Room temperature magneto-optic effect in silicon light-emitting diodes

F Chiodi,H Bouchiat,R H Friend,A D Chepelianskii,D Débarre,S L Bayliss,L Barast

doi:10.1038/s41467-017-02804-6

Abstract

In weakly spin–orbit coupled materials, the spin-selective nature of recombination can give rise to large magnetic-field effects, e.g. on the electro-luminescence of molecular semiconductors. Although silicon has weak spin–orbit coupling, observing spin-dependent recombination through magneto-electroluminescence is challenging: silicon’s indirect band-gap causes an inefficient emission and it is difficult to separate spin-dependent phenomena from classical magneto-resistance effects. Here we overcome these challenges and measure magneto-electroluminescence in silicon light-emitting diodes fabricated via gas immersion laser doping. These devices allow us to achieve efficient emission while retaining a well-defined geometry, thus suppressing classical magnetoresistance effects to a few percent. We find that electroluminescence can be enhanced by up to 300% near room temperature in a seven Tesla magnetic field, showing that the control of the spin degree of freedom can have a strong impact on the efficiency of silicon LEDs.

Highlights

In weakly spin–orbit coupled materials, the spin-selective nature of recombination can give rise to large magnetic-field effects, e.g. on the electro-luminescence of molecular semiconductors
As external magnetic fields can change the spin statistics and energy levels in the sample, magneto-electroluminescence (MEL) effects have been seen as the hallmark of spin-dependent recombination phenomena and have given important insight into the role of spin in organic materials used for light-emitting diodes (LEDs)[8,9,10]
Using our SiLEDs, we find that when classical MR effects are suppressed, EL can be substantially enhanced under a magnetic field near room temperature

Summary

Introduction

In weakly spin–orbit coupled materials, the spin-selective nature of recombination can give rise to large magnetic-field effects, e.g. on the electro-luminescence of molecular semiconductors. Observing spin-dependent MEL in silicon requires that the magnetic field and device currents are parallel to effectively suppress classical magnetoresistance (MR) contributions, which can enhance MR in silicon up to spectacular values even at room temperature[18,19,20,21,22] We address both of these challenges by developing a new fabrication method for efficient silicon LEDs (SiLEDs) using an original doping technique, gas immersion laser doping (GILD), and investigate spin-dependent recombination in SiLEDs. The GILD process[23,24,25,26] allows us to reach doping levels well beyond the solubility threshold, which, as we describe below, gives rise to efficient emission, while retaining the well-defined planar geometry necessary to align electric and magnetic fields. They highlight the importance of controlling the spin degree of freedom for the efficiency of silicon light-emitting devices

Methods

Results

Conclusion