New apparatus with double supersonic molecular beams for epitaxial growth and surface reaction studies

Abstract

To understand surface reaction dynamics in III–V compound semiconductor growth, we have developed an apparatus to study both surface chemical reactions and epitaxial growth. This apparatus has double supersonic III and V compound molecular beam cells and an analytical chamber with a rotatable differentially pumped liquid-nitrogen-cooled quadrupole mass spectrometer to measure angular and time-of-flight distribution of reflected beams. It also has reflection high-energy electron diffraction to analyze surface structures. Tertiarybutylarsine beam energies of 1.6 eV were obtained for He, 0.22 eV for Ar, and 0.06 eV for Xe seeding. An organometallic molecular beam of translational energy is varied over a wide range, enabling source molecules to be brought to a well-defined epitaxial surface in well-characterized ways. High-purity GaAs layers were grown by alternatively supplying triethylgallium and tertiarybutylarsine molecules to the analytical chamber. Our apparatus bridges the gap of studies between epitaxial growth and surface chemical reactions. Dynamic measurement on the growth surface revealed a number of interesting reactions not ordinarily observed on well-defined surfaces.