MAGNETOOPTIC STUDY OF THE INTERFACE IN SEMIMAGNETIC SEMICONDUCTOR HETEROSTRUCTURES - INTRINSIC EFFECT AND INTERFACE PROFILE IN CDTE-CD1-XMNXTE

This paper is devoted to the description of the interface between a se mimagnetic semiconductor (Cd1-xMnxTe) and a nonmagnetic one (CdTe), an d to the study of its magnetic and magneto-optical properties, as reve aled through the enhanced Zeeman splitting of carriers confined in het erostructures. The model (proposed earlier on phenomenological bases) takes into account both the chemical profile of the imperfect interfac e and the enhanced magnetism due to the reduced number of magnetic nei ghbors at the interface. We first justify the model (for low Mn conten ts) by considering the statistics of Mn clusters at the interface or i n a single Cd1-xMnxTe monolayer embedded in CdTe. We also show that th e sensitivity of the Zeeman effect to the presence of two-dimensional islands at the interface rapidly decreases as the island width increas es; i.e., the measure is sensitive to the presence of isolated magneti c ions and not (or less) to roughness, and it characterizes the interf ace on the scale of interatomic distance. Then we apply this tool to a wide series of samples with different nominal characteristics and dif ferent growth conditions. A unique profile (determined with a single a djustable parameter) accounts for the enhanced Zeeman splitting observ ed on samples grown at low temperature (250-280 degrees C) under exces s of Cd, independently of the details of the carrier-wave function and of its penetration into the magnetic barrier: this is a further (expe rimental) check of the calculation. The exponential profile deduced fo r these samples accounts for the larger enhancement of Zeeman splittin g at the inverted interface (CdTe grown on Cd1-xMnxTe), compared to th e normal interface (Cd1-xMnxTe on CdTe). It points to a complete excha nge of Cd and Mn atoms between the two surface layers during growth (i .e., a segregation process with a segregation energy determined to be zero). We found very little influence of growth interruptions and of g rowing the Cd1-xMnxTe barrier under Te excess. As the growth temperatu re is raised above 300 degrees C, the interface further broadens, the additional broadening being identical for the two interfaces. Finally, we found that the Zeeman effect of carriers confined in quantum wells incorporating a magnetic inverted interface (including symmetrical qu antum wells) is completely dominated by the effect of the nonabrupt pr ofile, while a small contribution of the intrinsic effect seems to exi st in a quantum well with only a normal magnetic interface or heterost ructures with single Cd1-xMnxTe monolayers.