Electrical excitation of carbon centers in hexagonal boron nitride with tuneable quantum efficiency

TL;DR

This paper demonstrates electrically driven light-emitting diodes using carbon defect centers in hexagonal boron nitride, achieving high efficiency and tunable emission, addressing a key challenge in defect-based optoelectronics.

Contribution

The authors present a novel electrically excited LED based on carbon centers in hexagonal boron nitride, with controlled charge dynamics and tunable emission energy, surpassing optical excitation efficiency.

Findings

Electrical excitation efficiency exceeds optical excitation by orders of magnitude.

Charge dynamics are controlled via van der Waals device design.

Emission energy is tunable through Stark effect and band electron screening.

Abstract

Defect centers in wide-band-gap crystals attracted considerable attention due to the realisations of qubits, sensors, or single photon emitters at room temperature. The family of these centers is constantly growing, including well-known examples such as nitrogen-vacancy centers in diamond, silicon-vacancy in silicon carbide, chromium substitutions in aluminium oxide, and many others. Unfortunately, such defect centers embedded in highly insulating crystals have been notoriously difficult to excite electrically. Herewith, we present a realisation of insulating light-emitting diodes based on carbon centers in hexagonal boron nitride. The rational design of the vertical tunnelling devices via van der Waals technology enabled us to control the charge dynamics related to non-radiative tunelling, defect-to-band electroluminescence, and intradefect electroluminescence. The fundamental understanding of the tunnelling events enabled us to achieve high efficiency of electrical excitation, which exceeded by a few orders of magnitude the efficiency of optical excitation in the sub-band-gap regime. A combination of a Stark effect and screening by band electrons provide a control knob for tuning the energy of emission. With this work, we solve an outstanding problem of creating electrically driven devices realised with defect centers in wide-band-gap crystals, which are relevant in the domain of optoelectronics, telecommunication, computation, or sensing.