Optical characterization of intersubband transitions in ZnxCd1-xSe/Znx'Cdy'Mg1-x'-y'Se asymmetric coupled quantum well structures by contactless electroreflectance

Contactless electroreflectance (CER) was used to characterize the possible optical transitions in a ZnxCd1-xSe/Znx'Cdy'Mg1-x'-y'Se asymmetric coupled quantum well (ACQW) structure grown by molecular beam epitaxy for quantum cascade laser (QCL) applications. CER spectrum revealed a wide range of the possible optical transitions in ACQW structure. The ground state transition was assigned by comparing with the photoluminescence emission signal taken from the same structure. A comprehensive analysis of the CER spectrum led to the identification of various interband transitions. The intersubband transitions were estimated and confirmed by FTIR measurements. The results demonstrate the potential of using CER as a complimentary technique for the contactless and nondestructive characterization of the wide band gap II-VI ACQW structures for QCL applications ([copy 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)