High resolution electron density distribution determination for GaAs and CdTe

The title compounds are typical III-V and II-VI-type semiconductors, having Zinc-blende-type isomorphous crystal structures. The present work was aime d to obtain reliable electron density distributions experimentally and theo retically by means of the maximum entropy method (MEM) based on X-ray diffr action intensity data and ab initio calculation. From the MEM calculation, the electron density maps were determined to an accuracy of 0.05e/Angstrom (3) in each 0.09 x 0.09 x 0.09 Angstrom (3) pixel at 200 K and ambient for GaAs and CdTe, respectively. An asymmetric charge distribution was clearly observed in the Ga-As bonds in the (1 1 0) plane even in ambient, i.e, an a ppreciable amount of electrons, being of the order of 0.1 e/Angstrom (3) or less for each Ga ion, are attracted from the Ga ion to the As ion. No obvi ous asymmetry was observed in the Cd-Te bonds on the other hand. (C) 2001 E lsevier Science B.V. All rights reserved.