Reduction of Interference Oscillations in Observing Intersubband Transitions in AlSb/GaSb Superlattices by Fourier Transform Infrared Spectroscopy

Intersubband transitions from L₁ to L₂ subbands in AISb/GaSb superlattices in the 8-18 μm wavelength range are observed by employing normal- and oblique-incident Fourier transform infrared (FTIR) spectroscopic techniques. Using AlSb rather than GaSb as the buffer layer, interference oscillations in normal-incident FTlR spectra are significantly reduced, which facilitates one to distinguish intersubband transition features. In the oblique-incident mode where a 45° thallium hexahedron is used for internal reflection, interference oscillations are eliminated, making it possible to observe weak intersubband transitions that cannot be distinguished in normal-incident absorption spectra.