Investigating the Effect of Piezoelectric Polarization on GaN-Based LEDs with Different Prestrain Layer by Temperature-Dependent Electroluminescence

C K Wang,T K Lin,Y Z Chiou,T H Chiang

doi:10.1155/2015/135321

Abstract

The effect of piezoelectric polarization on GaN-based light emitting diodes (LEDs) with different kinds of prestrain layers between the multiple quantum wells (MQWs) and n-GaN layer is studied and demonstrated. Compared with the conventional LED, more than 10% enhancement in the output power of the LED with prestrain layer can be attributed to the reduction of polarization field within MQWs region. In this study, we reported a simple method to provide useful comparison of polarization fields within active region in GaN-based LEDs by using temperature-dependent electroluminescence (EL) measurement. The results pointed out that the polarization field of conventional LED was stronger than that of the others due to larger variation of the wavelength transition position (i.e., blue-shift change to red-shift) from 300 to 350 K, and thus the larger polarization field must be effectively screened by injecting more carriers into the MQWs region.

Highlights

GaN-based materials generally exist in a wurtzite crystal structure which has a strong polarization field along the c-plane direction
These results show that the light output power can be improved obviously with inserting the prestrain interlayers between the n-GaN and multiple quantum wells (MQWs)
This means that the improvement of output power can be attributed to the release of the residual strain, the reduction of the polarization field and quantum-confined stark effect (QCSE), the enhancement of electron-hole recombination rate, the reduction the V-defect density, and the improvement of the crystal quality in MQWs for light emitting diodes (LEDs) II and III [20, 21]

Summary

Introduction

GaN-based materials generally exist in a wurtzite crystal structure which has a strong polarization field along the c-plane direction. The space charges induced by spontaneous and piezoelectric polarization fields were at the interfaces of heterostructure for GaN-based materials, for example, in the c-plane InGaN/GaN multiple quantum wells (MQWs) structure This inherent effect, which was called quantum-confined stark effect (QCSE), has resulted in the reduction of quantum efficiency for the GaN-based LEDs. This inherent effect, which was called quantum-confined stark effect (QCSE), has resulted in the reduction of quantum efficiency for the GaN-based LEDs This is because the QCSE within MQWs region lead to the significant spatial separation of the electron and hole wave functions and the reduction of the electron-hole recombination probability [1,2,3,4,5]. Prestrain layer were compared by using our previous method of temperature-dependent EL measurement

Experimental

Results and Discussion

Conclusions