High-reflectivity homoepitaxial distributed Bragg reflectors for photonic applications

TL;DR

This paper proposes a homoepitaxial design for distributed Bragg reflectors using doped and undoped layers of the same material to achieve high reflectivity across various spectral ranges, overcoming material system limitations.

Contribution

It introduces a theoretical approach to design high-reflectivity DBRs with homoepitaxial layers by leveraging doping-induced refractive index contrast, expanding material choices for photonic applications.

Findings

Achieved ~90% reflectivity with feasible doping levels.

Demonstrated applicability to hBN, InP, and Si for different spectral ranges.

Provided transfer matrix calculations for reflectivity spectra.

Abstract

Distributed Bragg reflectors (DBRs) are one of the basic photonic structures used to define microcavities for fundamental light-matter coupling studies, as well as to optimize performance of optoelectronic and photonic devices, e.g., lasers or non-classical light sources. The reflectivity of these structures depends critically on the refractive index contrast between the two quarter-wavelength thick layers constituting the DBR. At the same time, epitaxial fabrication process limits the choice of materials to those with the same, or very similar lattice constant to avoid strain accumulation in the relatively thick multilayer structure. This becomes very often a bottleneck for the DBR designs at certain wavelengths or for some of the material systems. Therefore, we explore theoretically DBR designs employing the reflective index contrast between undoped and doped layers of the same material, making the entire growth process homoepitaxial. The refractive index for a doped layer is calculated taking into account the free carrier absorption, carrier-carrier interaction, the Burnstein-Moss and plasma effects. The reflectivity spectrum of a DBR is further calculated using transfer matrix method. Exemplary results for three application relevant materials - hBN, InP and Si suitable for different spectral ranges, i.e. ultraviolet, telecommunication and mid-infrared, respectively, are presented. We report reflectivities on the level of 90\% for technologically achievable doping concentrations and moderate number of layer pairs.