Abstract
We demonstrate the highly efficient, GaN-based, multiple-quantum-well light-emitting diodes (LEDs) grown on Si (111) substrates embedded with the AlN buffer layer using NH3 growth interruption. Analysis of the materials by the X-ray diffraction omega scan and transmission electron microscopy revealed a remarkable improvement in the crystalline quality of the GaN layer with the AlN buffer layer using NH3 growth interruption. This improvement originated from the decreased dislocation densities and coalescence-related defects of the GaN layer that arose from the increased Al migration time. The photoluminescence peak positions and Raman spectra indicate that the internal tensile strain of the GaN layer is effectively relaxed without generating cracks. The LEDs embedded with an AlN buffer layer using NH3 growth interruption at 300 mA exhibited 40.9% higher light output power than that of the reference LED embedded with the AlN buffer layer without NH3 growth interruption. These high performances are attributed to an increased radiative recombination rate owing to the low defect density and strain relaxation in the GaN epilayer.
Highlights
Substantial progress in fabricating highly efficient, GaN-based, multiple-quantumwell (MQW) light-emitting diodes (LEDs) has proven these materials useful in a variety of applications, such as micro-displays, automobiles, general lighting, and optoelectronics [1,2,3]
We demonstrate that AlN layers prepared with NH3 growth interruption to be served as a buffer layer improve the crystalline quality and strain relaxation in GaN-based LEDs grown on Si (111) substrates
The X-ray diffraction (XRD) results revealed low FWHM values for GaN grown on AlN layers using the NH3 growth interruption method; it established substantially improved crystal quality compared to the reference LED embedded with the AlN buffer layer without NH3 growth interruption
Summary
Substantial progress in fabricating highly efficient, GaN-based, multiple-quantumwell (MQW) light-emitting diodes (LEDs) has proven these materials useful in a variety of applications, such as micro-displays, automobiles, general lighting, and optoelectronics [1,2,3]. GaN-based epitaxial-layers for LED devices are conventionally fabricated on sapphire and SiC substrates. The sapphire substrate has poor thermal conductivity—as low as 25 Wm−1 K−1 —that encourages heat dissipation. It is a critical issue in high-output LED operation. GaN and SiC substrates are expensive and still limitedly used in large-scale LED fabrication than a sapphire substrate [4,5]. The large-scale Si substrate has attracted significant interest in growing GaN-based devices owing to lower cost than the traditional sapphire and SiC substrates [6,7]. Si substrate can be integrated with electronic and optical devices [8]
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