An investigation of tunable spin–orbit interactions in front-gated In0.75Ga0.25As/In0.75Al0.25As heterojunctions

doi:10.1016/S1386-9477(01)00057-1

Physica E: Low-dimensional Systems and Nanostructures

Volume 10, Issues 1–3, May 2001, Pages 77-80

https://doi.org/10.1016/S1386-9477(01)00057-1 Get rights and content

Abstract

We investigated zero-field spin-splitting in normal-type In_0.75Ga_0.25As/In_0.75Al_0.25As heterostructure by magnetoresistance measurements at $1.5 K$ . The maximum value of spin–orbit interaction parameter, α_zero, obtained here is $32×10^{−12} eVm$ . We also confirmed a tuning of α_zero by applying gate biases. On the other hand, we observed no beat oscillation when the In_0.75Ga_0.25As well width decreased from 30 to $10 nm$ . These results suggested that interface contribution related to the asymmetry of wave function penetration into the barriers could be enhanced in our heterojunction.

Introduction

Generally, it is said that zero-field spin-splitting is derived from two different physical origins. The first effect is due to the bulk inversion asymmetry (BIA) of zinc-blend structure. The second effect is based on the structure inversion asymmetry (SIA), which yields local electric field due to conduction band bending. This is known as the Rashba mechanism [1]. Recently, gated control of zero-field spin-splitting has been reported in narrow gap heterostructures such as inverted In_0.53Ga_0.47As/In_0.52Al_0.48As [2] or In_0.77Ga_0.23As/InP [3]. On the other hand, in InAs/AlSb heterointerface, zero-field spin-splitting was not tuned by applied gate voltage [4], or no beating oscillation was reported [5]. Although several experimental [2], [3], [4], [5] and theoretical [3], [7] studies have been made, a complete understanding is not yet to be attained on this matter.

The purpose of this paper is to report zero-field spin-splitting in normal-type In_0.75Ga_0.25As/In_0.75Al_0.25As heterostructure by the analysis of magnetoresistance at $1.5 K$ . The maximum value of spin-orbit interaction parameter, α_zero, obtained here is $32×10^{−12} eVm$ . We also confirmed a tunable α_zero from $32×10^{−12} eVm$ to 14 by applying negative gate voltage. Nevertheless, we could not observe the beating oscillation when In_0.75Ga_0.25As channel layer thickness decreased from 30 to $10 nm$ .

These results lead to the conclusion that the origin of zero-field spin-splitting is mainly derived from the interface contribution [3] in the Rashba term, to put it another way, from the asymmetry of wave function penetrations into the barrier layer in our heterostructure.

Section snippets

Sample preparation

We prepared a layer structure of In_0.75Ga_0.25As/In_0.75Al_0.25As normal-type modulation-doped heterostructure grown by molecular beam epitaxy (MBE) [6]. The structure consisted of a semi-insulating GaAs $(0 0 1)$ substrate, $30 nm$ thick GaAs buffer layer, In_yAl_1−yAs step graded buffer (SGB) layer (y=0.15–0.75, $100 nm$ each steps), 30 or $10 nm$ thick In_0.75Ga_0.25As channel layer, $20 nm In_{0.75} Al_{0.25} As$ spacer, and $40 nm In_{0.75} Al_{0.25} As$ carrier supply layer doped by Si. On top of the doped layer, an additional $10 nm$

Results and discussions

Fig. 1 shows typical SdH oscillations of longitudinal resistance R_xx in Hall-bar sample directed to $〈−1 1 0〉$ with FFT results (inset) when the gate voltage (V_g) was zero. It is well known that the SdH oscillation for an ideal 2D system are periodic against inverse magnetic field, and the period is given by Δ(1/B)=(e/ℏπ)n_s⁻¹, where n_s is the carrier density with spin degeneracy of 2. The beat in Fig. 1, arising from the participation of two sets of oscillations with slightly different frequencies,

Conclusions

In conclusion, we have investigated zero-field spin splitting and obtained large α_zero values $∼30×10^{−12} eVm$ in In_0.75Ga_0.25As/In_0.75Al_0.25As normal-type heterostructure. We also confirmed that spin–orbit interaction parameter, α_zero, can be tuned by applied negative gate voltage, where the value of α_zero varied from $32×10^{−12} eVm$ to 14.

From the well width dependence of SdH beat oscillation and the corresponding self-consistent calculations, it is strongly suggested that possible origin of large

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Physica E: Low-dimensional Systems and Nanostructures

An investigation of tunable spin–orbit interactions in front-gated In0.75Ga0.25As/In0.75Al0.25As heterojunctions

Abstract

Introduction

Section snippets

Sample preparation

Results and discussions

Conclusions

J. Phys. C

Phys. Rev. Lett.

J. Appl. Phys.

Phys. Rev. B

Calculations and Simulations of Low-Dimensional Materials: Tailoring Properties for Applications

Ferroelectric control of Rashba spin orbit coupling at the GeTe(111)/InP(111) interface

Ferroelectric control of the giant Rashba spin orbit coupling in GeTe(111)/InP(111) superlattice

Effect of the doping concentration on the zero-field spin splitting and Rashba parameter in a p-InAs MOSFET

Anomalous spin-orbit effects in a strained InGaAs/InP quantum well structure

An investigation of tunable spin–orbit interactions in front-gated In_0.75Ga_0.25As/In_0.75Al_0.25As heterojunctions