^{1}, Hung-Chih Yang

^{2}, Ta-Cheng Hsu

^{2}, Yu-Jiun Shen

^{2}, Ai-Sen Liu

^{2}and Yuh-Renn Wu

^{1,a)}

### Abstract

This paper presents the findings of investigating core-shell multiple quantum well nanowire light-emitting diodes (LEDs). A fully self-consistent three dimensional model that solves Poisson and drift-diffusion equations was employed to investigate the current flow and quantum-confined stark effect. The core-shell nanowire LED showed a weaker droop effect than that of conventional planar LEDs because of a larger active area and stronger recombination in nonpolar quantum wells (QWs). The current spreading effect was examined to determine the carrier distribution at the sidewall of core-shell nanowire LEDs. The results revealed that a larger aspect ratio by increasing the nanowire height could increase the nonpolar-active area volume and reduce the droop effect at the same current density. Making the current spreading length exceed a greater nanowire height is critical for using the enhancement of nonpolar QWs effectively, when an appropriate transparent conducting layer might be necessary. In addition, this paper presents a discussion on the influences of the spacing between each nanowire on corresponding nanowire diameters.

This work is supported by National Science council in Taiwan by Grant Nos. NSC 99-2221-E-002-058-MY3, and NSC 100-2221-E-002-153-MY2.

I. INTRODUCTION

II. FORMALISM

III. RESULT AND DISCUSSION

IV. CONCLUSION

### Key Topics

- Nanowires
- 48.0
- Quantum wells
- 40.0
- Light emitting diodes
- 22.0
- Electrical resistivity
- 18.0
- Carrier density
- 12.0

## Figures

(a) A schematic model of the conventional planar LED chip. (b) A schematic model of a single CNL without TCL. (c) A schematic model of a single CNL with TCL. (d) A schematic distribution of core-shell nanowire arrays, which shows that the effects of the spacing between each nanowire is examined appropriately by the 3D simulation.

(a) A schematic model of the conventional planar LED chip. (b) A schematic model of a single CNL without TCL. (c) A schematic model of a single CNL with TCL. (d) A schematic distribution of core-shell nanowire arrays, which shows that the effects of the spacing between each nanowire is examined appropriately by the 3D simulation.

The schematic structure of a single CNL. (a) The simulation structure with mesh grids constructed by the GMSH program. (b) The cross-sectional (x-y plane) potential distribution from the view of the c-axis (z-axis). (c) The cross-sectional (y-z plane) potential distribution from the view of the x-axis.

The schematic structure of a single CNL. (a) The simulation structure with mesh grids constructed by the GMSH program. (b) The cross-sectional (x-y plane) potential distribution from the view of the c-axis (z-axis). (c) The cross-sectional (y-z plane) potential distribution from the view of the x-axis.

(a) The vertical line plot of normalized radiative recombination along the outer nonpolar QW with various nanowire heights at current density equal to 300 A/cm2. (b) IQE versus different current densities (A/cm2) with various nanowire heights. The inset in (b) is the ratio of Auger recombination versus different current densities (A/cm2).

(a) The vertical line plot of normalized radiative recombination along the outer nonpolar QW with various nanowire heights at current density equal to 300 A/cm2. (b) IQE versus different current densities (A/cm2) with various nanowire heights. The inset in (b) is the ratio of Auger recombination versus different current densities (A/cm2).

(a) The vertical line plot of normalized radiative recombination along the outer nonpolar QW with different resistivities of the TCL. (b) The cross-sectional radiative recombination distribution without the TCL from the view of y-axis (x-z plane). (c) The cross-sectional radiative recombination distribution with the optimized TCL from the view of y-axis (x-z plane). The current density is 300 A/cm2 for all cases.

(a) The vertical line plot of normalized radiative recombination along the outer nonpolar QW with different resistivities of the TCL. (b) The cross-sectional radiative recombination distribution without the TCL from the view of y-axis (x-z plane). (c) The cross-sectional radiative recombination distribution with the optimized TCL from the view of y-axis (x-z plane). The current density is 300 A/cm2 for all cases.

(a) The vertical line plot of normalized radiative recombination along the outer nonpolar QW for the optimized current spreading effect. The inset in (a) is the required resistivity of the TCL to optimize the current spreading effect with different nanowire heights. (b) IQE versus different current densities (A/cm2) for the optimized current spreading effect. The current density is 300 A/cm2 for Figs. 5(a) and 5(b) .

(a) The vertical line plot of normalized radiative recombination along the outer nonpolar QW for the optimized current spreading effect. The inset in (a) is the required resistivity of the TCL to optimize the current spreading effect with different nanowire heights. (b) IQE versus different current densities (A/cm2) for the optimized current spreading effect. The current density is 300 A/cm2 for Figs. 5(a) and 5(b) .

The comparison between the conventional planar LED and a single CNL. (a) The Overflow and Auger ratios versus different current densities (A/cm2). (b) IQE versus different current densities (A/cm2). (c) The lateral line plot of normalized radiative recombination along the nonpolar QWs at current density equal to 300 A/cm2.

The comparison between the conventional planar LED and a single CNL. (a) The Overflow and Auger ratios versus different current densities (A/cm2). (b) IQE versus different current densities (A/cm2). (c) The lateral line plot of normalized radiative recombination along the nonpolar QWs at current density equal to 300 A/cm2.

(a) IQE versus different current densities (A/cm2) with various nanowire diameters for 2D simulation. (b) IQE versus different current densities (A/cm2) with various nanowire diameters for 3D simulation. (c) The vertical line plot of normalized radiative recombination along the outer nonpolar QW for the 2D and 3D simulation. (d) The vertical line plot of normalized radiative recombination along the outer nonpolar QW with various nanowire diameters. The current density is 300 A/cm2 for Figs. 7(c) and 7(d) .

(a) IQE versus different current densities (A/cm2) with various nanowire diameters for 2D simulation. (b) IQE versus different current densities (A/cm2) with various nanowire diameters for 3D simulation. (c) The vertical line plot of normalized radiative recombination along the outer nonpolar QW for the 2D and 3D simulation. (d) The vertical line plot of normalized radiative recombination along the outer nonpolar QW with various nanowire diameters. The current density is 300 A/cm2 for Figs. 7(c) and 7(d) .

## Tables

The detailed parameters of each epi-layer for our simulation structures.

The detailed parameters of each epi-layer for our simulation structures.

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