refractive index, the PC structure is one of the most promising approaches to efficiently reduce the loss caused by the total internal reflection at the interface of the GaN and the air [3,4,5,6,7].
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