Real-time composition control of InAlAs grown on InP using spectroscopic ellipsometry

Abstract

Spectroscopic ellipsometry ͑SE͒ was shown to be an accurate in situ method for determining the composition and thickness of III-V semiconductor layers during growth. In order to fully exploit the potential of SE for real-time in situ control, one needs to acquire a database of optical constants. In this article, we present the acquisition and parameterization ͑both composition and temperature͒ of a fully dynamic database and its use in the real-time composition control of InAlAs grown on InP. This is accomplished by acquiring SE data from growing films of different compositions, while the temperature is controlled using feedback from band-gap thermometry. The layer compositions are assessed by fitting high-resolution x-ray diffraction patterns with a simulation based on dynamical diffraction theory. In order to improve the stability during real-time control, the database was parameterized using a transfer function model. The parameterized database was then used, in real time, during growth to control the In x Al 1Ϫx As film composition ͑x͒ to within Ϯ0.003.