All-BN Distributed Bragg Reflectors Fabricated in a Single MOCVD Process

TL;DR

This paper presents a novel method to fabricate all-boron nitride distributed Bragg reflectors using a single MOCVD process, enabling tunable optical properties without post-processing, suitable for integrated photonic applications.

Contribution

The study introduces a single-step MOCVD fabrication of all-BN DBRs with high reflectance and tunable wavelength, eliminating the need for etching or multiple materials.

Findings

Achieved 87% reflectance with 15.5 BN layer pairs.

Tunable reflectance wavelength from 500 nm to IR.

Demonstrated use in optical microcavities for photonic devices.

Abstract

Distributed Bragg Reflectors (DBR) are well-established photonic structures that are used in many photonic applications. However, most of the DBRs are based on different materials or require post-process etching which can hinder integration with other components in the final photonic structure. Here, we demonstrate the fabrication of DBR structures consisting only of undoped boron nitride (BN) layers with high refractive index contrast by using Metal-Organic Chemical Vapor Deposition (MOCVD). This has been achieved in a single process, without the need for any post-process etching. The difference in the refractive index of the component BN layers stems from different degrees of porosity of the individual BN layers, which is a direct result of a different growth temperature. The fabricated DBR structures consist of 15.5 pairs of BN layers and exhibit a reflectance of 87+/-1% at the maximum. The wavelength of maximum reflectance can be tuned from 500 nm up to the Infrared Region (IR), by simply adjusting the growth periods of subsequent BN layers. We also demonstrate that the fabricated structures can be used to create an optical microcavity. The fabricated DBRs are very promising candidates for future applications, for example in combination with single-photon emitters in h-BN, which could allow the building of a cavity-based all-BN single-photon source.