NEW STARTING MATERIALS FOR MOMBE

This paper reviews our knowledge on standard and alternative precursors for use in MOMBE (metalorganic molecular beam epitaxy). It first deals with replacements for the group V hydrides, which is attractive from a safety point of view. So far the results obtained with completely or partially substituted hydrides do not match those observed with AsH3 and PH3. However, for the monosubstituted arsines precracking is unnecessary. Important advantages are offered by the use of coordinatively saturated group III compounds. This way oxygen may be suppressed or avoided altogether, which is important for the preparation of Al-containing films. In addition, the approach using saturated sources may be extended to starting materials not containing metal-bonded carbon. Thereby the danger of carbon incorporation into the layers may be reduced. Based on the insights in the deposition process a number of requirements for optimized precursors is formulated.