Optical refractive index measurements of AlGaAs at high temperature for fully automated molecular beam epitaxy growth of Bragg mirrors

TL;DR

This paper presents precise in-situ optical index measurements of AlGaAs at high temperature, combined with automated growth of Bragg mirrors, enabling highly accurate and pre-calibration-free epitaxial fabrication.

Contribution

It introduces a method for in-situ optical index measurement at high temperature and demonstrates fully automated MBE growth of Bragg mirrors without pre-calibration.

Findings

Optical indices of AlGaAs measured with better than 1% accuracy.

Successful automated growth of GaAs/AlAs DBR with minimal wavelength deviation.

Validated approach for precise, in-situ control in epitaxial growth processes.

Abstract

In-situ measurement is a key feature to better understand and precisely control the growth of complex structures, such as vertical-cavity surface-emitting lasers. In this work, we are showing the precise measurement of optical indices of AlGaAs at 600 {\textdegree}C over a wide spectral range (450--1400 nm). To do so, in-situ spectral reflectance measurement is used, combined with ex-situ layer thickness and composition measurement by x-ray diffraction enabling for precise determination of the optical indices with an accuracy better than 1%. To validate our measurements, we realized the complete automation of the growth of a GaAs/AlAs 940 nm-DBR by molecular beam epitaxy, without the need to pre-calibrate cells fluxes. The fabricated DBR shows a deviation of 0.2 nm of the stop-band central-wavelength compared to the targeted one. This approach holds significant interest for the III--V semiconductor community and epitaxial growth techniques.