Defect-related photoluminescence of hexagonal boron nitride

TL;DR

This study investigates the photoluminescence properties of hexagonal boron nitride, revealing defect-related emission, photostimulated luminescence phenomena, and supporting the presence of Frenkel-like excitons with high binding energy.

Contribution

It provides new insights into defect-related photoluminescence and photostimulated luminescence mechanisms in hBN, including band analysis supporting Frenkel excitons.

Findings

Identification of defect-related emission bands.

Observation of photostimulated luminescence above 5.4 eV.

Support for Frenkel-like excitons with large binding energy.

Abstract

Photoluminescence of polycrystalline hexagonal boron nitride (hBN) was measured by means of time- and energy-resolved spectroscopy methods. The observed bands are related to DAP transitions, impurities and structural defects. The excitation of samples by high-energy photons above 5.4 eV enables a phenomenon of photostimulated luminescence (PSL), which is due to distantly trapped CB electrons and VB holes. These trapped charges are metastable and their reexcitation with low-energy photons results in anti-Stockes photoluminescence. The comparison of photoluminescence excitation spectra and PSL excitation spectra allows band analysis that supports the hypothesis of Frenkel-like exciton in hBN with a large binding energy.