Spin injection in n-type resonant tunneling diodes

Vanessa Orsi Gordo,Maria Jsp Brasil,Mohamed Henini,Helder Va Galeti,Yara Galvão Gobato,Leonilson Ks Herval,Robert J Airey,Gilmar E Marques

doi:10.1186/1556-276x-7-592

Abstract

We have studied the polarized resolved photoluminescence of n-type GaAs/AlAs/GaAlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. Under resonant tunneling conditions, we have observed two emission lines attributed to neutral (X) and negatively charged excitons (X−). We have observed a voltage-controlled circular polarization degree from the quantum well emission for both lines, with values up to −88% at 15 T at low voltages which are ascribed to an efficient spin injection from the 2D gases formed at the accumulation layers.

Highlights

In the last years, it has been an increasing interest in the manipulation of spin degrees of freedom in semiconductor devices
The confined levels in the quantum well (QW) and the contact layers split into spin-up and spin-down Zeeman states, and the optical recombination can occur with the defined selection rules giving information about the spin polarization of the carriers in the structure
It is well known that the relative concentrations of electrons and holes in the QW of resonant tunneling diodes (RTDs) structures can be controlled by external parameters [12,13,14,15,16,17]

Summary

Introduction

It has been an increasing interest in the manipulation of spin degrees of freedom in semiconductor devices. Under applied voltage and light excitation, electrons and photogenerated holes tunnel through the double-barrier structure creating a 2D electron and a hole gas at the accumulation layers next to the barriers These 2D gases can inject spin-polarized carriers into the QW under applied voltage resulting in high polarization degree values. Our results show that the QW circular polarization degree for charged and neutral excitons is voltage dependent with relatively higher values, up to −88% at 15 T for low bias voltages. This result cannot be attributed solely to a simple thermal occupation effect and is mainly attributed to the injection of polarized carriers from the contacts. The QW circular polarization is reduced, indicating additional contribution for the spin polarization in the QW such as the increasing of the density of carriers and the formation of trions in the QW

Methods

Results

Conclusion