Micro-Raman study on chirped InGaAs–InAlAs superlattices



The folded acoustic phonon and confined optical phonon modes in chirped InGaAs–InAlAs superlattices have been studied by micro-Raman spectroscopy. The folded and confined phonons were probed at the (inline image) and (001) faces. Raman scattering measurements for the chirped superlattices and an InGaAs film were performed at different temperatures. The temperature dependence of the longitudinal optical phonon frequencies indicates that a compressive strain existed in the InGaAs layers of the chirped superlattices, which is significant for analyzing the device failure of quantum cascade lasers operating at higher active region temperatures.