HYDROGEN-INDUCED BREAKDOWN OF LOW-TEMPERATURE MOLECULAR-BEAM EPITAXY OF SI

Low-temperature molecular-beam epitaxy of Si is characterized by the existence of an epitaxial thickness hepi, below which the film is epitaxial and above which the film turns amorphous. Epitaxial films with a thickness beyond hepi can be grown, provided a rapid-thermal-anneal (RTA) step to a sufficient temperature, TRTA, is executed before reaching hepi. Positron-annihilation spectroscopy shows that TRTA=450°C is not sufficient but 500°C is. We explain this cutoff in RTA temperature using a model based on Si-H bond breaking. Nuclear reactions analysis support this model and show a high concentration of hydrogen in films grown with RTA below 450°C. According to the proposed model, a reduction of the hydrogen content in the growth ambient should lead to larger hepi. © 1995 The American Physical Society.