A comparative study of efficiency droop and internal electric field for InGaN blue lighting-emitting diodes on silicon and sapphire substrates

H Y Ryu,Y H Choi,J S Lee,M G Kang,H K Yuh,K S Jeon

doi:10.1038/srep44814

Abstract

We investigated the efficiency droop and polarization-induced internal electric field of InGaN blue light-emitting diodes (LEDs) grown on silicon(111) and c-plane sapphire substrates. The efficiency droop of the LED sample grown on silicon substrates was considerably lower than that of the identically fabricated LED sample grown on sapphire substrates. Consequently, the LED on silicon showed higher efficiency at a sufficiently high injection current despite the lower peak efficiency caused by the poorer crystal quality. The reduced efficiency droop for the LED on silicon was attributed to its lower internal electric field, which was confirmed by reverse-bias electro-reflectance measurements and numerical simulations. The internal electric field of the multiple quantum wells (MQWs) on silicon was found to be reduced by more than 40% compared to that of the MQWs on sapphire, which resulted in a more homogenous carrier distribution in InGaN MQWs, lower Auger recombination rates, and consequently reduced efficiency droop for the LEDs grown on the silicon substrates. Owing to its greatly reduced efficiency droop, the InGaN blue LED on silicon substrates is expected to be a good cost effective solution for future lighting technology.

Highlights

Reported high-performance GaN-based light-emitting diodes (LEDs) grown on silicon substrates overcoming the large mismatch in the lattice constant and thermal expansion coefficients between GaN and silicon[18,19,20,21], and the successful commercialization of GaN LEDs on silicon substrates is expected to be realized in the near future
Compared to the template layers on the silicon substrate, the GaN template grown on the c-plane sapphire substrate consisted of a 30-nm low-temperature buffer layer and a 2-μm GaN layer
This study compared the efficiency droop and polarization-induced internal electric field of InGaN blue LEDs grown on silicon(111) and c-plane sapphire substrates

Summary

Introduction

Reported high-performance GaN-based LEDs grown on silicon substrates overcoming the large mismatch in the lattice constant and thermal expansion coefficients between GaN and silicon[18,19,20,21], and the successful commercialization of GaN LEDs on silicon substrates is expected to be realized in the near future. The efficiency droop of InGaN LEDs on silicon substrates have been relatively unexplored compared to the extensive results on the efficiency droop of InGaN LEDs on sapphire substrates. We compare the efficiency droop and internal electric field of InGaN blue LEDs grown on silicon and sapphire substrates. The electro-luminescence (EL) efficiency and efficiency droop of the LEDs on silicon and sapphire were compared. Numerical simulations were performed to interpret the experimental results on the internal electric fields and efficiency droop. To our knowledge, this is the first systematic study comparing the efficiency droop of InGaN LEDs grown on sapphire and silicon substrates in the view point of the internal electric fields

Methods

Results

Conclusion