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 ammon iacal medium was studied, and the activation energy of the overall reaction was determined. It was shown that diffusion influences the etching section s and the roughness of the etched surface. Optimal conditions for etching ( pH, temperature, agitation, thiourea concentration) were established by obs erving the samples' surfaces using optical microscopy and atomic force micr oscopy (AFM). The addition of thiourea to the etching bath leads to a very significant reduction in the surface's roughness. The increase in the inten sity of the photoluminescence at 4 K of the etched GaAs samples in the bath containing thiourea could indicate a definite reduction in nonradiative em issions, and therefore a passivation of the surface. (C) 2001 Elsevier Scie nce B.V. All rights reserved.