INSITU SPECTROSCOPIC ELLIPSOMETRY IN MOLECULAR-BEAM EPITAXY FOR PHOTONIC DEVICES

In situ spectroscopic ellipsometry (SE) has been shown to be a versatile technique for monitoring growth in ultrahigh vacuum epitaxial growth systems. For instance, typical MBE parameters of substrate temperature, growth rate, alloy composition and thickness of growing layers have been measured during the growth of heterostructures in solid-source and gas-source MBE. The growth of AlAs/GaAs quantum wells has also been investigated in studies where the growth was monitored in real time with and without growth interruption. The difference in interfacial abruptness of the heterojunction was then determined. This paper first discusses some practical considerations of implementing an SE onto a gas-source MBE. Examples of monitoring substrate temperature, oxide desorption, surface smoothing and heterojunction growth of a test structure will then be presented followed by a demonstration of quantum well growth and growth interruption. The first use of high-temperature GaAs and AlAs optical constants for thickness and alloy composition determination at the MBE growth temperature is presented which enabled the growth and calibration of distributed Bragg reflectors for use in vertical cavity lasers and modulators.