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A method is presented in which both optical constants and growth rates may be simultaneously extracted from the in situ normal incidence reflectance of a growing thin film. The method employs a virtual interface model, thus avoiding cumulative errors that are encountered if a standard multiple-layer model is used. No a priori knowledge of underlying film materials, structures, or locations of interfaces is required. A method to accurately estimate all parameters for starting values in the least-squares fitting of the data is also presented. This allows one to use a fully automated procedure for extracting information that requires no prior knowledge other than the starting reflectance of the substrate. Monte Carlo simulations are presented to study the ultimate accuracy of the method under ideal conditions for a film structure typical of compound semiconductor growth. Optical constants of GaAs and AlAs at 634 C have been obtained over a wavelength range of 400–990 nm with this method and agree with values obtained by others using ellipsometry. The method provides a pre-growth calibration tool analogous to the use of reflection high energy electron diffraction in molecular beam epitaxy (MBE) that can be used in chemical vapor deposition applications as well as in MBE. Multiple calibrations can be performed for different materials within a single growth run.

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Ultraviolet light emitting diodes (LEDs) have been grown using metalorganic vapor phase epitaxy, while monitoring the 550 nm reflected light intensity. During nucleation of GaN on sapphire, the transition from three-dimensional (3D) grain growth to two-dimensional (2D) coalesced growth was intentionally delayed in time by lowering the NH3 flow during the initial high temperature growth. Initially, when the reflectance signal is near zero, the GaN film is rough and composed of partly coalesced 3D grains. Eventually, the reflected light intensity recovers as the 2D morphology evolves. For 380 nm LEDs grown on 3D nucleation layers, we observe increased light output. For LEDs fabricated on GaN films with a longer recovery time an output power of 1.3 mW at 20 mA current was achieved.

Reactive sticking coefficients (RSCs) were measured for silane and disilane on polycrystalline silicon for a wide range of temperature and flux (pressure) conditions. The data were obtained from deposition-rate measurements using molecular beam scattering and a very low-pressure cold-wall reactor. The RSCs have nonlinear Arrhenius temperature dependencies and decrease with increasing flux at low (710 °C) temperatures. Several simple models are proposed to explain these observations. The results are compared with previous studies of the SiH4/Si(s) reaction and low-pressure chemical vapor deposition-rate measurements.

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