Epitaxial Defects in Nanoscale InP Fin Structures Revealed by Wet-Chemical Etching

In this work, we report on wet-chemical defect revealing in InP fin structures relevant for device manufacturing. Both HCl and HBr solutions were explored using bulk InP as a reference. A distinct difference in pit morphology was observed between the two acids, attributed to an anisotropy in step edge reactivity. The morphology of the etch pits in bulk InP suggests that the dislocations are oriented mainly perpendicular to the surface. By studying the influence of the acid concentration on the InP fin recess in nanoscale trenches, it was found that aqueous HCl solution was most suitable for revealing defects. Planar defects in InP fin structures grown by the aspect ratio trapping technique could be visualized as characteristic shallow grooves approximately one nanometer deep. It is challenging to reveal defects in wide-field InP fins. In these structures, dislocations also reach the surface next to stack faults or twinning planes. Due to the inclined nature, dislocation-related pits are only a few atomic layers deep. Extending the pits is limited by the high reactivity of the fin sides and the strong surface roughening during etching. The process window for revealing wet-chemical defects in InP fins is limited.