Optical Characterization of GaN-Based Vertical Blue Light-Emitting Diodes on P-Type Silicon Substrate

Yu Lei,Shengjun Zhou,Jiahao Miao,Bin Tang,Yingce Liu,Zehong Wan,Hui Wan,Shuyu Lan

doi:10.3390/cryst10070621

Abstract

Fabricating GaN-based light-emitting diodes (LEDs) on a silicon (Si) substrate, which is compatible with the widely employed complementary metal–oxide–semiconductor (CMOS) circuits, is extremely important for next-generation high-performance electroluminescence devices. We conducted a systematic investigation of the optical properties of vertical LEDs, to reveal the impacts of the manufacturing process on their optical characteristics. Here, we fabricated and characterized high-efficiency GaN-based LEDs with integrated surface textures including micro-scale periodic hemispherical dimples and nano-scale random hexagonal pyramids on a 4 inch p-type Si substrate. The highly reflective Ag/TiW metallization scheme was performed to decrease downward-absorbing light. We demonstrated the influence of transferring LED epilayers from a sapphire substrate onto the Si substrate on the emission characteristics of the vertical LEDs. The removal of the sapphire substrate reduced the adverse impacts of the quantum-confined Stark effect (QCSE). The influence of integrated surface textures on the light extraction efficiency (LEE) of the vertical LEDs was studied. With the injection current of 350 mA, vertical LEDs with integrated surface textures demonstrated an excellent light output power of 468.9 mW with an emission peak wavelength of 456 nm. This work contributes to the integration of GaN-based vertical LEDs into Si-based integrated circuits.

Highlights

GaN-based light-emitting diodes (LEDs) have been proven to have great potentials as next-generation solid-state lighting due to their high color-rendering index, high efficiency, long life, compact size, and so forth [1,2,3]
The Pt/Ti films deposited on the Ag/TiW films protected them from environmental humidity
LEDs the on the p-type siliconprocess substrate to contributed understand the impacts of the emission property for vertical on the p-typeWe silicon substrate to understand the impacts of the manufacturing process on the optical revealed the effect of transferring

Summary

Introduction

GaN-based light-emitting diodes (LEDs) have been proven to have great potentials as next-generation solid-state lighting due to their high color-rendering index, high efficiency, long life, compact size, and so forth [1,2,3]. Further enhancements in optical performance for high-power LEDs are extremely important to penetrate general lighting and automotive front lighting markets [4,5,6]. The silicon (Si) substrate is compatible with the widely employed complementary metal–oxide–semiconductor (CMOS) circuits. The combination of GaN-based LEDs with Si-based integrated circuits would expedite the wide application of GaN-based LEDs [7]. The reported GaN-based LEDs can be categorized as follows: (1) Conventional top-emitting LED. The top-emitting LED is grown on a sapphire substrate. It is well known that large compressive strain exists in the GaN film due to the large lattice and thermal mismatch between

Methods

Results

Conclusion