The role and mechanism of a ZnTe buffer layer on the structural properties of the strained CdxZn1-xTe/ZnTe double quantum wells

Abstract

Transmission electron microscopy (TEM) measurements were performed to investigate the role and mechanism of a ZnTe buffer layer on the high-quality structural properties for strained CdxZn1-xTe/ZnTe double quantum wells. The bright-field TEM image near the ZnTe/GaAs interface showed the Moire patterns, indicative of initial island growth and of a difference in the growth directions between the islands. The high-resolution TEM image indicated that the difference in the growth directions originated from the formation of the plane defects, such as a sub-grain boundary. When a 1-mu m ZnTe buffer layer was grown on the GaAs substrate, the ZnTe buffer layer could be used as a defect-free substrate, as shown by the thickness fringes observed from the TEM image. The formation mechanism for the thickness fringes in the ZnTe buffer layer between the CdxZn1-xTe/ZnTe double quantum well and the GaAs substrate is discussed. The results indicate that the ZnTe buffer layer plays an important role for strained CdxZn1-xTe/ZnTe double quantum wells grown on GaAs substrates by eliminating the defects due to the lattice mismatch. (C) 1998 Elsevier Science Ltd. All rights reserved.