The slow evaporation of In from wafers was investigated, and was identified as being a major cause of surface roughening during thermal annealing and mass transport under adequate P-vapor protection. Analysis showed that In evaporation could be prevented by covering the wafer during annealing. However, the usual graphite cover alone was an inadequate protection because the In vapor was able to permeate the graphite. On the other hand, the use of an InP cover alone resulted in problems which were caused by the mass transport that occurred between the InP wafer and the cover. A scheme was developed that used InP covers and a quartz enclosure in addition to a graphite cover. This arrangement permitted smooth wafer surfaces to be reproducibly obtained.

Z.L.Liau: Applied Physics Letters, 1991, 58[17], 1869-71