Structure of porous surface layers of single-crystal GaAs(001) wafers from data of X-ray diffractometry and reflectometry

The surface morphology and structure parameters of the surface layers of the single-crystal GaAs(001) wafers subjected to He + ion implantation ( E = 300 keV, D = 10 16 atoms/cm 2 ) and subsequent electrochemical etching in a 0.5 M H 2 SO 4 aqueous solution are investigated by X-ray reflectometry and double-crystal X-ray diffractometry. The strain and amorphization profiles over the layer thickness are determined from X-ray diffraction data. The density of surface layers, their thickness, and the changes of the surface relief upon etching are evaluated from the reflectometric data. The experimental parameters of the studied layers are compared with the theoretical distributions of implanted impurities and intrinsic point defects, which are calculated by the Monte Carlo method. A correlation is revealed between the layer thickness and the depth of the maximum defect concentration. It is found that the electrochemical etching predominantly occurs in strongly amorphized regions of the surface layer and does not lead to a change in the total layer thickness. The results of X-ray diffraction investigations are confirmed by scanning electron microscopy.