Temperature-Modulated Optical Absorption in Semiconductors

Abstract

Temperature‐modulated optical absorption measurements on Si, GaAs, CdS, and KTaO₃ near the absorption edges are described and interpreted. These measurements show that the experiment is a simple and accurate method of measuring the band‐gap energy of semiconductors, and of determining whether the gap is direct or indirect. Information is also obtained on phonon‐assisted absorption mechanisms near the band edge and some phonon energies can be deduced. The measurements on Si and CdS verify previous interpretations of the band edge based on optical absorption, and the results from GaAs are nearly identical to those obtained from the electric field modulated absorption experiment. The measurements on KTaO₃ indicate that this material has an indirect gap with an energy of 3.45 eV.