THE ROLE AND MECHANISM OF A ZNTE BUFFER LAYER ON THE STRUCTURAL-PROPERTIES OF THE STRAINED CDXZN1-XTE ZNTE DOUBLE-QUANTUM WELLS/

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 quan tum wells. The bright-field TEM image near the ZnTe/GaAs interface sho wed the Moire patterns, indicative of initial island growth and of a d ifference in the growth directions between the islands. The high-resol ution TEM image indicated that the difference in the growth directions originated from the formation of the plane defects, such as a sub-gra in boundary. When a 1-mu m ZnTe buffer layer was grown on the GaAs sub strate, the ZnTe buffer layer could be used as a defect-free substrate , as shown by the thickness fringes observed from the TEM image. The f ormation 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 a n important role for strained CdxZn1-xTe/ZnTe double quantum wells gro wn on GaAs substrates by eliminating the defects due to the lattice mi smatch. (C) 1998 Elsevier Science Ltd. All rights reserved.