SEMICONDUCTOR SUBSTRATE CLEANING AND SURFACE-MORPHOLOGY IN MOLECULAR-BEAM EPITAXY

In-situ laser light scattering shows that the surface morphology of Ga As substrates during the initial stages of homoepitaxial growth is a s ensitive indicator of substrate cleanliness. Oxide removal by atomic-h ydrogen etching has no effect on the morphology of polished (100) GaAs substrates, while thermal oxide desorption roughens the surface. Carb on contamination of the surface causes roughening during subsequent fi lm growth. Secondary ion mass spectrometry and photoemission spectrosc opy show that atomic-hydrogen etching reduces the carbon contamination on the substrate but does not remove silicon oxide. Synchrotron radia tion photoemission measurements show that some as-received substrates are contaminated with a thin uniform layer of SiO2. (C) 1997 Elsevier Science B.V.