Underetching from simple stochastic etching kinetics

The morphological richness of electrochemical semiconductor etching is not sufficiently counterparted yet by theoretical modeling. This paper investigates a minimal version of the Current-Burst model with Aging of F\"oll and Carstensen and demonstrates for a restricted geometry that the Aging concept is essential for underetching, or cavity generation. If the influence of Aging is neglected, the dynamics reduces to a Random Etching Model similar to the Random Deposition model. This computer {\sl gedanken experiment} demonstrates that the stochastic dynamics with ageing-dependent kinetic reaction probabilities accounts for the different etching morphologies compared to those obtained in surface roughening and related systems.