Accurate determination of effective quantum well thickness: Infrared absorption by transverse-optical phonons

We have studied far infrared transmission spectra of various AlSb/InAs/AlSb single quantum wells, where the well width ranges from 60 to 200 A. Because the quantum well is thin, the far infrared absorption due to transverse‐optical phonons is not saturated. We obtained excellent fitting to the transmission spectra by taking into account the complex dielectric functions with a transfer matrix formalism. The thickness of InAs quantum wells can be determined with monolayer resolution. High‐resolution transmission electron microscopy shows clear lattice images in a region away from the AlSb/InAs interfaces. The thickness of the pure nonintermixed InAs region is in excellent agreement with our far infrared absorption results. Phonon absorption can therefore provide a nondestructive method to effectively determine the number of pure InAs monolayers, in spite of interdiffusion occurring at the interface.

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