Photo-induced Hall effect in metals

D Li,A Ruotolo

doi:10.1038/s41598-018-22776-x

Abstract

The Hall effect in metals is too small to have practical applications. Instead, the same effect in semiconductors is the standard for magnetic field sensing. Yet, in semiconducting Hall-sensors, Joule heating severely compromises the linearity range. We here show that a Hall effect can be photo-induced in metals used for bias-free magnetic sensing. The system consists of a transparent metal that forms a Schottky contact to a semiconductor. Light reaching the interface results in the injection of charge from the space charge region. If a magnetic field is applied, a transverse, open-circuit voltage appears at the metal edges that is proportional to the field, as well as light intensity. The system shows sensitivities that are comparable to semiconducting Hall-sensors but no net current flows, therefore its performances are not affected by Joule heating.

Highlights

The Hall effect in metals is too small to have practical applications
As a Schottky contact is made, electrons in the conduction band of the semiconductor have a higher energy than electrons in the metal
The built-in potential Vbi prevents additional electrons to migrate. This equilibrium corresponds to the alignment of the Fermi levels

Summary

Introduction

The Hall effect in metals is too small to have practical applications. Instead, the same effect in semiconductors is the standard for magnetic field sensing. While Hall sensors have been replaced by magnetoresistive sensors in digital systems[3,4], they still retain two features which make them preferable to the latter in analog applications: they are intrinsically linear because they do not make use of magnetic materials and their sensitivity is directly proportional to the bias current J through the charge velocity v The latter of these features is more theoretical than practical. A magnetic field applied in the junction plane exerts a magnetic force on the carriers diffusing in the metal, which accumulate on opposite sides, according to their sign This charge accumulation can be detected as an open-circuit voltage transverse to the metal. The net current is zero and no Joule heating is produces, regardless light intensity

Methods

Results

Conclusion