OPTICAL STUDY OF INTERDIFFUSION IN CDTE AND ZNSE BASED QUANTUM-WELLS

The interdiffusion in single quantum well structures was studied for a variety of II-VI semiconductor materials based on CdTe and ZnSe. In particular we have investigated CdTe/CdMnTe, CdTe/CdMgTe, HgxCd1-xTe/Hgy Cd1-yTe and ZnSe/CdZnSe structures in which an intermixing of column II elements can be induced as well as ZnSe/ZnSSe allowing an interdiffusion within the column VI sublattice. The diffusion was induced by rapid thermal annealing (RTA) for 1 min at different temperatures. The resulting blue shift of the characteristic emission spectrum was analyzed using photoluminescence spectroscopy. We observed a significant difference of the diffusion behavior between both groups of materials. While in all three CdTe based material systems an almost complete interdiffusion within the column II sublattice could be obtained at a high optical quality of the structures, both ZnSe based quantum wells show only remarkably small diffusion lengths. For all three CdTe based quantum wells we derived an activation energy of the interdiffusion process from a simple Fickian diffusion model applied to our measurements. We obtained a value of 2.8 eV for CdTe/CdMnTe and CdTe/CdMgTe and a value 2.1 eV for HgxCd1-xTe/HgyCd1-yTe.