On the Factors Determining the Morphology of Wet‐Etched n‐ and p ‐ GaP Single‐Crystal Surfaces

Abstract

Wet etching of [111]‐oriented single crystals is performed in aqueous solutions at different anodic potentials for p‐type and at different anodic potentials and illumination levels for n‐type samples. Furthermore, both n‐ and p‐type crystals are photoetched in solutions at open‐cricuit potential. The influence of the rate‐determining step on the etching morphology is shown. The difference in etching selectivity between the (111) and (111) face is explained by the different orientation of the Ga‐P dipole, resulting in a different reactivity for hole capture. The photoetch results in the formation of etch hillocks at n‐type crystals, whereas etch pits are developed at p‐type crystals. This result is explained by the fact that only local variations in the anodic partial current of the process are reflected in the etching morphology.