Spin photocurrent spectra induced by Rashba- and Dresselhaus-type circular photogalvanic effect at inter-band excitation in InGaAs/GaAs/AlGaAs step quantum wells

Jinling Yu,Yunfeng Lai,Yonghai Chen,Qiao Zheng,Shuying Cheng

doi:10.1186/1556-276x-9-130

Abstract

Spin photocurrent spectra induced by Rashba- and Dresselhaus-type circular photogalvanic effect (CPGE) at inter-band excitation have been experimentally investigated in InGaAs/GaAs/AlGaAs step quantum wells (QWs) at room temperature. The Rashba- and Dresselhaus-induced CPGE spectra are quite similar with each other during the spectral region corresponding to the transition of the excitonic state 1H1E (the first valence subband of heavy hole to the first conduction subband of electrons). The ratio of Rashba- and Dresselhaus-induced CPGE current for the transition 1H1E is estimated to be 8.8±0.1, much larger than that obtained in symmetric QWs (4.95). Compared to symmetric QWs, the reduced well width enhances the Dresselhaus-type spin splitting, but the Rashba-type spin splitting increases more rapidly in the step QWs. Since the degree of the segregation effect of indium atoms and the intensity of build-in field in the step QWs are comparable to those in symmetric QWs, as proved by reflectance difference and photoreflectance spectra, respectively, the larger Rashba-type spin splitting is mainly induced by the additional interface introduced by step structures.

Highlights

Spintronics has attracted much attentions due to its significant role in both fundamental research and possible device applications [1,2,3,4,5,6,7,8,9,10]
Spin-orbit coupling (SOC) according to different sources of inversion asymmetry: Dresselhaus SOC induced by the bulk inversion asymmetry (BIA), [15] and Rashba SOC induced by structure inversion asymmetry (SIA) [16]
It should be noted that the circular photogalvanic effect (CPGE) spectra are only normalized by the common current j0 at the peak located near 908 nm, which corresponds to the transition of excitonic state 1H1E as discussed below

Summary

Introduction

Spintronics has attracted much attentions due to its significant role in both fundamental research and possible device applications [1,2,3,4,5,6,7,8,9,10]. Spin-orbit coupling (SOC) and the resulting spin splitting in a two-dimensional system have been used to create and manipulate spinpolarized carriers in nonmagnetic materials without external magnetic field [1,12,13,14]. There are two kinds of SOC according to different sources of inversion asymmetry: Dresselhaus SOC induced by the bulk inversion asymmetry (BIA), [15] and Rashba SOC induced by structure inversion asymmetry (SIA) [16]. These two terms can interfere with each other and result in an anisotropy of spin splitting. There are lots of theoretical [21,22] and experimental investigations [7,20]

Methods

Results

Conclusion