Study of GaAs chemical etching in a mixture of hydrogen peroxide/succinic acid and ammonia. Thiourea effect on the surface roughness and on the presence of surface states after etching

The GaAs etching by the hydrogen peroxide±succinic acid mixture in an ammoniacal medium was studied, and the activation energy of the overall reaction was determined. It was shown that diffusion in¯uences the etching sections and the roughness of the etched surface. Optimal conditions for etching (pH, temperature, agitation, thiourea concentration) were established by observing the samplesʹ surfaces using optical microscopy and atomic force microscopy (AFM). The addition of thiourea to the etching bath leads to a very signi®cant reduction in the surfaceʹs roughness. The increase in the intensity of the photoluminescence at 4 K of the etched GaAs samples in the bath containing thiourea could indicate a de®nite reduction in nonradiative emissions, and therefore a passivation of the surface. # 2001 Elsevier Science B.V. All rights reserved.