Evidence of nanoscale Anderson localization induced by intrinsic compositional disorder in InGaN/GaN quantum wells by scanning tunneling luminescence spectroscopy

TL;DR

This study provides direct experimental evidence of nanoscale Anderson localization caused by intrinsic compositional disorder in InGaN/GaN quantum wells, using scanning tunneling luminescence spectroscopy to observe localized emission states.

Contribution

It demonstrates the first direct measurement of Anderson localization at the nanoscale in InGaN/GaN quantum wells through local electron injection and spectral analysis.

Findings

Observation of nanometer-scale emission fluctuations

Resolution of narrow emission peaks from localized states

Theoretical explanation using localization landscape theory

Abstract

We present direct experimental evidences of Anderson localization induced by the intrinsic alloy compositional disorder of InGaN/GaN quantum wells. Our approach relies on the measurement of the luminescence spectrum under local injection of electrons from a scanning tunneling microscope tip into a near-surface single quantum well. Fluctuations in the emission line shape are observed on a few-nanometer scale. Narrow emission peaks characteristic of single localized states are resolved. Calculations in the framework of the localization landscape theory provide the effective confining potential map stemming from composition fluctuations. This theory explains well the observed nanometer scale carrier localization and the energies of these Anderson-type localized states. The energy spreading of the emission from localized states is consistent with the usually observed very broad photo- or electro-luminescence spectra of InGaN/GaN quantum well structures.