Analysis of factors influencing the process of selective etching of the {100} monocrystalline GaAs surface to determine the dislocation density

The purpose of this work is to evaluate the effect of crystallohydrate water in the composition of alkalis: potassium hydroxide and sodium hydroxide on the process of selective etching of single-crystal gallium arsenide plates used to identify dislocation etching pits on the crystallographic surface {100} as part of technological quality control of single-crystal GaAs ingots. Selective etching was carried out in melts of alkali crystallohydrates (KOH · H 2 O, NaOH · H 2 O), as well as in melts of anhydrous alkalis (KOH, NaOH). As a result of the experiments carried out, it was proved that when etching in anhydrous potassium and sodium hydroxides, the etching process of gallium arsenide plates does not proceed selectively — there is an almost uniform dissolution of the entire surface. At the same time, the formation of erosion zones occurs in the melt of KOH · H 2 O crystallohydrate — dislocation etching pits characteristic of the crystallographic plane {100}. In the melt of NaOH · H 2 O crystallohydrate, the selective etching process does not proceed, all other things being equal, under experimental conditions. As a result of the analysis of the experimental data, the mechanism of selective etching was identified and justified, which consists in the course of high-temperature hydrolysis of the {100} GaAs surface with the participation of crystalline hydrate water residues in the composition of KOH · H 2 O. It has been shown that the temperature and the presence of water in the composition of the selective etchant are the determining factors of the course of this process. The use of the results of this work will make it possible to control the process of selective etching of GaAs plates to a greater extent, as well as to standardize the methodology of their technological control.