It was noted that, when (111) wafers of Te-doped material were etched in H2SO4 + H2O2 - H2O (5:1:1 volume ratio) at above 700C for periods longer than 1h, abnormal etch pits of asymmetrical shape formed on the (111)P surface. These were in a minority when compared with normal triangular pits and spiral pits. Microscopic observations revealed that the abnormal pits had an etch beak which projected from the apex. Structural defects in the wafers were examined by means of transmission electron microscopy, after thinning. They were classified into several types, such as: dislocations, dislocation loops, precipitates and lineage defects which were composed of a dislocation bundle.

Formation of Abnormal Etch Pits on (111)P Surface of n-GaP Crystal S.Sugawara, K.Saito: Materials Transactions, 2000, 41[2], 268-71. See also: Materials Transactions, 2000, 41[2], 264-7