Hybrid simulation of light extraction efficiency in multi-quantum-shell (MQS) NW (nanowire) LED with a current diffusion layer

Abstract

A multi-quantum-shell (MQS) grown on a GaN nanowire is a promising three-dimensional active region and it is expected to show excellent performance, compared with conventional nitride-based LEDs. However, there are no suitable simulators for calculating optical properties of MQS-LEDs, because of their complex structure. In this study, a hybrid simulation, which is composed of the finite-difference time-domain method, the rigorous coupled wave analysis method, and the ray tracing method, is developed. Applying this useful tool to the calculation of the light extraction efficiency (LEE) of MQS-LEDs, we have found considerable light absorption loss by the large refractive index steps between the active layer, ITO layer and air in the commonly used MQS-LED structure with the ITO electrode. Thus, to eliminate the large refractive index steps, the MQS-LED buried with the n-GaN current diffusion layer, which has a high LEE, was proposed.

Structural and optical impacts of AlGaN undershells on coaxial GaInN/GaN multiple-quantum-shells nanowires

“…A plane-wave excitation source from the topside of NWs was used for the reflectance simulation. The details of the simulation process can be found in a previous paper [13]. The reflectance for MQS NW arrays was simulated for the macro-and micro-PL setup, as well as the case in planar multiple-quantum wells (MQW) structures.…”

“…Over the past decade, GaN-based nanowires (NWs) have received significant attention as a prime candidate for future high-performance nanoscale-optoelectronic devices, such as white LEDs, nanoscale lasers, and micro-LEDs [5][6][7][8][9][10][11][12]. GaInN/GaN coaxial NW structures have a large surface-to-volume ratio and possess intriguing advantages in comparison to their thin-film/bulk counterparts: (i) significantly reduced threading dislocations, (ii) improvement of light extraction efficiency, (iii) absence of the QCSE in nonpolar m-planes of the NWs, and (iv) large active regions with a core-shell geometry on m-and r-planes [3,13,14]. In addition, the incorporation of indium in GaInN/ GaN multiple-quantum-shells (MQSs) can be tuned with the NW diameter, providing the possibility to achieve monolithically integrated white light emission [15,16].…”

Three-Method Hybrid Numerical Simulation for Surface-Plasmon-Enhanced GaInN-Based Light-Emitting Diodes with Metal-Embedded Nanostructures

“…In this section, the LEEs of an LED with Ag-NP-embedded nanostructures are calculated by the RT method using data from the dispersion characteristics. To incorporate the effect of a periodical nanostructure array on the RT simulation, the dispersion characteristics from the RCWA method were referenced at the p-GaN surface of the LED instead of a simple n. In detail, when the rays reach the p-GaN surface, the data of the angle distribution of the R and T from the RCWA method are taken into account [28]. A configuration of the RT is shown in Figure 5A, and 500,000 rays were simulated in random directions from the MQWs.…”

“…Meanwhile, the finite-difference time-domain (FDTD) method is often adopted to calculate the SP effect in LEDs, but this method is only suitable for calculating one specific nanostructure. That is, it is unreasonable to practically use the FDTD method because it takes an enormous amount of time to expand and apply it to an entire LED structure [28]. Hence, the FDTD method is typically limited to the computational domains of a few micrometers, despite of advantages such as accuracy, considering the nature of the wave, and the dispersion relation.…”

Growth Defects in InGaN‐Based Multiple‐Quantum‐Shell Nanowires with Si‐Doped GaN Cap Layers and Tunnel Junctions

“…Owing to these advantages, a light-emitting device with an MQS structure can provide high luminous efficiency and new device structure. [18][19][20][21][22][23][24][25][26][27] For example, laser diodes (LDs) are promising devices that use MQS technology, where high light confinement can be achieved in the waveguide. [28] To widely commercialize such NW-MQS-based light-emitting devices, conventional processing technology should be applied.…”