INFLUENCE OF THE DOPING CONCENTRATION ON THE ELECTROCHEMICAL ETCHING OF SEMICONDUCTORS

The doping concentration influences transport properties at semiconductor interfaces. In the case of liquid contacts, studies suggest that the kinetics of dissolution of n- and p-type materials increase significantly above a critical doping level. Starting from recently developed Tafel plots of the GaAs/H2O junction which showed that the foregoing effect was depending on the origin of corroding free holes, the paper examines some hypothesis pertaining to experimental observations. The calculation of the three-dimensional potential distribution induced by a square array of point charges on the surface shows that the phenomenon most probably arises from a potential barrier induced by charged corrosion sites. The theory predicts that the barrier becomes thinner with increasing density of point charges, which suggests that the density of etch pits must be determined by the density of doping atoms below the surface. The effect becomes significant for doping levels greater than 10(18) cm-3. This work is a new approach which supports the observations of Tenne and Marcu about the photoetching of II-VI semiconductors [R. Tenne and V. Marcu, Appl. Phys. Lett. 45, 1219 (1984)].