Analysis of Factors Influencing the Selective Etching of {100} Surface of Single-Crystal Gaas Usedto Determine the Dislocation Density

Abstract—The results of assessing the effect of crystal hydrate water in the composition of KOH and NaOH alkalis on the process of selective etching of single-crystal GaAs wafers used to identify dislocation etching pits on the {100} crystallographic surface during technological quality control of single-crystal GaAs ingots are presented. Selective etching is carried out in melts of alkali crystal hydrates (KOH·H₂O, NaOH·H₂O), as well as in melts of anhydrous alkalis (KOH, NaOH). It is established that when etching in anhydrous potassium and sodium hydroxides, the etching of {100} gallium arsenide wafers proceeds nonselectively—nearly uniform dissolution of the entire surface occurs. At the same time, in the melt of KOH·H₂O crystal hydrate, erosion zones are formed—dislocation etching pits characteristic of the {100} crystallographic plane. In the melt of NaOH·H₂O crystal hydrate, the selective etching process does not proceed under all other equal experimental conditions. Analysis of experimental data makes it possible to reveal and substantiate the mechanism of selective etching, which consists in high-temperature hydrolysis of the {100} GaAs surface with participation of residual crystal hydrate water in the composition of KOH·H₂O. It is shown that the temperature and the presence of water in the composition of selective etchant are determining factors in the course of this process. The results can be used to control selective etching of GaAs wafers, as well as to standardize the methodology of their technological control.