QUANTITATIVE INTERFACIAL PROFILES IN CDTE MN(MG)TE HETEROSTRUCTURES/

We have measured by high resolution transmission electron microscopy ( HRTEM) the width of interfaces in two II-VI heterostructures: CdTe/MnT e and CdTe/MgTe, as a function of the growth mode. A critical review o f the different parameters involved in the direct determination of the chemical profile by HRTEM enables us to precisely determine the sensi tivity and accuracy of the methods on these particular materials. The measured interface width is of the order of 2.5-3 monolayers (ML) and Is compatible with an exchange mechanism involving the monolayer being grown and the last deposited monolayer. Several growth procedures wer e compared: conventional molecular beam epitaxy and atomic layer epita xy (ALE). In the case of saturated and oversaturated ALE the inverse M nTe/CdTe interface is no longer planar. A destabilization of the growt h front occurs when one or more Mn monolayers per cycle are deposited, through the formation of MnTe islands. Thermal interdiffusion seems t o be negligible in the case of Mn. The present HRTEM values for the in terface widths extend the results obtained by magneto-optical measurem ents to higher concentration values and confirm the exchange mechanism . The higher Value obtained by x-ray reflectivity (4.7 ML) is explaine d by the large difference of the average volume on which the measureme nt is performed. (C) 1998 American Institute of Physics. [S0021-8979(9 8)05214-1]