MEASUREMENT OF COMPOSITION AND DOPANT CONCENTRATION OF SEMICONDUCTORS USING FT-IR SPECTROSCOPY

In-situ techniques for the characterization of growing semiconductor films are required to enhance film quality and the productivity of deposition processes. This study investigates the feasibility of the in-situ measurement of dopant concentration and alloy composition of GaAs and Al_xGa_l-xAs films using FT-IR spectroscopy. Two different methods of extracting film characteristics from the radiative properties of a film-substrate composite are proposed: the photometric method and the spectral method. The feasibility of using the photometric method to measure dopant concentration is investigated by calculating the radiative properties of p-type GaAs films on undoped GaAs substrates and analyzing the sensitivity of these properties to a change in dopant concentration. The feasibility of using the spectral method to determine composition is investigated by analyzing the composition-dependent spectral shift of phonon frequencies and the band-gap frequency of Al_xGa_l-xAs. This research exposes the need for further experimental and theoretical work to determine the optical constants of semiconductors at processing temperatures and the need for improvement in the photometric accuracy and signal-to-noise ratio of Fourier transform-infrared spectrometers.