An investigation on surface conditions for Si molecular beam epitaxial (MBE) growth

Contamination-free Si substrate surfaces are vitally important to the subsequent molecular beam epitaxy (MBE) growth. A number of studies on the major contaminants, i.e., C and O, on Si surfaces have been done, and new cleaning procedures for reducing these contaminants have been proposed. However, to date the detailed behavior of C and O on Si surfaces and their effects on the subsequent Si MBE growths are not well established. In the present work, the behavior of the contaminants on heated Si surfaces were investigated using Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS). Also, the chemical bonding of C on Si surfaces was studied by analyzing the AES line shapes of carbon and comparing them with those known carbon chemical states. For the chemical cleaning procedures used in this study, a silicon oxide protection layer is grown onto the cleaned Si surface prior to sample loading. The property of this silicon oxide layer is studied using ellipsometry measurements. To verify the effectiveness of the cleaning procedures, MBE films grown subsequently are analyzed using Rutherford backscattering (RBS). The resulting channeling yield of 2.5% suggests the nearly perfect crystalline quality of these films. Deep-level transient spectroscopy (DLTS) is used to study the defect in the epilayer, and the defect concentration is determined to be in the 10¹³ cm^-3 range.