STUDY BY SPECTROELLIPSOMETRY OF THE InP SURFACE EVOLUTION BY CERIUM ACIDIC SOLUTION

摘要

Evolution of the InP surface chemistry by cerium acidic solution is studied by spectroellipsometry and high resolution XPS. The etching process is rule by two electrochemical processes linked together. The initial one injects holes inside the BV during the reduction of the Ce~(4+) in Ce~(3+). These holes are consumed by a classical anodic dissolution, conducting to the formation of P~(5+) and In~(3+) species in solution. This global mechanism gives rise to an electroless process ruled by the diffusion into the solution. On InP, this process can give rise to a side reaction that for high cerium concentration decreases strongly the etching rate and sometimes stops the process. This perturbation in fact is associated to the growth of an interfacial film that blocks the injection of holes inside the BV. We have followed for the first time this process by spectroellipsometry. This film has a complex chemical composition, which is a mixture of a cerium phosphate and InP oxides. Its structure is an opened question.