High-resolution X-ray diffraction and electron microscopy study of porous GaAs substrates

Abstract

ABSTRACT We investigated structural perfection of porous gallium arsenide layers formed in GaAs (001). Different modes of electrochemical etching of n-type GaAs(001) substrates in fluoride-iodide aqueous electrolytes were used to form porous layers. Their structural properties were investigated by high resolution X-ray and synchrotron radiation diffraction and electron microscopy (SEM, TEM) techniques. It was shown that a single current pulse with a high magnitude forms a discontinuous porous layer with a smooth surface. Subsequent etching with a relatively low current density forms a homogeneous porous structure in the depth with approximately 30% porosity. The porous layer thickness can be varied from a few microns to several tens of microns depending on the etching time. The lattice parameter of porous GaAs layers along the surface norm al is decreased by a factor of 1.5 u 10 -4 compared to the GaAs substrate. This contraction is related to the formation of vacancy type structural defects as revealed by the measurement of x-ray diffuse scattering. Keywords : porous semiconductors, structural defects, x-ray diffraction, diffuse scattering, reciprocal space mapping