Study of monolithically integrated 940 nm AlGaAs distributed Bragg reflectors on graded GaAsP/bulk Si substrates

TL;DR

This paper reports the fabrication and analysis of monolithically integrated 940 nm AlGaAs DBRs on graded GaAsP/Si substrates, highlighting surface quality issues affecting optical performance.

Contribution

It introduces a fabrication process for AlGaAs DBRs on GaAsP/Si substrates and investigates surface defects impacting reflectance spectra.

Findings

Surface cross-hatch causes lower reflectance

DBRs on GaAsP/Si have double peaks in spectra

Surface polishing improves reflectance quality

Abstract

We report the fabrication of monolithically integrated 940 nm AlGaAs distributed Bragg reflectors (DBRs) on graded GaAsP/Si substrates. Low-density surface bumps and cross-hatch patterns were observed on the DBR surfaces. Cross-sectional DBR layers are smooth and flat. The reflectance spectra of the GaAsP/Si DBRs have lower intensities than the GaAs DBRs and have double peaks. Transfer matrix method calculations, surface scratch and polishing tests were conducted, which suggest that the surface cross-hatch was the cause of the inferior DBR reflectance spectra.