RESIDUAL POLISHING DAMAGE AND SURFACE QUALITY OF COMMERCIAL INP WAFERS - A SCANNING PL STUDY

The photoluminescence (PL) method has been used to investigate defects associated with surface polishing damage present in as-received comme rcial (100) LEC InP wafers. The wafers were chemically angle-polished to produce a surface bevel angle of similar to 0.01 degrees using the method previously developed by Huber, but were not subsequently defect etched. For 'as-polished' wafers, total-light RT 2-D scanning PL imag es revealed on the bevel a 'good' zone extending to a depth of similar to 10 nm, a 'damage' zone extending from similar to 10 to similar to 70 nm, and an underlying 'bulk' zone. The defects in the damage zone a ppeared as irregular dark lines and patches of number density similar to 10(5) cm(-2) and these were interpreted as arising from dislocation s and mirco-cracks. The 'bulk' zone and unbevelled 'surface' zone show ed no such damage defects. Defect etching produced shallow S-pits in t he 'damage' zone, but not in the 'bulk' or 'surface' zones. Different 'as-polished' wafers showed differences in the amount and type of dama ge, while for 'epi-ready' wafers no damage zone was revealed. Possible reasons for the occurrence of 'good' and 'damage' zones in the PL ima ges of the InP wafers are discussed. During the course of this work, P L results were also obtained from the surfaces of a range of as-receiv ed commercial InP wafers and InP epitaxial layers (un-bevelled). When examining a particular area, the background PL intensity often increas ed and then decreased as the laser beam irradiation time increased, th e PL intensity sometimes changing by up to 5 x. The magnitude of the e ffect depended on the InP material and growth method and the power of the laser beam, and could be virtually eliminated by an initial low te mperature anneal. Possible reasons for this effect and its significanc e are discussed.