Abstract

Low temperature Metalorganic Vapour Phase Epitaxy (MOVPE) is critically dependent on the correct chemical and physical preparation of the substrate before growth. The major contaminants on GaAs substrate surfaces are oxygen, in the form of native oxides, and carbon. Chemical etching in 5H₂SO₄: 1H₂O₂: 1H₂O (1) followed by thermal cleaning (annealing at 560-580°C) removes the oxygen but leaves carbon. Other techniques, such as plasma irradiation or ion bombardment (2), remove C and O but may introduce surface damage and change the surface stoichiometry. One technique which is employed for carbon removal in both Si (3) and III-Vs (4) is reactive etching in an ozone atmosphere. We have taken advantage of the fact that ArF excimer radiation can be used to decompose O₂ to yield O₃ to devise an in situ cleaning technique for GaAs substrates prior to MOVPE growth. We report here the results of an Auger study of the contaminant species and the effectiveness of their removal as a function of laser power and oxygen partial pressure.

© 1989 Optical Society of America