Study on spin and optical polarization in a coupled InGaN/GaN quantum well and quantum dots structure.

Jiadong Yu,Bing Xiong,Yanjun Han,Di Yang Di Yang,Hongtao Li,Jiyuan Zheng,Zhibiao Hao,Jian Wang,Lai Wang,Changzheng Sun,Yuchen Xing,Yi Luo

doi:10.1038/srep35597

Abstract

The spin and optical polarization based on a coupled InGaN/GaN quantum well (QW) and quantum dots (QDs) structure is investigated. In this structure, spin-electrons can be temporarily stored in QW, and spin injection from the QW into QDs via spin-conserved tunneling is enabled. Spin relaxation can be suppressed owing to the small energy difference between the initial state in the QW and the final states in the QDs. Photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements are carried out on optical spin-injection and -detection. Owing to the coupled structure, spin-conserved tunneling mechanism plays a significant role in preventing spin relaxation process. As a result, a higher circular polarization degree (CPD) (~49.1%) is achieved compared with conventional single layer of QDs structure. Moreover, spin relaxation time is also extended to about 2.43 ns due to the weaker state-filling effect. This coupled structure is believed an appropriate candidate for realization of spin-polarized light source.

Highlights

The possibility to control electron spins in semiconductors has attracted a great attention for realization of spin-polarized light source, such as spin-polarized light-emitting diodes and spin-polarized laser diodes[1,2,3,4]
We report the spin and optical polarization based on a coupled InGaN/GaN quantum well (QW) and quantum dots (QDs) structure[24]
The strain within the QDs layer is weakened when it grown on InGaN QW26, the radiative recombination lifetime can be further reduced compared with the single layer of InGaN QDs structure

Summary

Introduction

The possibility to control electron spins in semiconductors has attracted a great attention for realization of spin-polarized light source, such as spin-polarized light-emitting diodes (spin-LEDs) and spin-polarized laser diodes (spin-LDs)[1,2,3,4]. For InGaN QW, quantum-confined Stark effect (QCSE) will lead to a relatively long radiative recombination lifetime and spin-polarized carriers will undergo more relaxation before recombination[21,22], the CPD of the emission light will not be high. We report the spin and optical polarization based on a coupled InGaN/GaN QW and QDs structure[24].

Results

Conclusion