GaP結晶(111)面におけるスパイラル・ピットの形成

Abstract

The (111) wafers obtained from a Te-doped GaP crystal were etched at 60-80°C over a time period of 1.2×103 to 7.2×103 s with a solution composed of H2SO4+H2O2+H2O (5:1:1 in volume ratio) and the etch-figures were observed mainly by optical microscopy.At temperatures above 70°C, spiral etch-pits developed on the (\bar1\bar1\bar1)P surface of the wafers in addition to the normal etch-pits. The spiral etch-pits increased in size with increasing etching temperature and etching time, while the size of normal etch pits remained constant. On the (111)Ga surface rather small spiral etch-pits were also formed at 80°C, but their size remained unchanged with increasing etching time. From the experiments of double etching with a H2SO4+H2O2+H2O solution and an RC etchant, it was concluded that the former etching produces normal pits at edge dislocations and spiral pits at screw dislocations, respectively, and that the latter etching forms dark pits at edge dislocations and S-pits at small lattice defects, respectively.