Optimized cleaning method for producing device quality InP(100) surfaces

A very effective, two-step chemical etching method to produce clean InP(100) surfaces when combined with thermal annealing has been developed. The hydrogen peroxide/sulfuric acid based solutions, which are successfully used to clean GaAs(100) surfaces, leave a significant amount of residual oxide on the InP surface which can not be removed by thermal annealing. Therefore, a second chemical etching step is needed to remove the oxide. We found that strong acid solutions with HCl or H2SO4 are able to remove the surface oxide and leave the InP surface passivated with elemental P which is, in turn, terminated with H. This yields a hydrophobic surface and allows for lower temperatures to be used during annealing. We also determined that the effectiveness of oxide removal is strongly dependent on the concentration of the acid. Surfaces cleaned by HF solutions were also studied and result in a hydrophilic surface with F terminated surface In atoms. The chemical reactions leading to the differences in behavior between InP and GaAs are analyzed and the optimum cleaning method for InP is discussed. Work supported in part by the Department of Energy, contract DE-AC02-76SF00515 February 2005 SLAC-PUB-11018