SELECTIVE ETCHING OF ALAS FOR PREPARATION OF III-V SEMICONDUCTOR THINFOILS

A new method of thin section preparation of III-V semiconductors and m ultilayers for transmission electron microscopy (TEM) is presented tha t exhibits considerable advantages over conventional methods such as i on beam milling and jet thinning. GaAs thin films and multilayers of G aAs/InchiGa1-chiAs/GaAs are grown over an etch release layer of AlAs o n GaAs substrates by molecular beam epitaxy (MBE). Planar TEM sections prepared by selective etching from these samples show improved abilit y to image film morphology and dislocation arrangements, and the resul ting large thin electron transparent areas facilitate dislocation dens ity measurements and detection of spatial variations. Avoidance of rad iation effects and wedge shaping, both common to ion milled samples, a llows this method to be used to prepare uniform thickness standards of single layer GaAs films for EDS analysis or lattice imaging.