Etching of GaAs substrates to create As-rich surface

Several different cleaning procedures for GaAs (100) substrates are compared using X-ray photoelectron spectroscopy and optical microscopy. This work emphasizes the effect of the last etching step: using either HCl, HF-ethanol (5%) or static deionized water after HCl cleaning. All the procedures except HCl solution (1:1) produce an As-rich surface. Also, none of the etchants except HF-ethanol solution produce Ga or As-rich (oxide free) surfaces. Optical microscopic study shows different etch pits produced due to etching in different solutions.