Fourier notch filter method and system

A method for determining temperature of a semiconductor film during multiple quantum well (MQW) film growth, the semiconductor film having a measurable optical absorption edge deposited on a substrate material having no measurable optical absorption edge, said method comprising the steps of:

• a) providing a substrate of material having no measurable optical absorption edge,
• b) depositing a film of a semiconductor material having a measurable optical absorption edge and a measurable thickness on the substrate by Metal-Organic Chemical Vapor Deposition (MOCVD),
• c) interacting light with the film deposited on the substrate to produce diffusely scattered light,
• d) collecting the diffusely scattered light from the film,
• e) producing a spectrum indicating optical absorption of the film based on the diffusely scattered light from the film,
• f) determining a thickness of the film,
• g) determining the optical absorption edge wavelength of the film based on the spectrum, and
• h) determining a temperature of the film at the film thickness as a function of the film thickness and the optical absorption edge wavelength,
• i) wherein said step of producing a spectrum includes reducing the intensity of thin film interference oscillations in the optical absorption edge wavelength using a Fast Fourier Transform (FFT) and a notch filter.